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Dual Battery Check

stansloski

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stansloski Enthusiast

stansloski

Posted
Posted

I have a 2500HD Silverado 6.1 gasoline engine. It has two batteries. It has had a snow plow installed in the past. Are both batteries used to start the engine? Or could they be? How can i check? Thanks for any help you can offer.

Formulabruce Enthusiast

Formulabruce

Posted
Posted

Some older plow systems used dual batteries so the hydro electric motors had plenty of power..

davester Senior Enthusiast

davester

Posted
Posted

doesn't it really depend on how the batteries are hooked up?

 

If they are just hooked up in parallel, then both batteries will be used.

 

you have to figure out how the batteries are hooked up to your truck to figure out if one or both batteries are used.

00Silverado4x4 Senior Enthusiast

00Silverado4x4

Posted
Posted

doesn't it really depend on how the batteries are hooked up?

 

If they are just hooked up in parallel, then both batteries will be used.

 

you have to figure out how the batteries are hooked up to your truck to figure out if one or both batteries are used.

Yes and no, yes they will be in parallel but no because he may have the isolator that prevents the second battery from being discharged while starting. On my truck I have the factory dual battery set up. The second battery is connected through the trailer wiring harness so it will send it's power to the trailer when plugged in. However, it will not help start the truck due to the isolator. However, it does get charged through the alternator when the engine is running. Now if the batteries were directly wired in parallel with no isolator then it would be in the circuit to used to help in starting. So as said you need to need at how the batteries are actually wired to know which set up you may have.

stansloski Enthusiast

stansloski

Posted
  • Author
Posted

Good morning. You folks did help me understand my question a whole lot better. So my real question is "How do I check if my batteries are parallel or series?" Also, "How can I tell if the isolating device is installed and working properly?"

 

thanks

don

00Silverado4x4 Senior Enthusiast

00Silverado4x4

Posted
Posted

Highly doubt the batteries are in series as this would cause your entire electrical system to be 24v vs 12 volt. On my truck the isolator is on the fire wall up behind the second battery on the passenger side. To check it I just checked both sides of the isolator when the truck is off. The second battery side will have 12v and the other side there is no voltage. When the truck is running you will have 12v on both sides since the isolator is energized so the battery is charged.

Chevyguy27 Enthusiast

Chevyguy27

Posted
Posted

Odd question but do they all come with dual batteries or just certain ones I as well have a 2000 2500 but only with one battery.

davester Senior Enthusiast

davester

Posted
Posted

Most pickup trucks don't come with dual batteries. Some may have a factory dual-battery install and others may be a second battery installed by their owner.

 

Probably your best bet for determining how the battery is hooked up is to track the positive cable on both batteries [the very thick one].

 

If one of them goes directly to the other battery, or they connect together somewhere, then both batteries are used all the time.

 

If they don't connect together, then you need to figure out what they are connected to and when it allows power through [ie, if it's a solenoid like described in post 7].

00Silverado4x4 Senior Enthusiast

00Silverado4x4

Posted
Posted

It wasn't installed on all of them. If you look at your RPO codes inside the glove box look for TP2. If that is one of them it had the factory dual battery set installed. Whether or not it's still hooked up like factory is what you have to figure out.

Cosmic Charlie Enthusiast

Cosmic Charlie

Posted
Posted

If you have a cheap battery / alt tester -Walmart- < $10 - it will tell you if both are being charged when the truck is running - newer trucks 2 battery OEM only use the 2nd battery when called for (electric switch will open / close ( per factory design ...)

stansloski Enthusiast

stansloski

Posted
  • Author
Posted

Good morning.

 

Thanks to all of you. I now know what my next step in testing is. After it warms up a little here I will try those steps. After that I will get back to you all and let you know what I did and find out.

 

thanks

don

dewfpo Senior Enthusiast

dewfpo

Posted
Posted

I have a 8.1L with the TP2 dual battery option. Only one battery is used for starting and keeping the clock and presets charged up when the engine is off.

 

DEWFPO

stansloski Enthusiast

stansloski

Posted
  • Author
Posted

Highly doubt the batteries are in series as this would cause your entire electrical system to be 24v vs 12 volt. On my truck the isolator is on the fire wall up behind the second battery on the passenger side. To check it I just checked both sides of the isolator when the truck is off. The second battery side will have 12v and the other side there is no voltage. When the truck is running you will have 12v on both sides since the isolator is energized so the battery is charged.

Good afternoon. It looks like I would have to take the battery out to reach the isolator. Does that make sense? Both batteries are at about 12 volts when the engine is not running and at about 14 volts when the engine is running. Does that tell me that I am ok? or do I still need to get to the isolator.

 

thanks

don

davester Senior Enthusiast

davester

Posted
Posted

what are you trying to accomplish and/or what is the problem you are trying to solve?

 

batteries at 12v off, and around 14V with engine running means the system is working fine.

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