Need ideas on dual battery setup with pics

[davidcyndi]

I have a sprinter 311bhs. It has a long battery tray but it has a metal electrical connections box blocking the way for a dual battery box. so what should I do if I want to run dual 6v batteries in series? Should I have two boxes and run cables between the boxes some how? Seems like the most logical idea but wanted to pick the brains of you guys that have been doing this waaaayyyyy longer than I have. Thanks and pics below so you can see what I am talking about.

[f6bits]

I don't have detailed pictures, but I did just buy a second box and stuck it in my tray. I bought a short battery cable and ran it between the two batteries. The existing + and - cables were long enough to reach the wider span of batteries.

No big deal to use a second box instead of a dual box. In fact, I think the single boxes are more purpose-made for batteries. The more affordable dual boxes all look like long tubs, and *still* more expensive than two single boxes.

[SteveC7010]

It sure looks like that metal tray was built to hold two batteries. But measure to be sure. If you wanted to move to a pair of 6vdc's you'd first want to determine the physical size of the battery you already have and plan on two 6 volters of the size. You'd also want to get a second battery box to match the one you have.

Cabling is not particularly difficult but you will need to purchase one or get a new one made to connect the two batteries properly. If you were installing a second 12vdc battery, you hook them up in parallel; ie. positive to positive and negative to negative. However, with 6vdc batteries, you want to end with 12vdc so they get added together (6+6=12) by connecting the existing positive cable you have to a positive post on one of the 6vdc's. This is called connecting them in series. The existing negative cable goes to the negative post of the other 6vdc. Here's where you need a new cable to connect the negative of the first battery to the positive of the second. This may help you understand:

positive cable to trailer ---> + terminal of battery A/// - terminal of A ---> + of battery B/// - terminal of B ----> trailer ground

The cable in bold is the one you need to get. You need to know what type of terminals are on the 6vdc's. If they are the old style lead posts, you'll a new cable with the right connectors and long enough to reach both posts. If the battery has wing nuts like most of the 12vdc RV batteries, it's a different terminal and the same wire. Now, these cables are easy to make up if you are comfortable with automotive wiring. If you're not, here are some pics to ease the way:

This is a cable that you'd use if it is wing nut posts. You can buy them in different lengths at any auto parts store.


If the batteries have lead posts, it's going to be a touch more difficult, but not really a problem. This is what a lead post terminal looks like:


You can readily purchase cables with a ring terminal on one end and a lead post on the other at any auto parts store. Here's one:


But you won't find ready made cables with lead post terminals on both ends. Some auto parts stores can make up custom cables and that would be a good place to start. I do know there are a number of places on the internet that will make them up as well.

Last point: The + and - cables of the trailer are probably made of #4, #6, or #8 stranded wire. Most battery cables are #2, #0, or #00. Determine what size wire your leads are, and don't buy a new cable that is made of smaller gauge wire (the higher the number, the smaller the wire.) Buy one of equal size if you can. If you have to go larger, no problem.

OK, I know it sounds complex, but it's really not.

• Know the physical size of the batteries you need.
• Get a matching battery box to the one you have.
• Determine the type and length of the new A- to B+ cable you need and get it.
• Set boxes in place.
• Set the batteries in the boxes.
• Install the A- to B+ cable.
• Connect the positive trailer wire to the positive terminal of A.
• Double, double check your work.
• Connect trailer ground to B- and it's Miller time.

If you get stuck anywhere along the line, stop work, take pics, and post them here. We'll figure out what's what and get you going again.

[SteveC7010]

And a big +1 on skipping the very expensive dual battery box!

[labs4life]

I have dual 6v's on my sprinter 311. No problem and just put them in 2 separate boxes. Tight fit but works fine.

[davidcyndi]

Originally Posted by f6bits

I don't have detailed pictures, but I did just buy a second box and stuck it in my tray. I bought a short battery cable and ran it between the two batteries. The existing + and - cables were long enough to reach the wider span of batteries.

No big deal to use a second box instead of a dual box. In fact, I think the single boxes are more purpose-made for batteries. The more affordable dual boxes all look like long tubs, and *still* more expensive than two single boxes.

Thanks for the reply f6bits. Yeah I think after what everyone said my assumption was right to just go with 2 boxes. Did you just drill a hole between the two boxes to run the cable to connect the two batteries (series)? or did you find a long enough cable that would go out of box one andmake it all the way to box two?

[davidcyndi]

Originally Posted by SteveC7010

It sure looks like that metal tray was built to hold two batteries. But measure to be sure. If you wanted to move to a pair of 6vdc's you'd first want to determine the physical size of the battery you already have and plan on two 6 volters of the size. You'd also want to get a second battery box to match the one you have.

Cabling is not particularly difficult but you will need to purchase one or get a new one made to connect the two batteries properly. If you were installing a second 12vdc battery, you hook them up in parallel; ie. positive to positive and negative to negative. However, with 6vdc batteries, you want to end with 12vdc so they get added together (6+6=12) by connecting the existing positive cable you have to a positive post on one of the 6vdc's. This is called connecting them in series. The existing negative cable goes to the negative post of the other 6vdc. Here's where you need a new cable to connect the negative of the first battery to the positive of the second. This may help you understand:

positive cable to trailer ---> + terminal of battery A/// - terminal of A ---> + of battery B/// - terminal of B ----> trailer ground

The cable in bold is the one you need to get. You need to know what type of terminals are on the 6vdc's. If they are the old style lead posts, you'll a new cable with the right connectors and long enough to reach both posts. If the battery has wing nuts like most of the 12vdc RV batteries, it's a different terminal and the same wire. Now, these cables are easy to make up if you are comfortable with automotive wiring. If you're not, here are some pics to ease the way:

This is a cable that you'd use if it is wing nut posts. You can buy them in different lengths at any auto parts store.


If the batteries have lead posts, it's going to be a touch more difficult, but not really a problem. This is what a lead post terminal looks like:


You can readily purchase cables with a ring terminal on one end and a lead post on the other at any auto parts store. Here's one:


But you won't find ready made cables with lead post terminals on both ends. Some auto parts stores can make up custom cables and that would be a good place to start. I do know there are a number of places on the internet that will make them up as well.

Last point: The + and - cables of the trailer are probably made of #4, #6, or #8 stranded wire. Most battery cables are #2, #0, or #00. Determine what size wire your leads are, and don't buy a new cable that is made of smaller gauge wire (the higher the number, the smaller the wire.) Buy one of equal size if you can. If you have to go larger, no problem.

OK, I know it sounds complex, but it's really not.

• Know the physical size of the batteries you need.
• Get a matching battery box to the one you have.
• Determine the type and length of the new A- to B+ cable you need and get it.
• Set boxes in place.
• Set the batteries in the boxes.
• Install the A- to B+ cable.
• Connect the positive trailer wire to the positive terminal of A.
• Double, double check your work.
• Connect trailer ground to B- and it's Miller time.

If you get stuck anywhere along the line, stop work, take pics, and post them here. We'll figure out what's what and get you going again.

Steve, man I have got to say wow on this post! You really went above and beyond. I really appreciate you doing so. I was educated on every aspect of my question for sure. Thank you. I think a mod should make your post and edu. for future newbs like myself. Thanks

[davidcyndi]

Originally Posted by labs4life

I have dual 6v's on my sprinter 311. No problem and just put them in 2 separate boxes. Tight fit but works fine.

what boxes did you go with? And nice to hear that the 2 boxes fit. Do you have a newer sprinter? Basically is it set up like mine?

[labs4life]

Originally Posted by davidcyndi

what boxes did you go with? And nice to hear that the 2 boxes fit. Do you have a newer sprinter? Basically is it set up like mine?

I have a 2013. I just bought boxes from Walmart. They are really not deep enough and I like the one you have better. You should be able to get a cable made that is whatever length you want. My Dad brought me the link cable when they came to see the grand kids. He works on golf carts in MS. Got a golf cart shop nearby? They can make you a cable that will be fine. Just tell them what gauge wire and what ends. They use the brass circular ends mostly and put a washer and nut on the post. If you don't have batteries already, that is also an excellent place to get 6v batteries. Most likely cheaper than a camping type store. They will need cores tho, battery cores of that size are $26 in MS.

[Comptech]

Here is a picture to better demonstrate...

Originally Posted by SteveC7010

It sure looks like that metal tray was built to hold two batteries. But measure to be sure. If you wanted to move to a pair of 6vdc's you'd first want to determine the physical size of the battery you already have and plan on two 6 volters of the size. You'd also want to get a second battery box to match the one you have.

Cabling is not particularly difficult but you will need to purchase one or get a new one made to connect the two batteries properly. If you were installing a second 12vdc battery, you hook them up in parallel; ie. positive to positive and negative to negative. However, with 6vdc batteries, you want to end with 12vdc so they get added together (6+6=12) by connecting the existing positive cable you have to a positive post on one of the 6vdc's. This is called connecting them in series. The existing negative cable goes to the negative post of the other 6vdc. Here's where you need a new cable to connect the negative of the first battery to the positive of the second. This may help you understand:

positive cable to trailer ---> + terminal of battery A/// - terminal of A ---> + of battery B/// - terminal of B ----> trailer ground

The cable in bold is the one you need to get. You need to know what type of terminals are on the 6vdc's. If they are the old style lead posts, you'll a new cable with the right connectors and long enough to reach both posts. If the battery has wing nuts like most of the 12vdc RV batteries, it's a different terminal and the same wire. Now, these cables are easy to make up if you are comfortable with automotive wiring. If you're not, here are some pics to ease the way:

This is a cable that you'd use if it is wing nut posts. You can buy them in different lengths at any auto parts store.


If the batteries have lead posts, it's going to be a touch more difficult, but not really a problem. This is what a lead post terminal looks like:


You can readily purchase cables with a ring terminal on one end and a lead post on the other at any auto parts store. Here's one:


But you won't find ready made cables with lead post terminals on both ends. Some auto parts stores can make up custom cables and that would be a good place to start. I do know there are a number of places on the internet that will make them up as well.

Last point: The + and - cables of the trailer are probably made of #4, #6, or #8 stranded wire. Most battery cables are #2, #0, or #00. Determine what size wire your leads are, and don't buy a new cable that is made of smaller gauge wire (the higher the number, the smaller the wire.) Buy one of equal size if you can. If you have to go larger, no problem.

OK, I know it sounds complex, but it's really not.

• Know the physical size of the batteries you need.
• Get a matching battery box to the one you have.
• Determine the type and length of the new A- to B+ cable you need and get it.
• Set boxes in place.
• Set the batteries in the boxes.
• Install the A- to B+ cable.
• Connect the positive trailer wire to the positive terminal of A.
• Double, double check your work.
• Connect trailer ground to B- and it's Miller time.

If you get stuck anywhere along the line, stop work, take pics, and post them here. We'll figure out what's what and get you going again.