How can I isolate this cell?

ebike11

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Hi guys
I had a question about charging a single cell.
I have a 20 cell pack divided into 4 packs of 5 cells.
I just got a new IMAX B6 and in one pack the cell that Id like to charge separately is the second cell in the JST plug...when i touch that cell positive with pack negative, I am getting a reading of about 7.5V...the cell before it is reading 4.2V and the low cell is reading 3.3V.
If the combined voltage is 7.5V then how can I isolate the cell so that I dont charge the cell before it?
Id rather not take apart the pack because its all assembled.
Thx in advance!
 
ebike11 said:
when i touch that cell positive with pack negative,
If you touch any cell's positive with the pack's negative, you've just shorted across that cell and all the cells more negative than it, which is a great way to start a fire. Don't do that.

how can I isolate the cell so that I dont charge the cell before it
Exactly like charging any battery of any kind: connect your charger's positive to the cell's positive, and the charger's negative to the cell's negative.

If you do not have external access to those points, you have to open up the pack to do it.
 
amberwolf said:
ebike11 said:
when i touch that cell positive with pack negative,
If you touch any cell's positive with the pack's negative, you've just shorted across that cell and all the cells more negative than it, which is a great way to start a fire. Don't do that.

how can I isolate the cell so that I dont charge the cell before it
Exactly like charging any battery of any kind: connect your charger's positive to the cell's positive, and the charger's negative to the cell's negative.

If you do not have external access to those points, you have to open up the pack to do it.

Ah sorry..i meant the negative on the JST plug of that 5 cell pack..not main lead negative
 
As you do a series string, say 5 cell, the negative of each cell is the positive of the next one.

So cell one has its own negative, the main negative. Cell ones positive connects to cell 2's negative terminal. and so on.

So if you want to check the voltage of cell 4 for example, you attach to the cell 4 positive, and the cell 3 positive, which is also cell 4's negative.
I think you read two cells voltage when you looked.

If you have jst balance plugs, you connect to any adjacent two pins, and that will be just one cell. So again, if you have a 5 cell jst, it has six female contacts. contact one is negative, contact six positive. Cell four would be contacts 4 and 5, with 5 the cells positive.

If no plugs, you have to open it up, if you have plugs to a bms, pin one may not be the negative. the pin one negative might be the main pack negative to the bms.. It just depends on the bms, how it wires.
 
ebike11 said:
amberwolf said:
ebike11 said:
when i touch that cell positive with pack negative,
If you touch any cell's positive with the pack's negative, you've just shorted across that cell and all the cells more negative than it, which is a great way to start a fire. Don't do that.

Ah sorry..i meant the negative on the JST plug of that 5 cell pack..not main lead negative

Doesn't matter--exactly the same thing applies to every cell other than the most negative cell on the connector.

You cannot connect any part of any cell to any other cell, across another cell, or you will damage things, cause fires, etc.
 
amberwolf said:
ebike11 said:
amberwolf said:
ebike11 said:
when i touch that cell positive with pack negative,
If you touch any cell's positive with the pack's negative, you've just shorted across that cell and all the cells more negative than it, which is a great way to start a fire. Don't do that.

Ah sorry..i meant the negative on the JST plug of that 5 cell pack..not main lead negative

Doesn't matter--exactly the same thing applies to every cell other than the most negative cell on the connector.

You cannot connect any part of any cell to any other cell, across another cell, or you will damage things, cause fires, etc.

Oh sorry again..i meant when i touched the negative of the jst and positive of the jst with the multimeter, i didnt touch positive and negative together
 
Find a single cell charger or a phone charger with a 4.2 V output at 1 amp or less and connect it to the JST connector pins corresponding to the low cell. Check and double check the polarity before hooking it up. It may take a while but it will bring the low group up. When it reaches the level of the other groups stop and let it rest for a while then remeasure.
 
Hwy89 said:
Find a single cell charger or a phone charger with a 4.2 V output at 1 amp or less and connect it to the JST connector pins corresponding to the low cell. Check and double check the polarity before hooking it up. It may take a while but it will bring the low group up. When it reaches the level of the other groups stop and let it rest for a while then remeasure.

But Id like to learn and get experience with the B6 since its first balancer
 
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