My backup power solution -- critique wanted.

One should note..that the charging requirements for larger batteries often exceed the ability of small UPSs. Big batteries often require many amps to recharge, and a small UPS will think its a dead short or work its little ass off, until it burns up.

Gunner

Have you noticed how these enviros have become alarmed by the proliferation of large carnivores in the boonies? I saw one remark to the effect that bears, for example, do not seem to know their place on the "food chain." Why should they? Only man comes up with ideas like a food chain, and with man the idea only makes sense because man is armed. Without his weapons, man is by no means at the top of any food chain. On the contrary, he is down in fourth or fifth spot, depending upon the environment in which he lives. Primitive man was under no illusions about this, nor are the backwoods folk in India today. To a tiger, man is a morsel, as these unarmed joggers seem to be to a cougar, upon occasion. Man is man because he is always armed. That is something they do not teach in kindergarten, nor for that matter in high school. A youth becomes a man when he is first presented with his own personal weapon. That is his right of passage, and those who do not understand that are questionable members of a free society. - Jeff Cooper's Commentaries, Vol. 9, No. 7, July, 2001

Reply to
Gunner
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yes, it is in fact AGM.

Thanks. I know that those UPSes are the greatest, I dealt with a few of them before.

i
Reply to
Ignoramus3934

Reply to
Ignoramus3934

On Mon, 18 Aug 2003 16:46:34 -0500, Bob Adkins snipped-for-privacy@charter.net wrote: <SNIP>

<SNIP>

Lead calcium & gel are not mutually exclusive terms; one refers to plate alloy & the other refers to the electrolyte. LC gel batteries are available.

As the OP confirmed, he has AGM, not gel, batteries. That's probably a good thing.

R, Tom Q.

Reply to
Tom Quackenbush

I have just ordered a battery isolator/switch for two batteries, it has four positions: off, Battery 1, Both, Battery 2. I will report when I create my backup solution. After I am done with it, I will go back to repairing my diesel generator. It is very nice to have two backup solutions.

Tom, I understand that if I directly connect two batteries in a very different state of charge, the current may be very high. But what if I hypothetically connect two well charged batteries directly? Then I guess that is safe, right?

i
Reply to
Ignoramus32317

Aug 2003 17:05:32 GMT, "Kev>

Sorry I was thinking more resistive loads. But I do believe that they use that VA term to confuse people into thinking that they are getting more than they are. An APC brand UPS that I have used is rated at 1400VA and has a prominent

1400 silk-screened on the front of the unit which is also the model number. However the max output is 950W at 120V. Why not show me 950 on the front as that is much closer to the real output? I think that they just chose VA because it looks bigger. One time our SA complained that the servers were only lasting a few minutes on a power outage. I found that they were using the VA rating as Watts. They ended up having to get the larger UPS's Kevin
Reply to
Kevin Ricks

I once had the same idea about using a car battery on an APC brand UPS unit for camping and extended power outages. But I found that it used 4 gel batteries hooked up in a series/ parallel scheme so that the battery output internally to the UPS is 24VDC. This would require 2 car batteries wired in series which is not feasible for me. Also there is no external cutoff switch for that blasted warning beeper. Kevin

Reply to
Kevin Ricks

Correct. The lowest charge battery will always try to bring itself up to the level of the highest charged, until they reach equilibrium. There are ways to prevent this such as the large diode Battery Isolators found on most motor homes and such, but if simply hooked together, the inrush current can be damned high.

Gunner

"The French are a smallish, monkey-looking bunch and not dressed any better, on average, than the citizens of Baltimore. True, you can sit outside in Paris and drink little cups of coffee, but why this is more stylish than sitting inside and drinking large glasses of whiskey I don't know." -- P.J O'Rourke (1989)

--------------------------------------------------------------------------------

Reply to
Gunner

You're probably right that some people are buying smaller units than they need based on the VA rating, but it's hard to fault the manufacturer for being accurate (I'm not vouching for APC, but it's _sounds_ like the're rating it accurately). Also, if the shopper knows he needs a higher VA rating, he'd buy a larger unit, which would be to APC's advantage.

Does the ouput rating only say 950W, or 950W at .x power factor? If it's really a 1400 VA unit, you should get 1400W if your power factor is 1.

R, Tom Q.

Reply to
Tom Quackenbush

Jesus, Tim, you're replying before I can see my post on my own news server. <g>

WRT E=IR, I agree. But, it's beyond my capabilities to determine the charge discharge characteristics of an AGM battery/flooded acid battery/NiCad using only E=IR and a pad of paper, so I look at the manufacturers spec sheets instead. Hopefully, their engineers confirm their results empirically after they calculate them. I trust empirical results more than theoretical. Of course, I'm a technician, not an engineer, so that might have something to do with it. Also, sometimes I forget to carry the one. <g>

R, Tom Q.

Reply to
Tom Quackenbush

On Tue, 19 Aug 2003 19:02:32 -0400, Tom Quackenbush snipped-for-privacy@kingcon.com wrote: <SNIP>

,which would come in handy in the _winter_ for my other lead acid batteries, as well.

R, Tom Q.

Reply to
Tom Quackenbush

obviously I won't let them self discharge.

The battery bank is actually fed with more electricity from the truck alternator, at the time when it is loaded.

I was planning to connect the UPS, via its battery or separately, to the battery posts of my truck and let it idle. I have a heavy duty alternator, and I calculated that it will produce enough amps to support the hypothetical expected load, with the batteried handling surges.

That is a very heavy sucker. Even without batteries it must be very difficult to lift. I handled a few 3.1 KVA units.

I like it too.

I would just rotate which batteries are getting charged.

i

Reply to
Ignoramus32317

Since you flamed the poor guy with the generator question, I must even the score. And remind you that anything you do which involves inverters or generators will overheat in your walls, and burn you to death while you sleep.

How'd it feel?

Reply to
Stormin Mormon

Very possible that I'm quite ignorant. Happens now and again.

How do you explain the VA and watts situation?

Reply to
Stormin Mormon

Ignoring for the moment some subtleties involving phases and power factors, the basics (for direct current) are:

Energy = power x time (force x distance)

Energy can be expressed in many units, including BTUs, calories, kilocalories, ergs, joules, foot-pounds, watt-hours, kilowatt-hours, etc. The exact conversion factors are easily located.

Power is a thus Energy divided by time, or a _rate_ of energy usage.

Power is expressed in various forms, including watts, ergs/second, BTU/hour, etc. Again, exact conversion factors are easily located.

Ohm's Law: Volts = Current x Resistance

E = I R

Power = I^2 x R

(power is "I-squared R")

Volts is volts, current is amperes, resistance is ohms.

By the way, these are really just basic _physics_ notions, such as power being the rate at which work is done. And Newton's famous equation, F = ma, is of course very central to these other equations.

All of these things can be combined in some pretty obvious ways.

Fiddling with these symbols shows that

Power = voltage x current

Power = V A

This is how people make simple computations of the power consumption for something drawing 1 Amp at 12 volts. (The subtle issues of a.c. power and subtle discrepancies between a simple V A calculation and measured wattage are not too important, especially not until the basics are understood intuitively.)

The usual way to understand all of this is in terms of water flow in a hose. The water pressure is the voltage. The resistance is the amount of constriction in the hose. The current is the rate of water flow. It's useful to think about work done (energy) in moving water to high locations, etc. Energy = power x time, as always.

A light bulb of 100 watts, which is power, dissipates a kilowatt-hour in 10 hours, or 2.4 kWH per day of continuous operation. Look on your electric bill to see how much your utility is charging you per kWH. (Probably around 10 or 15 cents, for a cost per day of about 24-36 cents to keep a 100-watt bulb burning.)

The important thing to note is that _rates_ of energy usage and total energy used are NOT the same thing, and the units should never be confused.

This is what a few people were commenting on. For anyone familiar with the units, referring to total energy usage in terms of _watts_ is just plain obviously wrong.

It would be like saying the distance from Buffalo to Albany is 76 miles per hour.

You can worry about the subtle differences between rate power and VA

--Tim May

Reply to
Tim May

Dear Tim, I'm familiar with evrything you wrote. I'm still quite clueless why someone else jumped my case.

Reply to
Stormin Mormon

The questi>Is it possible you are comparing "watts per hour" which would

Watts per hour? Presumably you meant watt-hour. There's a big difference.

1,000 VA battery? Assuming you were referring to battery capacity, the correct unit of measure would be amp-hours. It was especially confusing that you used VA, as that was one of the units in question. Volt-amps is the unit of measure of apparent power. See Ian's (or my) previous post for info on volt-amps.

BTW, the number on a light bulb is 95 watts, no unit of time needed (or wanted). If you run the light for an hour, you've expended 95 watt-hours of energy. If you run it for 30 minutes, you've expended

47.5 watt-hours of energy.

R, Tom Q.

Reply to
Tom Quackenbush

"Stormin Mormon" snipped-for-privacy@hotmail.com swore:

Didn't your good Mormon Mommy teach you not to swear? Great example you set for your religion promotion <grin?>

CM

Reply to
CM

Hmm. Using RU for Rate of usage, and AP for ammount of power, lets see if I'm doing any better.

Reply to
Stormin Mormon

Jesus called people ravening wolves, or hypocrites as the need showed itself. Why should I be any better?

Reply to
Stormin Mormon

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