Batteries

[Charles Steinkuehler]

Duane Attaway wrote:
> On Mon, 12 May 2003, Hanasaki JiJi wrote:
> 
>> Any recommendations on the best cost/battery life UPS's that also have
>> support for automatic shutdown via usb/parallel port interfaces?
> 
> I'm an extreme kind of guy, but I usually take an old junker UPS that was
> left for dead and stick a $75 Walmart 125Ah marine battery to it.  Who
> needs an alarm for battery life when it will last all day?

Note that using marine batteries solves another common problem with the 
lower-end UPS systems (including APC).  The gel-cells typically used in 
these sytems do *NOT* like being fully discharged.  If you do not shut 
down the UPS while the batteries still have a charge, you *WILL* 
dramatically shorten their life.

The marine batteries are typically constructed for "deep discharge", 
which means you can run them dry and only slightly shorten their lifespan.

Of course, for the truly power-hungry, take a page from the BattleBots 
folks, and run Hawker glass-mat lead-acid cells:
http://www.hepi.com/

Their batteries can handle phenominal charge/discharge rates, and 
provide better power/weight to boot (not that this matters a lot to a 
UPS, but it's critical in a BattleBot!).  I'm partial to NiMH batteries 
myself, but the BattleBots folks changed the rules (damn insurance 
carriers!) to prohibit the high voltages I like to run (I was running 96 
cell packs for 115V...enough to power line drive industrial DC servo 
motors, and plenty of power with 30-50 Amp discharge rates possible), so 
I guess it's back to lead-acid, fat wire (100's of amps), and big FET's 
for me if I ever build another 'bot.

-- 
Charles Steinkuehler
charles at steinkuehler.net