Replacing start batteries with deep cycle ones

[luvrbus]

It will work JC later change out the starter to the MT 39 Delco that doesn't require the 900 amps like the older Delco 42 starters do and you will be ok ,the 39 Delco is a amazing starter it reaches the magic number of 60 rpms on half the power

[dtcerrato]

Our main engine start batteries are a pair or NAPA commercial
8D deep cycle batteries that are labeled "also good for engine starting". Our house batteries are 3 group 31 deep cycle batteries. We can switch the house power draw to the engine start batteries & do so while driving as the alternator keeps them topped off. Our Onan generator has it's own dedicated start battery & when running is separately charging both house & engine batteries as two separate systems. The setup was originally our design due to a neg. ground house system on a positive ground chassis system. When we recently converted to negative ground chassis we maintained the original battery set up because it has worked well for us through the years. As of yet we don't have large inverter or solar power and rely mainly on 12 VDC & LP gas for house systems. It works well for us.

[Utahclaimjumper]

This reminds me of the old saying,: If it ain't broke don't fix it.>>>Dan

[Utahclaimjumper]

One other thing to remember about a single bank.. In a series parallel system no mater how large the "bank",, if you loose one battery you loose the bank.>>>Dan

[chessie4905]

And occasionally you should check and compare specific gravity of each cell to the rest. Some of these new battery analyzers may do this job quicker.

[buswarrior]

"Losing a battery"...

How would this go unnoticed?

With all the lovely monitors that have been available for many years now...

So much of the "advice" out there is to combat the foolishness of running blind. Mix in a set of crap batteries bought on the cheap...

Way too many variables.

Get the modern State of Charge equipment of your choice, PAY ATTENTION to it, do your proper, manufacturer recommended periodic battery maintenance and enjoy the reliability, and long life, of your large battery bank?

Happy coaching!
Buswarrior

[sledhead]

the use of a bogart system or same is a must

A bad battery can happen on any set up . I use a battery hydrometer on my coach system and record the readings . Worst case you could rewire out the bad battery ( or 2 ) to keep the system at the right volts on the road if you had to . I have a towed to boost the genny if I need to and as a last resort I carry a fully charged lithium 2000 amp boost pack .

the other problem I have is my start batteries ( 4 x group 31 's ) I can't open them up for testing or adding water ?? but have a 400 amp switch over from bank to start batteries now if needed

when my start batteries crap out I think I will do the change to one bank at that time

again go for it J C

dave 

[Utahclaimjumper]

Yah,, go for it JC,,you first... >>>D

[lostagain]

I will.

JC

[bobofthenorth]

Its a very sensible solution JC.  We had more or less exactly what you are proposing on the boat.  I was nervous at first but came to realize that it was a very sensible solution.  In the situation where you carry separate start/house batteries you are lugging around a bunch of lead in the start batteries which is only briefly used, at most once or twice a week.  As others have advised I would definitely put in a good state of charge monitor.  I'm a big fan of Bogart but there are others.  I set my Bogarts very conservatively and then use the batteries equally conservatively.  We absolutely never see 50% discharge but even if we did the batteries would still be above 50% because of the way I program the monitor.  My only caution in your situation is that I wouldn't want to mix ages on my batteries in the same bank which would mean either separating the banks for charging or replacing all the batteries.

[lostagain]

Thanks Bob. I do have a good state of charge monitor.

JC

[lostagain]

So I installed 4 deep cycle golf cart batteries (6V) in place of the 12V start batteries. They are tied to the existing 4 batt house bank. So now I have 8 batts in series/parallel as one bank. I also added a solar panel for a total of +- 700 watts.

We have used the bus several times since, and I am very happy with the results. The increased batt capacity is quite noticeable. The solar panels recharge the bank quite quickly when the sun shines. Of course it doesn't do sh.t on cloudy days, and we have to run the generator. Starting the engine is just as easy as before. It hardly takes anything away from the batts. Granted it is summer so it is warm. But as I mentioned earlier, I always preheat the engine in the winter before starting anyway.

So that was a good improvement to the bus.

JC

[sledhead]

Glad to hear you went for it and all is good

as my starts crap out I am going to do the same

dave

[bevans6]

Good to hear it worked out.  Thanks for coming back to us with the end of the story!

[buswarrior]

Lovely report, rounding out the thread.

Happy coaching!
Buswarrior