Li-ion chargiing failures

[Grow Pattern]

I have had a few (4) of my 2000 mAh Li-ions fail in the last couple of months.

The failure only occurs during charging and when the outside temperature is very hot. 

I was not sure what it was at first. I did read the warnings on some cell phone batteries that I use as set-up packs, and it says do not get hotter than 140F. Yesterday I actually caused it to happen at the field (and when I was taking notice.)

I had a spare 2000 pack in my van, left over from my Nat's trip. It was on the tailgate area and caught some sun. It was showing 8.12 V so I  plugged it in to charge it up. The meter did not move, so I tested the voltage again. No volts. My laser-temp showed 143 F. After a teardown I found one cell as good as open with .05V. 

Based on other feedback I believe that what happens is the cell blows a sort-of-fuse internally if hot (140+ F) and a charge is applied. Could be a safety feature for all that  know?

It does not (or has not so far) failed if current is drained when this hot. I have one in a Radio South ni-starter that get warm and is mistreated , but does not fail.

In practical terms what happens to you is that when you switch on there is no juice. So no juice, no fly, no plane loss....

Please regard this as a "heads-up' to not charge your Li-ions if they are hot. Wait until they cool down.

Regards,

Eric.

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