Battery Isolation Plan

[egarant]

There is no OEM battery isolator in either my RAM truck or my Eagle Cap TC.

I have been unplugging my umbilical cord when I stop to camp, thereby disconnecting house from starting batteries.

When I look at the 7 pin wiring diagram, if I disconnect the 12 volt feed wire from either the umbilical cord or the truck receptacle that should isolate the batteries. Of course I will not be able to charge the house batteries when underway, but I have full solar for the purpose.

Sound plan?

[bwc]

I also have a Ram that had to be disconnected from camper when parked for fear of draining the Ram's batteries as these trucks are live all the time, not off when ignitionis off. To keep it simple I mounted a Blue Sea m-series battery switch(PN 6006) in my camper that I turn off/on manually when parked for any length of time. I installed this switch between the 12V side coming into the converter and the 12v side leaving the converter. Works great, just don't forget to switch off when parked. I like KISS method. Have had it on for the last 5 years with no problems.

[RoyB]

I am using the Blue sea 7610 model ACR smart relay here.

The spec says "The ACR senses when the voltage of either of the batteries rises to a level indicating that a charge source is active (13.0V for 2 minutes). The ACR contacts then connect and the ACR applies the charge to both batteries. If the voltage on both of the batteries subsequently drops to 12.75V for 30 seconds, the ACR will disconnect, isolating the batteries."

My setup follows this pretty close. I do notice that the smart relay switches in the second battery at a somewhat higher DC voltage like 14.0VDC verses the 13.0 specified. My battery cable lengths for the second battery is several feet longer than the truck start battery to where my ACR smart relay is installed. This may be the reason for a different DC Voltage ACR switch-over sequence.

It does very well keeping my second battery charged at the same time the truck start battery is being charged by the truck alternator. When the truck engine is OFF then my battery drain on the second battery is isolated from the truck start battery wiring. Your start battery does not get run down on you.

There are other smart relays on the market other than Blue Sea. Blue Sea and SURE POWER Industries seem to be the most popular ones discussed.

In the old days we all used high current diodes to isolate the Batteries but the diodes designed built-in voltage drop in their operations makes it almost impossible to use when you are working with 14.4VDC-13.6VDC-13.2VDC levels associated with our modern smart mode charging systems... Smart relays that switch with has becomes the easiest way to isolate batteries these days...

Roy Ken

[CAJW]

You are correct. The ACR is an automatic charge relay whose sole purpose is to connect/ disconnect (isolate) the truck charging system from the house batteries. It does not regulate anything other than on or off, dependent on the presence of charging voltage from the truck.

[egarant]

I just completed the 12 volt power disconnect from the truck, took all of 10 minutes. It has a wire cap on that lead just in case I want to reconnect it for another purpose in the future. Now with the camper umbilical cord connected to the truck, when I switch off the house battery switch there is NO power at all in the camper, that was not the case before the wire disconnect.

I was also worried about over charging the expensive LIfeline batteries in the old set up. My MPPT controller was reading the house AND the starting batteries when determining how much amps to put out. Not good.

The other day with the umbilical cord plugged in, the solar charger was putting out 3.5 amps, when I unplugged the cord it dropped to 1.5 amps. I spent good money on a solar controller so I could dial in the exact charging spec.s of the Lifeline batteries, the charger outputting more than just the house batteries needed I felt was NOT GOOD.

In reverse, the trucks alternator/regulator when running is also charging the house batteries at starting batteries specifications, not Lifeline spec.s.

After reading the spec.s on the Blue Sea #7611 ACR, it just looks to me like a isolator, not any kind of regulator or charger. Please correct me if I am wrong on that.

Good to finally have totally separate charging systems.

[CAJW]

That'll work, but as you stated, you'll need to manually disconnect it to prevent battery drain. There are a number of methods to accomplish this automatically when the truck is shut off, but here's the route I went.

ACR install