Why Two 8D batteries?

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Why Two 8D batteries?

October 06, 2014, 11:57:07 am

Why two 8D batteries? One for coach and one for engine. Couldn't a regular battery be adequate for starting the engine?
I am always amazed how fast our engine starts. Not even one full revolution and it is running.

I have changed all our clearance lights to LEDs. All our interior fluorescent lights to LEDs. Even the porch light to LEDs. We do not drive at night or in the rain so draw on the engine battery is at a minimum.
Current coach battery took a dump so I am considering moving the engine battery over and putting a battery in that doesn't weigh 180#. I do have the current batteries connected and there is a boost/charge switch on the dash.

Lifting the 8D batteries out of the well under the steps is getting to be a bit of a hassle with the back issues I have.

Re: Why Two 8D batteries?

Reply #1 – October 06, 2014, 12:11:17 pm

Test results showed my 5.9 Cummins started with 336 amp @ 50 degree temperature so I purchased & installed a 800 CCA deep cycle battery original one was 1300 CCA. We live in TX so I don't need that.
And my house batteries are four 6 Volt deep cycle golf cart batteries; installed in series & parallel, double the voltage & double amperage.

Re: Why Two 8D batteries?

Reply #2 – October 06, 2014, 12:13:11 pm

Pretty sure if you wanted to change to 2 100cca truck battery you could. That way at least less weight from eack, should fit into that space eiser, you will need to rework the cables

That CAT3208 starts quick!

Re: Why Two 8D batteries?

Reply #3 – October 06, 2014, 12:35:30 pm

Sorry John, our engine is the old, crappy, unreliable, undesirable, least appreciated, underrated boat anchor of a 8.2 liter turbo-charged V8 Detroit Diesel with 78,000 miles on it and only gets 9MPG pulling our Saturn Vue. It starts easily, runs smooth, could use another 50 horse (another reason I am trying to get rid of weight) and hasn't cost us a dime over oil changes and a new air cleaner.

Re: Why Two 8D batteries?

Reply #4 – October 06, 2014, 01:00:44 pm

Engine types and seasons dictate the model and number of batteries needed. What may spin an engine easily in summer may not be do the trick in winter. The cranking speed can make the difference from a quick start to no start in winter as the faster the piston compresses the air, the less temperature/psi loss there is. As batteries age, they may loose a bit of CCA also.

On our fire trucks with Detroit 8V-71 engines, we had 8D batteries on each side with a Cole-Hersee selector switch under the seat. We normally switched between #1 to #2 position and then back every other day. After the Detroit conversion, we occasionally had a hesitation in cold weather so kept the switch in the off position turning it to the both position when the engineer opened the door. Never a spot of trouble after that. Both batteries were located within about 3 or 4 feet of the starter motor.

As we head into winter, good time to pull and clean the terminals and cable mating surfaces.

Pierce

Re: Why Two 8D batteries?

Reply #5 – October 06, 2014, 02:22:07 pm

Buy from O'Reilly's and they will do the swap

Re: Why Two 8D batteries?

Reply #6 – October 06, 2014, 06:46:56 pm

Tim, that only makes my wallet lighter, not the coach.

Re: Why Two 8D batteries?

Reply #7 – October 06, 2014, 07:24:19 pm

Ya know......that's a damn good idea. I hate my 8d where it is. Tomorrow I'm going to test my Die Hard from the pickup and see how that works out.

Re: Why Two 8D batteries?

Reply #8 – October 06, 2014, 07:27:27 pm

My 7.3 starts right up down to 20 without block heater

Re: Why Two 8D batteries?

Reply #9 – October 06, 2014, 07:54:47 pm

I have (2)two Interstate 8Ds for house batteries, (2)two optima red top cranking batteries. The house batteries work well(no inverter), all LED house lights, 2 12v TVs. The cranking batteries are super batteries. At 20 deg. and no block heater(cat 3116), I would have to crank for 2-5 mins(real hard start). I will also say that my optima red tops have done it(once in arkansas) and are still doing it and they are 10 years OLD. Right here in east texas(Lufkin) at 30 something without block heater, the cat will have to spin a bit before it will start to pur. I am amazed at how good they are.

Re: Why Two 8D batteries?

Reply #10 – October 06, 2014, 08:02:08 pm

If you have the height and room, It makes the most sense to me to use two 6 volt deep cycle batteries in series as apposed to an 8D. Easier to handle and will perform better if dry camping. Have a great day ---- Fritz

Re: Why Two 8D batteries?

Reply #11 – October 06, 2014, 10:20:50 pm

Hi Nighthawk 8d's are alot of battery power for your 8.2, but when things go a little wrong, bad fuel, filter, cold weather, etc. you will appreciate the extra starting power. All engines have these issues from time to time and when you cant crank them it makes the problem that much worse. If you decide to change, make sure you still have the battery power for the "problem times" Mark

Re: Why Two 8D batteries?

Reply #12 – October 07, 2014, 08:54:32 am

Twig, please let me know the results od your experiment.
Now that I have replaced the totally melted block heater plug end and the outlet my block heater works. Also, in cold weather (all the way down to 40) we do not boondock. We go to places with electricity and keep the engine and coach warm & happy.

Our coach does lean a bit down on the pass side. Think about it: 26 years old, leaf springs, 360# of batteries, 44 Gallons of propane x 8= 256#(approx.) plus all the "stuff" in the compartments on that side.
Our batteries are in a well under the lift-up stairs in the doorway. The batteries are almost impossible to check the rear cells or fill them. Lifting out or in is pretty much a one-man job when at-home or at the storage facility as the DW isn't allowed to lift.

Re: Why Two 8D batteries?

Reply #13 – October 07, 2014, 11:07:48 am

Unfortunately, not a lot of help for the pass side springs Nitehawk ........ but a gallon of propane weighs 4.24 lbs.

Re: Why Two 8D batteries?

Reply #14 – October 07, 2014, 11:30:49 am

Nighthawk. I had the same location for the 2-8Ds in the 93 ORED and always wondered why FT did not make the riser part of step drop down (on hinges) to make it easy for removing those big lugs? If I still had it I would have taken out steps and made a removable set just for this work. Should not be hard to do.
JohnH

Re: Why Two 8D batteries?

Reply #15 – October 07, 2014, 11:49:30 am

Well.......my experiment has hit a snag even before it got off the ground. My series 27 battery is 12 inches wide and the mh battery compartment is 10.

Re: Why Two 8D batteries?

Reply #16 – October 09, 2014, 12:12:21 am

Not really your situation but the previous owner of our coach changed the 3 34D batteries to a single 4D. It cannot start our coach, we have to use boost. Not the smartest modification which was done by an authorized cummins facility.

Re: Why Two 8D batteries?

Reply #17 – October 09, 2014, 12:22:11 am

3-34s for a 4d seems like a terrible swap. Why don't you swap back. Less than half the cranking amps.

Re: Why Two 8D batteries?

Reply #18 – October 09, 2014, 12:33:35 am

I will but I don't have the money right now and the current situation is (barely) acceptable. Our 3 GEL coach batteries are only really good for about 100amp/hours as well while they should be good for about 300. The rv dealer damaged them by letting them sit dead for months. We recently had to do $264 tag axle air spring, $350 aqua hot fuel pump, $100 deductible on vandalism, $100 deductible on windshield replacement, $3500 tires and more. We also burst a hydraulic hose and I will have to spend a lot of money getting that back into shape once I am not on the move again. The hose NAPA sold me doesn't seem to be as good of quality as a Gates hose.

But fixing the starting batteries is on the list.

Re: Why Two 8D batteries?

Reply #19 – October 09, 2014, 12:34:32 am

I misquoted too, I think it comes stock with Group 34 batteries, not 34D. If that makes a difference.

Re: Why Two 8D batteries?

Reply #20 – October 09, 2014, 11:32:09 am

Well, I went out and measured the "pit" where the 8D batteries reside. Open the door, lift up the steps (hinged on top), see the 2" lip, and behind that the tops of the batteries.
The compartment measures 27" wide x 20" x 11-1/2" deep up to the bottom of the first step.
27" width is left to right. 20" is perpendicular to the pass side of the coach.
I am thinking of (1) 12V 110CCA battery for starting the engine and (2) 6V deep cycle batteries for the coach lighting, etc.
I have a "salesman" switch, an unsophisticated inverter/charger, a boost/charge selector switch on the dash, an onboard Onan generator, and lots of LED lights inside and out.
Am I safe in using the batteries I specified above? Same wiring setup?

Re: Why Two 8D batteries?

Reply #21 – October 09, 2014, 11:47:50 am

The 2 6v will need wiring changes, but you might be able to reuse some of the cables since all the connections are right there in tht "pit".

Do me a favor and replace the solenoid, if its orginal mine cost me 2 batteries. Think its $20 bucks. If you have 1100cca battety, that is what I was changing mine to, but sold the 88. Also before you do get a new charger the one in the sewer cooks batteries. I know its tough to lean on the door, so I took a cutting wheelmon my grinder to take it out. Be careful I bet it weighs 35+ pounds. My new one was a 40a vs the 70a cost $50 had a float and weighed 20 pounds.

Hey since thes are wetcells, I used a plastic tube on a funnel, cost me 2bucks to water the back cells

PM if you want more details. If we were in a better situation I would come help you. We love Wisconsin.

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