In article ,
Jeff wrote:

I recently bought a yaesu vx-150. The manual doesnt state how long the
battery should be left on charge. I figure there is a formula to figure this
out. the battery is the fnb-64, which is 7.2 volts and 700 mAh. The wall
charger is 12 volts and 500 mAh. Just querious, thanks for any help.

To be certain, you'd have to actually measure the rate at which the
charger is delivering current. It may be less than 500 mA - that may
be the "nearly short-circuited load" safety current rating rather than
the actual rate of delivery. You could measure this with a
milliammeter and a bit of care, I think.

You can figure that NiCd batteries, if fully discharged, are going to
require a total charge delivery which exceeds their rated capacity by
some amount - the charging process is not 100% efficient. A fairly
common slow-charge regime is a rate of C/10 (that is, one tenth of the
rated capacity), delivered for a period of around 14 hours. In the
case of your radio that would be 70 mA for 14 hours.

If the charger is actually delivering a higher current, you'd divide
that into the 700 mAh capacity to figure the number of hours required
for a 100% charge delivery (e.g. 2 hours at 350 mA), and then add a
finagle factor of maybe 30-40% to compensate for the inherent
inefficiency of the charging process.

A good fast-charger will have a "smart" charge cutoff circuit - it'll
detect the state of full charge (the battery heats up and its terminal
voltage starts to decrease a bit) and turn off the current or switch
to a low trickle-charge rate.

Naturally, if you're starting with a battery which is not fully
discharged, it will take less time to "top it up" than it would
require for a full charge.

The best two bits of advice I can give you, with regard to NiCd
batteries, is:

- Don't run them down *all* of the way. When they start to fade
out - at the first sign that the "battery monster" is chewing down
on your radio's ability to transmit or receive - turn the radio off
and/or switch to another battery pack. Running down a NiCd battery
all the way to zerch is likely to reverse-charge at least one of the
cells and damage it. When the voltage drops to 1 volt per cell
(6 volts in the case of your FNB-64 pack) there's very little
power left in it... unplug and recharge!

- Don't let them toast away on a charger (even a trickle charger) for
days at a time. Recharge them properly and then unplug the radio
from the charger.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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