Computer UPS Built On Automobile Battery?

[(PeteCresswell)]

The "UPS Design That Doesn't Overheat" got me going on something that's been in
the back of my mind for a couple of years: Why not a PC UPS that uses a plain
old 12v automobile battery as it's storage medium?

Not pretty... but there's plenty room under my workstation table.

I'm just guessing, but I'd bet that Pep Boys would sell me more capacity and
longer life in a gas-less automotive battery for about half the price that APC
would charge me for a replacement battery.

 

[Chris Hill]

The "UPS Design That Doesn't Overheat" got me going on something that's been in
the back of my mind for a couple of years: Why not a PC UPS that uses a plain
old 12v automobile battery as it's storage medium?

Not pretty... but there's plenty room under my workstation table.

I'm just guessing, but I'd bet that Pep Boys would sell me more capacity and
longer life in a gas-less automotive battery for about half the price that APC
would charge me for a replacement battery.

Wrong kind of battery; you need a deep cycle. Only deep cycles that
are really suitable for inside use are agm, and they aren't cheap.

 

[JoeSP]

The "UPS Design That Doesn't Overheat" got me going on something that's
been in
the back of my mind for a couple of years: Why not a PC UPS that uses a
plain
old 12v automobile battery as it's storage medium?

Not pretty... but there's plenty room under my workstation table.

I'm just guessing, but I'd bet that Pep Boys would sell me more capacity
and
longer life in a gas-less automotive battery for about half the price that
APC
would charge me for a replacement battery.

Nothing wrong with that, but a car battery is designed to provide high
cranking amps, and isn't designed for deep-cycle charges and discharges.
For about the same money, buy an RV battery that's designed for such a
purpose. It's not the best battery for you could use, but it's good value.

 

[(PeteCresswell)]

Per Chris Hill:

agm

?

 

[William P.N. Smith]

The "UPS Design That Doesn't Overheat" got me going on something that's been in
the back of my mind for a couple of years: Why not a PC UPS that uses a plain
old 12v automobile battery as it's storage medium?

[Or, as everyone else has pointed out, a deep-cycle battery]

A couple of issues:

1) The charger in your UPS may not be correct for the battery you've
chosen. I've seen underpowered battery chargers boil batteries dry
because they can't reach what they think ig 'end-of-bulk'. Also, the
UPS battery is (nearly always) gelled, and the deep cycle battery is
(nearly always) flooded, and they need different charging regimens.

2) The UPS inverter may not be good for more than 10 minutes or so of
full-power output before it melts down. This is OK with it's supplied
batteries, as they only last 5 minutes at full-power, but adding
capacity may require adding cooling.

UPSen that are made to interface with external battery packs, like my
APC Smart-UPS XL, have cooling fans, for instance. This solves 2) but
not 1) above.

The real solution is _not_ cheap.

 

[Harry Chickpea]

Per Chris Hill:
?

AGM is a lead acid battery that doesn't create lots of hydrogen gas or
acid fumes, and because of being sealed can be safely used inside.

FWIW, I have a trolling battery sitting under one of my worktables,
and as long as I don't equalize the cells by overcharging, it doesn't
seem to cause any problems. However - equalizing is important to
extending battery life. Batteries are always exercises in trade-offs.

 

[(PeteCresswell)]

Per William P.N. Smith:

1) The charger in your UPS may not be correct for the battery you've
chosen. I've seen underpowered battery chargers boil batteries dry
because they can't reach what they think ig 'end-of-bulk'. Also, the
UPS battery is (nearly always) gelled, and the deep cycle battery is
(nearly always) flooded, and they need different charging regimens.

I wasn't thinking of grafting a foreign battery on to my existing UPS.

Instead, I was trolling for somebody who might know of a UPS that was
specifically designed for (deep cycle) automotive-type batteries.

 

[William P.N. Smith]

Instead, I was trolling for somebody who might know of a UPS that was
specifically designed for (deep cycle) automotive-type batteries.

Well, http://outbackpower.com/ has 2KW stackable modules...

 

[You]

AGM is a lead acid battery that doesn't create lots of hydrogen gas or
acid fumes, and because of being sealed can be safely used inside.

FWIW, I have a trolling battery sitting under one of my worktables,
and as long as I don't equalize the cells by overcharging, it doesn't
seem to cause any problems. However - equalizing is important to
extending battery life. Batteries are always exercises in trade-offs.

Aggreget Glass Mate = AGM Kind of like GellCell but a little
different technology. Designed to have the Power Capacity of a flooded
battery, but the sealed convience of a GellCell.......

 

[Vaughn Simon]

... A regular automobile battery is less likely to
*recover* from a complete discarge -

You are preaching to the choir here, but let's think outside of the box for
a moment...

It is rare for a UPS battery to get deeply discharged, most power failures
last for less than a minute or so. When you think about it, a UPS battery is in
float service with occasional, fairly short but heavy discharges...just like a
car battery. Also, you can buy two car batteries for what one good deep-cycle
battery costs, and they warranty car batteries...

Vaughn

 

[JoeSP]

You are preaching to the choir here, but let's think outside of the
box for a moment...

It is rare for a UPS battery to get deeply discharged, most power
failures last for less than a minute or so. When you think about it, a
UPS battery is in float service with occasional, fairly short but heavy
discharges...just like a car battery. Also, you can buy two car batteries
for what one good deep-cycle battery costs, and they warranty car
batteries...

Vaughn

If you're so sure it's only for a few minutes, use a couple of rechargeable
flashlight batteries. It's obvious he wants them to last more than a minute
or two, I mean that's the reason for using car batteries. You don't need
the high cranking amps of a car battery, so go for the deep-cycle batteries,
and you'll probably get much more life out of them, and they'll probably
still be working when you really need them.

Actually you get about twice as much stored energy in a deep-cycle golfcart
battery than you do for an automotive battery around here for about the same
price. A typical car battery has about 70-100 amp-hours, and the T-105 has
225. There isn't much difference in price, but a hell of a lot better
performance running inverters and such.

I've compared two 12V RV batteries in parallel with two 6V T-105s in series,
and there's no question, there's much better performance from the deep-cycle
batteries.

 

[sylvan butler]

Aggreget Glass Mate = AGM

Never heard that one before.

Absorbed Glass Mat = AGM battery. The electrolyte is Absorbed entirely
into a fiberGlass Mat so the battery is not just a tank of liquid.

sdb

 

[sylvan butler]

price. A typical car battery has about 70-100 amp-hours, and the T-105 has
225. There isn't much difference in price, but a hell of a lot better

And the car battery is 12v and so contains up to 1200watt hours, and the
t-105 is 6v and so it contains up to 1350watt hours. There isn't much
difference in energy storage either.

The big differences are in the ruggedness of construction (t-105 will
tolerate deep discharge without falling apart as quickly inside), depth
of sediment wells (t-105 can shed a lot more plate material without
shorting out a cell), and internal impedance aka maximum current
capacity (the car battery can provide much higher amperage to a load).

And around here at least, when you pay as much for a car battery as you
pay for a t-105, you get a 3yr free-replacement warranty on the car
battery. But not on the t-105.


sdb

 

[[email protected]]

the internal components of a regular automotive batteries
are not designed to hold up to a significant (e.g.>33%)
electrical discharge like a deep-cycle battery. A deep
cycle battery components has a greater ability to
recharge after being drained of a significant amount of
power. A regular automobile battery is less likely to
*recover* from a complete discarge - a better choice
for a UPS system would be electric golf cart batteries
(or batteries used by motorized wheel chairs ).

Take a look at the Optima battery line.
http://www.optimabatteries.com
I've used their deep cycle for emergency light situations. Even though
they are basically designed for the automotive market, their stuff has
reliability per cost that is quite good.

 

[Vaughn Simon]

Because I 've had to deal with blackouts of up to 3 days,

Then you are barking up the wrong tree. For a three-day blackout you don't
need a UPS. You need a generator or a PV system.

I also preferr smaller batteries because of limitation on physical space for
the system.

You are making my case for me. A UPS will not do what you want. Rethink.

Vaughn