12v Connector/Isolator

I installed a continuous duty solenoid which is triggered by an ignition wire. Any time the engine is running the solenoid is closed and is connecting the RV battery. When the engine is off the solenoid opens and the RV battery is disconnected from the alternator charging system.

It is a very simple and common system. No expensive isolator system is needed.

I have a 50 amp toggle switch on the dash that connects all the positives together whenever I want all batteries to charge. I turn it off when camping, and on when drving

If you have a memory like a steel trap use a 1 - 2 - both - off circular marine switch. You'll change your mind the first time you forget.

moved from technology corner

Thank you all gentlemen. I appreciate the input.
Roy B., King George, very beautiful area! I have friends that live there and I very much enjoy the ride down 301 to 17 to Va Beach. HATE trying to take I-95 to 64!

May I pick your brain some more? I am not so worried about charging the chassis battery as I rarely plug my unit in. I boondock for the most part, and when I am not on the road I remove both batteries and maintain them on a trickle charger. I also have a beefed up, 175 amp alternator that charged the coach battery fine for the most part until this part failed or whatever. What would you suggest for a simple coach battery charging circuit for charging while on the road that would keep the coach battery charged but not allow it to drain the chassis battery. Just a manual switch?

You may have trouble finding any of your answers as there are too many different layouts on how this works... Your setup is most definitely unique to your vehicle setup...

The original way to do this was with a three port DIODE COMBINER which would switch on based on the lower battery DC voltage when it it got drained. The HIGH CURRENT DIODEs in the modern day isolator circuit is not used anymore as the DIODE will have a very LARGE built-in VOLTAGE DROP which gets you into trouble with the modern day of using 14.4VDC, 13.6VDC and 13.2VDC using smart mode charging techniques.

Then the solenoid method came out where a large current 12VDC relay can be engaged combining two 12V Batteries to your ALTERNATOR circuit with a manual OFF-ON switch. When the AUX battery needs charged just flip the switch.

Of course now it all modernized again using smart relay solenoids that monitors the DC voltage coming out of your alternator and when that goes to 14.4VDC the solenoid kicks in and adds the aux battery to the charge circuit. They are only connected to the alternator when they are being charged - otherwise they are separated system and this idea keeps the TRUCK START Battery from ever being discharged from the trailer loads...

The biggest thing today is the larger aux battery banks can easily need more current than the standard duty vehicle alternators can produce and you might end up blowing those up. Now you talking some dollars to resolve that issue..

Using the Truck Alternator to do your aux battery charging can be tricky at best...

The smart solenoids are very popular. I will be using the BLUE SEA SI-ACR Model 7650 Smart Solenoid when I get to my aux charging going for my truck setup with additional batteries... You can go to the BLUE SEA site and read up on how the SI-ACR concept works... Pretty neat concept.

My setup may look something like this just to give you an idea what may be involved... With my HD Battery switch operations here my AUX batteries will most likely always be charged from the trailer side using the on-board PD9260C converter/charger unit.



Roy Ken

Chris said it, CON = Continous Starter solenoids are rated for like 30 seconds, try to hold them connected for 30 mintues bad things happen.

You can replace that 22 year old isolator with many isolator relays you can get at most any RV store If the vehicle is a motor home you can even upgrade to a bi-directional isolator (though that takes a bit more work)

A bi-directional lets the house converter charge the chassis battery when you have power to the house 120 system. Many models out there so I can not recommend one over another.. Just visit your RV store parts counter.

That con means it is rated for continuous duty, as opposed to a starter solenoid, which is intermittent duty.