This is fine
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That is a max rating, to be avoided if you want good performance. Itās only to help with safety and to prevent short cycle life.
Itās like a carā¦if the engine has a red-line spec of 7000rpm you would never say to yourself that itās okay to always run the engine that high. Same with cells.
If you want decent performance you should stay at under about 75% of the rating. Under 50% for the ultra-high capacity cells. This goes for continuous and pulsed use since the sag for either one is the same.
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Weirdness is weird.
So hereās what LLT is showing:
Meanwhile on the charger:
And heres my LLT settings for completeness of info:
My question is, is this bad/ how do I fix it?
Ps: My battery had a delta <0.2V before plugging it in, was almost dead. Iām not worried about my delta Iām worried about this odd. behaviour. Unless the two are related.
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Charger is broken.
I was afraid of that.
Well at least my BMS isnāt broken. Chargers are slightly easier to acquire.
In the meantime, would it be okay for me to use a lower or higher voltage charger? Iāve got some 10s, 13s and 15s chargers no spare 12s ATM.
Now might be a good time for me to consider a radium charger or a statiator
The problem with using a higher voltage charger is that the charger will never get to CV mode.
This can cause trouble with cells approaching full voltage too fast. If the bms is working properly it should cut off the charge, but once the cells rest theyāll probably end up lower than what they would normally be with a proper charger.
If the 13s charger is a reasonably low current charger you could use that but I definitely would not recommend it unless you are committed to watching the charge cycle and prepared to manually disconnect in the circumstance that the bms might not cut off the charge for you.
Definitely not a recommended practice. But you can get away with it if you are vigilant.
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If youāre lucky the 13S charger has a small poti inside that you can turn down to make it a 12S charger. Manufacturers are lazy.
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For 13s it would only be a pithy 2A, and Iāve got Bluetooth live data so I can just set my phone on a charger and glance at it every few minutes.
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I would and have done the same thing. Just be careful.
So my 13s charger behaves the same way, and a 3s charger is also behaving the same way on a 3s3p pack I built.
The flickering has different timing on all of them but is happening on all of them, using a DMM to monitor the 3s pack.
Seems the BMS is done then. Bump the charge overcurrent setting way up, if it still happens, new BMS.
Seems I need a new BMS. Fuq.
Iāve only got a 13s on hand.
+1s maybe? Might be able to squeeze it in.
Can I turn my 13s into a 12s?
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You could try tweaking the pots inside the charger to reduce the output current and see if that will help stabilize it. As long as youāre careful and donāt leave it unattended without confirming what your changes have done. (You donāt want to accidentally leave it turned up to 65v or something)
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Everything is glued inside the charger so itās hard to get at the pots but Iāll see what I can do to tomorrow. For now Iāve found a way to at least slow charge and ride for the day.
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Well fuck Iām guessing my BMS just got cooked.
Edit:
Fuck now it shows this
Iām scared, my BMS is probably fucked right? Think the cells are fucked? The groups were showing ~3.5V across all of them about 20 minutes of riding before this,
So I think somethingās not quite right with it:
No load is 39.4V at 48A Battery current I get 35.2V so thats 4.2V where I should have 2.8V sag
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That looks bad. Regardless you need to get that bms off the cells and check the voltage directly. If it is intermittent it may be damaged welds on the nickel but it needs to go on the bench asap before it gets more damaged.
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Iām on a ride home right now (public transit not esk8) about to tear into this. BMS is getting disconnected and the probes are gonna go wild,
Fuuuuuck I hope I donāt have to rebuild too much of this packā¦
Itās so weird everything looked great with a low delta, ride about 20km, groups were all about 3.5V then rode another about 10km and all of a sudden this crap happens.
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Your battery starts sweating:
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Real talk:
Iāve been watching the progression of your battery build, and while youāve gained a lot of knowledge and skills since you first started, the consistent issues with this pack might indicate that there are still some areas that could be improved.
Iād recommend tearing it down, and rebuilding it from scratch documenting the whole process in this thread for people to help out. Ask a ton of questions. I did something similar and it definitely helped.
See @drone001ās recent battery rebuild of his NESE to a welded pack for a great example. Iām really impressed with how his first welded battery build is progressing. Heās moving at the right pace, asking lots of questions, posting pictures, and taking feedback to heart. Heās not out to prove anything, he just wants a safe battery that he can enjoy riding with.
Battery building can be complex, and there are many things we donāt even think of. Leaning on the community for help is a great way to build a robust, safe and problem free battery.
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