Battery does not charge above 10% all of a sudden

[Cyclomania]

So I have been using this 48volt 18ah battery for quite some time now. But it has not shown any signs of diminishing amp hours or anything like that. Not anything that I have noticed.

But today the bike just stopped all of a sudden. And the battery was showing like 5 max 10% charge. I had to walk it home from there.

Well at home I tried to charge it. And I know the charger is not the problem because I have charged other batteries with it today.

I have tried both the regular hole for charging and going trough the xt60-connector as well, with one of those adapters to see if the hole could be the problem. But when trying to charge it through both of those ports the outcome is the same. The charger is showing the green light, for fully charged battery. I have no idea why. Because when I test it with a multimeter it is charged only up to about 40 volts right now. And this is a 48-volt battery.

Also, when having the charger connected to a wall and the battery connected to the bike, the bike will start. Because it seems the charger can then run current into the bike via the wall.

Any idea what has happened here? The cells just went caput and on strike one day and decided to not be charged anymore? Or am I missing something?

If the battery life is going down I thought it would be a more gradual decay? For example maybe one day it would only charge up to 80% or so? But not like this to just not charge anymore one day. Not above 5-10% at least it seems. At 40 volts the charger is showing the green light for fully charged when connected to this battery.

Maybe I rode the battery too close to being completely emptied one day or something? Anyoe has an idea?

 

[docw009]

To summarize your problem.
1. Battery stopped running the bike at 10%. Did the bike shut off. Could it be restarted if it did shut off? On/off switch on battery?
2. Battery now wont charge. It also will not charge thru the XT-connector. This is why I asked about on/off switch.
3. Bike is dead? No response with battery until you plug in the charger. Then it powers up, but still won;t charge,
4. You probed the battery. Two groups at 3.1-2.3 volts. The rest are 3.4-3.5V.

You might want ti make sure your meter is accurate. Measure the charger voltage to see if you get 54.6V. It's would be normal to see 54.8V. That's typical meter error, but if you read way above 55V, your voltmeter probably needs a new battery.

I would like to know if the above cell voltages are accurate before making any guesses as to what's wrong.

 

[Cyclomania]

To summarize your problem.
1. Battery stopped running the bike at 10%. Did the bike shut off. Could it be restarted if it did shut off? On/off switch on battery?
2. Battery now wont charge. It also will not charge thru the XT-connector. This is why I asked about on/off switch.
3. Bike is dead? No response with battery until you plug in the charger. Then it powers up, but still won;t charge,
4. You probed the battery. Two groups at 3.1-2.3 volts. The rest are 3.4-3.5V.

You might want ti make sure your meter is accurate. Measure the charger voltage to see if you get 54.6V. It's would be normal to see 54.8V. That's typical meter error, but if you read way above 55V, your voltmeter probably needs a new battery.

I would like to know if the above cell voltages are accurate before making any guesses as to what's wrong.

These are correct. But when probing the battery's xt60 output-connectors it shows around 37 volts. No idea why. It should show around 44-45 based on the different cell groups I guess? 3,4*12 = 40,8 + 3,2 = 44. Pretty strange huh?

I think my multimeter is correct. Yeah, all the groups show 3,4 or ,3,5 but one of them show 3,2. Maybe 3,2 might still be in the range ?
All the balance wire from the bms looks like they are still in place. Maybe I tripped the BMS or something? Any ideas?

 

[Cyclomania]

So what is even more strange. After disconnecting the balance wires from the bms I now get a more accurate reading of the whole battery. Around 43 volts when measuring the main plus and minus going out of the battery.

Any idea why that happens now that I have disconnected the balance leads from the BMS ?

sinokilovipp33's Video - Oct 17, 2024

www.veed.io

(sorry about the camera - it sucks)

Does this mean I can try to connect the balance wires into the BMS again now? Or would that lead to sparks/shorts or something similar in this situation?

I think it is strange that it now reads 43 volts without the bms connected. But maybe something happened to the bms? I have no idea what though, because it looks fine on the outside.

Thanks

 

[docw009]

These are correct. But when probing the battery's xt60 output-connectors it shows around 37 volts. No idea why. It should show around 44-45 based on the different cell groups I guess? 3,4*12 = 40,8 + 3,2 = 44. Pretty strange huh?

I believe that's the missing info. BMS is not allowing the 44V on the cells to get to your XT connector. If you were to go back and remeasure all 15 pins on the BMS connector, you'll have the 14 cell voltages for the battery. If all are at 3.1 or higher, i believe there is no reason to shut off the BMS. That would say the BMS is not working right.

 

[Cyclomania]

I believe that's the missing info. BMS is not allowing the 44V on the cells to get to your XT connector. If you were to go back and remeasure all 15 pins on the BMS connector, you'll have the 14 cell voltages for the battery. If all are at 3.1 or higher, i believe there is no reason to shut off the BMS. That would say the BMS is not working right.

Aha so you think the bms might be the problem? So perhaps switch it out to another BMS?