6 volt system/ 2 batteries

[Guest Carloco]

I recently purchased a 1946 dodge Pickup tht is original and complete. It is a 6 volt system but somewhere along the line another 6 volt battery was added. Im not sure how to attach the cables to each battery. One of the batteries is located under the floor board. I attached the positive cable to the negative terminal and ground to the positive terminal. I left the other battery(located under the hood) unconnected. There is also a kill switch on the dash. I turned on ignition and starter moter turned fine. My question is how do I connect the other battery and why is there 2? Thanks for any help?

[trimacar]

Someone was trying to "up the amps" to the starter motor. They'd be connected in parallel, i.e. positive to positive, negative to negative, which still gives 6 volts but combines the amperage.

If you connect them in series (for example, positive of one battery to ground, negative of other battery to starter switch, then connect two remaining terminals battery to battery), you've just created a big 12 volt battery.

If one 6 volt battery won't turn engine over fast enough, it's because battery is bad, starter is bad, cables are too small (6 volt cables are much larger than 12 volt cables), or you have poor connections. Sounds like you don't have that problem.

[keiser31]

I would NOT connect the two together. I can only imagine that the previous owner either needed an extra battery (under the hood) for added accessories or he was too lazy to lift the seat to work with the original battery.

[Rusty_OToole]

Probably best to leave out the second battery. It could have been installed for various reasons, such as to run a 12 volt radio, or for a starting boost, or maybe the original owner was a ham radio operator.

A careful examination of the wires to the battery should reveal how it is wired and what it was used for.

[Guest cben09]

Hows the compression,,???,,,If they ran for a day or 2 without the air cleaner in March,,,,,They call it the Abq bore job,,,Hope this is not it,,,but the extra battery might get it started for a while,,Just a thot' If it was up north,,,I'd say it was for the electric/hydraulic snow plow,,but the NM address says no to that,,,Cheers,,Ben

[Fred Zwicker]

See www.fzoldcars.com and click on "Technical Stuff" link at top of Home Page.

Then down to the article on hooking up two batteries. There are plenty of pictures showing the correct way to hook up two 6-volt batteries in parallel (still 6-volts but twice the amperage). Older Cadillacs sometimes have hard-start problems when engine is hot and this does the trick.

However, as others have said, be sure to check the battery cables, as often newer cables are substituted for the older cables. 6-Volt cables are about twice the diameter of 12-volt cables and the difference is critical.

Here is one of the pictures from the above link showing how to hook up two Optima batteries in parallel in a 1939 LaSalle.

Fred