[TenTec] emergency back up power

[Eric F. Richards]

At 12:20 AM 3/5/2007 -0500, Gary Hoffman wrote:
>Paul,
>
>My array of batteries can provide about 1500 amp hours, provided that the
>discharge rate is kept reasonable.
>
>No discount sources that I know of.  That's because most batteries that have
>seen use have been handled so poorly that they have been significantly
>impaired.

May I throw in a contrary opinion?

I'm running on 800 AH (24 VDC) of hospital pulls.  They saw one year of
service and were yanked.  80 AH gel-cells.

The inverter is an Exeltech XP-1100 (1.1 kVA) -- too small for a 
legal-limit amp, but a fine sine wave inverter with less than 2% THD.  A 
battery balancer lets me pull 12 volts directly for the various radios that 
use it.  A West Mountain Radio RigRunner distributes the 12 V through 
Anderson PowerPoles.

It goes without saying that I fuse the crap out of everything.  The 
inverter has a separate 200 A Class-T fuse.

The XP series from Exeltech is their "low cost" inverter line, and the 1100 
is as big as that series gets.  If you want more power, you need a rack 
mount module with 1 kVA modules stacked with controllers,  with the option 
of redundant power, etc.... and the cost goes sky high.

...oh, those batteries?  Well, they're getting old.  I've gotten almost 10 
years out of them, and need to replace them.   But then, they only have 
done two deep/complete discharge cycles.  I'll have no problem with using 
hospital pulls or NOS again.

For those still reading, the charging system is 400 W of solar panels 
through a PWM charger with sense lines and temperature compensation.  About 
$100 back in the day, and there are much better ones out there today.


>Special electronics are not especially hard to work up yourself.  You must
>avoid over or undercharge, which is pretty much a matter of voltage
>regulation.  And every so often you must apply an equalizing charge to make
>sure that all batteries are properly topped up.  You can Google that phrase
>and come up with lots of stuff.  Or look at Home Power Magazine.

That's fine for wet-cells, but I prefer the safety of gel cells at the cost 
of energy density and $$$.  I'd go with a commercial circuit if you haven't 
done a charge circuit before.  (You only equalize a gel-cell once, and then 
you throw it away. :-))



>Overspend on the batteries and make savings elsewhere if you can.

Again, I think you can get away with certain things with the 
batteries.  New-old stock is fine, as long as they aren't more than 18 
months old, as are hospital pulls.  Wet cell types that have never seen 
electrolyte should be fine as long as they weren't physically damaged 
(dropped, etc.).  However, UPS pulls from non-life-critical systems aren't 
worth it.  Pulls from repeater sites are a no-no.

It helps if you know people who've been through this before in your local 
area.  At local hamfests here in Colorado, there are dealers who work in 
good faith and there are the rest.  Find out from someone who's been 
through it all before.

Regards,

Eric F. Richards, KB0YDN

--
Eric F. Richards
efricha at dim.com
"The weird part is that I can feel productive even when I'm doomed."
  - Dilbert