battery charge

[Deleted member 4366]

OK, You now have to open the case, Remove the top (4 screws) and let it dangle while you look at the cell-pack. You need to locate the Multi-pin connector that joins the cell-pack to the BMS. Sometimes, it's there staring you in the face. Other times, its covered by heat-shrink. If you cut the heat-shrink in the four corners, you can peel it back. underneath is often a a square of GRP or cardboard stuck to the top of the BMS with double sided tape. The bond can be very strong so you might need some force to lever it off. Just be careful if you use a metal lever not to touch the BMS PCB to cause a short. Now the BMS should be exposed. It might be a PCB or a box.
If it's too far down to get access, you have to slide up the whole cell-pack, which means that you have to unscrew the bottom piece. Then you turn it sideways on, stand the pack on it and pull the case down. it should push the pack up through the case. you only need to move it an inch or so. Now you should be able unplug the 10, 11 or 12 pin connector and measure the individual cell voltages. Put your voltmeter probe on one end of the connector, and work your other probe along each position of the connector until you have 10 readings. They should increase in sreps of approximately 4v, i,e, 0v, 4v, 8v,......, 39.1v.

Please post the results here.

If you have any problems, or it doesn't work out like above. Please post a photo of where your problem is.

 

[robdon]

is it attached to a ribbon type cable, if it is it has a type of steel plate thing screwed to it , similar to the brass studs you fix a motherboard to a computer case, can1t see any where to test yet .the ribbon type cable has,1 red wire, 9 white wires, and one black wire, if I pulled it off, it might be hard to get back on
ROB

 

[Deleted member 4366]

Photos please!

 

[robdon]

Photos please!

 

[robdon]

I will post a photo tomorrow, going to bed, I do not think I should do this when I am tired.
thank you for all your help
ROB

 

[robdon]

took ages to get a photo, here it is
ROB

 

[Deleted member 4366]

That's easy then. Unplug it and measure the voltages. What's the problem?

BTW. You know what you have because it's there in front of you. We can only know from the photos you show. All we can see from that photo is a connector with a ribbon cable attached. The rest is a blur. Please think about that when you show more photos. There's no limit to how many photos you can put in a post. Try taking photos from different angles and distances so that we get the whole picture as if we were dismantling the battery. You don't have to go nuts, but until now, it's been like those puzzles where they show you half of a car tail-light and you have to guess what car it is.

 

[robdon]

do I measure on the plug or on the BMS, and do I start with the negative prong on the black wire or on the red wire.
ROB

 

[robdon]

tried all combinations cannot get any readings multi meter set to DC 200 v
tried negative on black to start then to red , then positive to red then black,
I must be doing something wrong
ROB

 

[Deleted member 4366]

On one side of the connector on the ribbon cable, you should see some littl

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e slots with shiny metal showing through. That's the best place to measure. You need points on your probes to get in the small slots. Start with your black probe on the black end. Keep it there while you move your red probe to each of the other positions. Be careful not to let your probes touch each other at position one. No harm will come, but you'll see sparks.

Did you have your meter set to AC or DC?

 

[robdon]

I have been measuring on the BMS not the ribbon cable , meter set to DC 200v, I have just changed the fuse although that was ok.
will try again
ROB

 

[robdon]

here are the measurements 1= 3.8v 2=7.6v 3=11.3v 4=15.0v 5=19.1v 6=23.2v 7=27.2v 8=31.1v 9=34.9v 10=39.0v
had to take my time as meter was fluctuating
ROB

 

[Deleted member 4366]

It's out of balance. When cell numbers 5 and 6 are charged to 4.1v, the BMS will shut off charging. Cells 1 and 2 have only reached 3.8v, so the capacity of your battery is compromised until you sort it. You could try leaving it on charge for a long time to see if it improves. If that doesn't solve it, more surgery will be necessary to determine which type of cells you have and to determine the cause of the non-balance.

 

[robdon]

I will try that see what happens ,thing is battery stays on green, so its not charging or is it.
ROB

 

[Alan Quay]

In the past, I have used a small load to get the cells down to the same voltage, and balance them. I found that a car rear lamp bulb (21w ish at 12v) will draw about 0.5 amps at 4v.

You would need to connect it up and keep a very careful eye on the voltage, and it may take some time (poss a couple of hours), but you should be able to bring the voltage of the high cells down, then put it back on charge as normal.

If, like me you are impatient, you could always use a few in parallel.

 

[Deleted member 4366]

You won't be able to charge the battery until the 4.1v cells are drained to a lower value. Although the green light is on, the charger still holds it's 42v, which can allow some balancing to take place with some BMSs. If that doesn't work you have to balance manually by draining down the high cells or charging up the low ones. Still the question remains though: Why is it out of balance?

 

[robdon]

I will leave it on charge for a few hours see what happens, bye the way the battery LED`s are now showing 3 lit , before only 2
ROB

 

[Deleted member 4366]

It'll take a lot longer than a few hours. Leave it on over-night to see what happens, but as a precaution, it might be best to do it where it can't set fire to your house.

 

[amigafan2003]

A friends "chinese special" battery took a full 36hrs to balance properly on it's first charge.

 

[NZgeek]

Thread Hijack: Does anyone (d8veh?) know if the BMS in my Golden Motor 36V 12AH aluminium cased LiFePO4 battery is likely to allow this type of balancing by leaving it on for long periods??? Probably worth doing now and then, isn't it?