Noticed lately that the house batteries seemed to be going down rather fast, our trip to the beach this week confirmed something is wrong! Left with a full charge and in one night down to 11.9 volts.

The house batteries are Optima blue top 31M. I removed the batteries and fully charged each one only to find that 2 of them would discharge under load to about 9 volts rather quickly. (I have a battery load tester) The third would peg at +/- 12.4 volts as I would expect! Although the batteries look fairly new I couldn't figure out why the problem---until I looked at the battery compartment---who ever put the batteries in there modified the retaining rails and did NOT remove metal flashing from the welds that were cut. The bottom of two batteries (the ones that failed) were punctured in a couple of places! I am sure that the incident that I had in LV going over the pedestrian speed hump didn't help! There were wear marks and puncture marks.
SO-

Making a new SS battery box now and will replace them (3 parallel 75AH =225AH) with 4 T-105 (4 series,parallel 225AH = 450AH) batteries from Costco, this will double my capacity at a lot less cost then AGM batteries but will require some maintenence on my part. Will be making some changes to the charging circuit/relays/inverter as well.

I too have a 94 Breakaway but with a Cat on a Gillig chassis...sure would like to know how you can fit 4 T-105 in your unit...my house battery tray is at rear just to the right in the engine bay (access door is from right side)and I just have enough room for 2 6 volt golf cart batteries. Would like to have another 2 but no room! Whats your secret? thanks

HI Bob:

Maybe I have more room because of the inline Cummins, I will post pictures of the tray and batteries installed as soon as I finish, tried to get it done today but the tray I designed didn't work out so I am starting over. 4 T-105 take 14.5" X 20.75", believe it or not, if I moved the PS resevoir, I could actually get 6 T-105s in there, tight fit but would go.

4 should be plenty for what I do, I have a 500 watt Ham Radio Xmtr that I will be installing later so I need all the AH I can get.

quote:

Originally posted by MWrench:
if I moved the PS resevoir, I could actually get 6 T-105s in there.

Ed, out of curiosity, what is the starting current draw of your Cummins?

quote:

Ed, out of curiosity, what is the starting current draw of your Cummins?

Hi Bill, don't know, never measured it, it is a geared starter so it s a high RPM motor and shouldn't be to bad.

One of the things I intend to do is to put in a monitoring system that will read and record all that stuff. I have a Dell desktop built in now for the GPS and other functions related to our travel, will also include diagnostics from the Allison as well.

quote:

Originally posted by bill h:
Ed, out of curiosity, what is the starting current draw of your Cummins?

I was taught (many years ago) that for CCA sizing purpose the general rule of thumb is...

For a gas job: 1 CID to 1 CCA
For a diesel: 1 CID for 2 CCA
For a diesel w/ an intake heater
or glowplugs: 1 CID for 3 CCA

Below are common engine sizes...

5.8L = 353.9 CID
5.9L = 360 CID
6.2L = 378.3 CID
6.5L = 396.6 CID
7.8L = 476 CID
8.2L = 500.4 CID
8.3L = 506.5 CID
10L = 610.2 CID
11L = 671.2 CID
14L = 854.3 CID

So, if you have a GM 6.5 Liter (litre) Diesel the minimum is 396.6 x 3 or 1189.8 CCA

CCA aka Cold Cranking Amps: It's a measure of how much power a battery can deliver at 0 degrees F. If you expect to use it in colder climates or want a wider margin of CCA then add a little to it. This is a general rule of thumb - add more if you want a wider margin.

If I missed one or you would like to do the math the formula used is 1 Liter = 61.02 CID.

Bill N.Y.

My (9.25:1 CR) 502 with a stock GM geared starter draws a measured 225 amps on a high 40s/low fifties morning with Mobil 1 5W30.

The unofficial, non-attributable word from unnamed people in high places at an unnamed battery company is that a pair of T105s have a CCA of 550. My testing with a Midtronics conductance tester pretty much confirms that.

With that in mind, I am giving thought to using a set of four T105s as both the starting and coach battery bank. The reason for this is my sliding battery tray will hold four of them, but no room for a starting battery. Right now, I am using two T125s and a size 27 starting battery. We are in year 7 of our batts, so the next year or two would be the time to do this. Of course, the experimenter in me wants to see how long I can use my present batteries.

Since all starters drop the battery voltage, a larger battery bank would keep the voltage up, lowering the amp draw to do the same amount of work. So the current draw could be well below 200 amps, perhaps.

Conventional wisdom is to match the batteries for their use. Starting batteries do not like low deep discharges, and deep cycle batteries are not able to withstand the high current loads of starting. If a person has a typical setup of one size 24 of each battery, then this is good advice. However, with a large coach bank, the CCA, rated or implied, can be high enough to start the engine without a problem. In my case, the mini starter is low current draw, and a bank of four T105s would provide over a thousand CCAs. We of course all know that many coaches happily operate with inverters that have a higher and (much)longer current draw than my starter.

A Mugwump approach would be to install a bank of four marine combination start and deep cycle batteries. But that would give me the advantage of four batteries that are sort of OK for both usages and not really good at either.

The only negative that I can think of is the danger of running the batteries down so far that neither the engine nor the genset could be started. This ain't gonna happen. I watch my batteries more than Donald Trump watches his hair. If I do drop the ball and the batts are too low, I will have the toad to jump the engine or genset to get started. When we are doing the off road thing in the 4WD toad, we always carry a spare battery, anyway.

Another possibility is to install a small battery in extra space in the genset compartment just for starting the genset. That would cover us when we do not take the toad.

Opinions?

I have 2 batteries on the opposite side for the chassis electrical which includes starting he Cummins and gen set. Of course I have a switch/relay that will allow connectiong the 4 T-105 coach batteries to the chassis batteries for more starting power but don't like the idea 'cause if the one set of batteries are way down there would be a huge current surge, not good for either battery set.

I don't see any reason why you couldn't use T-105 batteries for starting, I just choose to use separate systems for coach vs. chassis.

quote:

Originally posted by MWrench:
I don't see any reason why you couldn't use T-105 batteries for starting, I just choose to use separate systems for coach vs. chassis.

The only reason I am even thinking about this is the limited space in our battery tray.