# AC to DC help please



## Weedologist (Jan 7, 2007)

With the threat of power failure looming, I am curious about running the well pump and furnace fan from a heavy duty truck battery. Is an inverter needed? Also, we have an inverter for the car that converts from the cigarette lighter to three prong AC outlets. Will this work with what I want to do? How can I change the electrical connections from the well pump or furnace fan into a 3 prong cord so that it will plug into this inverter so that it will allow me to power these with the car. Is this possible? Thank you very much and good day.


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## mightybooboo (Feb 10, 2004)

I dont think it will work because the truck battery just doesnt have the capacity.For the power needed to run a well pump,it will destroy the thin plates in an automotive battery.

Maybe could run the well pump with the truck running,need to know the well pumps size and the math whiz folks here can help you.

Knowing what you want to run power wise is needed to determine what batteries and inverter would be needed.

It CAN be done,but not without some added things,like at least 2 trojan 6 volt deep cycle batteries(or equivalent) for instance.

You will get better answers,just wanted you to have some fast info.

BooBoo :gromit:


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## ET1 SS (Oct 22, 2005)

Our well pump is on a 220 VAC breaker, 20 amperes.

When it cranks up it uses like around 14 peak, and then drops back down to 7.

If you have an inverter that can handle that, it would be impressive.

I have looked into it.

Deep cycle marine batteries can handle it all. But the trick is the alternator.


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## Runners (Nov 6, 2003)

ET1 SS is describing a typical 1/2hp, 240 volt AC submersible well pump... 1680 watts! In a 12volt DC to 240volt AC conversion.... your talking a whopping 140amps running... maybe 300amps starting! Good LUCK finding an off the shelf 240v inverter! In case you're still wondering, your truck/car alternator usually falls into the 50-65amp range, not near enough power.

Furnace fan is another story - YES!!! Most fall into that small 3-5amp, 120volt range (plan on double amps to start), but many of them could run off a 600-1000 watt modified sine-wave inverter.

NEC says you need a means of electrical disconnect at the appliance (Furnace). This is usually done with a simple switch (like a wall switch mounted in a box).
...here's how you do it...
1. Turn off the breaker to the furnace - be absolutely sure it's OFF!
2. Replace the switch with a simple receptical, so the power coming from the fuse/breaker panel goes to the receptical instead of the switch.
3. punch out a knockout (looks like a quarter), add a romex connector to the hole, and wire in a short cord with a 3 prong plug (as you called it), wire it to the furnace leads/wires. If you can't figure out "where" to ground the green wire, it goes to the electrical box - you MUST ground it.
4 replace the switch cover with a receptical cover, close up the whole thing - DONE!

Plug in the furnace for GRID power, unplug and plug into alternative power source for OFF GRID power. You still have a means of disconnect at the appliance, and you can power the furnace from an alternate source. Granted the AC won't run, but if you got a typical LPG furnace, you're good to go. If you got an oil burner, make sure you get a big enough inverter to run it.


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## mightybooboo (Feb 10, 2004)

ET1 SS said:


> Deep cycle marine batteries can handle it all. But the trick is the alternator.


I would respectfully elaborate on that.An electric coffee pot,in 4 cycles (charged fully between cycles-EDIT), will take out a single 12 volt marine deep cycle battery.For good.They cant handle high amp discharges.The plates are just slightly thicker than an automotive battery,unlike a true deep cycle with much thicker plates.

BTDT,YMMV.

BooBoo :gromit:


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## ET1 SS (Oct 22, 2005)

Marine deep cycle batteries are used onboard live-aboard sailboats, because they can cycle from 90% charge down to 10% charge back and forth repeatedly. To power a radar unit, anchor lights, and coffee pots.

Obviously one charge will not last forever, eventually any battery will be empty and in need of being recharged.


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## mightybooboo (Feb 10, 2004)

I think we are talking apples and oranges.You are saying a TRUE deep cycle battery(marine),Im referring to what Autozone and Wally call 'deep cycle' marine.That can be stuck in a truck.

Now if were BOTH talking lead acid,90% discharge is death,stick to 50% or less.That seems to be the accepted norms.

Unless you can show me a link for lead acids that survive 90% discharges without radically shortening life.

Im not aware of them,doesnt mean Im not misinformed and can learn  

BooBoo :gromit:


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## ET1 SS (Oct 22, 2005)

This thing I am using must weigh 95 pounds.

It says marine grade deep cycle.

It looks just like those I have seen onboard sailing liveaboards. They are used to power everything onboard when the engine is not running.

Normal cycling usually takes them down to like around 50%. Though I have seen them taken down to 10% or dead.


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## mightybooboo (Feb 10, 2004)

ET1 SS said:


> This thing I am using must weigh 95 pounds.
> 
> It says marine grade deep cycle.
> 
> ...


10-4,we are on the same page,youre talking close to an L-16 trojan,eh? Question,is it 12 or 6 volts?

Booboo :gromit: <-----Likes Trojans,LOL,really LIKES Trojans


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## ET1 SS (Oct 22, 2005)

12 Volt.

I had originally put it into our motorhome, but now that has become a 'guest house' out close to the road. So I cannibalized it to provide power for our radiant heat circ pump.

If we lose Electric service, we can still keep our heat going.


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