[aprssig] NiCd Lessons relearned

[Gregg Wonderly]

The trickle charge is what allows them to recover.  Leave them on the charger at .1C for an extended period of time to help the cell stabilize at a full charge.  In a 12v pack, a small solar cell and a solar voltage controller can get you a pretty good trickle to pump as much charge in as possible.

Gregg

Sent from my iPhone

> On Jul 14, 2017, at 4:06 PM, Robert Bruninga <bruninga at usna.edu> wrote:
> 
> 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.
>  
> Bob
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