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Kingsong S18 BMS not charging one cell


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Hi,

My S18 would only charge up to 90% and on inspection I found that the Front Left battery only charged to about 79 volts.

Initially I thought that I had dead cell so I replaced it and it charged up to 100% again, however that was short lived and it soon only charged up to 90% again.

On examination I found the replaced cell was now dead and that on charging all the red LEDs illuminate except one. 

I suspect that the BMS is not charging this cell even though its fuse is intact

Is there a fix for this, as I am finding it hard to source a replacement BMS.

Cheers

 

 

 

 

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It is likely a faulty bms yes. It's contantly bleeding that group (perhaps). 

It's fortunate that you haven't had more than a dead cell. Because when you attempt to ride it or charge it to 90%, it attemps to charge that dead cell, which is very dangerous. 

I have a wheel where the balancing doesn't work. Luckily it isn't draining the cell so I've managed to manually balance it every 6-12 months and it's fine.

To you I suspect you need a new bms. How about buying a faulty pack and try your luck. Alternatively you could try to disable the bleed resistor for that cell group and perhaps balance it manually

However, that will be a compromised pack/wheel that you can't sell/give away.

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Perhaps it's something simple as in the transistor for that grouo that is faulty. Maybe an electrician, or a forum can help you failsearch it, and then possibly you could replace that part.

I don't want to get your hopes up but heck it's worth a try.

In the meantime maybe ride a second wheel so you don't need to stress.

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What would be the consequences of running the Battery pack with only 19 cells instead of the 20, with the none charging cell removed?

 

Apart from less range and power would it be dangerous? would it damage the remaining cells etc?

 

 

 

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36 minutes ago, NastyFartPants said:

What would be the consequences of running the Battery pack with only 19 cells instead of the 20, with the none charging cell removed?

While charging the cells of that pack would get to an overvoltage, which would then cut off charging (as long as that part of a broken BMS works) while the other packs aren’t yet charged to full. Riding range would be shortened because of this discrepancy between the cell voltages. Output power would be decreased on an already weak wheel. Depending on how the wheel reacts to voltage differences, it could enter an error state that would prevent you from riding.

 Don’t even dream of doing something like that. If you have to ask online how a battery modification you invented would work, you clearly don’t have the experience to do any battery mods safely. There are so many things to consider, at every step of the workflow. The most important being how to avoid the cells from bursting into a violent fire.

Check Li-ion or EUC fires on YouTube to see what you’re up against.

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If you want to circumvent the balancing circuit without making any changes to it I think you just need to connect a high value resistor in series between the cell group and the bms. That way the bms can read its voltage but it can't bleed any current out of it.

It is possible to connect two bms' to a single pack. If you attach balance leada you can connect them to a second bms that works and you trust in. 

The original is needed to turn the wheel on.

Edited by alcatraz
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44 minutes ago, alcatraz said:

If you want to circumvent the balancing circuit without making any changes to it I think you just need to connect a high value resistor in series between the cell group and the bms. That way the bms can read its voltage but it can't bleed any current out of it.

Wouldn’t removing the balancing resistor do effectively the same thing? I’d worry about messing up the overvoltage protection if I were to install a series resistor like that.

Though either way would be working with a live high voltage pack without the knowhow how to do it safely. Very risky.

 

42 minutes ago, alcatraz said:

I'm afraid you can't power on the euc with a cell group at 0v. That's something the bms usually checks for.

The GotWay and KS wheels I know about doesn’t check for undervoltage cell groups. They can be used with a 0V cell groups without the rider knowing anything about the issue.

42 minutes ago, alcatraz said:

 I just know that the Inmotion V8 doesn't power on with a group below 3.0v.

Are you certain that it checks for individual cell group voltages, and not just the total voltage of the pack?

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8 hours ago, mrelwood said:

Wouldn’t removing the balancing resistor do effectively the same thing? I’d worry about messing up the overvoltage protection if I were to install a series resistor like that.

Though either way would be working with a live high voltage pack without the knowhow how to do it safely. Very risky.

It's risky sure. What I'm proposing is merely theoretical.

I would only do this as a last resort. Before I'd try to disable the bleed, and see if I can turn on the wheel. First try get another pack.

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