# Rigging your car battery when the lights are out...



## mldollins (Jun 21, 2008)

I really do not want to bring my battery inside my home. However, I was thinking of using 12 gauge wire and hooking large alligator clips to it and have it around 300 feet long. However, rigging the other end seems more complicated. I know I could dice and splice but I hate to mess those things up. THoughts on how you do it?


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## PhilJohnson (Dec 24, 2006)

mldollins said:


> I really do not want to bring my battery inside my home. However, I was thinking of using 12 gauge wire and hooking large alligator clips to it and have it around 300 feet long. However, rigging the other end seems more complicated. I know I could dice and splice but I hate to mess those things up. THoughts on how you do it?


Rigging for what? To run a power inverter? 300 feet long is way too long for DC power. You'll get an extreme voltage drop. If your talking about running power for lights in a house off an inverter and your dead set against a battery in the house a power inverter inside the car would be a much better choice. When I was off-grid I started out swapping car batteries into the house and hooked up the inverter inside the house. Later after I got sick of dragging car batteries into the house I setup a deep cycle battery in the trunk of my car and it would charge while driving. There was also an inverter in the trunk. I just would plug in an extension cord and plug it into the house. AC current will go a lot farther before you get voltage drop but even so I wouldn't want to go much farther than 20-30 feet from where I have to plug into the house.


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## FarmerChick (Dec 28, 2009)

I understand the use.....but why monkey with your vehicle?
That vehicle might be needed for escape or more.......

I would find some alternative set up before wasting my only car battery for the vehicle.

There are tons of safe easy alternative power sources for lighting in the event of an outage.


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## TnAndy (Sep 15, 2005)

12v 300' drawing a >1< amp load will drop about 10% in that distance on 12ga wire

Increase the load to 5 amps, and you loose about 1/2 your 12 volts.

Better be a REAL light load at the house end.


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## mldollins (Jun 21, 2008)

sorry, I did not mean 300 feet. I meant 30. Sorry, I must have been heavy on the keys.


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## PhilJohnson (Dec 24, 2006)

mldollins said:


> sorry, I did not mean 300 feet. I meant 30. Sorry, I must have been heavy on the keys.


Okay that makes more sense


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## tamsam (May 12, 2006)

We have a battery bank here for the radio equipment and keep it charged . We currently use it for on piece of equipment as the power supply won't run the 2 hooked together at the same time. I do have a couple lights to hook to them if needed but we use lamps and candles and save the batteries for the radios. I am going to rig an alternator with a 3 1/2 horse motor to charge them when the power is off. This will also let me run a 12 volt heater in the pump house. I haven't noticed anything in the house rusting or noticed any other effects of the batteries being in the house. We never charge them on a high setting. Good luck with your battery plans. Sam


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## Gary in ohio (May 11, 2002)

The battery in your car is NOT designed for long term drain on it. It designed to provide a lot of power all at one for the starter then a small load after that. Unless your looking at 12 volt lighting for your home you not going to get much power out of a car battery when you add an inverter. Also I wouldn't risk draining the car battery.


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## Danaus29 (Sep 12, 2005)

I would rather use battery powered lanterns and flashlights and not mess with the car battery. It's not meant to be used that way.


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## Ernie (Jul 22, 2007)

According to one book I've got, a car battery will power a 200 watt bulb for 12 hours.


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## PhilJohnson (Dec 24, 2006)

When I ran my house solely off of car battery power (it was over a year before I got solar panels although I did get a generator in the fall) I found a good battery could run quite a bit and still start the car in the morning. Usually I would run a small fan all night, one light at a time for about 5 hours at a crack, a small black and white TV for about an hour or so, and a cell phone charger. I will warn you though using it solely for power for months on end will kill a car battery pretty fast. Mine was shot after 7 months. For a couple weeks with a fresh battery I wouldn't worry about it. I did upgrade to a single deep cycle battery in the trunk. It would go about 24 hours or so on a charge before I would have to run the car. Usually it took me about half an hour of drive time to charge the battery fully up to snuff.


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## Spinner (Jul 19, 2003)

If you want to make a permanent setup, here's what I did and it works great. I put a set of solar panels on the roof, there were 4 panels in the kit and I think it's something like 60 watts. I put a bank of deep cell batteries in the attic. The panels keep the batteries charged. Some 12 volt lights from an old camper run off the batteries, and will last several days even without sunlight recharging the batteries. It's nice to have lights in every room even when the power is out. 

I got lucky and DS ran across the set of new in the box solar panels for free. His boss deals in scrap metal and he picked up the deep cell batteries for $2 each, $20 got me a set of 10. If you look around it's amazing how you can find great stuff that people don't want and actually pay others to haul off. 

Make friends with a scrap hauler, they can be a great source. Just let them know what you want, when they come across it they call you to come get it at a tiny fraction of what it would have cost retail. I even got the rubber base mat that the batteries set on free from the scrap man.


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## GingerN (Apr 24, 2007)

mldollins said:


> I really do not want to bring my battery inside my home. However, I was thinking of using 12 gauge wire and hooking large alligator clips to it and have it around 300 feet long. However, rigging the other end seems more complicated. I know I could dice and splice but I hate to mess those things up. THoughts on how you do it?


My dh did this for me in the feed room of the barn using a marine battery and existing wiring...when he gets done on the phone, I will see if he will tell me his secrets for doing it. I don't speak electric.


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## trkarl (Dec 15, 2009)

A few things you want to consider are:

Is it a 12v load you are supplying such as a 12v light or appliance?

Are you powering an inverter?

What is the maximum load in amps?

Once you have the answers then you can design your "system" with a few calculators to see if it will work.

First find the ampacity of your cable with a table like this one:

http://www.cerrowire.com/default.aspx?id=46

That will tell you the amount of amps you can safely run through the cable.

Then play with some voltage drop calculators to see what would happen to the voltage in the circuit when you apply the load such as these:

At the bottom of the page: http://www.powerstream.com/Wire_Size.htm

or here: http://nooutage.com/vdrop.htm

You will see that 12 awg cable has an ampacity of 20 amps which is only around 240 watts nominal for your load.

Now run your cable 30 feet and you will find you lose around 8-9% of your voltage or more depending on how many amps you are pulling through the cable. At 20 amps you lose around 17% of your voltage. 

For example if you are running an inverter and trying to power 2 100 watt light bulbs you would have a load of about 20 amps off the battery.

A full battery is around 12.6v and you lose 17% of that do to the cable voltage drop. Usually 12v inverters have a voltage cut off where they shut off once the voltage gets too low which is usually between 10.5 - 11 volts.

Well with this load and the drop you are already losing over 2v so 12.6 becomes 10.6 at the inverter and it will shut off real soon. 

Worse yet once you put a load on a battery the voltage drops anyway at the battery so this just compounds the problem.

12v systems are extremely inefficient especially with longer cable runs but then again there are a ton of 12v appliances and lights that are designed for 12v so you don't have the losses of converting from dc to ac in an inverter.

Hope this helps.


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## texican (Oct 4, 2003)

They make 12vdc bulbs... they are energy hogs. I've been in deer camps where folks would have alligator clips to hook up to a battery... running to a 12vdc light socket, with 12vdc bulb. I'd rather use a fluorescent bulb of course, to save power.

Most car batteries aren't designed for long term draws (without being recharged). Deep cycle batteries are. Even with a deep cycle battery, you never want to discharge them completely down. You lose a little bit of capacity every time you do this, and it doesn't take long to destroy the usefulness of one. I never discharged my deep cycle batteries below 50%.

You can get deep cycle batteries, and have a bypass switch set up in your vehicle... so when you're running down the road, it charges your extra battery, without taking a draw off of it. Remove the charged battery, bring it onto the porch and hook it up. Or, better yet, make your own UPS... have your battery in a ventilated area, and have a 110 trickle charger on the battery... so it's always charged. When grid goes down, you still have some power.

Fooling around with your car battery, while still hooked up to the vehicle, is doable (I've done it many a time). However, be very awake when doing these procedures... I saw a guy destroy his alternator by hooking up a live load incorrectly... he said he knew what he was doing... after it 'sparked', I said you need a new alternator... two hours later he was indeed looking for a new alternator.


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## ||Downhome|| (Jan 12, 2009)

I ran over a year off my vehical and a inverter, yes car batterys are not ideal but if you know where to find cheap batterys you can refurbish (no you wont bring them all back to life but many you can) but I agree deep cycles are you better choice for long term use and dependability. I wired up a three regular auto batterys in the trunk and charged them up well going to and from work (and other places) you could put a isolation switch in (to keep from draining your starting battery down) or just do what I did and that was to disconnect the negative terminal on it. 

used a 100 foot extension cord (its what I had) hooked up the inverter and pluged it into a outlet strip and then pluging additional cords into that, then I got smart 
and made a patch cord (male on both ends) just pluged it into the nearest socket and use all the house wiring wich was much better. just make sure no kids can get ahold of it and you throw your main breaker if you do that so you dont back feed into the grid and disconnect from the extension cord first so you dont juice yourself. 

a cfl would run all night, small tv several hours, radio alone 8-10 hours, and once I knew what loads would run I could go start the car (you dont need to hook up your starting battery if you have the others wired right) and run it 10-15 mins at idle and get a few more hours before the got to low voltage. all in all I was happy with myself and really was more happy to have some decent light (I like kerosene lamps but not for certain things) it was also nice to use the radio. now I have a laptop wich would of been ideal with that set up, you can watch dvds or if you get a tuner TV too and use a whole lot less juice then a standard tv or tv/dvd combo. though I would maybe get too inverters if I had to do that again the one I had was 800 watts cont. I would shoot for maybe a 300-400 watt for running a radio and a few lights and the multi use laptop, and a 2000 watt for stuff like a microwave (that would be a little econo microwave and id be running the car when using that one though)


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## Spinner (Jul 19, 2003)

I don't know if it's still available, but you used to be able to buy a battery acid powder. You'd put some in the battery, then add water and it would return the battery to full function. Dad used to do that. I don't know the details, and I doubt he'd remember now, it's been a lot of years. He'd get batteries with dead cells free from the junk yard. He'd drain them, wash them out, then put a spoonful of the acid powder in them and fill them with water. They were as good as a new battery once it was charged up. IF that powder is still available, it might be worth getting some to keep in storage. Once a battery has dead cells, that method could be used to put new life into them.


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## Jim-mi (May 15, 2002)

Any time you use your "car" battery for anything other than what it was intended for you are just waiting for Murphy's Law to come bite in the @ss...............


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## ||Downhome|| (Jan 12, 2009)

Spinner said:


> I don't know if it's still available, but you used to be able to buy a battery acid powder. You'd put some in the battery, then add water and it would return the battery to full function. Dad used to do that. I don't know the details, and I doubt he'd remember now, it's been a lot of years. He'd get batteries with dead cells free from the junk yard. He'd drain them, wash them out, then put a spoonful of the acid powder in them and fill them with water. They were as good as a new battery once it was charged up. IF that powder is still available, it might be worth getting some to keep in storage. Once a battery has dead cells, that method could be used to put new life into them.


I dont know about the powder but you can get battery acid, and in severe cases you can build a Desulfation circuit to bring them back to function, cores are what 5-6 bucks, use to work in a garage they dont really care where they go as long as they get thier 5-6 bucks, when scrap batterys where high (more then core charge) we would take them to a small battery shop they in turn would take any that could be salvaged and recondition them and sell to used car lots for a fraction of what a new battery would. 
I think you can get batterys with out acid in them (not real sure how one that had acid and was drained would work in storage) but ya spinner that would be ideal for long term what if.

and Jim-mi murphys law is always in effect no matter what you do or dont do. hence

1. Murphy's Law
If something can go wrong, it will.


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