LRR Tires – Worth It

The Aptima Motors eCobra is coming along. We are in the final days of this project. It rolls and drives well.

One of the concerns with this car has been the amount of power required to move it. For a two seat convertible sports model, it is a bit heavy at 2961 lbs – no interior or paint yet at that. But as we have added pieces such as the hood and trunk, the aerodynamics have improved and the power consumption has fallen to more of the expected levels just over 300 wH per mile – about as expected for it’s weight.

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One of the eyebrow raisers from receipt of this car was the large wide tires that came on it. Lots of rubber looks good and rides well, but it usually means higher rolling resistance. Very early in the program we ordered a new set of lightweight WELD wheels with a carefully calculated offset so we could run Michelin Energy Saver A/S low rolling resistance tires on this car. The issue was having the offset such that the tires still filled the wheel well and didn’t look entirely odd on a Cobra.

Recall from our mystery surrounding the Porsche 550 Spyder and the Porsche 356 Speedster that we got a significantly better range and energy use from the heavier and rounder Speedster. Despite installing expensive aluminum rotors, calipers, low rolling resistance tires, and even ceramic bearings, we never did get the Spyder even close to the Speedster’s ability to roll much more freely.

As kind of a joke we ran what we called the Soapbox Derby – simply rolling the two cars down the street in neutral to see which rolled further. True to our range results, the Speedster rolled dramatically further than the Spyder.

We can of course do normal range testing but it is quite time consuming and subject to variabilities out of our control. If a tractor trailer blows past you, cuts in front of you, and then slows to 7 miles per hour below your target speed, there’s not a lot you can do about it in a small convertible. And the tests take hours and are much more accurate over a significant number of miles – 15 to 25 typically.

So we liked the quick indication of the Soap Box derby. But it didn’t actually provide much data – just a distance on a hill. And you have to use the SAME hill. So YOU can’t compare YOUR results to ours.

The way this is actually done in automotive testing is with a coast down test. And so we adopted the pretty standard procedure used in such tests – with perhaps less instrumentation and rigeur than is commonly done at the Chrysler Test Grounds. But we think it renders quite accurate information, and is reproducible by anyone anywhere on any car.

Basically, we go to a flat stretch of road sufficiently long to allow an acceleration to 75 mph and a subsequent unpowered roll to a full stop. Ideally, with very little traffic on it. We then accelerate to 75 miles per hour, and then remove all throttle input and place the transmission in neutral.

As the car speed decreases and passes through 70 mph, you take a time mark. As the point where it hits 60 miles per hour, you note the time from the 70 mph start time mark. As it passes through 50 mph, again take a time. And so forth until the car actually comes to a stop, noting the time each 10 miles per hour.

There is a human element using a stopwatch, and the incline of the road will affect the results, no matter how flat. So we run the test THREE TIMES in each direction, giving us six time sets. Then we average the times. We actually had little variation there.

The chart below shows this coast down test for the Michelin Energy Saver A/S tires/wheels, as well as for the Stinger Radial GTS tires that originally came on the car.

As you can see, the results are pretty similar at the higher speeds, where aerodynamics comprises the predominant effect. But as the speed deteriorates, the two curves diverge pretty strongly. Total time was a difference of nearly 30 seconds. That’s quite a bit of time and quite a bit of distance differential for two sets of tires.

We also did some actual range testing. Excluding extraneous factors such as hoods and trunk lids, we really only have directly comparable data for 40 mph and 50 mph.

But the results are startling. At 40 mph our max range calculates to 152 miles with the Michelins and 124 miles with the Stinger tires. LRR tires typically provide a 3-5% increase in gas mileage. But in this case, starting with tires that are so BAD for an electric drive application, this was 28 miles further than the Stinger results – a gain in max range of 22.58%. This is frankly just huge. Not precisely apples to apples as they are entirely differently sized tires, but it’s a real gain and we’ll take it.

The results at 50 mph are less as there is slightly more of an aerodynamic component at the higher speed – predictably enough. But they are still substantial at over 14%.

A number of people have waned us to keep the eCobra cobra like. We don’t know precisely what this means. But we think it has something to do with burning rubber. So we installed a line locker on the front brake line. This allows us to spin the rear wheels while applying brake to the front wheels. It worked well enough as you’ll see in the video. As an added bonus, it makes a very handy parking brake.

We also did some very preliminary testing of 0 to 60 times using the pretty basics device provided on the GPS speedometer. It would appear we ran 0 to 60 mph in 6.77 seconds and 360 linear feet. We think we can improve on that with practice, probably down to about six seconds.

We hope to get the car over to Slingblade Racing this week for a full dynamometer test.


78 thoughts on “LRR Tires – Worth It”

  1. This is much better than I expected to see but in retrospect it makes perfect sense. If you see 3% on an ICE vehicle that will reflect as much more on an EV because the power system is so much more efficient.

    It is a gain everywhere, and should be reflected especially during regen since you get to harvest all that normally wasted energy. You would have to be a saint to coast the extra distance you will get.


  2. I haven’t watched the latest two videos. Does the spread between the AH/Mile ratios of Michelin 40/Michelin 50 and Stinger 40/Stinger 50 reveal anything about the rolling resistance coefficients being inconstant? I’m amazed a car could roll down for >50 seconds from 10 mph. If the starting speed were only 15 mph would the car still roll down for >50 seconds from 10 mph?


    “The Shelby Cobra is particularly quick of the start on straight-aways, but the aerodynamics of the convertible was all wrong. Therefore Shelby designed the coupe version which helped to bolster the Shelby Cobra into the racing limelight.”

  3. It’s kind of a relative thing Perin, but yes, I would rate the Cobra aerodynamics as very poor. The huge windshield and the chopped off rear end undoubtedly contribute. But we still have that big scoop out there open. If we closed that off, I think it would make a difference.

    In fact, that is one of the options when they do paint and interior. By doing this test, we give them a baseline. They can temperatorily enclose it and see if their mileage differs.

    Jack Rickard

  4. Jack, do you guys plan to do the roll down test with the other vehicles? I think it would be very useful to have data from a variety of cars so others can use the numbers as a baseline. That way if they want to test their cars, they can see where they fall in the spectrum.

    It may be worthwhile to collect the data from others and post each online for all to see and use for comparison.


  5. I crunched some numbers and if we model rolling resistance as text book friction it means it’s a constant only proportional to the weight. the remaining component is the airdrag that grows with the square of the speed. within that model I get a Cd of 0.76 for the Cobra!
    that model doesn’t quite fit the curve though so I speculate that massaging the tires and perhaps the differential has a component that grows with speed so the growth is not only air drag. if I make an estimate on how to better fit the curve and allow for an unknown non constant rolling resistance it seems the Cd is around 0.58. probably no less than 0.5 and no higher than 0.7. this compares to the EV1 at 0.19 (both have similar cross section area)
    it’s good to get data on these things.

  6. Are we going backwards here?; the industry worked for years to perfect safe road tires…i.e., tires that would stay planted to the road and curves and pump the water away on rainy roads. now, as we develop low rolling resistance tires, are we building danger back into the cars? Seems to me that the harder compound tires would be poor in the wet and give up easily in the corners.

    It would be interesting to see the difference between the tires when tested on a skid pad.

  7. Lad, industry didn’t work to perfect anything. cars have been incredibly suboptimal for decades. it is marked by thoughtlessness and unwavering faith in status quo.
    try not to assume that a lower rolling resistance means less safe. the michelin has quite good performance allround iirc.
    in principle rolling resistance is independent of grip.

  8. Lad,
    It’s all a balancing act.

    Adding in lots of silicon instead of carbon speeds up the rebound rate but does not help with wet weather grip.
    To increase wet grip you need a softer compound tyre and plenty of grooves which in turn will wear down more quickly.

    A fast wearing eco tyre is no eco tyre.

    Parameters, parameters
    If you are not confused now. Help me!

  9. I forgot to say that the look of this car is growing on me. Still prefer the bathtub. I think the car’s aesthetic is improved with a bilaterally symmetrical roll bar instead of the driver only roll bar.
    Jack, If you’re considering viewer input, I vote yes on permanently closing the scoop and ‘painting it black to make it disappear.’ I saw a racing website article on the use of thin strips of duct tape to block off/aerodynamically improve the frontal area air intake by degrees.
    Dan, I may be counting cocounts on the pineapple farm with AH/Mile: Michelin 40/Michelin 50 = .8698
    Stinger 40/Stinger 50 = .9281
    In the equations you are using, what changes between 40 and 50 with each set of tires other than the Crr? I’m only 26 mins into last week’s video, so I don’t know tire sizew. Shaving off a sliver of vertical tire profile [x 2 tires] would impact aerodynamic drag so much. Should there be a .0583 difference between the aforementioned ratios without an inconstant Crr? Again, my apologies if I’m counting coconuts or tilting toward windmills.

  10. Somthing completely different. I would like go deeper to the Batterie question. I am still looking for the best available LIFePO4 Batteries. Sinopoly, Calb or Winston. The specs are different and to many questions are not answered.

    CALB SE 130AHA
    L:182 B:56 H:275
    Weight: 4,4 Kg
    Nominal Capacity(Ah):130
    Nominal Voltage(V):3,2
    Internal Impendance(1Khz AC,mo):<=0,8
    Charging Cut-off Voltage(CCCV Model,V):3,65
    Discharge Cut-off Voltage: 2,5
    Standard Currrnt Charge: 0,3C, 39A
    Standard Currrnt Discharge: 0,3C, 39A
    Max Constand Current Charge: C, A
    Max Constand Current Discharge: C, A
    Max Impuls Current(10s) Charge: C, A
    Max Impuls Current(10s) Discharge: C, 1000A
    Operating Temperature Charge: 0C-45C
    Operating Temperature Discharge: -20C-55C
    Self-discharge Rate: <%
    CALB SE 180AHA
    L:182 B:71 H:275
    Weight: 5,6 Kg
    Nominal Capacity(Ah):180
    Nominal Voltage(V):3,2
    Internal Impendance(1Khz AC,mo):<=0,6
    Charging Cut-off Voltage(CCCV Model,V):3,65
    Discharge Cut-off Voltage: 2,5
    Standard Currrnt Charge: 0,3C, 54A
    Standard Currrnt Discharge: 0,3C, 54A
    Max Constand Current Charge: C, A
    Max Constand Current Discharge: C, A
    Max Impuls Current(10s) Charge: C, A
    Max Impuls Current(10s) Discharge: C, 1000A
    Operating Temperature Charge: 0C-45C
    Operating Temperature Discharge: -20C-55C
    Self-discharge Rate: <%
    Sinopoly SP-LFP200AHA
    L:182 B:71 H:280
    Weight: 5,6 Kg
    Nominal Capacity(Ah):200Ah, 640Wh
    Nominal Voltage(V):3,2
    Internal Impendance(1Khz AC,mo):
    Charging Cut-off Voltage(CCCV Model,V): 3.8
    Discharge Cut-off Voltage: 2,8
    Standard Currrnt Charge: 0,3C, 60A
    Standard Currrnt Discharge: 0,3C, 60A
    Max Constand Current Charge: 3C, 600A
    Max Constand Current Discharge: 3C, 600A
    Max Impuls Current(10s) Charge: 3C, 600A
    Max Impuls Current(10s) Discharge: 5C, 1000A
    Operating Temperature Charge: 0C-70C
    Operating Temperature Discharge: -20C-70C
    Self-discharge Rate: <3%

    Winston WB-LFP160AHA
    L:209 B:65 H:276
    Weight: 5,6 Kg
    Nominal Capacity(Ah):160Ah
    Nominal Voltage(V):3,2
    Internal Impendance(1Khz AC,mo):
    Charging Cut-off Voltage(CCCV Model,V): 3.8
    Discharge Cut-off Voltage: 2,8
    Standard Currrnt Charge: 0,5 CA
    Standard Currrnt Discharge: 0,5 CA
    Max Constand Current Charge: >=3C
    Max Constand Current Discharge: 3CA
    Max Impuls Current(10s) Charge: 3C
    Max Impuls Current(10s) Discharge: 20CA
    Operating Temperature Charge: -45C-85C
    Operating Temperature Discharge: -45C-85C
    Self-discharge Rate: <=3% Thanks

  11. Perin, the ratio of energy consumption between 40 and 50mph is expected to be higher for the michelins since the lower rolling resistance makes the growth in air resistance dominate more. but you’re right that the wider tires can have an effect on aerodynamics. it’s hard to say how much.

    I did the Cd calculations for the michelins only though.

  12. Typing myself smart, I would think that tire carcass material and construction plays a role in changing rolling resistance. At higher rpm’s the centrifugal force acting on the tire would tend to reduce the amount of flexure thereby reducing energy losses, not to mention less time for the flexure to occur. Though, at 45psi tire flexure would seem to be minimal.

    Which brings me to wider tires putting more rubber on the road. I don’t follow. I though the amount of rubber on the road was determined by tire pressure, all other variables except width being equal.

  13. I was under the impression Tuesday afternoon was the usual post time for new videos. On a positive [energy • mudita] note, I hope Jack decided to jet over to the Smithsonian EV exhibit or got an invite to spend the weekend with Elon Musk. Given there is an atomically small chance Mr. Musk might read this note, please consider employing SpaceX talent to develop a modernized, high tech optimized passenger carrying Zeppelin–bring back the air cruise and introduce the sky yacht, sans combustion engines, of course.

  14. Stan, it sounds like you are blaming the fire on the EV when the article clearly states that it is merely one of the things being investigated. The power company is taking a knee jerk reaction to this. Naturally we should all hope it is not caused by a charging car. If it turns out to be the case, all of us face potential unfavorable regulations.

  15. It looks like the Volt uses the more volatile Lithium-Ion pouch cells, like the ones that have burst into flames in laptops and cell phones. The Volt has a BMS that is supposed to monitor the system 10 times a second and provide “Thermal Management” of the battery pack. The Volt has the J1772-2009 connector, so the “Siemens Charging Station” referenced in the article is almost certainly NOT the cause of the fire. The Siemens station is just a fancy AC outlet and not much more likely to start a fire than your dryer outlet.

    The article states that the car was plugged into the charging station at the time of the fire and that the fire originated near the station. I’m betting on the car being the source of ignition. I could be wrong, but I’m not betting that way.

  16. Knowing the stuff that is in a charge station it could be the source. Its not just an outlet. Theres plenty inside one to go wrong. Parts must be top quality. You can’t just dump in cheap garbage. It does happen even with big companies because they want to get the jump and never really tested in tough conditions. So in short, it could be the station which would be close to the vehicle too. The BMS on board the car can’t fix a fault in a charge station. Has no way to know anything is cooking away. Could be just faulty wiring to the station too. Home install maybe? I took extra precautions on my install. Mine is however portable and can be unplugged.

    Hope they find and publish the outcome of the fire and not just bury it.

  17. If it is a Siemens 30A wall mounted charging station, then I’ve seen the guts of it, and the 240VAC side is very simple (AC relay, GFCI breaker and low-voltage supply). The low-voltage side has a lot going on, but I don’t see that starting a fire… The AC side really isn’t much more than a fancy, remote controlled outlet.

    Anyway, the article states the fire started NEAR the charging station, not IN the charging station. According to the article, Duke Energy (the local power utility) had installed the charging station, so not a “home install”.

    Hopefully we will find out what caused the fire soon.

  18. I’m in eCobra Dyno Data hell. I’m having to manually transcribe about 10 values, every 3rd frame from video into Microsoft Excel. I’d just as soon give myself a root canal with a wine corkscrew.

    Fires. I’ve sounded the alarm on this. But it is very awkward. I was recently pasted by “Gadget” over his fire. And I take heat from others. I can relate the following.

    There are ALWAYS insurance issues. And as House says, ALL PATIENTS LIE. Wat I’ve taken to doing is trying to talk to the principal, and I do NOT press them. I just accept their story, whatever it is, and establish a relationship.

    Call three months later, and simply “revisit” the story. Again, whatevber they say. At 6 months, 9 months and a year. You have to be patient with this.

    THE STORY CHANGES. As you get PAST the embarrassment, and the insurance issues, it slowly changes. At 9 monhts or a year, I drop the bomb. All right what REALLY happened, here’s why what you told me DIDN’T happen.

    The answer is generally nobody knows. But yes, the car I said wasn’t charging turns out to have been charging. And the BMS that we weren’t using, we were using. ANd yes, it was very hot and started around the batteries.

    The EV press is just HEROIC in explaining these away. The article you sight claims that it was PROVEN tat the Volt was not involved in starting the Connecticutt fire. Tis is TOTAL BULLSHIT. In fact, the Volt REIGNITED four days later. But no cause of the fire has EVER been determined.

    Now this was a VERY hot fire. The VOLT was burned. They put the fire out. Four days later the Volt AGAIN caught fire. But no cause of the fire wAS EVERY DETERMINED. And in this report it is stated as fact that the Volt was fully exonerated.

    Jack Rickard

  19. Now we have another Volt fire. It did an estimated $800,000 in damage. That’s a LOT of damage.

    My family has been in the construction business for SEVEN GENERATIONS. I grew up in it. I’ve cleaned up a LOT of burned buildings. I can buy an electrical fire. This had a factory EVSE (not charger). Sure, it could have malfunctioned and caused a fire.

    When such a device malfunctions, it can melt some insulation and wiring, and it does get pretty hot. IF there is something for it to burn. Sheet rock doesn’t do it. But it has to have some fuel from there.

    If it came in the vicinity of the EVSE, by definition it kind of came from the vicinity of the Volt if the Volt was plugged in. AND it had to take out a LOT of building to get to $800,000.

    My knee jerk reaction is this again HAD to be a battery fire. You just don’t get the heat and total destruction from a panel fire unless there’s a ton of oily rags stored in the panel.

    Volt uses Litium Manganese Oxide Spinel cells from LG Chem. I don’t know about the BMS and thermal management in any detail.

    Jack Rickard

  20. I’ve been glued to your programmes for a couple of days since discovering it, but not so much for the EV side of things. More on the Winston batteries.

    I’m looking to replace my 24V lead acid house bank that charges off of a 2.5kW solar array.

    Winston do a sealed 12V mono block at 90Ah that is supposed to not need a BMS/balancer so long as you keep it between 11V and 16V at all times. My solar charge controller can do that just fine with a max bulk charge rate of 75A and then when it hits the float or absorption voltage it will hold and taper the current. All this is programmable on it.

    But watching your Nov 4th show, I’m wondering if I can just use eight regular 200Ah individual cells without a BMS (as you do in the Mini). Of course, the distributor wants to sell me a 500 Euro BMS with the cells… :/ But I’m wondering if it’s rubbish (especially if the mono blocks can’t even have a BMS connected to the cells).

    If all I have to do is bottom balance the cells individually and then make sure the top charge Voltage is a bit low (3.45V / 27.6V) and let the solar charger do its thing then I might go that way. It seems better to use 200Ah cells in a single series string than four 12V 90Ah blocks in series & parallel (to get to 24V at 180Ah).

    They claim that the mono block 12V cells are closer tolerance capacity than the individual cells, and that’s why they don’t need (or provide any way of) balancing the 4 cells inside the block.

    For solar applications you actually never want to fully charge the battery in the day. If you do, that means your battery wasn’t big enough and you missed out on collecting some energy for the night. Partial charge of 20% to 80% is the ideal state. Sadly this is the opposite of what lead acid batteries want. Partial charge kills them.

    The Winston battery sounds like an ideal solar battery, as you can leave it partial charged or even nearly discharged for ever and it won’t rot like a lead one will. Very handy for the UK winter where it can be dark & wet for a week at a time.

  21. Be sure your charge controller will shut off when the voltage reaches a specific voltage and amperage. So CC then CV until the current reaches a specified point then shut it off. Do not let it continue to feed in current. I’d go with the 400AH cells if you can but you can put other cells like 50AH or 100AH cells in parallel to make a large capacity cell in the 200 or larger AH range. Be sure your system does not allow you to draw off power after a specific voltage level either. As in a car you do not want to over discharge your cells. In a solar array I am sure the amp draw is minimal compared to the automobile. I will be using lithium in a small solar array setup.

    Stay tuned for more on this one as well.

  22. After hunting around a bit, I found an interesting tidbit in (I know it isn’t authoritative). It seems that the LiMn2O4 pouch cells are in plastic frames holding pairs of cells that sandwich an aluminum cooling fin.

    I wonder if arcing from damaged cells to the aluminum cooling fins could have been the cause of the ignition/re-ignition of these Volts?

    Could we be seeing a problem similar to the plasma fire in the MetricMind battery that also used aluminum plates for cooling?

  23. The LiFeP04 cells are ideal for solar applications. That’s where mine are headed when they have too little range for a car.

    The reason they are ideal,

    1. They have no internal self discharge.

    2. There is no sulfation of the plates.

    3. They have no memory or hysterisis.

    So partially charging them is not only ok, it is actually preferable to fully charging them. In fact, if you could manage to charge them to 51% and discharge to 49% I truly believe they would last for centuries.

    They do NOT like to be overcharged – so no maintenance bobbing or “floating”. CC/CV to the cutoff current and SHUT OFF.

    They also do not like to be overdischarged. Running them to zero is not an option. Do not allow these cells to descend below 2.5v at 0.3C. Better, do not allow them below 3.00v at all.

    If you stay within these two parameters, absolutely no BMS is required and no thermal management and the bottom balancing is a bit salutory.

    We charge Winstons to 3.65v x N where N is the number of cells in series. This IS slightly unddercharged for these cells.

    Life is simpler in such an application with the large 400 Ah cells. But 200Ah cells will work just fine. Eight cells would be 26.8 volts nominal and you would charge to 29.2. Don’t let it go below 24. And you can see the math for 7 cells then.

    Eight 200 Ah cells then would be 5360 wH, about enough to drive a bicycle. 5.36 kw hours is about 45 cents worth of electricity here.

    When are you going to start a car project?

    Jack Rickard

  24. On the $800K fire, Siemens has been making industrial controllers for a very long time and has a good reputation in the industry. I’d be more suspicious of the wiring between charging station and the grid. Was it up to code?

    When I ask where’s the most energy, the batteries come to the top, especially when fully charged. We have little history when it comes to batteries with such a high energy density combined with capability to absorb and dump that energy so quickly and with the ability to add fuel to the fire when overcharged / overheated. Add to that battery chemistry that is in a constant state of flux and pressure to put out batteries that will propel a BEV 300 miles down the road without recharging and the most likely suspect becomes the battery pack. I’m not saying it was the battery pack The energy density, level of complexity, lack experience and history and pressure to get product out the door just point that way for me.

  25. Thanks Jack & GreenEV.

    I traded in my 2.2L Honda Accord for an Insight two years ago. Halved my monthly fuel bill. Maybe I can upgrade the tiny battery to give the Insight a few miles of pure EV range. Enough to potter round my town without using any gas.

    I’m with you on the LRR tyres. Noticably better acceleration and longer roll down time (with more regen energy captured) with my tyres pumped up to 45psi (33psi stock). It’s good for an extra 10 mpg (UK) on long trips. Not so good for ride comfort or handling though. 😀

    Back at my solar battery…

    I’d considered 7 cells for my solar bank but I thought the nominal Voltage was 3.20V per cell, as that’s what the data sheets say.

    Watching you unbox new cells; they all read 3.30V. Does that collapse to 3.20V as soon as you put any load on them? Your test was 0.5C and initial Voltage on load (just after full charge) was 3.18V.

    3.20Vpc gives only 22.4V with 7 cells and the AC inverter sounds a low-volts alarm at 22.0V. But it would fit nicely with the inverter’s built in low voltage shut-down at 20.3V (2.90V per cell)…

    It all depends on how much the cells sag when you pull 134 Amps (0.67C for a 200Ah cell). If the pack goes below 20.3V, the inverter will shut down and then wait until the input Voltage rises above 25.2V before it will restart.

    Not that I run 3kW loads often. My biggest common load is the washing machine that pulls 2.5kW intermittently and typical house loading is only 100-300W in the evening and 50-100W between midnight and 6am.

    With 8 cells, I figured 25.6V nominal (3.20Vpc) and then having to rig a contactor to cut off the inverter. The built in LVD shut-down would be too low at 2.53Vpc with typical 200W (0.03C) discharge rates.

    I have two Morningstar MMPT solar charge controllers and one has a load control output that can drive a contactor to shut the load down at any battery voltage I want.

    I’m afraid float charge is a way of life for my system. The battery pack is always on load as the inverter is on 24hrs and (during the day) always on solar charge. If it gets to float at all, it will generally be for maybe a couple of hours at most.

    After the daylight fades from the noon maximum, the system often goes into PV assisted discharge (PV and battery share the load) for the late afternoon before unassisted discharge in the evening.

    On sunny days, the PV has more than enough power to charge the battery and during the CV phase of absorption, I monitor the available excess charge power and dump it into an AC water heater (through the inverter). It works pretty well and means I get a full battery and hot water.

    So I can’t really shut the charger “off” when the battery voltage has reached the top, as I progressively divert some/most/all the PV power to the water heater and other daytime house loads (like the washing machine).

    But the chargers do have three target Voltages in acending order: float, absorption, and equalisation. I can disable two of them if I want fewer CV charge phases.

    My thought is that I could use the absorption level set at 3.45Vpc and the lower float level set at the nominal cell voltage level (3.20Vpc). The chargers will not allow discharge through them so a low float Voltage will effectively end the charge cycle.

    When the cell discharges a bit (down to the float level), the charger will try hold the cell at that partial charge level by feeding current to the load.

    Ideally, on most days the battery would not even make it to “full”, so the issue of floating would be moot.

  26. Outtasight said…
    ” I traded in my 2.2L Honda Accord for an Insight two years ago. Halved my monthly fuel bill. Maybe I can upgrade the tiny battery to give the Insight a few miles of pure EV range.”

    The Insight assist motor is directly connected to the motor’s crank shaft. This means that the crank shaft has to turn if the motor is turning causing the engine to turn too. There is no simple pure EV mode like there is in a Prius. You might want to look into the MIMA device ( which would allow you get the assist motor to run more than normal to lower the fuel consumption.

    David D. Nelson

  27. Thanks David.

    I think the MIMA gadget only works on the much older Gen 1 Insights by fiddling with the control line signals. The Gen 2 is much too software driven to hack like that, although I think people are trying.

    That’s true about it always turning the engine when assisting but it can do so without using fuel. It closes the intake and outlet valves and turns off the fuel injectors. The cylinders are then like air springs and it can run at up to 30mph on the 10kW motor only.

    Granted, there’s friction there but on the flat, in heavy creeping (10-15mph) traffic, it uses maybe as little as 25-50 Amps to go along in “no petrol mode” (if we can’t call it “EV mode”). At 50-75 Amps it can make nearly 30mph.

    If the battery were much bigger, it could do that “no petrol mode” thing a LOT more. It will always use gas when pulling away or accelerating but as soon as you lift off and feather the throttle it can cruise on electric alone at 25-30mph.

    Dunno if the pancake motor could take lots of 100 Amp duty without some additional cooling but at the moment the battery is really limiting what it can do.

    A bigger battery would at least allow much more aggressive regen. At the moment, it’s capped at just 50 Amps due to the small battery.

  28. Thanks Jack and Friends.

    Wouldn’t be hard to reach $800k if your volt was parked between your Ferrari.

    People with that problem have good insurance.

    What kind of precautions for fire would be reasonable?
    Different battery cases? Non-plastic?
    Fire stop in the battery box?
    Automatic discharge extinguisher?

  29. lithium iron phosphate, perhaps combined with emergency ventilation to reduce thermal exchange.
    air cooling/heating of the pack could double as that.
    you could also have robust detection of danger conditions and avoid them. presumably a battery can be developed that doesn’t burst into flame unless mistreated. then simply avoid mistreating them.
    I don’t think fire is a real concern beyond what good engineers can solve.
    we have 20k+ mass EVs in the world now and no confirmed report of unforced battery fire.
    I seem to recall the occasional ferrari spontaneously bursting into flame..

  30. Jack, why not tell us who the new A123 supplier is?
    23.8$ per cell can revolutionize DIY EVs. that’s 360$/kWh. that can give homebuilders access to 3 second cars. and then some. a potent weapon for taking over the world.

    as well as blitz charging. A123 cells can comfortably charge 40% in 6 minutes.
    a 100kg pack can deliver 500 ponies.

    I think the packaging issue can be solved to satisfaction.
    this is no time to withhold information..

  31. Dan:

    Thou thoughtless twit. This past week I was pleasured to receive Mr. Dale Friedhoff of St Louis. Dale brought down one of his BRAND new CALB cells for me to test and I showed him a few experiments illustrating the nature of the cells

    Dale had paid $16,500 for a set of such cells a year before. To the firm in Oregon who ALSO bilked ME out of $9,800 in cells.

    Dale never did recover. Even the 23 man legal class that sued them and recovered about half the stuff, has devolved into a total hopeless and helpless mess while they decide how to slice and dice the 59 cents on the dollar promised during the settlement that will of course be more like 16 cents on the dollar in the end.

    And so it goes. I had not only recommended this firm to Dale, but had remonstrated with him about delaying. And he did JUST get his check in under the wire before the shit hit the fan.

    So I’m a little reluctant to recommend battery suppliers Mr. Friedrickson. Especially suppliers I’ve never purchased anything from.

    This is no time to withhold information?

    Actually it’s precisely the time – BEFORE DOING DAMAGE.

    Actually we will NOT precisely be “recommending” a battery supplier ever again. I may release information on availability of certain types of batteries from certain sources verified to have them and be selling them. But we won’t ever be recommending them per se again.

    Lesson learned there……

    Jack Rickard

  32. If I’m not mistaken Jack, you are talking about a now defunct firm in Washington state that used to sell lots of LiFePO4 cells. My pack may be from some of the last cells they actually delivered. What an ugly mess that turned into.

  33. If OILigopolists and/or agents of planned obsolescence were, at the very least, successful in mandating the zeroing of every battery pack’s state of charge after even a fender bender, how would this affect useful life? Insurance companies will seizing the day as well.

    Has A123’s policy changed?

    “Please be aware that A123 is focused on high volume commercial applications and does not supply battery cells or systems for hobbyists and custom vehicle conversions.”;_ylt=Ap1qhwt_j53dq70C4vanClCiuYdG;_ylu=X3oDMTQ0M3Q1MXFxBG1pdANGaW5hbmNlIEZQIFRvcCBTdG9yeSBSaWdodARwa2cDNjIxYTMzZWUtMjI4NS0zNTQ4LWEzMzctZWMwZWNjZmU1YmJlBHBvcwM1BHNlYwN0b3Bfc3RvcnkEdmVyAzFkYTIxN2UwLTBjYmQtMTFlMS1hZGYxLTMzZTRiY2ZhMjMwMA–;_ylg=X3oDMTFpNzk0NjhtBGludGwDdXMEbGFuZwNlbi11cwRwc3RhaWQDBHBzdGNhdANob21lBHB0A3NlY3Rpb25z;_ylv=3

    Electric car battery catches fire after crash test

    “General Motors spokesman Greg Martin said the test did not follow procedures developed by GM engineers for handling the Volt after a crash…procedures, which include discharge and disposal of the battery pack, he said.”

    “In a real-world crash, GM would be notified through its OnStar safety communications system and would send a team out to remove the battery for research purposes, he said.”

  34. Jack, I didn’t ask you to vouch for them. and a caveat is perhaps prudent. but I did ask you for the name and you are withholding.
    you are the thoughtless one Jack with your eternal abuse. I forgive you for you don’t know what you are doing but it is really something you should stop doing.

  35. Dan,

    You have the power to find the information on your own. You don’t need Jack to hold your hand. If you are really wanting that information you have work to do. Work is not a bad word. But it does require you to do something.

    Pete 🙂

  36. Jack,

    As this is a blog about conversions and many of the viewers are converters, it would be good to see a segment based on the retail value of converted cars, what could one expect a completed speedster to sell for and what are conversions selling for in the open market. That would help converters know how much they could invest in a porject and still expect a profit. What type of conversions have the best market and so on.



  37. Randy:

    This is a blog about what I did this week. I agree it would be fascinating to see market data on converted vehicles. But I didn’t do any of that. We’ve never sold one. So this isn’t the place to find it.

    My sense is that a car converted to electric drive is worth about 30-50% of the original retail value of the components used to convert it. This from observations on eBay. You can basically buy someone else’s conversion there for about 40-50% of the cost of doing it yourself with the same components. The car itself having no value at all.

    Why? Well first, a lot of conversions are just really bad to begin with. And many use lead asid batteries. After two or three sets of Pb cells, the owner is tired of the whole thing and just wants to be rid of the car.

    In the few examples of pretty GOOD conversions done in lead acid, you can often pick up a bargain for $5000-$6000 and about all it needs is some lithiums. We did a Vantage Green Van that we bought on eBay for $4000, pulled the AGMS and put in some not really very good Hi-Power LiFePo4 180 Ah cells. The thing does 100 miles on a charge now – albeit at 25 mph. My daughter drives it to school here in Cape.

    The largest problem with conversion values is that they are orphans. The guy who built it can generally work on it. But there isn’t a second guy in the country who can. And so how do you get them worked on or repaired?

    There is no warranty of course. And the local garage is unlikely to be familiar with this thing.

    We convert them, and assume we’ll be driving them for life. Picture the whole planned obsolescence thing in reverse. We’ll have a few cars, and we just keep refurbing them until we’re dead.


  38. ******Your Video about a rusty car is so boring.*******

    Rusty? Hardly. Its a start and it was good enough to be published on EVTV. Where is your video of YOUR project? Goofy, Boring, So what. Its me. Im not Jack.

    Thanks for your positive comment.

    Pete 🙂

    The battery video has been posted before and is quite boring too. As for your needs. Looks like you have all the information you need and you get to decided which one is the best for YOU. There is so much information not given that there is just no way to determine which is best and in the end it is YOUR choice. Jack did not ignore you. You ignored the premise of the question. We are not here to hold our hand. Information is given and you determine what you can or can’t use or what you want or not. My build is different than yours so my needs are different.

  39. Jack,

    Thanks for the insite and I ment to post that EV TV was about conversions not that “this blog” as you are correct, the blog each week is about your adventures in the current video.

    Wayne Alexander’s experence kind of implies “if you build them they will come” but as you pointed out, that is not necessaily what you see on EBAY. I do notice that well built pick up trucks seem to sell better that some of the roadster type vehicles and even saw a seller state that he was going to put the gas engine back in a fiat roadster conversion because it did not meet his reserve as an electric conversion. As you pointed out, this may have been because of the quality of his conversion.

    Some of the most interesting presentations in EVCCON, (other than the Helwig brush presentation:), were the ones that discussed the early adapter stage and predictions of where the industry was headed. I talked to some converters who were really excited about the future of the industry and some who were frustrated. It left me wondering what the difference in their business plans were that resulted in their differences in perception of the industry.

    Anyway, your comments on the subject are appreicated.


  40. Pete,

    I enjoyed watching your video and thought your fast motion in certain sections helped keep the video from being boring. Rusty must not understand that you have to do mock-up before worrying about the final finish, just as Jack did on the Cobra. That will be a fine looking conversion in it’s final form just as I am sure your conversion will be.


  41. Ok. I did not want to insult you. But I see in your responsive that I did. Sorry for that!! We are sitting in the same boat, and there is no YOU and ME… and I thought about this batterie question as a WE thing. I was not amused and my words are misunderstandable, in the way that you feel insulted.
    I am sorry for that.

  42. ohne unterbung
    When it comes down to LiFePo4 cells, its a case of what you can fit, what you want to fit and how much money you are going to play with to do it.

    As goes the cells you listed, at this date there is nothing in it worth arguing over. All are good.

    What are you intending to make/convert?

  43. Heck, no one here sends anyone there, those that go do do quite well on their own. 🙂

    I do have a bit to learn about video production and it’s going to evolve.

    The Ghia is also a test bed for a few things so it will be an interesting work in progress while at the same time working on the bus project and not breaking the bank. Forgot to mention, even my old hi-power cells are good but I will say to at least stay away from the old lifepo4 cells. Stick with new ones.

    Pete 🙂

  44. I fear OILigopolists and others may be trying to mandate Draconian post-accident battery handling practices. If laws are enacted which require draining a battery pack after even the most minor accident…well, just how damaging is it to a battery pack to drain it to 0% state of charge? Sounds like it could be a ‘plan’ on the part of manufacturers to sell more batteries mandated obsolescence fashion. Will conversions have to get an onerous and impossibly costly safety engineering analysis? The sky isn’t falling, yet, I acknowledge.


    “Electric car battery catches fire after crash test” by Joan Lowy, Associated Press | AP – Fri, Nov 11, 2011 6:27 PM EST

    “NHTSA did not drain the battery of energy as recommended by GM’s crash procedures…In a real-world crash, GM would be notified through its OnStar safety communications system and would send a team out to remove the battery for research purposes, he said.”

    Youtube: The Light Bulb Conspiracy – English Subtitles – PART 1/4

    Youtube: Ford Hemp Car

  45. Perin,
    Lets not compare apples with oranges. These production cars use a completely different chemistry. What ever caused the change of state after dumping the car for three weeks is down to guess work.

    Nobody released the packs from the car. For all we know its BMS (Burn My Steed) kicked in after one cell was noted low in voltage and caught fire attempting to provide the current for this bad cell.

  46. Andyj, The point is that driving a stake through the heart of the conversion industry is just a ‘stupid’ line of code [in a bill] away. Consider industrial hemp production in the United States:

    5. Q: Is industrial hemp illegal to grow in the United States?

    A: … Jean Rawson, of the Congressional Research Service, also noted this in her 2005 CRS Report “Hemp as an Agricultural Commodity” for the U.S. Congress:

    “Strictly speaking, the CSA does not make Cannabis illegal; rather, it places the strictest controls on its production, making it illegal to grow the crop without a DEA permit.”

    Growing hemp is kind of like driving, you can’t drive without a license and you can’t grow hemp without a permit. The difference is that it is almost impossible to get a permit from DEA to grow hemp. An excellent example is John Stahl, of The Evanescent Press, and his DEA permit story.

  47. Once again Perin, apples and oranges.

    Arguing over conjecture lowers yourself to the likes of a politician who wants even more thought crime laws.

    G.M. was abound with cars bursting into flames after minor accidents in times past. What was banned? Nothing.

  48. Yes, Andyj, I shared two links above which deal with fires and industry response. Also see The Light Bulb Conspiracy. I think you fail to appreciate the big picture: petroleum is controlling, not challenging. An obscure line of code added to a new bill could really be a headache for a lot of ‘pesky’ converters. IMHO, the LiFePo battery makers had better get Jack on board to testify before Congress. just in case.

  49. Perin,
    Never wondered why the power companies have never fought the AGW conspiracy? It’s because its another business opportunity that cannot fail due to state support.

    I’m sorry, to me you are bringing up chem trails and crop circles as proof we are all now run by lizard pod people. The pressures are too great to save on fuel usage. What does the state care if some cars burn down for the greater good. Darwen is right.

  50. The testing of the 180AH / 207AH cell was a little discouraging to me. Seeing the voltage climb like it did after the .3C load was disconnected at the end made it look like it had high internal resistance. I’d be curious how the others cells behaved once Jack gets around to it.

  51. If anybody see’s me as off-base, please say.

    It’s nothing to do with high resistance or it would be unable to supply a high current; its an ionic device. It’s regaining its surface charge from the electrolyte. Perfectly natural, all Li cells do this which is why I used to decry the measuring of voltage to determine state of charge unless, of course, it has been resting for a good while at room temperature.

  52. It was Jack’s comment at the end of the discharge cycle that the cell voltage was climbing higher than he’s use to seeing that made wonder about the internal resistance. If memory serves, the most basic model of a typical battery is a constant voltage source in series with a variable resistor where the resistance increases towards infinity as the battery is discharged. Though the LiFePO4 cell is not typical, it seems to basically follow this basic model. His comment made me wonder about the “strength” of the cell. I recall Jack calculating internal resistance on one of his “watching paint dry” battery shows.

  53. Klaus:

    I have written on this topic before in this blog so I’m a little unclear as to the need to revisit it. I do not believe in “internal resistance” in a battery cell and I have always found the “model” you suggest as inherently simplistic and flawed as applied to chemical batteries.

    I would also suggest the proper term for what you are trying to describe is “equivalent series resistance”. Battery cells simply do not have “internal resistance” because they are not electrical devices in the first place. They do exhibit a voltage drop when providing current. It is not precisely linear, one of many reasons I do not find ESR model appropriate, but yes you can calculate it and it does have some application in noting the state of a cell’s health.

    Current is actually produced by a chemical reaction, the oxidation reaction specifically. We are perhaps more familiar with this in its literal use. If we oxidize iron it rusts. If we oxidize firewood at a faster rate we have a fire. If we oxidize TNT at a faster rate, we have an explosion. A battery cell is oxidating at a rate somewhere between rust and fire. Like a very low fire.

    It doesn’t actually combine oxygen. It is the oxy/redux reactions of electron addition or subtraction that have been termed after this more familiar literal “oxidation” with operates the same way of course at the sub atomic level.

    There is additionally a diffusion delay that relay has nothing to do with ESR.

    So I have never personally found the simplistic models of equivalent series resistance, capacitance, and inductance particularly useful in picturing battery activity. They leave MUCH unaccounted for and lead to all manner of ridiculous discussions as extant on DIY etc as people try to actually picture a battery as an electrical component. It is a chemical source of electricity.

    Jack Rickard

  54. Hi Jack,
    I understand your objection to the term internal resistance. For me personally, ESR, apparent internal resistance, internal resistance and so on are all the same thing. I even consider the chargers you use to charge your cars a battery management system, not to be confused with a BMS.

    Be that as it may, do you have any further thoughts on the higher than you expected no-load voltage the battery rose to at the end of the discharge test? The battery was sold as a 180AH unit, factory tested to 207AH and tested by you to something like 189AH. Very nice battery testing setup, btw!

  55. Hi Jack,

    A couple of thoughts about your DIY A123 pouch cell modules (I’m a week behind with the Friday show so forgive me if things have already moved on)…

    Could you re-do your ‘tab slot form’ in sheets of polyethylene instead of aluminium (?) to make it non-stick and easier to remove from the mould? Also, if you made the ‘leafs’ of the form a lot thicker and then tapered them you would end up with tapered slots (wider on the battery side) which would make threading the tabs into the slots much easier.

    Have you considered using some sort of compressive material under the tabs to make a better connection when clamping the tabs? This would make the clamping force much more evenly distributed between tab and metal plate thereby making a better electrical connection.

    I was holding my breath when you first assembled you module fearing that you were going to short out the cells by losing control of one of the clamping plates. To prevent this and make it much easier to assemble the module, perhaps you could have a temporary cassette into which you place the cells making them all line up neatly and keeping them steady and then put the moulded lid on. Then you could do with some means of isolating one side of the tabs whilst attaching the clamping plate to the other side and vice versa. Perhaps a hinged flap with velcro attachment?

    Regards, Martin Winlow.

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