[aprssig] NiCd Lessons relearned

[Glenn Little WB4UIV]

Nicads are current charged.
SLA are voltage charged.

73
Glenn
WB4UIV

On 7/14/2017 5:06 PM, Robert Bruninga 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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Glenn Little                ARRL Technical Specialist   QCWA  LM 28417
Amateur Callsign:  WB4UIV            wb4uiv at arrl.net    AMSAT LM 2178
QTH:  Goose Creek, SC USA (EM92xx)  USSVI LM   NRA LM   SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
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