Electric Bikes - Battery or charger problem

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View Full Version : Battery or charger problem


sim559
09-03-09, 11:54 AM
I have a 36v 9.6 ah lion battery.
came with a kit with 600w motor. I could get about 9 miles out of it here in Three Rivers. worked fine never got hot and then just quit. I then bought 36 SLA battery pack and it did not last very long. Gave up for the winter last year.
About a month ago I cut open the lion pack and found one of the straps the gang the battery together had disconnected. I re solder it and charged the pack. It took some time for the pack to charge. Started with a pale green light then turned to red and then to bright green. It did work for about 5 more cycles but each charge started normal. Which is Red and then Green. Now it just goes to Green and the battery does not charge, The charger will blink red and then go green when first plug into the wall with out battery plug to charger.
I did a V test on each gang of batteries in the pack and all looked good.
The charge out put is 36 to 40 v but I do not know if allows current to flow.
Any Ideas
Thanks
Sim


donob08
09-03-09, 12:44 PM
It's pretty easy to put a small (hopefully known value of ) resistance in one of the leads to the charger and then measure the voltage across it. I = V /R. That is the current in amps is the voltage in volts divided by the resistance in ohms. No volts would say no current.

The BMS (battery management system) my be blocking current if it thinks the battery is Full or it is otherwise mislead/ broken.

sim559
09-03-09, 02:57 PM
Hi
I did something like that but used a 12v test light. I think the charger is ok as I need to buy a new bulb for the test light.
What would happen if I removed the circuit board from the battery and just charged the battery directly?
I know I would loose the balancing that the board gives.But I would still get some use out of the pack
thanks
Sim


sim559
09-19-09, 04:14 PM
up date on this problem I took a V meter the the circuit board and battery pack.
The pack needs to be charged but something was preventing it from charging.
I had 34 v at the battery. I also had 34 V on the circuit board where the power came out. also had voltage on resistors but decreased as I went down the line.
did the same thing on all the little black boxes. so I going nothing wrong with the circuit board. So i got a little piece of wire plugged in the charger and held the wire to the connection where the charger entered the circuit board and touched the other end to where the black wire left the battery pack to power the bike. Both of these points were Negative The light on the charger went to red. I left it this way for a bit then removed the wire. Light on charger still red. So it is now charging.
Do not know how the circuit board controls the charge but it must have had a problem with too low of voltage and would not charge the battery.
Any one else have this problem?

sim559
09-20-09, 12:46 PM
did not work batter did charge but only got 100 yards before it cut off.
Now going to remove circuit board and use a Volt or amp meter to let me know when battery is too low

SeizeTech
09-21-09, 01:57 AM
it is possible for the battery to not charge due to one cell at 4Volts, yet the battery pack is useless because it goes into Low Voltage Cutoff due to another cell at 3.4Volts.

Check each individual cell voltage. They should be balanced, if they aren't balance, you can probably correct your problem for a few months by manually balancing the cells.

Good BMS boards self balance, but it is surprising how often the BMS boards are built without this capability.