Battery check up

[Milou]

Hi: I have this 48V 15H lithium battery pack I would like to take apart to check on individual cells (see attached images for explanation). The unit is suppose to be 48V but it only reads 32V and will not charge beyond. Each cell look like they are flat??? In any case, given the attached images is it OK to cut out the blue covering to expose the cells? Anything special I should be careful about (besides shorting out)? What are the wires about?

Red = Positive
Light blue = Negative
Yellow & Black = ???

I imagine the square gray gizmo is the BMS? I only have a multimeter for checking. Would I need another special tool? Thanks in advance for response. Regards JJ

 

[dnmun]

you do not have to take the plastic sleeve off. those black connectors are on the sense wire cable and each wire has an adjacent cell positive terminal attached so you can measure the individual cell voltages between adjacent pins in the plug. usually the bottom or negative of #1 is the big black wire to the battery from the BMS and you can stick the point of the voltmeter probe through the insulation to make contact with it inside to measure the voltage on #1.

 

[Milou]

Hi Thanks for the reply. I need to get a better idea of what all this stuff is about. Is there a thread or web page that can explain the wires from battery pack to BMS to plug? A diagram, schematic or drawing would help me to visualize how this is hooked up? Thanks JJ

 

[dogman dan]

Here is something I wrote on another website. Shows one method for checking voltages of each cell. If your bms is not sealed up in shrink, then you can check voltages right on the bms.

http://www.electricbike.com/lifepo4-battery/

 

[Milou]

Hi: You have been a "god sent". Thanks so much. Your documentation you wrote was exactly what I needed. Very well written.

I did the checking and out of 13 cells I found one really bad. As follows:

one at 0.8V
one at 3.4V
nine at 3.6V
two at 3.8V

The strange thing about all of this is that there are 13 cells. I would think it would be even number?

The next thing strange is the sensing connectors. From the battery the connection is male from a female housing (see attached)??? This is strange as the power comes from the battery and can be shorted out easily, even with the housing protecting them as a group. It made the testing difficult not to touch the next pins.

Knowing myself, I am the kind of guy who will change just one cell. Although, I am not an expert I follow very well. Any suggestion? Thanks JJ

 

[Ypedal]

Using a short piece of electrical tape, cover your multimeter probes to form a tube that protects and prevents shorts while you check the pins.. :wink:

 

[dnmun]

to open it. use scissors so you can pull away from the inside while cutting.

first cut to the corners, diagonally on the end where the wires come out.

then cut along the centerline on the side where the sense wires go up into the sleeve and watch the tips of the scissors so you don't hook any of the sense wires as you cut, pulling the plastic sleeve up as you go forward to make the scissors clear the insides.
cut from the other end when you get halfway, save the sleeve so you can tape the pack back into it later.

 

[Milou]

Using a short piece of electrical tape, cover your multimeter probes to form a tube that protects and prevents shorts while you check the pins.. :wink:

Thanks for the suggestion. Great idea.

to open it. use scissors so you can pull away from the inside while cutting.

first cut to the corners, diagonally on the end where the wires come out.

then cut along the centerline on the side where the sense wires go up into the sleeve and watch the tips of the scissors so you don't hook any of the sense wires as you cut, pulling the plastic sleeve up as you go forward to make the scissors clear the insides.
cut from the other end when you get halfway, save the sleeve so you can tape the pack back into it later.

I do not visualize it but, I will try the best I can. Thanks a lot guys for the help. Regards JJ

 

[Milou]

I need some information regarding the changing of one battery cell from my pack. See attached images for information. I tried to google the info from the battery without luck.

1. Where do I get one?
2. Does it have to be the exact same (obviously 3.2V 15Ah)?
3. Should I keep the other good cells in charge?

Thanks. Regards JJ