Battery - no power

daPoppa

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May 11, 2022
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Hi folks, I have a Michael Blast ebike, which I've owned for about 3 years. Recently, I went to start the bike, but there was no power. I removed the battery, took the case apart and checked the following points: (battery is 48v 13ah)

1- the charging port has power - about 42v
2 - the check light on the battery shows 1 green light (out of 3)
3 - no power showing on the output connectors on the battery
4 - fuse is OK
5 - not actually charging at all

Does this mean my battery is hooped? If so, and I get a replacement battery, could I just get a similar one and splice it into the bike? The battery sold specifically for this bike is $800, but I could get a similar generic one for $440.
eg:
1- there are 3 wires currently coming from the controller, 1 for the pedal (not used), 1 for the display and 1 for the motor.
2 - with a new battery/controller, they all seem to come with only 2 wires (red/black for power)
3 - would that mean that the wires currently going to the motor/display are just 48v power?

Any suggestions would be appreciated.
cheers
 
If it’s a lithium battery then your 48V battery will have 13 cells. 42V is then 3.2V average per battery which is on the low side but not dead. Most likely cause for the discharge port being off is that the BMS has turned it off due to low voltage on one or more cells.

If the charge port is showing voltage but it doesn’t charge is strange, to get the bms to turn on again you need to get the low cell(s) back to normal voltage. If this really is a good idea depends on how tech savvy you are and what the cell voltages are.. If any cell is close to zero then this cell might be irreparably damaged and you risk a fire if you charge it.

If you have a multimeter you could open the battery and check the cell voltages (if you’re confident to do that)

Be careful when measuring though, lithium batteries are powerful so don’t cause a short :wink:
 
daPoppa said:
eg:
1- there are 3 wires currently coming from the controller, 1 for the pedal (not used), 1 for the display and 1 for the motor.
2 - with a new battery/controller, they all seem to come with only 2 wires (red/black for power)
3 - would that mean that the wires currently going to the motor/display are just 48v power?
You say "wires"; do you mean "cables"? (a cable has more than one wire inside a sheath or housing, a wire is just one conductor (stranded or not) inside it's own sheath or housing).

I ask because you're saying things that equate the two, but it's important to know which is which; to figure out what you need for parts requires knowing how many actual wires are in each cable to/from each part of the bike (or at least, how many pins are on each connector, if you can't see the individual wires).

Batteries don't usually have the motor controller in them. A few "bottle" batteries do, but not most batteries in general.

If your battery actually has the motor controller in it, there will be at least three thicker wires go the motor from it, and probably five or six smaller ones. There will then also be five or so wires to any display you have, and three to a throttle (if it's separate from the display), and three (or more) to any PAS unit (pedal sensor). There are often pairs of wires for ebrake levers.

If so, then that's one possible reason the battery costs more from the manufacturer--if you change that controller out you'll also need to change the display, and possibly rewire various connnectors on the bike to match your new stuff, or change the new ones to match the existing ones. You'll also change the way the bike works; it is probably not going to respond quite the same to your inputs as it does now.


If your battery only has a single pair of thicker wires then the controller is not inside it; it will be in wherever those wires go to.
 
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