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[aprssig] backup pwr systems

Tad Burnett tburnett at vermontel.net
Sun Dec 10 04:38:20 UTC 2006


The secret is to not let the battery voltage go above 14.2 volts...
13.8 will not fully charge a battery so you do need to charge up to 14.2...
I found that I could do this with an old unregulated charger with
110 volt light bulbs wired is series with the 110 v primary of the 
charger...
socket the bulbs so you can easily change them to find the right ones
to match your average load.. Use lamp sockets with a built in switch and
you can can switch them in and out if you are doing extra TX for a while...
You need a meter that you can easily see 1/10 th volt in the area of 13.8
to 14.2....
You can do that with a 1 mil amp meter and a 12 volt zener and some 
resistance
in series across the battery and then calibrate the face with a good 
digital....

I ran a BBS with an old lap top with no internal battery in northern Vermont
where the power dropped out quit often and the battery lasted for years and
was always charge well enough to keep the laptop and radio going for about
10 hours before I had to jumper it to the car for a while to charge it 
back up...

I don't know that I ever saved any life or anything at all but it is 
kind of fun
to have a packet station running just to see who else is still running 
too...

Tad N1QAG
 

Dale Blanchard wrote:

> A.J. Farmer (AJ3U) wrote:
>
>> Just some food for thought, if you have the battery hooked up to a
>> load while you are charging it, this prevents even a "smart" charger
>> from properly determining the state of the battery and that is why it
>> boils over the battery.  It is not a problem with the charger - the
>> charger is designed to charge a battery under little or no load.
>> _____________
>
> I have a Marine charger that is designed to work with light loads or 
> no loads.
> That is what the book says and why.
> I have been using it in my Ham station with some radios on 24/7.
> Keeps up OK. But it is a $150.00 charger.
> It is difficult to find a proper charger due to the snake oil marketing.
> If a company does not publish full specs. I will not buy one.
> That is why I do not use a  Deltran Battery Tender.
> They publish the charge curves, but do not list the voltages.
>
> A cheap charger normally has wide ranging manufacturing tolerence.
> Some smart chargers are reverse engineered in China and do not meet 
> the origional makers specs.
> Dale
>
>
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