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device to protect from draining a 12 volt battery
On 12 Dec 2003 23:57:13 -0800, wrote:
(Larry W4CSC) wrote in message ...
You're not going to run the car battery down charging the cellphone 24
hours a day,
Hello Larry.
Actually looking to maintain one of those portable power
supplies/jumper boxes with my alternator system by feeding it 12 v as
I run.v I also charge 8 nimh batteries used by my radio sometimes too.
The gelcell power supply you can simply hook up in parallel with your
other battery ONCE YOU GET IT STARTED and it will charge it fine. The
gelcell will only charge at its own pace from a voltage regulated
alternator, just like your car battery does. If you're using an
outboard, it doesn't have much ampere capacity, anyway. I don't know
who propagates this BS about lead-acid gelcells and special chargers,
but I'm sure it's from sales and manufacturing...)c
I use a 2.2AH gelcell in my good-working old analog cellular bagphone,
an $11 generic gelcell from Batteries Plus. I charge it with one of
those Shumacher SE-1-12S 1.5A, automatic shutoff 6-sided black boat
battery maintainers that cuts itself off when the battery reaches
14.2V and turns itself back on at around 13.3V. The red CHARGED LED
is blinking away on the charged gelcell on my desk, here, as the phone
uses some current on standby. It's a fantastic charger for these
small gelcells. If you put an ammeter in series, it will charge the
2.2AH gelcell about 800 ma that tapers off to 600ma before the voltage
sensor in the charger cuts off the juice. After that, it simply
pulses to keep the charge up. As the gelcell gets old and its
capacity drops from lack of electrolyte gel, the charger starts
pulsing faster and faster, which lets me know when I need to replace
the old gelcell.
In my work stepvan and cars, I have a matching connection with a
simple 2.5A silicon diode that allows charging current IN to the
gelcell, but doesn't allow the car to draw current out as the diode is
reverse biased (just put the banded end of the diode towards the plus
terminal on the battery in the positive lead to the car). The car
will charge the little gelcell in about an hour from when the phone
starts beeping to signal low battery voltage.
I've been doing this for years. Works great.
The NiMH batteries require a special charger to taper their charge
rate. The deal here is to find a NiMH/Ni-Cd charger that uses
12-15VDC to power it. Look at chargers that have wall bricks and DC
plugs the wall brick plugs into. Read the voltage the wall brick puts
out and buy the one that runs on a 12V brick. Then, just buy a DC
cord from Radio Shack that allows you to plug the charger into the
cigarette lighter socket in your car/boat/truck. The charger will
handle the charging pulses to the NiMH cells, but from your car
battery, not the wall brick. Charging underway, whether your boat's
running or not, by the way! Works just as good docked.
Larry W4CSC
NNNN
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