# Thread: Tank Circuit Schematic Question

1. ## Tank Circuit Schematic Question

I have a design for a tank circuit, but I'm not sure how well it would work. Here's what I've got drawn up so far.

The only thing I didn't add is that all the wires on the right will only go to my M2. Meaning, the only thing on the "switched" side of the relay would be the battery and the M2. Any suggestions are appreciated.

Edit: Also, is there any suggestions for a second battery. I'm thinking a marine deep cycle because I'm doing this so I can leave the PC on standby, but really have no clue. Any suggestions there would be greatly appreciated as well.

2. Are you building the tank circuit to survive crank? Im assuming no since you have an M2. It seems here that you are mostly just trying to put an auxiliary battery in the back isolated from the starting battery. You can just go out and buy a battery isolator for that. Might want to consider a diode based isolator for reliability.

As for the battery, you could look into the optima blue or yellow top. The good thing about those batteries compared to standard marine deep cycles is that they can be charged at higher currents, so they should charge up faster. You dont want to take energy from the battery faster than you can put it in, so a faster charge rate is good for this application. Just something to consider.

3. I'm wanting to add the tank circuit so I can leave the PC in standby and not have to worry about my car starting.

After looking at a battery isolator, I'm worrying about the current going the wrong way during crank. I would like to avoid running large gauge wires, that's why I went with the relay. I know I can wire up the relay so it's off during crank, but on otherwise.

4. A diode based isolator isnt going to let the current go the wrong way during crank. Current can only go from the alternator to the batteries, not from one battery to another. With the relay, to prevent current going from the aux battery to the starting battery on crank youll have to make sure the ignition wire isnt live on crank.

5. Ok, so if my relay isn't "live" during crank, there should be no issue with what I've drawn up, correct?

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