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Topic: Eliminate Start Batteries (Read 951 times) previous topic - next topic

Eliminate Start Batteries

I am wondering what experience other folks have had regarding using the coach deep cycle batteries for starting and having NO start batteries.

On my previous motorhome, a 1986 Chev P30 with a 454 V8, I installed 2 8D Gel Cell deep cycle coach batteries. I reset the alternator and solar controller charge voltage to 14.2 volts. I noticed that each 8D Gel battery was rated at 1030 CCA, so 2060 CCA was available for engine start as long as the batteries were in a high state of charged. A wet cell start battery is rated at perhaps 800 - 900 CCA and would require a higher charge voltage. I did not reinstall the starting battery. Starting with the coach batteries worked very well for 7 years.

I currently have two 8D AGM and one 8D Gel for coach batteries and am considering replacing the three red top Optima start batteries  with another 8D AGM. The three Optima start batteries provide 2400 CCA for the Cummins M11. The four 8D batties would provide up to 4100 CCA. I could then remove the diode isolator block and use the four 8D batteries as a single "does all" bank.

Feedback, anyone?   
Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: Eliminate Start Batteries

Reply #1 –
Quote
I am wondering what experience other folks have had regarding using the coach deep cycle batteries for starting and having NO start batteries.

What happens if you inadvertently run down the single bank or have a cell go bad, etc?

Re: Eliminate Start Batteries

Reply #2 –
I dry camp for weeks with 650 watts of solar and check batteries morning and night.
The batteries are fully charged every day, except during cloudy days. Perhaps, two or three days during the 5 months I am in California, batteries are not fully charged during the day.
In seven years I never experienced dead batterys, or even batteries low enough that they would not roll the motor over.

A shorted cell would also be a risk with a start battery bank.

Thanks for the feedback.
Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: Eliminate Start Batteries

Reply #3 –
Quote
A shorted cell would also be a risk with a start battery bank

My thought was that if you had two battery banks and a bad cell in the start bank, you might get enough power to start the engine by using the boost switch  to tie in the house battery (and perhaps running the generator too to maximize the voltage).

Re: Eliminate Start Batteries

Reply #4 –
IF, repeat IF you are electrically savvy, I see no problem with eliminating the starting battery bank.  I will also tell you less than 5% of RV'ers are electrically savvy enough to pull it off.

We are sitting here right now in Green Turtle Cay in the sail boat on a mooring.  One battery bank.  No generator, only the main engine and its excellent alternator/external 3 stage regulator.  Been "dry camping" for 10 days.

So, yes, it can be done.  And "on land" you have lots of options if you happen to mess it up, the main one being your toad and jumper cables.  Your toad battery should easily have enough juice to start the coach generator which will quickly charge the batteries.

Do I recommend this for the majority of RV'ers?  NO.  But, clearly, your 400+ amp hour deep cycle battery bank WILL start your main engine.

Brett
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Eliminate Start Batteries

Reply #5 –

It will be great until you leave the inverter on all night with current drawing items turned on until morning and wish to start your generator or engine. Good luck with that. I could do it as I only have to wait for the sun to come up and my solar to charge them back up. I'd guess you'd have to jump start off of the toad to get going, eh? Me, I wouldn't eliminate the Start battery. Redundancy is mandatory for me when practical.

Regards,
Jon Twork
JON TWORK KB8RSA
Full Time RVer (10+ Years) & Dedicated Boondocker
Retired, Unemployed, Homeless Transients
1996 Foretravel U270-36 w/24' Timberwolf Trailer
I firmly believe that tomorrow holds the possibility for new technologies, astounding discoveries, and a reprieve from my remaining obligations.
Welcome to WeRV2 (Under Construction)
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The Second Amendment is in place in case they ignore the others.

Re: Eliminate Start Batteries

Reply #6 –
Wyatt,
I agree with Brett.  My only suggestion is to consider that the cable size and run from your house bank back to your starter may not load all the batteries equally while cranking.  I would guess the lions share of the power will be coming from the 8D that replaced your Optimas.  It might be good to verify that new 8D has at least the minimum CCA requirement that Cummins publishes (if that's available) - then the extra from your original house batteries is gravy.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Eliminate Start Batteries

Reply #7 –
Wyatt,
I strongly recommend YOU should try it and give a full report after a full season of the results.
Frankly, I also agree with Brett, but there is always  room for trial and error.
One of my fears, waking up with a weak battery system, not able to start the generator, not able to start the coach and hungry, no microwave, and warm ice cream.
Why I think YOU should try it, not for me.
Cheers