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Author Topic: Start Batteries  (Read 1021 times)
txjeff
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« on: April 28, 2010, 09:46:06 AM »

Im looking at changing the two 8D start batteries to 4 group 31s. My batteries are stacked on two slides in the compartment. It doesnt look like two 31s will fit in the same area that a 8D is. Im curious how anyone else has done this......


jeff
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73 MC-7combo
Brenham, Texas
Len Silva
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« Reply #1 on: April 28, 2010, 09:53:30 AM »

Here is a table of all battery sizes:  http://www.rtpnet.org/teaa/bcigroup.html

The 8D is 20.75" X 11.125"  and a Group 31 is 13" X 6.375"

I was able to get three Group 31's in the space of a single 8D on my 4104, with room to spare.  It depends on how thigh the battery rack is.
« Last Edit: April 28, 2010, 09:55:09 AM by Len Silva » Logged


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Ed Hackenbruch
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« Reply #2 on: April 28, 2010, 10:30:30 AM »

I replaced 2 8D's with 2 Group 31"s and have had no starting problems. I do try to stay out of cold weather and will use my block heater if it is less than 40 degrees out. I also have a rebuilt 8V71 that only has about 50,000 miles on it so it usually fires up as soon as i hit the switch. Grin
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
Stormcloud
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« Reply #3 on: April 28, 2010, 10:34:51 AM »

I replaced my 2 x 8D with 4 auto batteries (series-parallel arrangement)
I dont have OTR air. It seems to work well (for 3 years now) starting the coach both summer and winter.

They were a matched set originally, but one of the batteries failed internally and drained all the batteries,so theres one oddball.
 
My only other suggestion would be when paralleling the 2 batteries is that there be a provision for isolating each of the batteries from its mate (in case of failure,etc).

It works for me!

Mark
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Mark Morgan    near Brandon, Manitoba, Canada
1972 MCI-7     'PapaBus'  8v-71N MT654 Automatic
txjeff
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« Reply #4 on: April 28, 2010, 11:19:47 AM »

I have the OEM 8D trays and was trying to see how anyone modified them to fit the 2 group 31s. I guess just using two 31's might be a option to try since I dont use the OTR air either....
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73 MC-7combo
Brenham, Texas
Sam 4106
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« Reply #5 on: April 29, 2010, 01:01:00 AM »

I also use two group 31 batteries to start our 8V92. When one failed the guy at the battery store (they only sell batteries, mostly wholesale) suggested a used one to go with the good used one I had. So for a small fee I have a good working pair again. I don't know how long they will last, but they won't leave me stranded because I can also start off of the new six battery house bank if needed.
Good luck, Sam MC8
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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