# Battery hook up



## lazydaisy67 (Nov 24, 2011)

Does anybody know if two batteries need to be grounded to each other or can/should one battery be grounded to the motorhome? We have a black cable that is currently screwed into the side wall of the battery compartment, but videos we watch show the black cable being hooked up to both negative posts on the two batteries.


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## hiwall (Jun 15, 2012)

With a two battery 12 volt set up the battery negative posts are linked together(like the positive posts). They are also sometimes hooked to the vehicle frame or run to the the appliances that you want to run.


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## phideaux (Nov 7, 2015)

The black cable, you have, connected the side wall should connect to either negative battery terminal, as long as the negative battery terminals are connected to each other.

btw, I am assuming its a 12 volt , 2 battery system.

Happy motoring.

Jim


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## Tirediron (Jul 12, 2010)

Lots of good answers so far, but there are a few things that need sorted, 
Assuming that this is your Winnie. 

1 battery will be for engine cranking, it should have a large negative cable going to the engine block, as well as a 10 guage or thicker wire going to the body ,body ground is important for gage panel and lighting to function as designed.
2nd battery probably for "home" accessories needs a 10 or larger body ground wire and the same to the engine block.

the positive sides should be fed by the alternator through an isolator to prevent one circuit from draining the other. 

While we are on the electrical stuff, if you change out the starter motor, get one for a mid 90s 350/ 5.7, they are far more reliable and use far less power, the down side is that they are not field rebuild able as easily (but they rarely need it)


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## zombieresponder (Aug 20, 2012)

If you have a two battery, 12v system, using 12v batteries, then the negative from battery 1 is connected to the negative of battery 2. The same goes for the positive. Doing this will keep voltage the same, but double(roughly) the amp-hours/cranking amps available at any given time.

If connected as above, both batteries should be the same brand/size and lot number. Without an isolator between them, the weaker of the two will drain the stronger battery.

10 gauge cable is puny, and entirely inadequate for cranking an engine much larger than a lawnmower. Most vehicles will have 4 or 6 gauge...some will have 2 gauge or heavier. The length of the cable needs to be taken into account as well. Longer runs need larger cable to deal with the increased resistance and voltage drop. Welding cable carries more amps with less drop than "battery cable" and is more flexible as well.


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## hiwall (Jun 15, 2012)

I assumed this was your chassis batteries not your engine starting battery.


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## lazydaisy67 (Nov 24, 2011)

Auxillary battery. Is that the same as a chassis battery? Anyway, we tried just hooking one deep cell up. It was fully charged. The lights worked fine, but when he tried to start the generator and it wouldn't crank over right away, it drained the battery dead almost instantly.


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## Tirediron (Jul 12, 2010)

The distance from the generator to the battery that is powering it's starter can make a huge difference in the cable size needed, it is often better to move the auxiliary/chassis battery closer to the generator than to try to install heavier cables just to start the generator. 
Your deep cycle battery depending on the type may not be designed for cranking loads, although a small generator shouldn't need a whole lot of amps to crank.


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## hiwall (Jun 15, 2012)

> Auxillary battery. Is that the same as a chassis battery?


Yes the same.


> but when he tried to start the generator and it wouldn't crank over right away, it drained the battery dead almost instantly.


I am surprised that the generator would use the chassis battery as a starting battery.


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## phideaux (Nov 7, 2015)

I am surprised also that the starting battery is the deep cycle batteries, as they are not designed for high cranking amp output.

Your vehicle battery ,that starts the RV engine should be used , or a separate automotive type battery, tied to charging system should be the setup.



Jim


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## lazydaisy67 (Nov 24, 2011)

He's going to clean up the carb on the generator this week to see if it will fire any better. 

We took our first overnight trip Friday! We live 10 miles from a state park, so it's super nice to get our feet wet there while we're learning. This thing could turn out to be a money pit, but I absolutely adore it and the kids had a blast!


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