Ballancing 18650's. Charged voltage leeway between batteries

[RiverRat]

Hey Im ballancing my 25r's before assembly and after throwing them all in a box and retesting most are from 4.14v- 4.16v but the odd one comes in at 4.13 on the low end and 4.18 on the high. After throwing the 4.13v's back to charge they come out at 4.20v.

How close do they need to be ?

Cheers River

 

[ridethelightning]

cant learn enuf of this stuff.
sory i cant enlighten more..also keen for more info.

 

[RiverRat]

Fwiw im using 2 x xtar w2p chargers and a soshine 4 battery charger which are giving exactly the same slightly varied results.

 

[Nobuo]

I suppose You are not using a BMS, and the charging is done with an individual cell charger. If You want to balance the cells on the high V cut, let them on the charger a pair of hours after the charge is finished. Then all the cells should be on 4.20 exactly during a week or two. Remember that you should use the pack as soon as possible and avoid storing the cells at 100% as much you are able to. anywhere outside 40% is outside the comfort zone for a lithium-ion cell

 

[docnjoj]

You could parallel 10 or 20 of them and do a 1S charge. They would equalize. If these are used cells, let them sit a week off the charger and get rid of the low ones, separate of course.
otherDoc

 

[RiverRat]

I suppose You are not using a BMS, and the charging is done with an individual cell charger. If You want to balance the cells on the high V cut, let them on the charger a pair of hours before the charge is finished. Then all the cells should be on 4.20 exactly during a week or two. Remember that you should use the pack as soon as possible and avoid storing the cells at 100% as much you are able to. anywhere outside 40% is outside the comfort zone for a lithium-ion cell

I will be using a bms . Thanks for the info regarding not letting then sit around with allot of charge in them. I'm building a13p 14s pack so it has taken awhile and they have been sitting around charge for the last week already.

You could parallel 10 or 20 of them and do a 1S charge. They would equalize. If these are used cells, let them sit a week off the charger and get rid of the low ones, separate of course.
otherDoc

Sounds good and this will would allow me to get on with it and weld them up now into parallels straight away. Batteries are new btw. Cheers.

Im still wondering though how crucial it is getting the voltages aligned to the exact spec....

 

[Ypedal]

1st... don't stress over leaving cells at full charge voltage..

2nd . doc is right, parallel as many cells as you can and charge them up to 4.20v .. then remove the parallel connection and let them sit overnight or a couple days.. good healthy, quality cells, should all be above 4.17v.. anything below 4.14v should be set aside.

As far as hooking them up with slightly different voltages, no worries as long as they are all 4.1x volts and up, there will be very little current flow and should not create any heat at all..

Now if you mess up and slip a 3.5v cell with a 4.1v.... expect something a bit more .. uhm.. well you get the idea. :wink:

 

[RiverRat]

1st... don't stress over leaving cells at full charge voltage..

2nd . doc is right, parallel as many cells as you can and charge them up to 4.20v .. then remove the parallel connection and let them sit overnight or a couple days.. good healthy, quality cells, should all be above 4.17v.. anything below 4.14v should be set aside.

As far as hooking them up with slightly different voltages, no worries as long as they are all 4.1x volts and up, there will be very little current flow and should not create any heat at all..

Now if you mess up and slip a 3.5v cell with a 4.1v.... expect something a bit more .. uhm.. well you get the idea. :wink:

Brilliant thank you!