Adding a second battery to truck

I'm thinking about adding a second battery to my truck to run things like...space heater, reading light, etc...

I seem to recall dude_le doing this last year but I can't drag up any threads on it.

What I'm thinking of doing is putting the second battery in the bed of the pickup and charging it off the alternator when it needs it. It will not be for starting the truck.

Is it possible to install a switch to route power from the alternator to the secondary battery while the truck is running. IE- Start engine on normal battery, flick switch in cab and route power to secondary battery in the bed. Ideally all of this would happen without burning the truck to the ground.

Any idea, resources, etc to get this to happen?

instead of putting in another battery just put in a bigger alternator. you can keep the same battery, and only one, and with the bigger alternator you can run a lot more electronics in the car. it will be alot easier too b/c you wont need to do any rewiring or extra wiring just upgrade the alternator, it will fit in where the old one was. if you try to run 2 batteries off the same alternator you will burn up your stock alternator.

I think I need to clarify:

The point of the second battery is to allow me to run lights, heaters, etc. independent of the trucks electronic system. This will allow me to nearly discharge the entire battery while say, living in the back, without fear of not being able to start the truck.

if you want to do that just buy a battery charger and charge the battery and hook up all the electronics straight to that battery, without hooking it up anywhere to your car. keep the charger in your car and when you need to just charge the battery with it.

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Originally Posted by hucksquaw

if you want to do that just buy a battery charger and charge the battery and hook up all the electronics straight to that battery, without hooking it up anywhere to your car. keep the charger in your car and when you need to just charge the battery with it.

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Thanks for the advice, but that is not what I want to do.

Go here:

http://www.painlesswiring.com/

Check out the online catalog and look under "battery accessories."

Lots of Jeep owners buy this dual battery setup. Give them a call if you have any questions. They have a great reputation for aftermarket automotive wiring, especially for old Jeeps.

you cant run another battery off the stock alternator unless you get a whole second battery conversion kit, like arty was talking about, but in this case you will have both batteries powering the car, along with the electronics, just like i was saying in my first post.

The Painless dual battery setup allows you to run your truck off battery A, B, or both (note the toggle switch in the picture). This also allows you to isolate one battery for running your truck and use the other for running accessories. Just like you want. So even if you drain one battery with accessories, the other will still be charged up fully to start your truck.

another good thing about the painless set up is if you leave your lights on and you have a charge in the second battery you can still start your truck.

Arty's right. You can buy a switch to allow you to go between batteries. People run their winches off second batteries.

Nothing wrong with a higher capacity alternator either. Or getting your current one rewound for higher output.

I have mucho experience with this stuff..dual batteries/winches..4x4's/plow etc.
Start with 2 NEW batteries and new/hd alternator and GOOD wiring!and a good ammeter in the system that reads ALL the vehicle electrical load except the starter. batt./grnd etc., make sure all the grnds/connections are good.I wire BOTH batteries into the system for starting(obviouslly heavier cable) and charging.I use a Ford firewall type starter solenoid to ISOLATE one battery for auxillary use.To prevent me from draining the starting battery when I go auxillary.When I want to start..I flip the switch to get both batteries on line.When I want to charge the run down auxillary battery ditto.Even if you suck both dry..new batteries are happy to charge right up.NOT old ones.
Simply adding another battery and an isolator switch is ok..PROVIDED that the battery you are adding is pretty much identical..in terms of manufacture/output and age AND your alternator is powerful and young enough to charge them.
Failure to to this will see an older alternator NOT!! happy with the differences in load it sees and the changes in charge output it has to cough up and has to work with.Especially in bitter cold.This simply places too great a strain on the internal regulators that can't cool like the older external ones.Charging REALLY dead batteries can be a killer for alternators..especially older ones.This is SO common in cold/damp climates like where I am..dead worn out battery=new battery.THEN the alternator goes..not long after..common to change the battery and the alternator at the same time. Expect a short alternator life..perhaps burning it out in the mdidle of nowhere.OR switching the battery selector switch to a dead..ya ya..you'll charge it in the morning when it is FROZEN battery..to charge can see you come back to your truck after getting a coffee and seeing SMOKE pouring off the belt..or out of the alternator..Keep in mind too that modern batteries when they get a few years old DO NOT! tolerate this kind of having the life sucked out of them like the older types that you put water in.MANY newer batteries..you really bone them once..when they are a couple years old..you gotta go do the warranty thing..they are toast..or WORSE..short out and toast the alternator trying to charge it.

2 new batteries and a new/h/d alternator will start super easy in cold weather..with practically NO effort/drain on the batteries..OR the effort to charge them.This will also allow you to drain one ..or end up with one drained and charge them up.

Totally FORGET rinky dink hookups for using the auxillary battery and charging it.Pretty much guaranteed is that the switch will get left on and you or someone else will then start the vehicle..burning up that wire/switch set up.

Even a pair of those new Wally Everready(yeah the flashlight people) car batteries for $50 Cdn each will lay out a good solid 1300 cold cranking amps..NONE of those so called 1,000 amp batteries will pull even 800 when it gets down to doin' the dirty in -30 or so.I have a pair of these Wally's and they will light up my 5 ton truck like a christmas tree when I hit the key.

For SERIOUS battery power go to a LARGE truck/tractor-trailer parts place.They have commerical EXTREME duty 12 volt batteries in sizes that will fit most vehicles that can take a large battery.(no they are not much heavier)These are designed for abuse and have serious power.Don't mistake one of these babies for those tinny supposedly heavy duty batteries at car parts places.These are manufactured different.Drawback..only 12 month warranty.But they will last for years and years.'bout the same price($90 Cdn here)

Sorry this is long..but I know this stuff..been there/work with it/ and don't wanna see anyone "testing" the -20 bag PLUS the OTHER bag for a liner that I keep with me.

A battery isolator (the relay kind, not the diode kind) is a good first step. I'm not sure what Arnold is talking about. Whenever I plug in my trailer for a tow the trailer battery is in parallel with the truck battery and they both charge. No smoking belts or burnt out alternators. One problem is that the engine is really a big trickle charger which tops up the battery after a start. It won't charge up a dead battery for days. Even after 8 hours of driving my trailer battery isn't fully charged. You might be better off with an inverter to fast charger setup. Or a fast 12VDC charger if they make such a thing.

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Even after 8 hours of driving my trailer battery isn't fully charged. You might be better off with an inverter to fast charger setup. Or a fast 12VDC charger if they make such a thing.

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Useful info, might change the whole plan.

Char,

It sounds like from what you say that you are trying to set up a system so that you can power things while camping the back of your truck? If so, getting a true deep cycle battery is important because you will probably be draining it a significant amount repeatedly, something that will destroy a normal car battery within months and in the long term the extra cost will be worth it. Not only that but what Snow Dog says is true, even after hours of driving you are not going to charge up a battery because the current from the alternator is simply not high enough.

The solultion is as follows, but be forewarned, it can get spendy to do it right. What you need is an aftermarket regulator for your alternator that allows you to pass high rates of current to the battery so that it can recharge quickly, something that the stock regulator isn't designed to do since giving most batteries a high rate of charge will cause them to boil off explosive hydrogen. This leads to the second part, you need a good deep cycle battery that can accept a high rate of charge without outgassing. The best aftermarket regulator is made by Ample Power and is called NextStep or something like that. It has a computer chip in it that automatically monitors the charge and will avoid overcharging your system which can be a problem when using high charge rates and can sometimes ruin batteries. You can visit them at http://www.amplepower.com, they also have lots of good wiring information and other goodies. The best batteries for high rate of charge applications are called absorbent glass mat batteries or AGM and a good example can be found here. These two items in addition to a isolator switch, as mentioned previously, will provide what you are looking for. A high-output alternator would be nice addition but it isn't a requirement. Hope this helps. :smile:

Edit: Don't run a space heater off of this system as it very inefficient and will run you down extremely fast. A better way to get heat is to buy one of those Coleman catalytic heaters, which supposedly can be run with very little ventilation and run off of propane. This leaves lots of power for other things like a laptop, light, vibrator, etc....

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Originally Posted by Pig Bodine

Char,

It sounds like from what you say that you are trying to set up a system so that you can power things while camping the back of your truck? If so, getting a true deep cycle battery is important because you will probably be draining it a significant amount repeatedly, something that will destroy a normal car battery within months and in the long term the extra cost will be worth it. Not only that but what Snow Dog says is true, even after hours of driving you are not going to charge up a battery because the current from the alternator is simply not high enough.

The solultion is as follows, but be forewarned, it can get spendy to do it right. What you need is an aftermarket regulator for your alternator that allows you to pass high rates of current to the battery so that it can recharge quickly, something that the stock regulator isn't designed to do since giving most batteries a high rate of charge will cause them to boil off explosive hydrogen. This leads to the second part, you need a good deep cycle battery that can accept a high rate of charge without outgassing. The best aftermarket regulator is made by Ample Power and is called NextStep or something like that. It has a computer chip in it that automatically monitors the charge and will avoid overcharging your system which can be a problem when using high charge rates and can sometimes ruin batteries. You can visit them at http://www.amplepower.com, they also have lots of good wiring information and other goodies. The best batteries for high rate of charge applications are called absorbent glass mat batteries or AGM and a good example can be found here. These two items in addition to a isolator switch, as mentioned previously, will provide what you are looking for. A high-output alternator would be nice addition but it isn't a requirement. Hope this helps. :smile:

Edit: Don't run a space heater off of this system as it very inefficient and will run you down extremely fast. A better way to get heat is to buy one of those Coleman catalytic heaters, which supposedly can be run with very little ventilation and run off of propane. This leaves lots of power for other things like a laptop, light, vibrator, etc....

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Thats what I was looking for. Thanks.

That seems a little out of my price range so I will probably just buy a couple extra blankets.