Bearprint Battery Problem

[Henry A Turner]

I have owned a Bearprint Sports Tourer for about 4 years without any significant problems until now. I've not used the bike for about 2 months. I used it 2 days ago, with a fully-charged battery, but when I went to pull away the electrics just died. The system came up again after I had switched off on the battery key, then switched on again. It seems that when there is any load on, something drops out. I've done all the normal checks for bad connections and broken wires but everything seems fine. does anyone have any suggestions on possible faults?

 

[Deleted member 4366]

Start by charging the battery fully. Leave it for about half an hour. Then check the voltage on the terminals underneath. Next, ride it for a bit until it cuts out, then check the voltage again straight away.If you haven't got a voltmeter, you'll have to get one because it's impossible to diagnose without one.

 

[Henry A Turner]

Start by charging the battery fully. Leave it for about half an hour. Then check the voltage on the terminals underneath. Next, ride it for a bit until it cuts out, then check the voltage again straight away.If you haven't got a voltmeter, you'll have to get one because it's impossible to diagnose without one.

Hi d8veh. Thanks for your suggestion. I have a 36v battery on this bike. Shortly after a charge I took a reading which was 41.5v. After my next "failure" I got the same reading, which seems to rule out a battery problem.

 

[Deleted member 4366]

Did you check the voltage immediately after cut-out at 41.5v?

 

[Henry A Turner]

Did you check the voltage immediately after cut-out at 41.5v?

Yes.

 

[Deleted member 4366]

That probably means that your battery connections are corroded of bent. Does it cut when you go over a bump? There's also a common problem with the key-switch. Some aren't soldered very well (dry) even though they look OK. They can also wear out inside.

 

[Henry A Turner]

Did you check the voltage immediately after cut-out at 41.5v?

That probably means that your battery connections are corroded of bent. Does it cut when you go over a bump? There's also a common problem with the key-switch. Some aren't soldered very well (dry) even though they look OK. They can also wear out inside.

Hi d8veh, my latest battery checks are: I connected my meter leads to the base of the + - posts then fitted the battery. At this point the meter gave the battery voltage. By raising the motor wheel off the ground the motor ran (as there was no load). Once I put the load on the power failed. The meter went to zero, confirming the fault is at the battery end. I then connected the key switch wires together (thus by-passing the switch). On replacing the battery, feeling quite confident, on test the power failed. I now intend to by-pass the fuse-holder arrangement. If the power still fails there is nothing else in the control system to by-pass, so my feeling is the problem must be inside the battery. What's your views?

 

[Alan Quay]

Sounds like a balance/bms problem to me...

 

[Deleted member 4366]

You still haven't eliminated the battery connection because your voltmeter was connected to the controller side. Once you've checked that out, you can focus on the BMS and the cells. I'd check the cells first.Identify the two wires that come from the pack. The lack one will go to the BMS, and the red probably to the keyswitch. Attach your meter to them and see how much sag you get as you increase the load on the battery until it cuts off. It'll bounce back as soon as it cuts off so you need to try and slow things down. If there's hardly any sag, you need to check what happens with your black probe on the output side of the BMS to confirm whether the BMS is switching off.