How soon can I charge my Lipo batts?
 

Hi, I am trying a new setting for my truggy. But the race has very short turn about time.

I only have 2 packs of 4s Lipo & I have 3 finals to run. Can I charge the Lipo immediately after the first final without cooling down?

After each 10min run the batt is About 50degree.

You have to let it cool down to at least room temperature prior to charging them. At least that's what I do :whistle:.

Is there any reason y? Can I use a fan to cool it?

A fan would be fine to cool it, only problem with that is the inside might still be warm, while the outside feels room temp. I've never really waited to throw them back on the charger and haven't had any adverse effects. You should be fine, but do it at your own risk for sure. With LiPos though, stuff like that isn't that big a deal like it use to be with NiMH and even NiCads.

So it's safe?

I do it all the time. As long as the lipos are a safe temp, under 140*F, and you don't try a fast charge they still cool down while charging. If you are going to try a 2C or higher charge rate I would mnitor the battery temp while charging. As long as it is still cooling while charging I wouldn't worry

Personally, if the lipos are getting too warm where pre-charge cooling is even being considered, I would look at either new packs with lower IR, or raising the LVC point (lipos get almost exponentially hotter at the very end of the cycle).

At the end of a run my packs are generally 115-120*F, I throw them right on the charger at just above a 1C charge rate and by the end of the charge they are cooled down to ambient temp

Brian, do you have any other info on this? (lipos get almost exponentially hotter at the very end of the cycle)

In otherwords it would not be a straight angled line if the temp were graphed?
Or to put it another way: run the same current for 70-80% of the discharge , and then allow a complete cool-down. Then continue the rest of the discharge and at the end of cycle the temp may sky-rocket?

Hopefully I am understanding properly what you are saying.

I have a 12v Power supply hooked up to 2 120mm fans to cool everything down :) and i charge right out of the car.