warming up lipos

[boatinjoe]

what the scientific reason, for this? what is proper temp. will voltage increase with rise in temp

[m4a1usr]

what the scientific reason, for this? what is proper temp. will voltage increase with rise in temp

The technical reason behind using warmed lipos is related to state of the electro chemical conditions inside the battery. The chemistry of a battery requires a medium that provides the ion transport mechanism between the positive and negative electrodes of a cell. When cold, this action is slower. Warm the reaction and it speeds up. So the short answer is warmer cells carry the process somewhat faster. The electrolyte is the media for which ion transfer occurs. Warming it increases eff between the plates.

There is a temp limit or ceiling with lipo batteries. Its due to the mechanical or structure properties of the design. Plate seperation/ degradation occurs when the temp gets too high. Thats not good. Advertised operational temps are basicly 0 to 60 degrees C. You should use prudent judgment and use an upper limit no higher than 140F. Remember that 130F degrees is the temperature threshold where you do not want to hold that item. I.E. where you drop the SOB to the ground because it feels HOT!

With all of that being said, the reason we like our lipos warmed is the internal IR, which effects the electron movement, becomes lower as the internal temp goes up. But then there is the wall or upper limit we dont want to cause damage to our packs.

Does all this make sense or did I go too far?


John

[Fluid]

It used to be de rigeur to heat LiPos before running them for two reasons. Both had to do with the decreased internal resistance of the packs as the temperature increased. It was common to see the boat's speed increase on the course as the packs heated up, so there was a power increase. Second was protecting the cells from over-discharge at high amp rates. Cold packs with high internal resistance combined with high discharge rates resulted in many packs giving up after a short life.

Today I'm no so certain this is as necessary with the newer cell chemistry. Data logging with modern packs (45C) does not show a voltage increase as the packs heat up, just the expected continuous drop in voltage during the run. (This is with packs starting at 90-100F, not with cold 60-70F packs.)

Regardless, I 'believe' it is best to start with your packs at least 80F, and 100F may be better. Anyone with data logging info is welcome to comment.



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[boatinjoe]

I asked for technical, and got it. very good info from both replies, thankyou