I am officially an "Old Fart", even though my DGD hates when I say that and I have been around a lot of stuff in my 73 years here on earth. I have learned an awful lot both formally (16 years of school and hundreds of hours of seminars and workshops on the job) but here...I didn't know how little I knew until I bought a MoHo and joined this Forum. My rig's engine alternator charges my chassis and the house batteries, I have wondered for some time how physically this occurs. What devise connects the two for charging? I just never asked you fellow members, last week someone was questioning why his engine alternator didn't charge his house batteries. Someone mentioned a "Trombella Relay", I have been working on cars for over 60 years, been in the electrical trade for nearly 60 years, owned an RV for 14 years and never heard of a "Trombella Relay". So I did a search on that name and boy are those things used in so many things you come in contact with daily. Mostly we call them solenoids but they can be so much more. It is amazing how much you folks know and share freely with those of us who ask. I ponder things for hours, days or even years and in three minutes after asking a question here, magically, there is the answer. Even my DW said how, even with all I know about things, that I learn something new and (to me) exciting just reading posts on this forum So Thank You to Marcus and his predecessors for starting this school and to all you Professors, an even bigger "Thank You".On edit; I think I figured out my misspelling of Trombetta. When I wrote it down on my scratch pad, I forgot to cross the double "t". I checked my search for Trombetta Relay and it was spelled correctly. Such is the result of being in a hurry and not proofing what you write, the dyslexia doesn't help any either.

Generally speaking the more education and experience a person has the more they realize what they don't know. Just ask any teenager-- they know everything. Then ask a retiree and it is amazing how much we unlearned since our teen years. Unfortunately there are not a lot of teenagers on these forums so we depend on each other and that is good.

I have never hear of this "Trombella Relay" brand before either. I think this is just another manufacturers name for a CONTACTOR type relay.What is becoming popular now is the SMART MODE TYPE CONTACTOR relays that senses the different type DC Voltages to determine when to switch-in. The smart mode DC voltages levels are so close to each other when charging deep-cycle batteries. Roy Ken

It is actually Trombetta and is the name of a manufacturer of DC contactors. But is often used generically to refer to a relay something like saying Xerox machine when you mean a copy machine.

Your post was refreshing and spoke volumnes to the importance of these forums.

David, The answer to your question is somewhat model dependent. I don't know which your Bounder will have, so I will tell you of both and you can go find out what you have and then you should be very capable of dealing with it. As your search confirmed, the "Trombetta" relay is just a continues duty version of a Ford starter solenoid or as an electrical guy will call it, a contactor. They make a bunch, but so does Borg-Warner. Yes, there is a lot of knowledge here, but you have to be careful to include enough information so the providers can correctly sort it for a response. For charging, these are more common on class C than class A, as a C builder doesn't want to mess with the chassis electrics. The contactor is just a means to parallel the house and chassis banks while the main engine is running. Sometimes they have a voltage detecting circuit so it won't engage until the chassis battery has recovered form the main engine start. Other units have a diode isolator. This is just two big diodes buried in large heat sink. The alternator feeds both anodes and the chassis and house bank are each connected to an cathode. Simple, self regulating and effective, but somewhat spike sensitive. Matt

Thanks for the education | Good Sam Community

travelnutz
Explorer II
Dec 11, 2013
I've made my own battery isolation properly fused switching devices for nearly 40 years now using a simple cheap Trombetta HD isolation solenoid, an 80 amp marine slow blow large fuse in it's screwed on holder, and 2 small pieces of 1/8 X 1-1/4 angle iron screwed together for mounting the components on and the assembly under the hood. Takes less than a hour to make with most household tools. Bomb can prime and paint the angle iron the color you desire after drilling all holes.

Carry a spare fuse in your glove compartment if it should be ever needed and if the solenoid should ever go bad, you can get another at about any auto supply store or so many other places in nearly any city or population center. Sometimes called an HD starter solenoid. OR, just carry a new one with you if you're paranoid. They are cheap and small and takes only a couple minutes to replace but not likely you ever wiil. I have never had one go bad yet!

A fraction of the cost of purchasing a manufactured battery isolator and totally fool proof to even RV beginners. Most solenoid's terminals are marked as to 12 V in and out and positive (+) current wire actuator connection from the ignition on wire which is what powers the solenoid's magnetic coil to connect the 2 battery systems together. Also if a toggle switch method is wanted to couple the batteries together. Turning the vehicle ignition key to off and the 2 battery systems (RV and vehicle) are disconnected immediately. Most solenoids have the steel housing ground (negative) and/or offer a negative (-) current stud also if the solenoid is bolted to a non-electric surface like plastic or if the vehicle etc system has an isolated ground (very rare). Must have both + and - feed to the solenoid for it to activate.

I won't go into depth about other solenoid hookups such as an inverter or other items you want to turn high current off and on as desired remotely either automatically or manually by remote control activator or a handy close by toggle type switch. It's easy but you need a little understanding of electrical system hooking up so you don't burn something out or fry wires.

Edited to fix mispellings in my haste, DUH!
Old-Biscuit
Explorer III
Dec 11, 2013
Ain't learning fun & refreshing!!!!

When I was 16 my Dad was not so smart
When I turned 21 it amazed me at how much he had learned in those 5 yrs :B

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