Confused about Batteries

[Pete Masterson]

The folks with the FCs can advise better on which batteries go where. 

In general, the choice between 12 v deep cycle or 6 v deep cycle Trojan 105s or "golf cart batteries" is to get the maximum amp-hours each. The Amps you've reported are the CCA (cold-cranking-amps) these are most important in a starting battery as that is the maximum current available for a very short period to start the engine. 

For the house batteries, you want to compare the 20 hour rate amp-hours.

For example, the 6v Trojan T-105 is rated at 225 amp-hours at the 20 hour rate. That means that 2 T-105s will give you 12 volts with 225 amp hours. Note that if the T-125 or T-135 will fit (they're the same width and depth, but taller), they'll give you more amp hours of capacity. See

<http://www.trojan-battery.com/> for details.

In a 12 volt battery, of the same general physical size, you might only get 85 to 105 amp hours at the 20 hour rate. (The 12 volt battery must have 6 cells that are half-the size of the 3 cells in a similar sized 6 volt battery.) So, the primary advantage of getting several 6v batteries is that you end up with more amp-hours available in the space you have for batteries.

Selecting the engine battery, there the focus is on the CCA rating, and I'd bet the 875 amp battery is the engine battery. Someone may be able to tell you which battery size is correct for the Cat 3208.

Finally, if you have an old battery boiler charger, you might want to upgrade to a modern 3-stage charger. The batteries will last much longer.

Pete Masterson

'95 Blue Bird Wanderlodge WBDA 42

El Sobrante CA

"aeonix1@mac.com"

On Jun 27, 2008, at 4:15 PM, Jack & Donna Smith wrote:

I need a course in Batteries for our 1973 Coach.   When we bought it 

they claimed the batteries had just been replaced.  It has 2 units in 

the drivers side front compartment, one more under the entry steps, 

and the 4th in the Generator compartment.

The batteries in question are all Walmart 12 volt Deep-cycle Marine 

units of 675 & 875 amps each.  (The big yellow ones).

Now 2 or 3 are bad or going south.  

Most I have seen are 6 volt units.  Why are these considered better 

than the 12 volt ones.

Since I will be replacing these soon, which should I use, and why?

Jack Smith

1973FC31

SoCal