GM: 2 batteries on a gasser. Why?

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Woman brought in her truck (2007 w/ 5.7 GAS motor) for a new battery. She flipped when we told her it had 2 and both had to be replaced. Why 2 batteries on a gas motor pick up truck, and is it possible to jury rig it so one can be used?
 
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it has the dual battery or aux. battery option those usually also have the 160 AMP alternator option. They were popular on plow trucks.
 
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Nick1994

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It's an option or added on by the owner for if you have/want a winch, big stereo, auxilary lights etc.
 

ls1mike

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Probably set up for towing, it is an option from GM, it was option 6a6 or something like that. Build code TP2 my truck has it. No battery. What 2007 has a 5.7? You were looking at a 4.8, 5.3, 6.0 or 8.1. I think the last GM truck to use a 5.7 was sometime around 1999, unless you got a van.
 

Nayov

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What part of towing requires a second battery? Must have been a 5.3. edit: I mean what extra electrical load is imposed by towing?
 
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ls1mike

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Got me. I only have one. I think guys with larger trailers, bigger brakes, and extra axles like it for the amount of power it draws. Edit: I do know some guys who run the coach, trailer off the aux battery. Not sure why.
 
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When I do a cowl intake on my Cherokee, I plan on adding a second battery where the original airbox was - there is even a spot for it! But I will have a winch on it by then.
 
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A lot of guys run 2 batteries around here for running a plow. Maybe it was a plow truck? 07 definitely didn't have a 5.7.
 
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I added the diesel tray and a second battery in my old truck. I did this because I had multiple amplifiers with about a 400amp load, and it was really nice. I looked into doing the same with my new truck, but the air box setup on it sits in the spot where the other battery would go, so no go frown But year, a lot of people did what I did and added the second battery setup. I've never seen a 1/2 ton truck come with dual batteries from the factory. Is here as 1500 or 2500? Possible someone added it if she is a second owner, or maybe it was built with some auxiliary package.
 
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In theory if they are 12v,I assume they must be in parallel and you can just leave one battery out with no issues. I'd look to see how the starter is wired to decide which one to keep. I have no experience though of what happens in practice though.
 

ls1mike

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Originally Posted By: zrxkawboy
Originally Posted By: ls1mike
What 2007 has a 5.7?
a Dodge
He said it was GM. No 5.7 in a GM in 2007. smile
 
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Sorry, just trying to be humorous. You are correct about the GM engine, of course.
 

ls1mike

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Originally Posted By: Donald
Only a diesel needs a 2nd battery.
Why? Lots of plow truck have them for the extra accessories. My Gasser came with it as an option for the government. I don't think it was installed because they didn't add anything.
 
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Originally Posted By: ls1mike
Originally Posted By: Donald
Only a diesel needs a 2nd battery.
Why? Lots of plow truck have them for the extra accessories. My Gasser came with it as an option for the government. I don't think it was installed because they didn't add anything.
With the engine running the vehicle's battery should be able to handle the load. With one or ten batteries the alternator will need to charge the batteries back up or you are in a downhill situation. For a diesel, you need to get the glow plugs warmed up then crank the engine and in dead winter a 2nd battery might be helpful.
 
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I thought most of the plow setups these days used what looks like an auto starter. Might not draw 200+A while moving the blade, but it's no 10A load, not with jumper cable sized wiring running to it. Miller88's winch is also likely going to be a heavy amp draw. A second battery makes sense to me--instead of the alt going from 20-40A (running lights and ECU) to 100+ suddenly, the second battery can help buffer that load. And help reduce how far down the battery might get drawn during usage (since the load is being split across two).
 
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My tracker has a second battery tray, but I suspect its more for the RHD versions than having two batteries. The diesel version is a 2.0L as well so I don't think it needs 2 batteries either.
 
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