Low voltage problem

[Feraslan]

Hello.
i have 350 watt 48 volt china ebike.
When I put my battery in the bike, the battery indicator shows on the screen and the engine starts. But after 5-10 minutes the voltage drops and the indicator goes down to zero. First I thought the battery was exhausted and I bought a new one. The same problem happened when I inserted the new battery.
Ps:There are 5 minutes between two pictures

 

[Jan-Erik-86]

What battery are you using, and what controller? Also, is that 5-10 minutes of riding, or does it simply drop down to empty by itself?

Since it's happening with two batteries one would suspect something else to be the issue, but to drain a decent sized battery in 5-10 minutes would usually require so much power that the battery, controller or motor would be very hot, unless it's a microscopic battery you're using. Is any parts running hot during these 5-10 minutes?

The start and end voltage does indicate both near full and near empty, but do you have access to measure individual cell banks in the battery? It could be a very out of balance battery, but if so the BMS should have shut down the battery if this was the case, and your controller is clearly still receiving power.
Does battery recharge take about the time estimated for the battery size, or is it done in almost no time?

 

[john61ct]

Did the setup ever work?

If so, was this symptom sudden or increase over time?

Link to the battery?

 

[dogman dan]

Did either battery get fully balanced? They often come quite unbalanced if the shipping took very long.

Charge, unplug, sit half an hour, charge again. Repeat many times. If the charger won't restart after half an hour, ride it for 2 min, then recharge. During that half hour, the bms should be discharging the highest charged cells, and on restart, the battery can again fill the low cells a bit. It can be tedious, and take many repeats.

In shipping, the bms runs on just a few cells, then the charger and bms has a hard time getting the battery fully balanced when you start to use it. Only two cell groups are more discharged, but the charger stops when the other 11 groups get full.

The other possibility, is the shipping took so long the bms killed those two cell groups. Or some random defect causes the same thing.

Winter is coming, charge those batteries at least monthly all winter, then do the balancing again in spring.

If you get them to perk up, you can put both on the bike, using a home made Y connection. This doubles the battery, and makes each cells life easier. Charge them separately, and never connect unless both are full.

 

[obcd]

Does your voltage drops instantly or gradually.
You could test the battery by connecting 4 12V hallogene spots in serie and using that as a load on the battery.
The odds are small that both batteries are bad, but you never know.
If the voltage drop is instantly, I would expect a bad contact somewhere between the battery holder and the controller.

 

[dogman dan]

True enough, a bad plug can drop your voltage by 10v, and then your controller reads less than 30v, and that is empty.