Installing relay type isolator
 

Hello Guys,

I am looking to do an experiment of sorts with my car: i would like to install a second lead acid battery in it. I already tried using a diode isolator but it proves to drop the voltage too much (usually between 12 and 13 while driving). In this process I also found that the voltage regulator has issues so I am replacing the alternator as well with a 90 amp unit.

Anyway I am looking to install one of the relay-type battery isolators for the second battery. My question is what is the best place to look for the "wire which is 12v while the engine is running". I understand that one of the ignition wires will work for this, but is this the best to tap into? Does anyone know where the ignition wire is under the hood? Does this wire need to be low gauge (thick) like the other charging wires, or it does not carry much current? I would appreciate any insight into this process, as information seems scarce for some reason from google.

Thank you for reading.

the wire controlling the relay coil can be small, 14awg is fine.

there are many ignition wire sources in the car, under the dash. behind the radio is a good ignition source.

keep_hope_alive,

Thank you for the information. It is good to know that I can use the common 14 wire for this purpose.

For the wire location, besides the general area, do you know what type or color or wire I should be looking for? I would prefer to avoid splicing many wires to find the right one if it can be avoided.

Thank you again;

Sorry for the delay, you'll want to consult a Haynes manual for wiring schematics, but you can always get an ignition wire behind the head unit.