Battery failing! Danger?

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Debunker   1 mW

1 mW
Posts: 19
Joined: Mar 09 2017 4:52pm

Battery failing! Danger?

Post by Debunker » Nov 04 2018 2:56pm

Hi, I got a 1 year old battery, very well cared, last time I charge it at 80% as usual, put in the bike, grease the chain and ride a few minutes at the garage, everithing seems ok... but in the morning when I ride the bike to work, the thumb indicator shows a dramatic drop off, the motor starts moving, and suddenly cutts of power... (BMS does his work cutting off the power I guess)

-Shit! this thing is gonna allahu akbar in my balls!! (I thing at that moment) so in a desperate and brave moment, I jump of the bike, trow it at ground, open the bag and quickly disconect the battery whit the nerve of a profesional bomb defuser.

The black cable are notoriously hot, the pack itself are cold... I wait a bit whit everyone in the street watching the scene confused, afther a segond try, same result, so of course I had to return and leave the battery in the garage, inside an old PC chase box reinforced whit migthy aluminion thinfoil.

Today I try to figure out what happen and where is the problem, well... turns out that the problem is in the battery itself, strange thing is... the build in indicator shows 58v has it is correct whit a 52v at 80% charge, but as soon as I plug the pack in a watt metter (even disconected from the system) it starts building up voltage pretty slowly, and stops around 32v, this time the cables don't burn but I don't trust the pack anymore...


I barely understand the basics of batteries, and I'm afraid that thing may go allahu akbar on my garage at any moment... What the frock happens? any simple way to repair it? should I just trow the thing in the trash and hope no hobo put his hands on it? that cost my more than the bike itsef!

electric_nz   1 µW

1 µW
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Joined: Jan 07 2019 8:33pm

Re: Battery failing! Danger?

Post by electric_nz » Jan 09 2019 3:11pm

A hot wire indicates a short circuit somewhere in the wiring between battery, controller, BMS and motor- the whole thing needs to be taken apart. I would seriously not ride this and if you're not comfortable repairing it, take it in to a professional to look at. Battery is probably OK

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dogman dan   100 GW

100 GW
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Joined: May 17 2008 12:53pm
Location: Las Cruces New Mexico USA

Re: Battery failing! Danger?

Post by dogman dan » Jan 10 2019 8:15am

Well, it would not go in my garage, brand new. Not after the garage fire I had. So that's my advice for the garage.

The battery itself sounds bad. Not sure what you mean by the notoriously hot wire, but a warm wire from battery to controller is fairly normal, but it could get hot just from a really bad connector getting hot. This would also cut voltage to the bike.

So,, your battery could be fine, just a f---ed contact on the plug. Fix that first, if it does not look shiny cherry.


You say charging normally to 80%,, this means you never got a balanced charge. this could be half your problem. To check out the battery, charge to full, and see how much it discharges itself. It will discharge itself a little in an hour or so, as the now fullest cells discharge. Repeat the charge. If the charger won't start, try to ride around the block, and recharge, till the battery will hold some charge overnight.


My bet is you just fried the plug on the battery wire to the controller. But if you don't balance your pack from time to time, it will definitely die an early death, because you are stressing it on the discharge end of the cycle, trying to save it from a full charge.

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