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Topic: How to install group 31 batteries in your coach (Read 1372 times) previous topic - next topic

How to install group 31 batteries in your coach

I finally lost one of our 34 series batteries in our U300. Ours has three batteries just in front of the rear bumper and I thought it might be a tight squeeze as the 31 series are about 3 inches longer and a little taller but the same width.

So, why the 31 series? They are commercial batteries with 950 CCA compared to about 850 CCA or so with a 34 series. But there is a lot more differences. The 31s have heavier cell connectors, greater distance between the plates and the bottom of the battery. Battery weight is usually an indication of the quality with the Autozone 31 series coming in at 59.9 lbs compared to 42 lbs for the 34 series. Sam's Club has a less expensive 31 series at $97 but it's five lbs. lighter.

Price: I dickered with Autozone over the price for three. They agreed to sell three of them for $107.99 each plus exchange. These have 1/4" screw on connectors so a conventional post has to be purchased. $2.99 for a set of two at O'Reilly's. I like their post better as they have the polarity marked clearly on the top of the post.

The batteries would not fit even if I modified the existing rack so I built a copy with four tabs at each end to bolt to the existing rack below. This allows me to move the batteries one inch toward the engine but two inches to the rear for clearance. I turned the batteries around so the positive posts are at the rear. This way, there is no possibility of a hot post touching the power steering reservoir. I did have to adjust the reservoir up about an inch and turn it about five degrees or so.

Cost: Home Depot for (2) three foot 1-1/2" x 1/8" angle iron. About $8 each. A three foot strap to help distribute the weight and a 3'x5' Hardie Backerboard. 4 sets of 5/16"x 1"  stainless nuts/bolts/washers. I painted the backerboard so it would not absorb any grease/oil. The hold down bolts have to 12" plus I purchased stainless nylocks/washers also. The rack was too big to fit in my powder coat oven so I just painted it.

Now, I have about 2 inches between the batteries and the crank pulley. Plenty of room.

Pierce


Re: How to install group 31 batteries in your coach

Reply #1 –
Pierce,

Nice job. How did you attach the battery tray to the beam? Welded?

see ya
ken

Re: How to install group 31 batteries in your coach

Reply #2 –
Quote from: kenhat –
Pierce,

Nice job. How did you attach the battery tray to the beam? Welded?

see ya
ken
Ken,

Thanks!

No, I was in a hurry and you can't see the four tabs in the photo. The new rack is exactly the same width as the old one. It has four tabs welded on the ends (two on each end) and a 5/16" hole you drilled about an inch down on each one. Place the new tray down on the old tray and then move it so it extends about one inch forward of the front of the old tray and about 2 inches over the back of the old tray. Once you are happy with the location, take a pencil and mark where you are going to drill the  two holes in the RIGHT SIDE. Drilling the holes is a little tricker on the left side as I lifted the tray up a little and moved it over to the right about a quarter inch so the left hand tabs are inside the old rack below. I then marked where the holes are going to be drilled. I drilled them 3/8" as the accuracy is not perfect. The new rack is bolted to the old one below by four 5/16" stainless bolts/nylocks/washers. Then you raise it again and lower it so all tabs are on the outside of the old rack, insert and tighten the 5/16" fasteners and you are all set. You must remove the 10" battery hold downs first to make it an easy job. The hold downs must have some strong back and forth action or they will only go straight down. They need to be tilted about 10 degrees so you can remove them and replace with the 12" new ones.

If the new rack is a tiny bit narrower than the old one, the tabs won't go down the side of the old one. Have to bang it out or tack at the top when welding, bend it out a little and finish welding.

Sorry the photos were not better as I'm still on one leg and have trouble getting out to the coach and back to the house. Welding was outside in the wind so not the prettiest.

Attached is the photo showing the tabs. Please post if you have questions.

Pierce

Re: How to install group 31 batteries in your coach

Reply #3 –
Nice job I think your going to like those group 31 we used those in our big trucks. b^.^d

Re: How to install group 31 batteries in your coach

Reply #4 –
Thanks Pierce! My coach didn't come with a battery tray back there. I have 3 8D's in the wet bay. 1 coach 2 house. I've fantasized about adding 3 coach batteries to the engine compartment and dedicating the 3 8D's for house.

As an experiment I've combined the 3 8D's. Since we fulltime I watch the charge state pretty close when we are dry camping. So far no issues with starting but I do understand I'm rolling the dice a little bit. Which is why your battery tray peaked my interest.

see ya
ken

Re: How to install group 31 batteries in your coach

Reply #5 –
I wanted to make it so no one would have to do any welding, just bolt it on. If you have a side radiator, the space between the back bumper and the crank pulley is perfect. I used the OEM cables.

Pierce

Re: How to install group 31 batteries in your coach

Reply #6 –
Pierce,
Nice job!  We are going to change our tray to accommodate the group 31's also when we return to Florida.  My tray currently just holds 3 automotive batteries. I have easy access to the tray and batteries.  What were the overall dimensions for the group 31!tray?
John M.

Re: How to install group 31 batteries in your coach

Reply #7 –
John,

Your wish is my command! OK, here are a couple of photos with a tape measure included. I used 1/8" angle iron. To easily use the Foretravel cables, the batteries are spaced about 3/8" apart at the top with about 1/2" at the bottom. The width allows about 1/8" or a little more at each battery end.

For the small angle iron hold down, I turned the bottom angle toward the positive posts. If it happened to come loose, it's less likely to make contact with the hot side and turn into a welder. Foretravel used double nuts on the long fastener but I chose to use stainless nylocks. I can't see them coming loose.

The OEM 34/78 series batteries weigh about 42 lbs each. The 31 series are 60 lbs each so the three are about 54 lbs heavier.

Pierce
 

Re: How to install group 31 batteries in your coach

Reply #8 –
Pierce,
Thank for the info!
John M.