Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 11, 2025 ...

Re: Engine Start Battery Options

Reply #50 – July 16, 2018, 10:52:49 pm

"Most"  is a big corral to be generalizing.  Not so on the Delco.

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Re: Engine Start Battery Options

Reply #51 – July 17, 2018, 10:01:24 am

Seems this thread has run its course, so I will wrap it up with my conclusions (for what they are worth).  I have considered the info presented here (thanks to all) and believe the following plan will work for our crew, the way we use our coach, and based on our level of technical expertise.

1.  I will replace our two old Red Top start batteries with a new O'Reilly AGM8D.  It will (hopefully) fit in the existing battery rack, and will work just fine with the existing cables.  I will use fresh "military" style battery connectors to hook up the cables.

2.  I will replace our still functional 25-year old Hehr Powerline diode isolator with a new Victron ArgoFet 200 amp 2-bank isolator.  By doing so, I retain the original factory alternator-to-battery charging layout, while enjoying the benefits of more modern technology.  The new isolator should be a bolt-in swap, and will be connected to the existing battery cables, which are in good shape.

3.  I will retain the Trik-L-Start "thief" battery maintainer that has served us so well for 4 years.  It does a fine job of keeping our start batteries topped off when our coach is parked (plugged in to 50 amp) in our driveway and when camping at full hookup parks.

4.  I will replace the existing boost solenoid with a Blue Sea Systems 7701 ML solenoid, which has a 500 amp continuous rating, 1450 amp 30-second cranking rating, and zero power draw in "ON" and "OFF" position.  Doing so will retain the OEM boost circuit design and function, while providing me with additional battery charging options when in dry camping mode.  If I wish to utilize our augmented battery storage capacity, I can simply activate the 7701.  Combining the battery banks will increase my available amp hrs by 50%, and will allow rapid recharging of both banks using our solar panels and/or generator + inverter/charger.


I believe the above plan will add extra capability and options to our battery system, while retaining the elegance and KISS-ness of the original FOT factory design.  I hope this will meet with the approval of the electrical gurus on this Forum.

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Re: Engine Start Battery Options

Reply #52 – July 17, 2018, 10:18:37 am

Sounds like a good plan Chuck. We have certainly well chewed this subject. Please keep us informed of your progress and results. 😎

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Re: Engine Start Battery Options

Reply #53 – July 17, 2018, 10:58:42 am

Chuck, you might want to replace the 4 ga cables from the two battery posts on the isolator to the two sides if the boost solenoid with bigger cables.  The 4 ga cables are probably the minimum size for the amps for that length of wire but bigger would not be a bad thing.  Your alternator to the isolator is perhaps a 2 ga cable, this would be a good size to go from the isolator to the solenoid.

If you have an easy source for cables great but you can order any size and length cables from Bay Marine Supply with the lugs you need on both ends.

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Re: Engine Start Battery Options

Reply #54 – July 17, 2018, 11:08:50 am

Thanks, Roger, for the tip.  My OEM wiring schematic shows the wires to be "2RD" from alternator to isolator, and also "2RD" wires from both of the isolator battery posts to the boost solenoid.  I assume "2RD" means a red 2 gauge wire?  If so, I should be good?

I will verify the actual wire sizes next time I'm under the coach, just to be sure.

My OEM cables from the boost solenoid to the batteries, and all my battery cables, are shown to be "000" which I think is called "triple-aught"?  When AM Solar installed my solar system and Magnum inverter, they used "000" and "0000" cables for the high amperage circuits.

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Re: Engine Start Battery Options

Reply #55 – July 17, 2018, 04:40:43 pm

I think your isolator may have originally been over by the wheel well?  If so then the longer cables from the isolator to the boost relay would make a 2 ga cable make sense.  At the head of the bed box the cables were maybe 16" long so 2 ga was probably sufficient.  Yes 4RD means 4 ga Red.  With a bigger alternator I just didn't want those smaller wired to be choke points.

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Re: Engine Start Battery Options

Reply #56 – July 17, 2018, 04:45:24 pm

Here's my isolator panel as it is now, in factory stock configuration (plus the add-on Trik-L-Start).  The big fat muffler is long gone...

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Re: Engine Start Battery Options

Reply #57 – July 17, 2018, 05:18:26 pm

Chuck,my panel looked exactly like yours,redid the whole thing,all new components and put back in the same spot,after sanding and painting all rusted frame parts.We went with the smaller 28si alternator,keeps the 13.8 even at low idle.

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