Backup Battery for Gas Fired Boiler

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  #1  
Old 10-16-14, 06:44 PM
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Backup Battery for Gas Fired Boiler

I have an indirect fired boiler and I want to setup a battery backup.

I was thinking that I could start with a 110v battery charger to 12v battery to inverter 12v to 110v to automatic transfer switch to fuse to boiler switch.

My question is if I have a 12v 110 Ah battery and the boiler draws about 5-6 amps, how long will this battery power the boiler?

Whats the math for computing this?
 
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Old 10-16-14, 06:49 PM
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Welcome to the forums.

If efficiency was 100% then it would be 110 / 6 = 18 approx max/hours.
Realistically more like 12-15 hours.
 
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Old 10-23-14, 12:48 AM
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now i am confused.. i have this other reply from another site...

6a x 120v = 720w.
720w / 12v = 60a.
Average size car battery = 120ah.
120 / 60 =2.
Theoretical maximum.
Reality probably 1 hour.

Help.. Who's on First???
 
  #4  
Old 10-23-14, 01:30 AM
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Hey.... I'm on first but incorrect. I didn't convert to 12v.
 
  #5  
Old 10-31-14, 02:00 PM
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ok.. expanding.. i found that my boiler draws 3-3.2 Ah ... i also found a 6v 208 Ah Energizer Golf battery for $85.. if i tie two of these together.. will i have a 12v 416 Ah battery system... if so.. will the Ah keep increasing for additonal batteries... if not.. what???
 
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Old 10-31-14, 02:14 PM
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Whatever you do make sure the batteries are either stored outside, or are very well ventilated. Hydrogen gas will vent from the batteries and create an explosion hazard if they are indoors. For indoor use, something like a computer UPS which utilizes sealed lead acid batteries would be more appropriate.
 
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Old 10-31-14, 02:15 PM
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If you tie two together in series you'll have 12 volts 208 ah.
If you tied them in parallel you'll have 6 volts and 416 ah.

It would take 4 batteries to get your 12 volts and 416 ah.
 
  #8  
Old 03-14-15, 02:52 PM
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Smile Done It Already

I have an indirect fired boiler and I want to setup a battery backup. I was thinking that I could start with a 110v battery charger to 12v battery to inverter 12v to 110v to automatic transfer switch to fuse to boiler switch. My question is if I have a 12v 110 Ah battery and the boiler draws about 5-6 amps, how long will this battery power the boiler? Whats the math for computing this?

I did this last year. 100 amp hour, DEEP CYCLE, SEALED, marine battery, no hydrogen gas issue with SEALED battery (no caps, no maintenance whatsoever). 1000 watt PURE sinewave inverter, automatic transfer switch (I think used with RVs on campsites to switch from gen to grid), and a 7 stage smart charger.

It lasts about 18 hours on an average winter day about 30 degrees. Two such batteries (200 amps total if connected in parallel) would last a day and a half.

I also hooked in a 4 switch reliance control bypass, and so we have heat, AND LIGHTS, during a power outage, after we shut the generator off for the night.

BOOYA.
 
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