Battery Size

[LarryB]

Hi All, aside from the obvious reduction in amp/hrs. what would be the disadvantage of going from 8D to 4D. Marathon tech claims all their new coaches are equipped with 4D. Physical size/weight was not the reason. He was hard to follow but, claims there is little difference in performance. When comparing 4D to 8D on Lifeline's chart, there is a real reduction both in 'Rated cap.' and Minutes of discharge.

Any thoughts?

Larry

[garyde]

Hi Larry. Did he say how many 4D's?

[Ray Davis]

My Marathon has 6 4D's, rather than 4 8D's. Not sure if that's a similar capacity or less.

[LarryB]

Gary and Ray, the number of batts. per unit wasn't discussed but, if taken battery to battery the 4D doesn't have the capacity. When grouped together I don't have a clue. Must work OK.

Larry

[LarryB]

Ray, you said your bus has 6 4D batts. rather than 4 8D batts. I wonder how [what sort of formula] they use to determined how many 4D it takes to equal 8D.
I know what ever configuration they use is working and wonder if there is a benefit to replacing 8's with 4's when the time come. I do know that folks in other motorhomes have replace their batts with golf cart batts for more amp/hrs for dry camping but have no idea how they derived at the number of batts to exchange.

Just curious.

Larry

[dale farley]

According to the Lifeline chart, it appears that it would take 7.3 4-D batteriess to have the same "minutes of discharge" as six 8-Ds. So that really means you would have to have eight 4-Ds to equal six 8-Ds.

Six 4-Ds would give about the same capacity as five 8-Ds. Unless you are doing a great deal of dry camping, I wouldn't think it would make that much difference.

[LarryB]

Dale, I figured it the same way you did, adding amp/hrs. for 6 8D and finding the equivalent foe 4D. I just thought when connected in parallel the numbers for a single battery might change.

Well, I guess this is why they let me drive but won't let me play with the horn.

Thanks, Larry

[dale farley]

Larry, The capacity will be multiplied by the number of batteries when conected in parallel. The voltage will be the same as one battery.

[truk4u]

I think sometimes with the Converter it's a space issue. My 97 Marathon had 6 4d's and only 4 8d's would have fit in the same space due to the 8's being 2" wider than the 4's. Also, almost a 30 lb difference. Just a guess..

[Ray Davis]

My first coach had golf cart batteries in it when I first purchased it. That was a mess, as there was no way to fill the batteries (the were not maintenance free). I assume a previous owner tried to save money using these batteries.

I replaced those with 4 4D batteries, and never had an issue. I could run a normal coach all night long without generator coming on, using normal stuff like TV's lights etc.

Now, my Marathon has 6 4D batteries, and I've camped as much as a week without power, running the generator once a day for a couple of hours, and this worked out fine.

Ray

[BENC]

The difference in 4d's versus 8d's are as follows:
4D = 210 amp/hours
8D = 255 amp/hours

Multiply the appropriate number by how many batteries are in your "bank" to give you a numberical reference. Marathon Coach has placed 4D batteries in the rear compartment behind the tag axle of the XL and XL2 Prevost coaches ever since the 45ft models were introduced. Six are simply ALL that will fit in this compartment. It does work well and has been the "norm" for several coach converter for over 10 years.

The other consideration is total number of plates you will have in the overall bank, determined by combining all the batteries. You will have much greater surface area, which equates to greater current potential out of the bank, for surge starting of air conditioners, etc with 6-4D batteries versus 4-8D batteries. That is a real world fact you really don't get from just comparing battery to battery.

Hope that helps.
-ben-