Parallel Charging and Voltage Difference? - RC Groups
Mar 11, 2011, 09:37 PM
Artillery! King of Battle!
Question

# Parallel Charging and Voltage Difference?

Quick question; what is the acceptable voltage difference for parallel charging between battery packs? The packs are same make, model and capacity.

Thanks

Brill
 Mar 11, 2011, 09:39 PM Registered User My rule is .1 volt per cell. This guarantees that there will be no problem. Mark
 Mar 11, 2011, 09:43 PM Registered User I think 0.05V is acceptable
 Mar 12, 2011, 04:34 AM Registered User If you mean the difference between the packs before you connect them together in parallel for charging I don't really worry about it so long as I'm sure I don't have one empty pack and one full pack . They soon equalise themselves. Steve
 Mar 12, 2011, 05:25 AM JustFlying It is even not a problem connecting a full and empty pack together, only negative point is that you waste one cycle of the full pack, the same as you waste a cycle when you discharge a full pack you did not used at the field with a charger. You can do storage charge / discharge at the same time with a full and empty pack together without charger.
 Mar 12, 2011, 07:40 AM Southern Pride The fact that you can nonnect two LiPoys of greatly difference voltage to gether and not have smoke is one thing but please be advised that initial current in-rush to the lower voltage one can be extreme. https://www.rcgroups.com/forums/show...6#post16290354 How many would chage at such a rate? How much long term damage does ir do? Charles
 Mar 12, 2011, 08:27 AM Registered User Of course the inrush current lasts only for a short time. I don't think anyone has yet worked out how much damage, if any, a very short period of high rate charging will do. It would be interesting to know but it would be a really tricky experiment to conduct, particularly if you wanted accurate and repeatable results. Steve
 Mar 12, 2011, 08:52 AM Registered User I am a noob, but i have read that it is wise to connect the discharge plug first and then the balance plug as the initial rush of current goes through the bigger wires of the discharge plugs and that makes sense to me .
 Mar 12, 2011, 08:55 AM John Foltz If the cells are off much, they should be discharge-balanced before charging any of them.
 Mar 12, 2011, 09:19 AM Southern Pride Balancing discharged LiPolys is not a very good idea,IMO also cells which are completely or worse yet over-discharged should really be charged at a lower rate initially. Charles
 Mar 12, 2011, 01:21 PM Registered User What slipstick says is the same as my findings; as long as one of the packs does not have a shorted cell, one can be fully discharged and the other fully charged and you can still connect them in parallel.
 Mar 12, 2011, 01:38 PM Artillery! King of Battle! Cool! Thanks for all the replies!