Time to replace the 8ds! Going to Group 31s!!! Need help!

[grantgoold]

Looks like it is time to replace the two 8ds in the bus. I sure would love not to change out the wiring setup with both posts on one end of each battery. I know that many have transitioned to group 31s.

Looking for suggestions on make and model #

Thanks


Grant

[Ed Hackenbruch]

Go to a battery distributor that carries different brands if possible so you can compare. One of the main things to look for is high CCA  which is Cold Cranking Amps.  The higher the better i believe.

[Nellie Wilson]

Hi Grant -

If it's like mine, doubt you'll have to change setup - seems like there is plenty of cable to reach opposing terminals?

I'm in process of doing the same, only more gradually. One 8D went bad but the other seems okay. So I'm hooking two new batts (group ) to the good 8D for now. Then, when the other 8D croaks, I'll still have two fresh batts (re-connected in series) to get out of trouble. Don't know if that's workable but limited resources lead me in strange directions.

One thought: If you find you must re-wire, consider moving your 31s to the rear...much shorter cable = less loss of 'juice.' (This tip came from Ralph P. on BNO board).

FWIW.

Nellie

[grantgoold]

I appreciate the input. I am hoping to simply take out the big 8ds and swap for group 31s with the same pole configuration.

Thanks

Grant

[rv_safetyman]

First, the mixing of old and new batteries is regarded by most knowledgeable folks as being a very marginal practice.  If the old battery is on its last legs, the new batteries can be forced to be "work harder".  Sorry, there are better technical descriptions, but you get the idea.  I have never seen a case where folks say that mixing old/new, mfgr., or sizes is good practice.

As Nellie says, it is good practice to get the new batteries close to the starter.  The current draw for the starter really demands very large cables for long distances.

Lastly, most folks have migrated to 3ea 31 batteries.  They are pretty inexpensive relative to the 8D and a lot easier to work with.

No matter what you do, if you change to 31s, you will need to make up some battery cables.  That is not a big deal.  You can buy the correct size welding cable and copper ends at any welding shop and make your own.

Now is the time to remove the old cables, inspect them, clean the terminals and ground connections and reinstall them correctly.  You need to be very sure to route them carefully and secure them very well.  A large number of fires occur as the result of grounding of the positive cable on a frame structure.

Jim  

[luvrbus]

A good G-31 battery will have a high reserve, cold cranking amps are important also but that is only for a short period like 20 seconds buy good batteries and cables you will need 4 for a 24V system and 3 for 12v system some guys get away 2 for a 24V system I would not go with 2 myself just my way YMMD sooner or later 2 G-31 batteries on a 24v system will cost you a starter


good luck

[TomC]

I took out my 2-8D starting batteries and replaced them with two 31 batteries from Interstate.  The 8D's have 1200CCA and the 31's have 1100CCA so starting has not been an issue. There was enough cable to just hook up the new batteries.  I used various sized wood pieces to create new battery hold down in the original battery tray.  I also have 2-150amp bridging solenoids in parallel that I can kick on from the dash to tie the 2 deep cycle 8D AGM batteries to the 31's.  I have started the bus on the deep cycle batteries when the 31's went dead once.  If you have a bridging solenoid, you can get away with not having to use 3 or 4 batteries.  Good Luck, TomC

[mc5a Jon]

Could someone explain why 2 batteries could cost you a starter?

[rv_safetyman]

Ron, the statement was two 31 batteries in series for 24 volts.  That still only gives you 1110 CCA and only for a short time.  The voltage will drop fairly quickly if you have to crank on the starter andn1 that will cause the current to go up and that hurts a starter.

Jim

[Fredward]

Grant,
I have two AGM group 31s in for coach batteries in my MC-5a with 871. They work fine even up here in Minnesota. If its cold I plug it in or use the bump and roll method. They are connected to the original cables as far as I know; the coach was set up that way when I bought it four years ago. The batteries must be five or six years old. So we know it works even up here in Minnesota although I don't use it December - February.

Definitely replace both batteries not just one in a group; the older one will parasitically drag the new ones down and cause premature failure of the new ones.

To use two pairs of Group 31s to replace two 8D would be the smartest thing to do I'm sure but just wanted to share my experience with only two batteries on a 24 volt system.

Fred

[grantgoold]

Thanks for all the input. I will work with my local battery dealers to come up with the solution. I will replace all the batteries at once!

Grant

[HB of CJ]

Which, in a pinch, may make the difference between an old coot like me changing out my starting batteries during some emergency where I have no choice but to do sosss and by myself.

Be amazed how lousy the voltage drop is from the batteries to that hogg starter motor using factory designed battery cables.  Sometimes such engineering decisions are based on cost.

Now would be a good time to, if possible, to shorten up the cables as much as you can AND, if possible, INCREASE the size of the cables.  Be amazed how much of an improvement it will make.

Especially when it is extremely important that your engine start up the first time with no second try available.  I would go with some very nice group 31 batteries with fat, short cables.  HB of CJ (old coot)

[Ace]

I replaced my 4 group 31's with batteries from my local Sam's club! I know, they aren't the top of the line you guys would recommend but I look at it this way. First off, since I installed my on board 24 volt battery charger/maintainer they have lasted for the last 3 years and kept charged with no problems. Second, If the time ever does arise that I have a problem while on the road or even here, there is a Sam's club almost in every city where I could replace them, plus, from past experience, they have been warranted for N/C but that was before I installed the charger!
If you purchase from a battery source that isn't well known like Sam's or Napa, then replacing them might come out of your pocket IF your on the road and miles away from the original place of purchase!
Sam's, to me, is the simplest, easiest and no questions asked kind of place plus they have a large enough parking lot to pull in and park where you could replace them if you had to. Don't ask me how I know this but I do! That was when I had the "never wanting to re-start" Eagle with 8D's.

[grantgoold]

Ace, always love stories that remind us that when a bus dies along side the road, you have a real big problem. I like the idea of pulling into a parking lot and doing the replacement as necessary.  I was told by the Interstate Dealer today that many "high" quality batteries are made in the same place just change out the sticker they slap on the front. With cores so popular many batteries are rebuilds.

Thanks again for all the input.

Grant