something like this
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When I applied a load with battery modules, the p-groups would sag wildly enough to trigger the mismatch alarm. I also noticed arching marks on the tabs inserts and the cells. When the voltage was lower, the worse it got. I purchased a battery a few years back, and it also did the mismatched thing. When I rebuilt the battery with nickel strips (12s8p P42A), the groups sagged without a mismatch alarm.What causes the mismatch?
Was looking at the pics you posted of the evidence of arching and looks like one or more modules were faulty. Bad/loose connections or the like. Same goes for the arching inside the modules. There could have also been some minor deformities in them causing loose parallel connections caused by heat over time.
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Hi all!
I am currently working on reworking a pack that I recently received and wanted to get some feedback on a couple things.
The pack is made for a HAYA deck, and has very little clearance above the cells. The lid has a 1/4 rubber gasket material along the entire bottom side. I am moving the balance wires above the cells because the old wiring harness was a bit of a mess, as well as connected to the positives of all the cells rather than the negatives. Is it OK to have the rubber gasket compress directly onto the balance wires or should I carve out a section where the balance wires are to give them a bit of room between the bottom of the lid?
Also is there any reasonable way to wrap this pack in heatshrink or should I just leave it as is and wrap the whole thing in fish paper/fiber tape after I am done sorting out the balance wires?
Picture for reference:
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I think with the quarter inch gasket youâll be fine as long as none of the balance wires are crossing one another.
I thought we do want them connected to all the positives, at least last I readâŚ
So if my understanding is correct connecting to pgroup1 pos and pgroup2 neg is basically the same thing because those are connected in series already. So you start with BC0 always going to the neg of group1, then BC1 can connect to the pos of group1 or the neg of group2.
I read earlier that the second is preferred due to outer can of the cells being neg. So if there is ever a short due to abrasion it is ok because it is neg->neg.
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Ah ok, yeah I donât know how much it matters. I think I read if the groups get disconnected then youâre still reading that last connected group or something
My LLT BMS stoped showing the charging Amps
I was messing around with it and now although it is charging, I donât know at what amps it does so.
Also the little arrows in the charging side donât flash green anymore as they did.
Anyone knows how to turn that back on?
This was also my understanding but itâs incorrect. The only reason itâs safer to solder to a neg terminal has to do with the nickel youâre soldering the balance wire to. In short, the nickel from a positive terminal folded over the shoulder of the cell has the potential to short at the shoulder. Otherwise, it has to do with the difference in voltage potential between two different parts of the pack and has the same chance for shorts regardless of the balance wire being soldered to a pos or neg terminal.
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This is why the wiki would be good, a common place that can be edited
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I think you should be more worried about how unbalanced the pack is
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I was. Thatâs why this pack is out of the board and was going to get a surgery, but my gangsta DIY spot welder decided to stop working also, so Iâm looking at my options.
On the BMS subject, I was trying to lower charge current from 5A to 1A to be safe and probably messed something up on the configuration. But now itâs back to normal.
The worst of it all, is that the weather is still great and I canât go skateâ:rofl:
The BMS cannot control charge current. It can only stop charging if you exceed it. If you want to charge slower get a smaller charger.
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I wouldnât say Quinnâs take is incorrect, both points are valid.
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Part of her statement was definitely correct but there was some inaccuracy in there as well. Edited above for clarity.
I thought I was live on Instagram. I welded a entire 12s5p pack in 40 min.
Used both kweld and malelectrics (bc hot probes).
Appearently I wasnât live. My weld placement was extra shity bc of the pressure of being live (but I wasnât live. )
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How long can I keep a battery at 48V? Iâm hoping the snow will be gone by the weekend.
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a 12s battery? That puts it at around 80%. Shouldnt be a big deal.
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12s8pâŚ
P count shouldnt matter. Keeping it at 48v for about a week shouldnt be a problem at all. Storage voltage is more for long term storage. Of course there are benefits to always storing a battery at storage voltage, but I wouldnt fret about this at all.
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