[aprssig] NiCd Lessons relearned

Robert Bruninga bruninga at usna.edu
Fri Jul 14 17:06:36 EDT 2017

Lesson relearned on NiCd charging:  Several years ago I made three 12v
batteries from D cell NiCd’s.

They have been a huge disappointment.  They are only used once or twice a
year on critical field work and always fail far earlier than estimates.
But I always just charge them the night before with a fixed voltage charge
of 14 volts since I most often forget about batteries I put on charge and
end up ruining most of them.  Charging at fixed voltage is safe…

For the AT Golden Packet event tomorrow, last night I left them on my usual
14 volt overnight charge and they were “fully charged” by morning, only
drawing a 50 mAh each in the morning at 14 volts..

Put them on a battery analyzer and their capacities came in at 10%, 8% and
3%.  Then the battery analyzer quick charged them at 1C rate for 1 hour
with them getting up to 16 or 18 volts, then a 4 hour equalization charge
of 0.1C or 400 mA.

Then it retested them and got 75%, 65% and 85% of rated capacity!

So, Apparently little-used NiCd’s are not going to get a good charge from a
FIXED voltage charge!

Wish I had time to cycle them two more times.  On batteries at work we see
huge recoveries from little used NiCd’s when “rejuvenated” which is the 3
cycles of charge and discharge I started with above.

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