This is my upcoming problem - I want to have two 150AH batteries on the tongue of my trailer and an additional two 150AH batteries in the bed of my truck. This layout gives me 300AHs capacity to run my two way radios when I am just in my truck alone or 600Ahs capacity when connected to my OFF-ROAD POPUP trailer when camping off the power grid.
According to the experts I ran into discussing all of this is what we come up with. The answer was to get a SMART RELAY setup...
BLUE SEA SI-ACR SMart RelayMy concerns now is will I blow up my truck alternator system for adding additional 40AMPs current drain over what it currently is doing with its single truck start battery installation.
The smart relay monitors the DC VOLTAGE from the truck start battery and when it gets to an adjustable trip point showing the alternator has started a 14VDC charge mode the smart relay will switch the remote battery circuit into the truck alternator charging circuit paralleling the truck start battery. This is suppose to charge both battery systems while the alternator is in its charge output mode. This is how the big boys get around the sensing problem. When the truck alternator eventually reverts back to its 13.2 float mode then the smart relay disconnects the remote battery connection. This is how the big boys keep you from running down your truck start battery. The downside of this system is it cannot detect the remote batteries being discharged below the trip point to tell the alternator to start going into charge mode . They added a manual battery switch to overcome this situation. Sounds like a good plan to me...
All of the experts I talked to indicated the remote battery being so far away from the truck alternator would not provide good sensing information to overcome the already charged truck start battery sitting within inches of the alternator. You also do NOT want to drain the truck start battery down and get you stranded somewhere.
In the old days the DIODE BASED battery isolators did this just fine but the 0.7VDC voltage drops associated with these heavy duty 200AMP DIODE units really messes up the proper amount of DC charge voltage you want to go to the remote deep cycle battery banks if you want to re-charge them to their 90% charge state in a short three hour time frame.
The deep cycle battery science rules indicate your need to get around 14-15VDC charging voltage with a capacity of around 20AMPS of DC current for each battery you are trying to charge if you want to re-charge this battery in a short three hour time frame.
I do not think just taping the start battery 12VDC cable 15-feet away from using 12-14 gauge wire is the way to go. I guess I am guilty of over-thinking this problem. Maybe that works OK with a single deep cycle battery... Maybe not...
If I am camping way back in the woods like I usually find myself doing I have to add the word "SUCCESSFUL" to the situation.
Just my thoughts on the subj... Of course this is my problem not anyone elses... Just passing on some of my experiences here...
Roy Ken
