12s and FOC
@anon42702729 12s FOC burns up vescs? I keep getting told that high voltage has less chance of burning stuff because of the lower amps.
@JohnA Just got 10 ATL flat packs delivered from Battery Hookup. About to do some testing to see if what they sent me is any good! I think Iām going to build a 10s pack out of them and buy a separate 10s BMS for it and bypass the bms for discharge. Probably will do 5 or 6p depending on how much space I end up with. You know if cheap Chinese bmsās are worth it? I thought about doing the 6s in series with the included bmsās but 12s would put me at 34 mph at my current gear ratio and I donāt want to go anywhere near that on my mountain board yet. Also didnāt know if I was more likely to burn up a 4.12 with higher voltage, Ive had some mixed feed back on that.
I would love to hear how your flat pack project is going or if youāve made any progress on it yet!
@JohnA Any tips for disassembling packs? I got one cell off a pack so far but it was a fight. I just cut the foam separations with a razor knife and cut the cell terminals with a razor but I feel like there should be a safer way thatās less risky of shorting something.
@cskarke I personally wouldnāt trust the cheap BMSās, if they do something wrong it can be a fire hazard so I think itās worth buying something from a good brand like supower or bestech. Iāve tried 7 or so of the BMSās included with the ATL packs and I canāt get one to work with my 6s pack. Not sure if the BMSās are mostly bad or I was doing something wrongā¦
Basically what I did was put the packs in my lab oven for a few hours and heat them to 100F, then take them out and use a heat gun to remove the metal sides to minimize the lifting of the aluminum cell pouch. I then took a old gift card and sanded it down making Into a sharp knife and used that to cut the foam and help split the clear adhesive. I would be worried with a razor blade about puncturing the cells. Beyond that I take some edge cutters and pry and roll the top plates one by one and the cells drop out the bottom. Once they are removed one by one itās hard to short. Itās hard to describe the last part so Iāll try and post a video tomorrow. Also check your voltages, possible most are 0v asleep so donāt worry much about shorting
Hereās half of my ebike battery, and some of the assembly pictures. Using foam to apply a constant pressure to the cells and also allow for expansion during charging. I noticed that most of the cells expand .1-.15mm or so when cycling 3-4.2v.
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Thatās lookin awesome man! And gift cards are a good idea! The razor was making me nervous, I was super cautious but got a few of them out. Out of the 18 cells Iāve tested so far, 16 of them have been at 3.5-3.6v and 2 have been at 0v. That makes me pretty optimistic for the rest, but weāll see.
@cskarke thanks brother. Yeah the card sounds like a safer bet. Sounds like you got some good packs though, only 14 of the 26 I ordered had voltage, the rest were 1v or less for the whole pack. But some are able to wake up and have a decent capacity still.
So thatās what I thought as well. I checked all my pack voltage out of the xt60 and only had 2 packs above 5v, the rest were <1v. I thought they were all toastā¦Then I opened the pack that had the lowest voltage and tested each cell and I was getting 3.5v on all but 1 cell. Seems like the BMS was shutting down the whole pack output due to 1 bad cell. You may want to check all of them again if you havent checked voltage directly off the power distribution board. That may be why you cant get the bms to work for your 6s packs, it might think you have dead cells.
@cskarke nah, I fully disassembled all of my packs and already measured each individual cells voltage. I musta just got a little unlucky with the packs they sent. My last order I ordered 5 more and all were dead, no cells over .5v. And two were totally puffed. CS wouldnāt do anything about it either, they just replied they are salvage packs
And for the BMS not working, I looked up the TI controller on it and itās supposed to work from 6s-10s, wired it all up correctly and no dice: they just got warm after being connected to the battery.
Dang man you got screwed. So you have enough good ones to make it work or you gunna have to roll the dice and order some more? Now Iām anxious to test the rest of mine.
@cskarke I was able to make the 6s9p I shared earlier with all good cells, and I have 3s of the second battery. But now Iām forced to go through each cell and cycle them to determine capacity. Iām seeing some are good and test 2900mah or higher but some test lower then 2400. All of my good cells that came with voltage have been testing 2900-3100 mah. But the long term stability has yet to be seen. The most Iāve cycled any is 10 times. Iāll prolly end up picking one bad cell by mistake that destroys my whole pack.
I will say, do a really good physical inspection of them. Any looseness in the internal laminations or any gas inside the cell alludes to them not being stable. And Iāve had ones that look perfect externally but test kinda low
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I really really didnt want to spend 35 bucks on aluminum solder and Iām not extremely confident in soldering unfamiliar materials so I quickly whipped up this spot welder from my motorcycle battery and a relay. I have 10ft of nickel strips laying around anyways. The spot welds are legit and hopefully the relay will hold up through all 60 cells that I plan on tying together.
How many amps are you gonna try to pull per cell? And whatās your plan for connecting balance or end wires to the batteries? I would be weary of that spot welding setupā¦ But if you are confident them go for itā¦ (maybe add some capacitors for extra performance). That relay shouldnāt last too long. 35 bucks for some extra secure connections might be worth it in the long run, and one roll is plenty to make my 108 cell pack. Are you going to use a good BMS?
I not 100% on the amps yet but I wont go over 10a per cell (10a per parallel). Will most likely have a 6p pack so I wont ever need 10amps per cell. Right now Iām pulling 30a total from my current pack and already have great acceleration and hill climbing ability so Im sure Iāll never even go over 50a total draw. And I realized I have some old 4 wheeler starter solenoids laying around so I will use one in place of my relay. I plan on spot welding nickel strips directly from one positive of a cell to the negative of another cell and then flipping the cells 180Ā° on top of one another. (Iāll post a pic once I get started) and Iāll just solder the balance leads directly to the nickel strips. And yes, with all this work going into this, Iāll find a good bms.
@JohnA Out of 90 cells, I miraculously only had 7 cells below 3v. Most were at 3.2-3.5v. Idk if I got really lucky or if you got really unlucky.
Quick question, are the blue and white wires coming from the bms supposed to be charging leads or is that some kind of battery cut off? I ask because I had multiple packs with all good cells but none of my pack gave me full voltage out of the xt60 so the bms was cutting off power for some reasonā¦
@cskarke Hah, good for you, I must have just been very unlucky. I think the blue and white are the charge wires, but havenāt been able to test it. Thatās why earlier I was saying that I think the BMSās are broken, I havenāt been able to get one to workā¦ like my guess is these packs were scrapped for a faulty bms batch or something.
@JohnA Yeah I tried shorting the white and blue on a complete and good pack and nothing happenedā¦ I have 2 spare packs I was planning on just using as a remote charge bank but if the bmsās are trash then Iād have to build my own pack from scratch with another 10s bms and a dc-dc converter to throttle the amps.
So are the bmsās that you reffered me to able to balance a 6p pack ok? Or will I need more than one to get the job done?
@JohnA Whats the best way to group together cells based on their capacities? Im making 10 individual 1s6p sub packs and Iāll be joining them in series for my 10s6p. So should I group each 6p pack all with similar capacity cells or should I make the total capacity for each 6s pack as similar as possible to all the others. In other words, average out the capacities of each 6p pack so that the bms dosent have to work so hard to balance.
If all 6 in a pack on the low end were 2700mah and all 6 on the high end were 2900mah then the totals would be 16,200mah on the low and 17,400mah on the high. Seems like a lot of work for a bms.
I hope that all makes sense, kinda hard for me to communicate what Im trying to say.
Btw, I ordered a bluetooth smart bms that I can set custom parameters on and monitor everything. Its not a high dollar one but ill be able to monitor everything and that gives me a bit more peace of mind while not breaking the bank.
Youāll probably have to look it up to be certain (Iāve looked and struggled to find solid info). I personally would group the like MAH with Like MAH. Your idea of making the P groups the same total sounds like it would work on paper. but I canāt find anything online to verify itā¦ I would just be worried about one lower capacity battery being a strain on the higher capacity cellsā¦ your guess is as good as mine though :). if you can check the Internal resistance it might be worth trying to group by that also, that determines more so how the cells will act under load. I probably measured 1/4 of my cells, only the ones that I had to āwake upā and some other randoms to test. Iām interested to see how hard itāll be to keep my 9p pack balanced.
Cool about the BMS! I ended up ordering one of the XiaoXiang smart bmsās for my ebike too. I feel like itāll be a good way to monitor the balance of the pack and also set it up to only charge too V4.0 each cell to preserve longevity.