Shorter Show – Shorter Build.

We managed to do a show in LESS than two hours this week which was a considered accomplishment in which we take no small pride.

I tend to through everything I have on hand into each weekly missive. But we’ve had too much. A three hour show is too long and it’s too hard to deal with with regards to file size as well. So I’ve hired three 24 year-old blond coeds to replace Richard and I and the missing Noto.

We’ll add some rapper music and a lot of sliding video cuts and be kind of like trick television.

[jwplayer file=”news101912-iPhone.m4v” hd.file=”news101912-1280.mov” image=”http://media3.ev-tv.me/news101912.jpg” streamer=”rtmp://s3einxnpkaij93.cloudfront.net/cfx/st/” provider=”rtmp” width=”950″ height=”584″ html5_file=”http://media3.ev-tv.me/news101912-1280.mov”]

Or maybe not.

I am kind of excited about something on the video front. November 1 marks the release of Popcorn and Popcorn maker. EVTV operates on two fronts. It IS all about electric vehicles. But not entirely. It’s also an experiment in video production, editing, and monetization. I kind of predicted a merge of video and the web back in 1994. I’ve been carefully watching the perfect storm of video cameras, video editing on the PC, and bandwidth strategies and the web for 18 years since. EVTV is an experiment in that. ANd it is coming along famously.

But so far, video is a picture pane in the space of the web. You have web text and links surrounding a window onto video that is remarkably as video always was. Popcorn is the earliest of a predicted series of innovations that actually COMBINE video with the Internet in ways you might only
imagine. Far beyond clickable links in video but just imagine THAT. Popcorn is a Mozilla project to do a javascript version of HTML5 that is truly interactive video. Popcorn maker is of course the editor. It is very early and very ugly. But it will come. Kind of if you show up they will build it. November 1 is supposed to be their 1.0 release. Another learning curve. But it should take us to entirely new frontiers.

The extant video of Cable TV and discovery channel I have marked down as the walking dead for several years. We don’t do oxyclean and I can’t fire 45% of our viewers who are outside the U.S. and Canada. But the Internet Nerd part of Jack Rickard is still very much involved in the network and in aspects of future video. In fact, I how have TWO daughters in mass communications programs at two different universities learning about what I think of as OLD style video editing and broadcast. But they are both way out ahead of their class with cameras and video projects all about the net. It’s ok for them to pick up a little history in a formal classroom. But futurevid is going to be VERY disruptive to “TV” as we know it. But the past few years, with the wars between Flash and Apple and what HTML5 would look like and the browsers has been a mess. Something like POPCORN will build a fire under that and cause it all to gel.

The big news this week is probably the Society of Automotive Engineers SAE J1772-2012-10 Electric Vehicle and Plug in Hybrid Electric Vehicle Conductive Charge Coupler of course. We finally have a standard for fast charging. It is replete with sly efforts to shut out non-OEM participants but we are confident we can find a wormhole to slither through to get there and I would hope by Spring to be fast charging at will. I think using PLC as the digital communications path is a huge mistake. But it’s all doable. Protocols are in the end just protocols.

As to our PulsaR, five of our initial 10 are already bespoke. Non-trivial at $3499 I think. The bad news is the November 15 date appears to be slipping. We’ve never hit a date or a 50/50 shot in all my years. Not once. But we’ll not take money until I’ve had one in my hands and made it charge in front of me several different ways and then have 9 more in the shop.

That Tesla is talking about a national grid of supercharging stations NOT of the SAE variety is madness. I suppose they COULD force a secondary standard. They kind of did with the Roadsters. But this is not good medicine.

I am very encouraged to be hearing from a LOT of new blood with NEW builds getting into the game. I think we are going to get to a place where these components are more plug and play like stereo components where just about anybody can wire them up easily. That’s very much how it needs to go. And I think you’ll have a couple of DC and a couple of AC options to pick from depending on vehicle size and desired performance.

I referred to a gentleman in this video innovating an ammo box bottom balancer and noted that we would probably carry it in the store. He has this morning taken great joy in informing me in very gloating fashion that he found a source for our voltmeter that is less expensive and “sorry – have to do it on a budget.”

Knowing the history, I’m trying to picture his car if we had sought to do EVTV “on a budget”.

I’m sympathetic. Who wants to “pay more”. But that ragpicker mentality is precisely what has driven EV DIY conversions to 30 years of electric junk cars and a very very bad reputation. EVTV is hell bent on moving toward the custom car SEMA model featuring gorgeous builds and high craft builders. And to do that we need better components more slickly packaged where everyone doesn’t have to go on an easteregg hunt for every cable, wire, and nut to piece it together AFTER they’ve bought the thing and waited for two months to receive it. That’s not the program. If you want to dig through the junk pile and take delight in every quarter saved, be my guest. I’m kind of picturing that in the end, you’ll wind up with a car about like the ones you were gleaning parts off of. But like Bridge, Chess, and Hand Grenades, it can all be played on a lot of different levels.

And we’re going to have to leave a few behind. It’s true, you can download our instructions and bird dogging and selection, and then go find the piece for less money elsewhere. If that’s your game, you move off my radar screen. It’s like painting an L on your forehead with lipstick. And I don’t want my mommy to find out I’ve been playing with those kids again. Everything we offer here we get somewhere else. The mission is to make it easier for our builders and give them a place to get it where they don’t put their funds at risk of predators. Which is precisely the way predators think too.

A LOT of reaction to the bottom balancing segment already before I even had a chance to blog this. To me it sounds repetitive. But I guess we add a few new viewers each week. With several years of successfully running these batteries, and several years as well of successfully ruining batteries, battery care boils down to a couple of things that are pretty simple.

1. All cells in a string need to be at more or less the same state of charge.

2. Don’t overcharge them.

3. Don’t over discharge them.

Can a cell simply fail and cause problems? I guess so. But we really have only had this happen on brand new packs within the first cycle or two. Once they are cooking, we just haven’t had cell “failures” in the expected sense.

You DO have to guard against accidentally introducing small parasitic loads. Lke you wouldn’t want to jump start an ICE car off of four of your cells because it would unbalance them. And instrumentation famously causes small parasitic loads.

There is even a school of thought out there that swelling is normal and you should constrain your cells to mechanically limit the swelling. Swelling is NOT normal. It comes from overcharge or overdischarge and in all cases represents cell damage. It is caused by gassing of the electrolyte solvents.

To prevent overdischarge, we bottom balance the cells. You can still overdischarge. But the cells cummulatively can’t make enough current to drive the car and damage a weak cell because they are all weak to about the same degree. Then we undercharge them slightly so none of them are unhappy or overcharged. And with today’s cells, the differences in capacity tend to limit that to a couple of amp hours of undercharge. Maybe a mile of range. Small price to pay for long cell life.

In practice, after just a few days I know what my pack voltmeter should read after charging. It is just very consistent. The charger is kind of hardwired and so are the cells. So a 36 cell pack is going read about 119-120 volts and actually mostly 120. If it reads something different on any particular morning, I’m going to wind up wanting to find out why. My 57 cells in the Escalade just always wind up at 188. Same thing. We had one cell fail in the first couple of cycles. I kind of had it marked as a possible bad just from bottom balancing it. It didn’t “feel” right. The first morning it wasn’t 188 I went and checked it. Sure enough, it was about 0.8v. I didn’t even bother. Just swapped it out. Some you gotta throw back. Fortunately, we have had this with two or three cells in four years.

As I explain in the video, a thing can be technically true without being technically relevant. It’s all a matter of context. The example I uses was heat. Perhaps heat shortens the life of the cell. But what does that mean. If extreme and constant heat – 120F all the time, cuts 1% off your cell life, why would you worry about heat? If it’s 24% cut in cell life, you cool em. Can it be in between? Sure. Nissan reports they think they see a 4% decrease in cell life for 300 cars in Arizona. At that rate, I don’t care.

They think a BMS is absolutely necessary. So far, it has got them a lot of angry Leaf owners in Arizona and a class action lawsuit in California. And when they say the batteries are good I tend to believe them. Their BMS hasn’t burned down any of the cars. But it has the potential to burn down the car company. Before it’s all over, I would predict they will be taking a closer look at bottom balancing as well.

We have added the Revolextrix PowerLab8 Battery Workstation to our online store and are now a dealer for them. Yes, you can probably find them for less. But we’ve packaged the items you need to do largish cells for EVs rather than radio controlled helicopters. The more I work with this device the better I like it. It can charge, discharge, and cycle cells. It makes pretty graphs and you can easily export the data to tab delimited format for import into Excel. You can set the period you measure at. And it is just endlessly configurable allowing you to easily setup configurations for each type of batery you use. It is reasonably hardy. I don’t know that I would do 40 amps with it but at 30 it seems to work well off a 12 volt battery. Discharge is limited to 10A internally but if you are dumping it in a battery you can do up to 40 amps in theory. Beautiful graphs and unattended operation. It’s basically a PulsaR in miniature. As Peter McWade points out, you can even do a constant current constant voltage discharge to take them down almost exactly where you want them.

We had another major discovery with Speedster Nippon. Ok. We didn’t discover anything, we just stole it from Fred Behning. I would have bought it from him but he doesn’t sell it. ROCK-IT. Spray on bed liner. I love it. Black textured finish that hardens to an unbelievably durable finish that is non-conducting and best of all BLACK. As we say at EVTV: paint it black and it will disappear. Fred’s MG TD replica was just gorgeous and while the exterior paint was nice, his engine compartment was what wowed me with this black, sound deadening finish.

Parts selection is what it is all about. I have done these Speedsters before but somehow ordered a 1/4 NPT version of the MEAS pressure transducer. Ordered a 1/8 NPT and our problem with it extending below the level of the lower front shield just went away. The controller won’t be able to tell the difference of course. No idea why the 1/8th NPT is also a LOT shorter than the 1.4, We now offer both in the store. And undoubtedly you can get them less expensively somewhere else.

Hoping for a good week with Speedster Nippon. Keep building. Keep driving. Keep grinning.

Jack Rickard

63 thoughts on “Shorter Show – Shorter Build.”

  1. Hello Jack,

    Another great show. I like the streamlined timeset involved.

    As for finding parts cheaper, you addressed this quite nicely when I spoke with you in semi-private while setting up for EVCCON. In summary you said sure you can find things cheaper but your not in the business to price match people or go for rock botom pricing. You would rather offer a trusted source for componants (of which we are lacking, even still today) and I see it as helping fund a value Added Service that is your show.

    Keep up the great work!

    All the best,
    Aaron Lephart

    1. The value of trust is great. I’d prefer to spend a bit more and sleep well at night knowing I will get what I ordered. It’s kinda like where I work. I commute to a hospital 22 miles away but we have a local hospital that would gladly have me. I don’t work local because they don’t work as a team and many have absolutely crappy ethical work standards. The worth of an excellent far exceeds the worth of a short commute.

      Pete 🙂

  2. I am confused now. Maybe I wasn’t paying attention or perhaps your battery techniques are evolving. What is your charge voltage? It seems before you said 3.85 volts but this week I thought you said 3.55 volts?

      1. Thanks, i see my error now. I was thinking of my battery spec sheet that says 3.85 volts. I bought Bestgo batteries. 100Ah. I did a couple of cycle tests on them when I got them. They were 3.37 volts each when I started. I discharged them at 60 Amps for 1 hour and 50 minutes. By my calculation that is 110 Amps. The final voltage was 3.17 volts per cell. I think you said you bottom balanced to 2.75. With these batteries it doesn’t seem like I even need to go that low. I charged them back up 4 hours and 25 minutes at 15 Amps to a voltage of 3.67 per cell. I think they fell down from this final voltage after sitting a day but I didn’t record that number.

        1. Ok, ignore my last post. I read the spread sheet wrong. I ran two tests. The cells were at 3.35 volts when I got them. I discharged them to 2.8 volts at 60 amps for 1 hour and 34 minutes and 5 mins at 30 amps. Around 96 amp hours. I charged them back up but there was something wrong with the power supply display so I don’t know how much i put back in. I discharged them a second time as stated above. They were 3.37 volts each when I started. I discharged them at 60 Amps for 1 hour and 37 minutes. By my calculation that is 97 Amp hours. The final voltage was 2.82 volts per cell. Then I charged them back up 4 hours and 25 minutes at 15 Amps to a voltage of 3.67 per cell. Again my power supply current meter was not working right on the charge cycle.I had it set to 15 Amps by that would only be 67.5 amp hours. It calculated to 67.35 amp hours on the first charge so at lest it was consistent. I am going to try again after I calibrate the power supply.

  3. Hi Jack,

    I’ve had my powerlab for about a year now and use a combination of the banana jacks and the balance port for bottom balancing.
    Using preset 8 in the library as a master I copy and paste into one of the LiPo spots I’ll never use like #4.
    Then I set the charge and discharge voltage to my targets and the amp settings on both to 2.5 amps.
    I’ve attached numbered alligator clips to the Cellpro (JST PA) Battery Pigtail.
    Then while disconnected from the powerlab I clamp them in order to the braided straps of the cells I’m bottom balancing.
    The Cellpro battery clamps / banana jacks are attached to the ends of the string of cells.
    This gives me two seperate means of connecting the 8 cells to the Powerlab, never connecting both at the same time.
    Important, make sure to have all clip and clamps attached to the battery before plugging it into the Cellpro!
    Important, unplug the banana jacks and the balance pigtail from the Powerlab before rearranging any clamps or clips!
    Logging onto the computer and connecting the small balancing pigtail I start the preset #4 discharge only.
    The graphing function will display the state of all 8 cells.
    The cell tap show the voltage of each cell to 3 decimal places.
    You can use a resistor and a single cell charger to bring the extreme cells close to the rest of the pack.
    After doing that stop the discharge, unplug the balancing pigtail from the Cellpro.
    Connect up the banana jacks and discharge using another preset you have setup to .2 volts over your desired finish point.
    Periodically stop the process as the cells discharge, switch to the balancing system.
    Observe how the cells are staying in balance and tune their alignment.
    Then switch back to the banana jack system and proceed till it finishes.
    Then use the balancing system to do the last .2 volts of the bottom balancing process automatically.

    1. Don, that post was hard to read before my coffee this morning, and after I re-read it and had an afternoon cup of java I still find it difficult! I did however just purchase a unit from Jack. Perhaps after I have one in hand it will better come to light.

      All the best,
      Aaron Lephart

      1. Aaron, I’m with you. Don, I do appreciate you sharing your experience. Perhaps you could step it out in more of an outline format.

        I’d like to share an experience of my own as well; Don’t trust the clear shrink tube over the fuses!!! I was very lucky when the shrink tube melted itself away. While bottoming, I moved the wires in a wrong way and they drooped more than expected and shorted out across the middle of the pack. The short blew a hole in a connecting strap instead of welding to it. It had shorted on the side of the fuse that was nearest to the lead end – the active part of the fuse was not in the short circuit. So again, I’m grateful of the plasma ball inducing power output of these CA cells. In short, put much heftier shrink tube over the inline fuses provided.

        1. Hi Nabil,
          Everyone building a car or dealing with these cells. Think of how large a gun you would have to mounted on your car to have the recoil shove it down the road at 100 mph. These cells have the power to move your car with great force, It’s all available instantly faster than you can react. Be sure of your connections before making them or disturbing them!

      2. Hi Aaron,
        I’m sure you will be pleased with the unit from Jack when you receive it. I think it’s advisable for the additional cost to get the small balancing pigtail as well. Primarily it gives you additional information during the bottom balancing process if you are going to bottom balance a string of cells all together instead of in a single cell at a time process. The balancing pigtail system is only good for a maximum of 3 amps so it is useless for a major way of charging or discharging large prismatic cells. That being said, hooking it up gives you a visual graph of all the cells connected up to 8 all at the same time. So what you see on the computer screen is a 8 traces of cells, different colors to identify the particular cells and how close in state of charge to the rest of the cells in the group. When you bottom balance a single cell at 20 amps it will take you 8 times longer than doing 8 at a time. But you don’t know which cells in the string are going to show up as the ones of lower or higher capacity. You need to know this or keep track of it when bottoming the cells in a string. The computer screen makes this a lot easier. When all the cells are hooked up to the balance pigtail and discharging at 2.5 amps you can watch the trace line on the screen for a cell move in relation to the rest as it is charged or discharge from a separate source to that individual cell in the string.
        The pigtail balancing system is not required to do bottom balancing but using it will give you a real graphical understanding of the concepts and understanding of how difference in cell capacity affects your battery pack.

        1. Thank you Don. Your advice is appreciated. Since this is a new store item for Jack maybe this would be carried in the future. I agree however, a 3a drain on even a 100AH cell could be tedious unless it is brought down via other means beforehand.

          All the best,
          Aaron Lephart

          1. Aaron,

            I use my motors for draining the cells. This process needs to be monitored but if you used one of those little meters you can buy from jack and a contactor you could set up a way to drain using a motor to drain the cell to a specified voltage then kick it off so you don’t have to worry about killing your cell when it drains. I actually used three motors that were not being used at the time to drain at 100 amps. You could do this with your motor in your vehicle too if you connect up some sort of system to just cable it for that purpose. When done you could remove it. Or if you have a motor sitting around just use that if needed. Not elegant but very useful. I would then use my Powerlab to finish. The motor is to drain the bulk. I use this method with the cells out of the vehicle. Here is my little vid.
            http://www.youtube.com/watch?v=xr1j0bq_fA8&feature=g-upl

            I still have two motors available to draw amps. The little motor did not add much to the draw current. The Warp motor has advanced brushes and the GE was neutral timed as was the tiny starter/generator. Makes a difference with low voltage systems.

  4. Jack, I’ll try not to type myself smart here and I readily admit that I have no data other than the voltages that I recorded from my CALBs when I took them out of the crate but it seems to me that the cells were already well balanced. As you have noted in your past shows and I have confirmed on a total of 86 cells, the “shipping” voltage is consistently at 3.30 volts. Have you considered counting the number of amp/ hours that you are removing from each cell when taking them down to 2.75 volts? If this number is the same for each cell then does bottom balancing still make sense? It would appear as if the cells were sent from the factory “middle” balanced. I will test this theory before my next build. Any thoughts or data?

    1. For quite some time we just installed cells and let them go that way. But we’ve gradually moved to bottom balancing as a normal procedure with a new build. Largely because we started doing builds for other people and wanted to ensure they would have no problems with their packs.

      But no. The 3.30 volts is at 60% SOC and so in the flat part of the curve. It is nice to see them all come in the same, but for bottom balancing purposes meaningless. And this brings up another point about top balancing vs bottom balancing. Top balancing occurs WHILE you are charging and the voltages are almost meaningless.

      Bottom balancing is a bit more open circuit. And what I mean by that is that we bring them down to 2.50 v and let them bounce up to about 2.8v. Then we slowly bleed them down to 2.75 and let them rest for a day. Then we read the voltages AGAIN and trim them again for 2.75 volts. Notice that the day after, we are measuring the TRUE open circuit voltage of the cell, and we are doing it at a point in the dishcarge curve WELL AFTER the knee – really on the vertical face of the cliff. At this point very tiny changes in AH are reflected in immediate voltage changes. I mean to go from 2.85 to 2.75 is not a fraction of an ampere hour.

      Bottom line is that at 60% charge on the flat part of the discharge curve, small voltage changes represent LARGE changes in SOC. But at 2.75 volts small voltage changes represent TINY changes in SOC. Apples and Oranges. But it had completely escaped me in explaining all this that in bottom balancing, you are
      dealing with true open circuit voltage. ANd in top balancing you absolutely are not. You’re trimming a voltage in a procedure that is causal, but NOT a true open circuit voltage of the cell. 24 hours AFTEr you top balance, your cells will show true voltage, but then the differences disappear.

      By bottom balancing we precariously perch the cells on the vertical face of the discharge curve at the end. But we are dealing with true open circuit cell voltages – at least after a day’s rest.

      I knew this, but in all this time, have never been able to articulate it adequately. Top balancing and bottom balancing are NOT simply the reverse of each other.

  5. Hey Jack why don’t you embrace the rag picker mentality.. I have one too! Most likely a medical condition. By offering to pre-crimp cables at requested lengths for peeps who don’t want to buy a huge use once crimper. Maybe pre-bottom balancing then charging to a set AH for the market? Heck, you have already done the engineering on battery boxes for various vehicles that would be just the ticket for some builds. It’s all about the “value added” 😉

    Evnetics have already engineered various hardware solutions along with other trustworthy manufacturers…. This is where a trading union of trustworthy EV suppliers comes in. Considered a joint catalogue?

      1. Then the sue happy side will have to bear the brunt; buy, rent or borrow the crimper. What comes round eh? 🙁
        Testing a crimped cable is simple enough. Can be sold as untested.

  6. Jack,
    The JLD404 kit, that you are now sending out, does not include the Murata DC-DC convertor. The wiring instructions no longer show the DC-DC convertor isolating the JLD404. Have you determined that the JLD404 does not need isolation?

    Regards,
    Larry

          1. Jack or Larry,
            Glad to know I don’t actually need a DC-DC converter for isolation but, I also noticed with my recent JLD404 kit that the shunt (150A) did not come with a base. This is a little disappointing from a “value add” point of view. Was this just an ooops moment or is the base no longer included; or is it only with the higher Amp shunts?

          2. We’re learning a lot from our viewers and buyers. They wanted to mount it their own way. I didn’t really get it myself as you can always remove the base the way we were doing it. But that has been the feedback several times.

            An episode ago I talked about including the programmer with the AC50 and was blasted to make that an option as well. We’re learning some of this the hard way.

            I can sure do one for you.

            Jack

  7. Hi all.

    I just ordered a PFC2000 charger and asked for 3.5 per cell charge curve, I gave an example of a 501 curve to the supplier, I get an email back claiming they do not know this curve, I send them a pdf file of the Elcon 501 curve, but stated that I don’t care about the curve just charge CC/CV to 3.5v per cell. I haven’t got any return mail, so not sure if they will understand the request. I don’t understand whats so difficult about a 3.5v CC/CV requested….am I missing something here ?

    On another note relating to charging. If one charges a pack at a fast rate, what is the optimal percentage of the cell ah, were one doesn’t spend a large amount of time at the CV phase ?

    Another words, if one charges a 100ah cell at 50 amps, the cell voltage will climb rapidly to 3.5 v per cell, and one will now spend X amount of time waiting for the CV phase to finish. Has anyone found the best balance point for such a fast charge scenerio ??

    Roy

    1. Roy
      That’s not precisely what happens. I know that makes sense, but it isn’t what happens. I’m working of fast charge today and we did 97 percent charge to HIT CV. We didn’t do CV at all and were 97 percent full – with a 3C charge.

      And that is kind of the optimal answer. In fast charge, you charge at full current until hitting the CV voltage and then quit. No CV phase at all. I was astounded at how late in the charge game that is with these CA cells.

      Jack Rickard

      1. Our Fast DC test was not so high of C rate but we did get to the CV stage but it remained there for a very short time. Kudos on your fast charging. I await a video of the process. Should be fast drying paint this time. 🙂

      2. Jack,
        So in essence what your saying is that LiFePO4 is easier to charge than any other battery and we could very well do with a simpler charger that just does the CC phase with full blast until 3.5 cell is reached and that’s it?

      3. Roy,
        I’ve found it easier not to start specifying a voltage per cell to the manufacturer, but instead just pick a voltage level they already have and divide it by 3.5 to get your cell count. For example on my motorcycle I got a 87.6V charger which they specified as a 24S LiFePO4. That’s 3.65 per cell. As per Jack’s suggestion I put in 25 cells to get 87.6/25=3.5V per cell. For my car I’ll probably move to a 116.8V charger which is rated for 32 cells, but I’d use 33 cells to get 3.54 per cell. I’ve ordered a couple of chargers from evassemble.com. They have delivered in a couple of weeks. They package very lightly though, which has resulted in some shipping damage on both occasions, but the chargers are quite affordable and have been delivered timely.

        1. I too have a charger from evassemble.com
          Great turn-around time and they gave me the charger at the voltage I wanted. I cant remember what the packaging was like but nothing damaged.

          1. Yes I got both lots of Headways and two 24 volt chargers from evasssemble. Two swallows don’t make a summer, but so far everything arrived undamaged, to specification and in a timely fashion

  8. British Gas and Chargemaster are offering free EVSE for home users in certain parts of the UK. In practice it seems to be production EVs only however: I had a long debate with them about getting one but there wasn’t a tick box on their form for an ex-diesel Civic despite my making it quite clear that it would adhere both to J1772 and to the relevant charge protocols.

  9. Hi Jack, As you know, a significant number of my batteries have deteriorated prematurely due to my top balancing, and it took your phrase “burning the spots off” to understand why. As you say, we have to make a distinction between the battery terminal voltage and the actual battery voltage. If you top balance by holding the terminal voltage at a level greater than the fully charged battery voltage, so that the rest of the batteries can catch up, you will damage that battery. The longer you hold it, the more the damage.
    I found the comment that bottom balancing is inconvenient interesting, because with the bottom balancing of new batteries, you only balance once, and generally thats it. With top balancing, if the new batteries are significantly out of balance, using shunts to drag them into balance will damage(maybe slighlty, but damage none the less) the batteries with the highest initial charge. The only way the initial damage could be avoided is by charging each battery individually. At this point, other issues like parasitic loads makes ongoing top balancing complex The point is that this is just as inconvenient if not more so, and more costly, if you want to avoid damage.

    1. Walter:

      Unfortunately, you have discovered one of the cruelties of lithium batteries. We learn with our checkbook. Given little useful information from the manufacturer, we are left to experiment on our own, and the price tends to be more batteries. Anyone viewing my slag pile would be discouraged.

      My thought was and is that if I do this publicly, then others won’t have to. But there is a heady attraction to building and marketing a BMS system and I’m a bit surrounded and outnumbered by the “experts.”

      So who’s to be believed – the overwhelming majority of knowledgeable parties, or the old crank in the shop in Missouri who blows up batteries?

      I recognize the problem. But we really have developed a strategy that works.

      We got the Escalade heater working last week. Somehow, it DID break down and bleed the pack of 57 cells down to 95 volts. – under 2 volts per cell. Because they were bottom balanced, I put a slow 30 amp charge on them and they are all fine. No swelling. No death. It all worked.

      This happened overnight. It was an equipment failure (we have them) a BMS would have done NOTHING. It wasn’t even charging at the time.

      Bottom balancing works.

      I rarely mention it, but the idea is not preposterous. DeWalt has a patent on their bottom balancing charge system for their power tools.

      Jack Rickard

      1. Hi Jack, point finally taken.
        Another thought I had when you said that your batteries charged to 97% at 3C was to use a CC/CC profile to get the batteries closer to 100%. That is, charge at 3C until you would normally change to CV and instead of switching off, charge at C/20. This would drop the pack voltage, and you would turn off when it returned to a 3.5V/cell pack voltage.

          1. Jarkko, you are right, but the point of the idea isn’t only to get it to 100%. I realise that when you charge a car at 3C it is most likely when you are in a hurry, so hanging around for that last 3% is the last thing you want to do.
            I was thinking more about the people who are worried about the voltage of their chargers being just right so that they can go into CV mode easily. This CC/CC idea is an easy way to allow them to get closer to 100% charge if the voltage of their charger is higher than the desired pack voltage. For example, if you have a charger that is 3.65V per cell and you now want to charge your pack to 3.5V per cell because you feel that will increase the longevity. This of cause is provided you can control the current of the charger.
            You may even be able do this when the public charging stations supply a minimum of 200 Volts, if they allow you to change current on the fly.

  10. Walter,
    I’d add a cell or two if possible to get from 3.65 to 3.5 volts per cell. If that’s not possible one could add something like a JLD404 and drive a contactor with it to stop charging at exactly the desired voltage.

    I’m not sure if the voltage will drop if you reduce the charging amps from 3C to C/20, but you might be able to maintain a reached voltage. This could be useful with inferior cells which charge to say 80% at 3C, but with cells that reach 97% quick I still don’t think it’s worth it.

    1. I’ve a point to make on battery charging I’ve mentioned before. Take a new(ish) laptop, inside it has 6 lithium cells and your supply is 19.8V.
      Try dividing 19.8 by 6 and we get 3.3V.
      After all, who wants to burn peoples houses down?

  11. Jack great show. Really enjoyed it…

    I am a little down this week due to personal issues…

    I did some work to the EVthing. I rebuilt the rear suspension and brakes. It is moving quite slow, but at least it is moving forward…

    Thanks for the few guy who sent words of encouragement. I really appreciate it…. It has been a rough week….

  12. Jack,
    Very interesting show this week as you did show that fast charging did not effect capacity. I thought Rich said that his client specified that he had to fast charge and then immediately discharge. I do not remember what C rate they specified he discharge at but I thought he said the procedure called for him to cycle them several times. I guess if it was a company manufacturing forklifts, delivery trucks, or port mules, like Balqon, they would probably be interested in the performance over a specified period that would simulate a shift. I believe I read an article about the Balqon mules not performing as specified when they were put in use and I assume they were probably using the Winston/Thundersky batteries. You used those in the past and while I realize you like the CALBs better, do not recall you having any problems with the Winstons. Did Rich ever send you any data from his tests? I am just wondering if fast charging with an immediate discharge, then repeating this cycle could cause a temporary reduction in capacity during a specific period of time? Your testing has shown it would not be permeate if allowed to rest, so If this were the case, it could effect an application that was using the vehicle constantly over a period of time and depending on fast charging so they would not have the equipment out of service very long during a shift. Have you seen any indication of this?

    Randy

    1. Rich never quite comes up with “data” in the sense of the word you mean. He likes to hit me with what he “knows” from “thousands of hours of testing” but I never see any data points or graphs or anything like that.

      In all fairness, we did not test Thunderskies here. I have charged them at 200 amps but that would be more like 2C at best.

      We charged and discharged as fast as we could although the discharge was at 30 amps.

      What he told me was that a single 3C charge would take out a Thundersky cell. I didn’t quite believe it and still don’t. But we did not test them in this test.

      Jack Rickard

      1. Jack,

        I agree, if you can not get a procedure or data to try to duplicate it is like shooting at a moving target. I guess using your going into a bar illustration made me wonder if the ions are lined up outside the door when the fast charge ends and if you start to discharge immediately, they just turn around and go home. This may be why Rich saw a decrease in battery capacity when he was testing. After the charge is stopped if the battery is allowed to rest, those ions that are stacked up would be able to enter and you wouldn’t see a decrease in capacity. I wouldn’t think he should have seen a cooked battery unless he was possibly testing with a BMS hooked up.

        Randy

        1. It’s kind of hard to separate it all out. He also claims that swelling is normal and you have to build your battery boxes to constrain it. Swelling MEANS damage. The cells will still work, but it means you have overcharged or overdischarged to the point of lost capacity.

          The night club analogy probably doesn’t fit as you describe. But it is part of what causes the top balancing to come unraveled. I’ve long suspected it doesn’t even do what they think it does – equalize state of charge.

          More likely, moving electrons around in response to varying diffusion delay. Diffusion delay is the period between when a battery reaches a certain state of charge, and when all the ions space themselves through the SEI layer and into the structure to optimal position. This is the “bounce” you see. The bounce is so pronounced, that the little differences they see at the top of the charge curve are not likely very good indicators of SOC at all.

          Bottom balancing on the other hand, you can take your cells down and leave them there. Overnight if you like. THen adjust them. They are static voltages. So you can get a pretty true SOC from them.

          Charging is a procedure and an apparent voltage. If you wanted to truly “top balance them” you would have to wait 24 hours and minutely adjust them to 1/10,000 of a volt. On the bottom side, you can stop it on the vertical face of the cliff and allow them to stabilize, and repeat a day later. So larger voltage differences indicate smaller changes in SOC.

          Jack Rickard

          1. Hi Jack, I know that when you stated “If you wanted to truly “top balance them”, you were suggesting that it was extreemly difficult to do. So in my experience, even a minute voltage 1/10,000V can give a minute overcharge, because one doesn’t exactly know at what voltage the battery is when it is 100% full. One only knows that it is somewhere around 3.4V.
            So my take to “truly top balance them” is that you have to accept that :
            1. it is near impossible to balance all the batteries in a series string to 100% without some form of minute overcharge.
            2. Don’t attempt to hold a battery at any voltage when charging while the others are catching up.
            3. If you use shunts to bring the terminal voltages into line (to say 3.5V) after charging has ceased at a predetermined voltage , then although the resultant balance should have removed any small imbalances due to small parasitic loads, the batteries will not all be at 100%
            So the conclusion, unless you absolutely want to monitor each battery, save some money and bottom balance.

          2. Walterk:

            I don’t know if you are attempting to restate my message or introduce something new. I can’t make it out.

            What I was saying is that it is very easy to communicate top versus bottom balancing in simple ways. But truly, it is much much more starkly worse. What I have never quite gotten across, is that the CHARGE VOLTAGE NEVER WAS REAL. It isn’t anything. It’s a measurable mark in a recipe – a procedure. Beyond that, it is
            almost totally meaningless. And the shunting of current between cells used in top balancing BMSs may not, read that probably IS not, doing even what they purport to BE doing in the first place. More likely, it is a frenzied effort to move electrons about in meaningless patterns. I suspect it never did “balance” anything to any specific degree.

            Why would I take such a bizarre position. Surely you have observed your “top balance” shunting and are familiar with the apparent effect. But the SOC open circuit voltage of the cell takes hours to settle. Really overnight at least. THAT voltage is probably indicative of SOC but since it is on the flat part of the curve, the differences are minute. So we can’t tell much about SOC there. Sure, 3.35 is more than 3.34. But it’s very hard to read.

            There IS no way to perch the cells on the vertical cliff face on the charge end of the curve. They immediately start dropping toward open circuit. And THAT has a curve.

            But if we go to the other end – the discharge end of the charge curve, we actually CAN stop the cell at any voltage we want on the vertical face of the discharge curve. And tiny changes in SOC result in largish changes in voltage. So 2.750 and 2.758 are two voltages, with different SOC. And we can adjust them.
            Now there is some reaction – again a diffusion delay. But you can eventually work them into a very close static open circuit voltage that really IS indicative of their SOC.

            So my point was TOP balancing and BOTTOM balancing are not precisely the reverse of each other. One is a true open circuit voltage. And the other is a procedure to approximate a result 24 hours later. And bottom balancing is simply enormously more prophylactic to cell destruction. The whole top balancing thing is theoretically a mess. It is left over from lead acid thinking where intentionally overcharging brings cells to a similar state of charge – all overcharged. But in lead, the energy beyond fully charged is wasted off in hydrolysis. In Lithium cells it exhibits in lithium metallic plating and cell destruction. A big difference.
            Top balancing evolved in an attempt to do something similar to lithium cells. I doubt it even does what they think it does beyond a very rough point.

            If you bottom balance to a precise point. And then put a measured amount of Amp hours into the string, anything less than the least capacity cell, you are good to go. And better, you don’t have to do it over and over again.

            Jack Rickard

  13. Jack, I was restating what you said, while trying to emphasis how easily overcharging can happen and that top balancing doesn’t do what top balancers think it does. You have said it very well in your reply.

    1. Sorry Jack, I was draged away from my other post, so I’ll finish it. If you couldn’t make it out because I mentioned the shunts, then let me explain. As an ex-top balancer, I know they won’t believe you and always come back with something or other. I was saying that if they were able to balance away any parasitic load, by perhaps using shunts as an uneven load, then the result is still not a balanced battery pack.They may be able to bring the batteries to a consistant level of charge after each charge, but by using shunts they are actually unbalancing them, which is of cause what you have said.

      1. Parasitic loads are indeed a problem Walter. Keep on the alert for them because they show up in places you don’t expect. I’ve been bitten by this myself REPEATEDLY. And even tiny ones are cummulative. Reference John Hardy’s adventure building a testing apparatus.
        Bottom balancing does not address this. Rebottom balancing is the tedious cure if you catch it in time.

        But bottom balancing does work. Our heater on the Escalade, using a GOOD Tyco Kilovac contactor, crapped out the other night and drained my VERY EXPENSIVE pack of 57 400Ah cells down to 100 volts. Got it on a charger and no apparent swelling or damage. It’s only a 20 amp
        drain so no high currents and it just gradually bled them down but none were reversed certainly. Should I have let this happen? No. But it did. Would a BMS have helped? Not unless it actually disconnected the pack at some voltage (hmmm, JLD404 application here….).

        As to their intransigence, it becomes a religious discussion, not a technical one. I have no religion when it comes to batteries. I a tech ho. Any shiny tech bauble can win me for a night.

        1. Walter,
          Tip top charging every cell is a complete waste of time because each cell, (note the weakest), has a fixed energy capacity. When driving they all drain down at the same rate together. The cell with the lowest capacity restricts your mileage because it empties first.
          Therefore there is no change of mileage between bottom balanced and top balanced packs.

          If you have 100 cells with a one amp shunt each. Thats dumping up to half a horsepower because you overcharged them in the first place. You’ve went down the wrong route is all.

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