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Definitely check each cell individually with a multimeter through the BMS ribbon cable when you replace the BMS
 

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I'm far from an electrician but I suppose I could give it a shot, what's the worst that could happen right? 馃敟馃拃馃槀
That's how you learn :) keep a fire extinguisher around

Get yourself a good multimeter and start testing each cell through the balance port.
 

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Razor mx500 (mildly modded monster)
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Discussion Starter · #24 ·
I'm starting to wonder, could it actually be a charger issue? According to the battery indicator the battery goes to 100% with the battery charger hooked up but when I unplug it the indicator reads 75%. I can swing a new charger for 25 bucks right now... but a $350 battery replacement is gonna take a month or so to factor into expenditures and I'd like to avoid shelling out money where I don't have to
 

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I'm starting to wonder, could it actually be a charger issue? According to the battery indicator the battery goes to 100% with the battery charger hooked up but when I unplug it the indicator reads 75%. I can swing a new charger for 25 bucks right now... but a $350 battery replacement is gonna take a month or so to factor into expenditures and I'd like to avoid shelling out money where I don't have to
The BMS is responsible for managing and charging the individual cells the plug in the wall box just gives the BMS power.

When the BMS starts having problems it leaves the pack un balanced or it does something really really stupid like give the cells a bunch of voltage then thinks the batteries are full and cuts off charging and never fills up the individual cells with the milliamp hours they need.

Or worse it starts over charging some cells leaving other ones completely empty and in this case it's going to catch fire eventually if you keep trying to use it while it has a problem.

The first thing that I would do if it was my pack would be to carve out the BMS figure out exactly which one it is and get a replacement.

The second thing that I would do would be to get out the RC car charger and start charging each cell individually then try it again with the new BMS.

If that didn't work then I would break the pack completely down and charge each cell individually with one of those fancy e-cigarette 18650 MOD chargers ( these style of chargers are surprisingly good at figuring out if the battery cell is good or bad)

Then I would replace any of the bad cells and rebuild the pack with one of those screw together kits.


This is why I always suggest just buying individual cells and the kit and the BMS and putting the battery together yourself then if anything goes wrong you can easily service it ( with plenty of how to guides all over the internet )
 

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Razor mx500 (mildly modded monster)
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Discussion Starter · #26 ·
As always, great advice! Looks like I'll have to take some refresher courses on electrical...
 
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