Battery isolator

ScottG wrote:

YC 1 wrote:
Newer vehicles already have a relay. Some need to have a fuse installed to activate them. Check the manual.

In regards to a relay, Fords do, GM and (thankfully) Dodge/Ram don't.

What ?

Where is your expertise and can you explain. Sorry, 40 years in the industry begs for a clear and concise answer.

YC 1 wrote:
Newer vehicles already have a relay. Some need to have a fuse installed to activate them. Check the manual.

In regards to a relay, Fords do, GM and (thankfully) Dodge/Ram don't.

kayco53 wrote:
I used to just put a solenoid in the charge line to the rv

This is what I did on my 2009 Chevy

A fuse and solenoid are still the best, the most reliable, and the cheapest. (and use heavy gauge wire - 2g) Charge circuit (2006 GMC)

You need to use the RELAY TYPE system if you want to use smart mode charging. The HIGH CURRENT DIODE TYPE Isolators like we all used to use in the past have too much VOLTAGE DROP for smart mode charging techniques.

If your truck system is producing 14.4VDC BOOST charge mode your batteries will only be getting 13.7VDC after going through a DIODE TYPE ISOLATOR. You certainly won't get the benefit of a three hour 90% charge state doing this...

I will be using the BLUE SEA SI-ACR RELAY here for a similar setup. Check out the BLUE SEA Home Page for great info along with schematics etc...



Roy Ken

Newer vehicles already have a relay. Some need to have a fuse installed to activate them. Check the manual.

There are voltage controlled "battery combiners" specifically made for this. They sense voltage above the fully charged battery (usually around 13.1V) and close a relay when it is exceeded, indicating that something is charging the system. This has the advantage of not needing a connection to the ignition, not connecting if the ignition is left on but the engine is not running, and a contactor specifically designed for continuous high current. They cost a little more than a simple relay though. Search Amazon or your favorite marine supplier for "battery combiner".

Ignition controlled (w/manual on/off switch on trigger wire) constant duty solenoid, simple inexpensive. Works well for us.

After having a nice over sized diode isolator die on me at the worst possible time, I started using a 100% duty cycle solenoid type relay from Napa. I used it for nearly ten years before trading the truck in. Plus I didn't have to deal with the diode V drop.
My mechanic buddy warned me against diode iso's but I had to try.
I'd never go back now.