It's dead Jim. Dead battery pack

BCBeaver · Sep 18, 2020

Magnum bike with a 48V, 13AH battery. Woman left her house with a full charge, rode 3km, had coffee, hopped on her bike and it was dead. I put a meter on it and it shows 0.6V. I now sits on my bench. I checked fuses on both ends both good. Dead cell or BMS?

Addy · Sep 18, 2020

Could be a low cell group or flaky balance wire connection. Have you tried waking up the BMS by charging the battery?

Balmorhea · Sep 18, 2020

BCBeaver said:
Magnum bike with a 48V, 13AH battery. Woman left her house with a full charge, rode 3km, had coffee, hopped on her bike and it was dead. I put a meter on it and it shows 0.6V. I now sits on my bench. I checked fuses on both ends both good. Dead cell or BMS?

Either. A dead cell will make a working BMS do its job and cut the pack off. I'd charge it through the discharge port for a minute or so, then see if it shows normal voltage. If it wakes up, it's probably either a bad cell or a badly imbalanced condition.

If it doesn't wake up, you'll have to open it up and start checking cell voltages and sense wire continuity.

BCBeaver · Sep 18, 2020

Hooked up the charger to the discharge port and it's now alive. 53.6V. I had 4 lights on the battery indicator so I installed the battery in the bike and the bike wouldn't turn on and 4 lights on battery were now out. I got a flash of light from the direct connected headlight (has a switch but not operated through controller) but the bike would not turn on. I disconnected the controller and tried a new one and it worked. I plugged the original controller in and it now works. I'm left wondering why and will it die again soon?

I feel like I treated the symptom but not the disease.

Balmorhea · Sep 19, 2020

BCBeaver said:
Hooked up the charger to the discharge port and it's now alive. 53.6V. I had 4 lights on the battery indicator so I installed the battery in the bike and the bike wouldn't turn on and 4 lights on battery were now out. I got a flash of light from the direct connected headlight (has a switch but not operated through controller) but the bike would not turn on. I disconnected the controller and tried a new one and it worked. I plugged the original controller in and it now works. I'm left wondering why and will it die again soon?

I feel like I treated the symptom but not the disease.

Leave it on the charger for a day or two (to let it balance), then check the voltage. It should be 54.6V. If it holds that voltage for a day after it's removed from the charger, then it's probably fine.

If it cuts out quickly in use after it has been balanced, then there's a very weak cell, a faulty connection somewhere, or a fruity BMS.

LeftieBiker · Sep 19, 2020

That bodes ill for my Magnum Metro. I left it charging for several days by accident early last month, and now I get a drop of about 1.5 volts within 2 blocks of leaving my house. It behaves normally otherwise, no additional extra voltage drop, but I probably also have a weak cell now.

It's dead Jim. Dead battery pack

BCBeaver

10 mW

Addy

100 W

Balmorhea

100 kW

BCBeaver

10 mW

Balmorhea

100 kW

LeftieBiker

100 kW

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