nuckolls.bob(at)aeroelect Guest
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Posted: Sat Jan 25, 2020 9:38 am Post subject: To charge or not-to-charge, that is the question |
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At 11:10 AM 1/25/2020, you wrote:
Quote: | Do we have a consensus on how charged a battery must be before starting? Is it ok to hand start the engine and charge a very discharged battery with the alternator or is there some point at which a charger must be used? As long as there is enough power left to close the master relay and get the alternator going I've used the engine to charge the battery rather than a charger. |
The IDEAL answer is, don't use the ship's
power sources to charge a depleted battery.
This is echoed in the AFM for virtually
all of the TC aircraft I've had contact
with. Not that it's a guaranteed formula
for system compromise . . . it's the SAFE
formula to avoid system compromise.
The REAL answer is, probably okay
but with reservations. Depending on the SIZE
of battery, SIZE of the alternator and battery
CONDITION, the battery recharge rate MIGHT be
hazardous to battery health. In extreme cases . . .
catastrophic. In the earliest days of
wet ni-cad batteries, numerous incidences
of thermal runaway culminating in a battery
fire were experienced. This condition prompted
the 'band-aid' battery temperature monitor
mandate in some aircraft
[img]cid:.0[/img]
The PRACTICAL answer is, don't do it unless
you've got no other options. I've brought
airplanes home with crapped electrical
systems in what I call the J-3 mode. If
you're off home field and have no way
to gently charge the battery, then consider
propping the engine and coming home dark.
You DO know how to do that . . . right?
Consider charging the battery through
el-cheepo jumper cables from a car. The
$10 cable sets from Dollar General are
small gage wire . . . generally 8 or
even 10AWG. This small wire will limit
recharge rate. Leave connected to the
car with engine running for 10 minutes
or so, THEN start ship's engine and let
the alternator take over.
There is no one-size-fits-all, simple
answer beyond don't do it. But with some
careful implementation and skill, it
can be done with little if any risk.
Bob . . .
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