Li Poly battery resuscitated

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Wan - 24 Jul 2004 00:42 GMT

My friend and I were out at the field when he tried to turn on his
electric motor, the battery gave no response. Checking, the 3S Kokam
had only about 2.0 V in it.

We had been admonished never run Li Polies below 9 volts for a 3S
pack. Then the 2 V becomes about 0.7 V per cell. Way too low. He
remembered that in haste because of a threatening thundershower, he
neglected to turn off the battery and remove it from his airplane.

We tried to recharge the battery out on his open patio deck with a
long extension cord. At first the Triton charger had the error
warnings 2 - 3 times. We persisted and the battery began to come up to
voltage slowly.
Finally it was brought up to 12.66 V.

Took the plane out the next day for a couple of 12 minute test
flights, battery OK. Remember, the battery was drained over a period
of 2 days. Could this recovery happen if the battery was drained to
such a level during flight?

Hope I'm not being long winded,
Wan

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Bill Sheppard - 24 Jul 2004 02:13 GMT

One question, Wan. You say the resusitated battery gives 12 minute
flights.
How long was the typical run time before the 'incident'?
I have a 2 cell pack that i inadvertantly ran down to
2.35V per cell, and now the pack is hosed, and gives roughly half the
run time it did before.

Bill(oc)

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Wan - 24 Jul 2004 09:09 GMT

> One question, Wan. You say the resusitated battery gives 12 minute
> flights.
[quoted text clipped - 4 lines]
>
> Bill(oc)

Bill,

My friend's battery typically gave three 10 minute flights before the
failure occurred. When he flew the plane for two 12 minute flights, it
checked out to still have about 11.44 V, enough for another flight. We
left because of gusty winds.

I am not an expert on Li Poly batteries, but perhaps your battery was
run down during flight, a faster discharge, instead of a slow drain?
That was my question. Would the recovery happen if the battery was
overdischarged during flight?

Wan

Wan

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Ash Wyllie - 24 Jul 2004 03:39 GMT

Wan opined

>My friend and I were out at the field when he tried to turn on his
>electric motor, the battery gave no response. Checking, the 3S Kokam
>had only about 2.0 V in it.

>We had been admonished never run Li Polies below 9 volts for a 3S
>pack. Then the 2 V becomes about 0.7 V per cell. Way too low. He
>remembered that in haste because of a threatening thundershower, he
>neglected to turn off the battery and remove it from his airplane.

>We tried to recharge the battery out on his open patio deck with a
>long extension cord. At first the Triton charger had the error
>warnings 2 - 3 times. We persisted and the battery began to come up to
>voltage slowly.
>Finally it was brought up to 12.66 V.

>Took the plane out the next day for a couple of 12 minute test
>flights, battery OK. Remember, the battery was drained over a period
>of 2 days. Could this recovery happen if the battery was drained to
>such a level during flight?

I've had a simular experience. I lost the same battery (in different
airplanes) with a Castle Creations ESC up some trees. The Planes took a couple
of days to get down. After recharging the battery is still good.

Maybe the discharge rate is important.

-ash
Cthulhu for President!
Why vote for a lesser evil?

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Wan - 25 Jul 2004 02:07 GMT

> Wan opined
>
[quoted text clipped - 27 lines]
> Cthulhu for President!
> Why vote for a lesser evil?

Ash, I'm almost certain the rate of discharge has something to do
with the battery's recovery after it was drained below the recommended
level. Because my friend took his plane for a few flights today,
totalling about 25 minutes on the same battery.

Wan

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Model Forum / Radio Controlled / Air Models / July 2004

Li Poly battery resuscitated