Battery / charging isolator.

As my truck is a "Camper Special", I'm installing a second battery. Tray is in and a "so-so" battery is in as well.

I would like to be able to charge both batteries, however I wish to isolate the Aux. battery output from the main battery. I was told to get a battery isolator.
I've seen 3 post isolators for $180.00. (Really? It's just a freaking diode)
So, my question is for those who have been down this road.
What isolator did you folks use?

Thanks.

How fast do you want to charge it and what do you want to use it for. This is dirt simple sold cheap dual battery charging kits for years on ebay. Simple cheap charge at 15 amps can be done under 10.00

I use a minute mount 1 during plow season on my bobcat 873 skid steer. The plow has its own battery and charges thru an isolator that most likely came from amazon (P/N BTI-140) 12v 140A. After three winters nothing has caught fire or exploded yet.

Rather than wait for your reply,I'll put the nuts and bolts of it up,from there you can do what you want. I put a thumbnail of a relay at the bottom, not necessarily recommending that relay it was the first one that popped up with the schematic on the side ,for explanation purposes. If you hook terminal #30 to your original battery (use a fuse in that lead) hook #87 to your second battery. Number 85 hook to a 12v trigger that's only on with the engine running,easiest is probably alternator charging light lead,or choke wire if you have electric choke. Hook to #86 to ground. Now with the engine running power goes through 85/86 closes the relay which allows current to flow from 30 to 87 charging the second battery. The gauge of your wire will dictate charge rate,just like using a bigger or smaller garden hose. I usually sold relays with 16 gauge pigtails a 20amp fuse and a 40 amp relay. To get approximately 15amp charge rate. If you use bigger wire you need a bigger fuse and a bigger relay.

@hey mister
There’s several ways to skin that cat that may be more economical, but if you want a whole setup including the wiring to go to a truck camper plug, maybe I can help.
Prev owner of the C10 had all new camper wiring and isolator installed along with dual battery setup only a couple years ago.
I have zero use for it in a C10 or the K20.
If you’re interested, I could remove the whole setup and send to you ready to plug n play. I only haven’t removed it because it will be another pile of parts and wires sitting in a box somewhere. Right now it’s just charging a new battery under the hood that doesn’t get used.
Message me if interested.

Grit dog said:

@hey mister
There’s several ways to skin that cat that may be more economical, but if you want a whole setup including the wiring to go to a truck camper plug, maybe I can help.
Prev owner of the C10 had all new camper wiring and isolator installed along with dual battery setup only a couple years ago.
I have zero use for it in a C10 or the K20.
If you’re interested, I could remove the whole setup and send to you ready to plug n play. I only haven’t removed it because it will be another pile of parts and wires sitting in a box somewhere. Right now it’s just charging a new battery under the hood that doesn’t get used.
Message me if interested.

Click to expand...

That might be the "Bingo" I'm looking for.

PM sent.

The original setup on my '75 Camper Special had a relay (silver body, similar looking to the blower relay on the A/C plenum) mounted on the driver's side fenderwell.
There was a three wire plug for the relay (mine is still on the truck):
1 - charge wire (10 gauge?) that ran from the power junction next to the brake booster over to the relay
2 - battery positive wire running to the battery
3 - wire from the fuse box over to the relay plug, and it had ignition-on power to activate the relay
Negative post of the battery was grounded to the radiator support

When the truck was running (ignition on), the charge wire for the 2nd battery was connected to the power junction through the relay, so the 2nd battery was charging. When the truck was not running, the 2nd battery was isolated.
There was apparently an additional wire and fuse(s) that powered the camper from the 2nd battery. This wiring is long gone from my truck.

This is a much simpler wiring setup than most isolators, so I'm sure it had disadvantages. However, it also apparently worked.

Have 2 batteries in ‘81. Attached a wiring diagram.