[TenTec] emergency back up power

[Dr. Gerald N. Johnson]

On Sun, 2007-03-04 at 17:15 -0800, Paul wrote:
> Gary,
> What are the total amps your batteries supply? Is there any 
> "discount" sources you know about? We have a lot of golf courses 
> where I live. Maybe I can talk to the golf course guys and get a deal 
> if they replace batteries every year - whether they need it or not. I 
> guess the total amps of the batteries will dictate the size of the 
> charger. But I was wondering about that. I had two batteries on a 
> sailboat once and I recall special electronics were needed to make 
> sure both got fully charged.
> Thank you and 73,
> Paul
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Old batteries are no bargain. I haven't detected that golf course
batteries are changed before they fail completely.

6 volt batteries in series sometimes benefit from an "equalizing" charge
where you overcharge the pair to make sure all 6 cells are fully
charged. This is more important when the two batteries haven't had the
same history of loads and charges. That's also useful in a 12 volt
battery about as often because cells don't always maintin the same
capacity as they age and chunks of active material fall off the plates.

Charge current times charge time has to be greater than load current
times load time. This is complicated by the fact that the proper float
voltage charger leads to declining charge current as the battery
charges. There are DC watthour meters ($200 and up) that keep track of
charging and loads and toss in a battery charging efficiency factor.

When buying batteries its worth the effort to slip around to the back of
the display rack and pick those with the most recent manufacture date.
Batteries that have set on the shelf without being charged for 3 or 6
months are no bargain at any price.

-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer