Customizing UPSs

[Duane Attaway]

On Thu, 16 Dec 2004, Jonathan Hutchins wrote:

> I've been under the impression that the more conventional liquid-based 
> automotive or marine batteries were more prone to discharging noxious 
> fumes - vaporized acid and hydrogen being of chief concern.  In 
> discussions of using them for solar power they warn to make sure that 
> the batteries are both enclosed and safely ventilated.

Lead acid batteries will stink when they become low on water and the 
plates start to sulfate.  We see this at work when one of the batteries 
hasn't been maintained.  We have several hundred 1,500 to 3,000 pound lead 
acid batteries and they are quite friendly to be around as long as they 
are maintained.  The sulfuric acid should not create gases if there is 
enough water to stabilize the electrolyte.

> The term Gas Recombinant cells certainly implies that they wouldn't pose 
> as much of a problem.  What about the "gell cells" that are originally 
> supplied with stock UPSs?

Gell cells are usually much more expensive and have half the usuable high 
current discharge per weight.  We have this option with the forklifts, but 
they just don't last long at all.  Also, they have a shorter service life.

> If the stock cells are as bad as conventional "wet" cells, then wet 
> cells wouldn't be any worse and all you'd need to worry about is keeping 
> the "box" upright.

Yep!

> Motorcycle batteries are subject to more radical changes in orientation, 
> and usually vent through a tube that can be routed away from things that 
> acid might harm.

The motorcycle batteries I use are maintenance free and don't have a vent 
tube, but I believe they have to stay upright.  But they are expensive! 
$50 for a little pint sized one.

> Miatas and some other cares now use a battery that has a sponge-like 
> fiberglass fill that gives some of the advantages of a gell cell while 
> not having the problem of the gell shrinking away from the plates.

Hopefully, lithium and nickel hydroxide batteries will overtake lead acid. 
Lead is so cheap to make batteries with, so it might be a while.  Lead 
acid batteries go for about $1/pound.

> In aviation, it's more common to see "wet" Nickel-Cadmium batteries as 
> well as conventional lead-acid batteries.  NiCads deliver higher current 
> for a longer time than equivalent weight lead-acids. (There has been a 
> lot of advance in conventional battery design, but aviation tends to 
> stick with old tech because it's tried and true.)

At my last job, we couldn't find a way to dispose of a bank of nicad 
batteries used to fire up our generator.  Those were mighty powerful 
cells.

> There's a lot of information on the web and in the public library on 
> alternative power systems, particularly oriented toward solar and wind, 
> that use batteries for storage and load leveling.  I'm sure some 
> research would pay off.

Its really getting better each year.  The newer silicon power transistors 
have made it possible to make very small and powerful voltage inverters. 
Ten years ago, these high voltage, high speed transistors didn't exist and 
such equipment was very expensive to make.  We are going to see a lot more 
of this stuff as soon as the patents run out.  Competition starts to enter 
the market when a bunch of people with free time can legally sell their 
projects and not lose their house to lawyers.

I found another good marine battery, so I may make that HOWTO soon!

-=Duane
http://dattaway.org