Hot weather charging

[WAM]

Thought I'd throw this out here to see if anyone has any concerns I haven't thought of.

Very hot here, over 100 every day. This has always been battery puff season. In an attempt to make life easier for my Lipos, I'm trying a new charging program. Instead of setting the charger to Lipo, I'm setting it to LiIo which I believe is lithium ion. Nothing seems to be different except the full charge voltage is now 4.1 volts per cell vs the normal 4.2. (Lithium Ion cells are nominal 3.6V vs Lithium Polymer at 3.7V)

My batteries are balancing nicely at the 4.1V and it takes a little voltage stress off the battery. It will cut my capacity a tad, but I have extra.

All other settings, time-outs, charge rates and such remain unchanged. Anyone see any problems here? Keep in mind, this isn't just theory -- I've been doing this and have seen nothing surprising or alarming.

[ickabob]

Sounds like I'm about to learn something here. Thanks for posting up.

[EddieO]

Hotter cells produce more voltage and lower IR. In racing, they have banned heating the cells for safety issues, as people were taking it to the extreme heating them up a lot. The extra heat takes life off the cells, but is worth it for the racers. They charge at 20+ amps too.

Losing a few cycles is worth the lower IR and having full voltage in my opinion.

Later EddieO

[WAM]

Yeah but, at your suggestion I recently stepped up to 4S. So I have more voltage on tap to start with. Again, a tad less probably won't be noticeable.

[EddieO]

Well, it is less run time too....not fully charging the pack.

Later EddieO

[KJ10]

Do you charge in a bucket of sand? If so, stick your hand about 4-6" down in that sand on a hot day and feel the temperature. That's where I charge my batteries. Keeps them nice and cool. Make sure to keep the sand dry, of course. Out of direct sunlight helps, too.

[WAM]

I'm liking this more and more. I just ran an 850 4S to LVC and on recharge it took 767mah. It used to take 800 to 825 so the lower max voltage hasn't reduced capacity too severely.

A typical 10 gate course takes 270 mah with this car, so I have huge margins. I could actually use a smaller battery, but small 4S lipo's seem hard to come by. At least with this largish battery and 45/90C, I get a lot of pop. Gotta feed that Axle-Buster, right Eddie?




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[Dialed]

Originally Posted by EddieO

Hotter cells produce more voltage and lower IR. In racing, they have banned heating the cells for safety issues, as people were taking it to the extreme heating them up a lot. The extra heat takes life off the cells, but is worth it for the racers. They charge at 20+ amps too.

Losing a few cycles is worth the lower IR and having full voltage in my opinion.

Later EddieO

Bingo we have been warming our pack for years in stock buggy.

[el_Fernando]

Man I left 2 big ol' 3s 5000 mah lipos in my car (temps here on the Yay Area are 90 plus) and I forgot about em'. Puffed up like a bag of popcorn and I had to toss them. Sucks.

[Olle P]

Originally Posted by WAM

... the lower max voltage hasn't reduced capacity too severely.

Of course not. At 4.1V the charge level is about 90% (in room temperature).
Charging it to only 4.1V instead of 4.2V also typically doubles the number of cycles you can use the battery.

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