Ah good shout, I think I’ll give that a go for practice
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So I just got my battery bms set up and charged, but unfortunately I checked on it and it #1, charges beyond 4.2 volts which is frustrating, and #2 appears that’s it’s not even trying to balance. I’m using a lithiumbatterypcb bms btw. Any ideas what is wrong?
Looks like when I turn balancing on to always, then it’ll balance out. Otherwise it doesn’t. Since the charger stopped charging when it got full, it stoped balancing as well.
Any recommendations?
Have you tried a static balance?
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It’s likely your BMS is set to overolt cutoff at 4.25v thus the “over charge” so that’s normal for an out of balance battery.
how did the battery get out of balance?
double check the readings of the BMS at the cells and at the connectors with a multimeter make sure there’s not poorly connected balance leads throwing off readings. (or poorly calibrated BMS)
then set it to always on balancing until it balances out. (and then can switch it back)
drain the pack and watch for signs of the delta between pgroups growing too large. difference in pgroup capacity/IR will show more as you drain more. hopefully you see none. and you just needed an initial balance for some reason.
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Thanks for the response. Well that would make sense. I just assembled this pack, so it was not quite perfectly balanced, but it was good enough to put the cells together. Seems like you are right, static balance allowed the pack to balance out to where it should be. Now do you think I should set it back to charge only balancing, or leave it to static?
set it back to charge only. if a pgroup goes bad and things start getting way out of balance you want hat to show up and not be covered up by the BMS constantly draining the other pgroups to match. eventually it’ll show anyhow. but it’s a waste. if it’s not staying balanced on charge only you probably want to check some things anyhow.
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Makes sense. Thanks again!
I agree putting stress on the welds is bad idea
I am wondering if you can achieve the same by just potting the battery? Or potting alone is not enough?
I also don’t know the answer to that. Most of the potting compound I’ve seen has been soft, so I don’t think it’s very good for rigidity
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Depends on the potting compound. Some are rigid (epoxies and similar) and some are quite flexible.
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Yerp. Thats the ones I use!
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Ah when you said Stanley I think of these.
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Is this a good charger for a 12s6p setup with an LLT BMS.
50.4V 6A Charger 50.4V Lithium Battery Charger 44.4V Charger with Cooling Fan Aluminum Case Used for 12S 44.4V Lithium Battery DC XLR 3pin Connector https://a.co/d/dOckZv0
Brandon
“good” would be impossible to know without people trying it first. But yes that would work on a 12s6p
I’m working on my first battery build and I would appreciate any advice. The dimensions of my board are locked in since it is based on the onewheel xr frame. I currently use the Chi Battery 15s1p, 21700. It fits in my battery box like so.
I found by drawing the battery layout that these are not close packed. They are spread to reduce the height like this.
I am locked into that height and width so I will increase the battery box length. I plan to add 5 cells for 20s. I don’t see an arrangement with better density and weight distribution. So it looks like this.
I plan to 3D print spacers, shown in orange, to control the dimensions as I glue it together. I made one 90 degree and one 180 degree nickel strip to transition between the groups. I’m not sure if this is conventional or if there is some other trick. I have not seen many packs with abnormal geometries.
I appreciate any advice about these transitions or issues that could arise from the geometry. Particular, from Mario @TheBoardGarage since he has worked on onewheel packs. Reading his battery articles has been super helpful.
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Would anyone be willing to rent or loan a kweld to me, I would send you a deposit for the full value, and when you get it back, which would be right away, you would return my deposit. I just can’t spend the 250 for a new one right now (my wife was miserable and quit her job to start her own business and it’s not profitable yet) but would like to finish my pack.
In the US.
I practiced on a spare cell, cut, pre-soldered, and cleaned the nickel, cleaned the cells, and got the first tab welded now
Does this look ok? I both really want to try a pull test in place, and really don’t want to muck up the surface of the cells that I’d have to grind down after. These settings on a pull test of a spare cell shredded the nickel
These are the prepped tabs, I cut the corners that’ll be over the positive terminal because I want to minimise the nickel that could wear through but seeing it in place doesn’t seem to be worth the extra steps now
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