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-   -   Why lipos taking longer to charge now? (http://www.rcuniverse.com/forum/batteries-chargers-84/10963591-why-lipos-taking-longer-charge-now.html)

wildbills rc 02-17-2012 02:25 PM

Why lipos taking longer to charge now?
 
My sky lipos have always taken 60 minutes to fully charge. They are 5000 40c 2 cells. Now all of a sudden they are taking 100-120 minutes to charge. What gives? It seems later in the charge cycle the amps go way down. Usually the batteries charge at a consistant 5 amps. The volts stay high liek they should normaly. What gives? I have a nice tenergy balance charger

guver 02-17-2012 02:33 PM

RE: Why lipos taking longer to charge now?
 
As they wear out the IR goes up and sometimes even the two lead connections increase in resistance as time and use go on. (only if this isn't a balance issue) This is characteristic of a very long CV stage.

An imbalance issue can give certain chargers fits and cause them to slow down , but I suspect that isn't the trouble here because you said the voltage is high.

wildbills rc 02-17-2012 02:46 PM

RE: Why lipos taking longer to charge now?
 

Quote:

ORIGINAL: guver

As they wear out the IR goes up and sometimes even the two lead connections increase in resistance as time and use go on. (only if this isn't a balance issue) This is characteristic of a very long CV stage.

An imbalance issue can give certain chargers fits and cause them to slow down , but I suspect that isn't the trouble here because you said the voltage is high.
they are still very new batteries. Same ocurance with my hexfly lipo. Maybe an issue with the charger? hmmm. They all still charge fully though

bgosselin 02-17-2012 02:48 PM

RE: Why lipos taking longer to charge now?
 
Sounds like the cells may be getting out of balance to the point where the charger has to slow the rate wayyy down to keep any single cell from exceeding 4.2v...

Not sure if your charger has it, but some allow you to look at each cell voltage during the charge cycle. If not (or to double-check) use a meter and measure each cell when the slow down happens.

guver 02-17-2012 03:15 PM

RE: Why lipos taking longer to charge now?
 
A good indication (depending upon how the particular charger works) will be to see at what point the cv is hit.

If the cv is hit very early on then my guess is right. If the cv isn't hit early on (and 1 cell is 4.2) then bgosselin's idea is right. OR we could both be wrong, lol.

Another way to differentiate between the two is to charge without balancing and see if it speeds up a lot.

bgosselin 02-17-2012 03:49 PM

RE: Why lipos taking longer to charge now?
 
Your idea of the high IR would make more sense for older packs, but the OP said these were newer packs where I would hope IR isn't increasing already.

guver 02-17-2012 04:02 PM

RE: Why lipos taking longer to charge now?
 
I should hope not , but some of us can degrade packs in a hurry. ;)

Anything in that series circuit can add to the resistance. I've seen lots of old worn out banana jacks and connectors that might do this.

It does seem that it is occurring with more than one pack. Kinda points to a common item (charger or lead?)

wildbills rc 02-17-2012 05:17 PM

RE: Why lipos taking longer to charge now?
 
Im gonna try to charge but not balance and see what heppens tomorrow. Im also gonna make sure all my connectors are clean. I have been running in water and mud lately

Mikecam 02-17-2012 09:16 PM

RE: Why lipos taking longer to charge now?
 
If you take them down low even once the cells can become way off in balance and so the extra time it takes to charge. Check the separate cell voltages and see if they are out when charging.

guver 02-18-2012 08:27 AM

RE: Why lipos taking longer to charge now?
 

Quote:

ORIGINAL: wildbills rc

Im gonna try to charge but not balance and see what heppens tomorrow. Im also gonna make sure all my connectors are clean. I have been running in water and mud lately

Please pay attention to the balance or max voltage of each cell during the charge if you do a non-balancing test charge. If it is way out of balance then 1 cell may grossly overcharge causing danger. If the pack was balanced before last use it will be in balance even with this non-balanced charge.


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