Date: Sun Aug 27, 2006 2:13 am. By: Neon John

On Sat, 26 Aug 2006 22:24:35 GMT, "Him" wrote:

I know this is basic math but I don't know all the capacities .... can someone help fill in the blanks?

My pellet stove runs on 350 watts 120v power.

I have a the recommended 500 watt inverter for backup power and I plan to run it off a standard marine battery. How long will the stove run on this battery?

Here's the math.

Assume that the fan does really draw 350 watts at unity power factor. 350/120vac = 2.9 amps. A 12 volt in, 120 volt out inverter has a current ratio of about 10:1. That is, for every amp out the 120 vac outlet, 10 amps of 12 volts must go in. Thus, about 29 amps will be drawn from the 12 volt supply.

A pair of 6 volt golf cart batteries in series is 220 amp-hour at 12 volts. 220/29 = 7.6 hours to 100% discharged. Limiting discharge to 80%, 7.6 * 0.8 = 6 hours.

Will the run time double if I hook two batteries together?

IF in parallel, yes. The more amp-hours, the longer the run time.

How long will the stove run off a golf cart battery I saw at Sam's Club or the huge truck batteries .... or are these not a good idea?

Golf cart batteries - yes. Truck batteries - no - they're not deep cycle. Even better are floor scrubber batteries. They're the same footprint as GC batteries but taller and of higher capacity. More importantly, they're designed to have long lives at about the same discharge rate as you're looking at.

For duration I will be able to charge them off my Coleman generator with a 12v output or off the car.

Coleman generator - no. Car - probably not. The coleman output is essentially a trickle charger. A car alternator does not produce enough voltage to properly charge a deep cycle battery - especially after the voltage drop through the connecting wires.

Keep in mind that the charger must be capable of restoring all the charge in the time available between uses. If it can't do that then the battery will eventually run down.

For example, if your stove runs for 8 hours a day, that would be 29 amps * 8 hours = 224 amp-hours. (assumes more than just two golf cart batteries). You have 24-8 = 16 hours to recharge the battery. Therefore to restore 224 amp-hours in 16 hours your charger must be capable of 14 amps.

It will actually require more than that because charging is less than 100% efficient and because the battery won't accept that much current through its entire charge cycle.

You will need a smart fast charger to charge the battery in the shortest possible time. In this range of capability I recommend the Vector 1093 smart charger. Here's Amazon's ad:

http://www.amazon.com/gp/product/B00009RB0T/sr=8-1/qid=1156651359/ref=pd_bbs_1/103-6208755-0942207?ie=UTF8

This charger is also available for about the same price from Wal*mart, sometimes under the Vector brand and sometimes under the Black and Decker brand. Do NOT buy the similar Schumacher smart charger, as it reacts poorly to dirty power and frequently lets the blue smoke out when operated from a generator. personal experience speaking.

For totally unattended operation (just start the generator and walk away), I recommend the more expensive Progressive Dynamics Intellipower with the Charge Wizard. This is an RV charger/converter available in capacities up to 80 amps.

I should point out here that with this large a load you'd be better off with one of the small inverter generators from Honda or Yamaha, both in terms of money and in terms of hassles and noise. Forget the batteries and inverter and just let the little generator sit there humming along and barely sipping fuel. That Coleman is a fuel pig and will use more fuel running intermittently than the Honda or Yamaha will continuously.

John

Thanks in advance for your ideas ....

Winter will soon be here.

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John De Armond See my website for my current email address http://www.neon-john.com Cleveland, Occupied TN Don't let your schooling interfere with your education-Mark Twain