Another isolator thread...help

[TubeTruck]

Ok, so I'm feeling a little dumbfounded when it comes to installing this battery isolator. I'm trying to install a 2nd battery (obviously) and can't seem to wrap my head around the wiring. I understand the drawing that came with the instructions but where do you run the cable to the starter? Factory it goes from the battery positive to a lug on the starter. Do you just theoretically split the cable and mount it to the Start battery terminal on the isolator?

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I'm switching main batteries also, making the driver's side primary. This way when I put the EFI BBC in I can mount the PCM and fuse box on the wheel well and run it off the main, assuming that's what you are supposed to do. Also, and I'm trying to think, There are 2 more wires on the starter terminal, aren't there? You have the main cable, the cable from the alternator and a wire that goes to the factory fuse box, is this correct? (plus the ignition wire on the smaller stud). Would I take the fuse box wire and move it to my aux battery? Also I'm assuming the alternator wire stays where it is.

Ok, school me

 

[bucket]

Maybe I'm reading this wrong, but it sounds like you still want the starting battery to run everything? What do you want the aux battery to power?

 

[Ricko1966]

Anytime I've done one, original wiring was left alone 2nd battery was charged to run other equipment, winch,inverter,etc. Both batteries wired in parallel and charge when the engine is running. Battery 1 and battery 2 are seperate with the engine off.You can run your winch, inverter whatever until battery #2 is dead but battery 1 will still start and operate the truck as normal. The isolator is just a relay. It's probably even numbered, big terminal #30 to battery 1 positive lead. Other big lug #87 goes to battery 2 positive .The low side leads #85 and # 86 run one to ground, the other to a hot that's only hot with the engine running . That is engine running not just key on power,the alt idiot light, or an oil pressure switch are good options.

 

[theblindchicken]

Starting battery is the main battery in that everything original runs off of it. You'd use the aux battery to run all the additional accessories such as lights, winch, inverter, power to a camper, fridge, etc.

Isolators are used to charge the battery when there is power on the system and disconnect when you shut the truck off. You can also use an override/lock on to give yourself a self-jump if the starting battery is run down without using a set of jumper cables between the two batteries.

Also, while you're in there, check your battery cables to make sure they aren't corroded under the sheathing. Good bit of future proofing there.

Hope that helps.

 

[Frankenchevy]

I agree that using a relay to isolate auxiliary battery seems the most simple. Relay closed with an ignition on 12v source. That way when the ignition is off the relay is open and the start battery is isolated from auxiliary battery.

One could even switch the 12v trigger wire to the relay so that the auxiliary battery could also be isolated with ignition on, if so desired.

 

[theblindchicken]

The isolator I have in my truck is a Wirthco 20092 Battery Doctor 125 amp/150 peak amp.

It's pretty much a "smart" relay in that it automatically connects the two batteries when there is at least 14v on the starting battery. When it falls below that, it will automatically disconnect the two batteries. For a fuse, I used a 150amp circuit breaker that can be easily reset with the flip of a switch.

Another advantage of using an isolator was being able to use non-identical batteries at the same time. So you could utilize batteries with different ages, makes, CCA's, types, etc. without any issues. Hardwiring the two batteries together without an isolator could cause issues as if the batteries weren't the same, you'd always have the stronger battery trying to charge the other.

The old way of running dual batteries was with a manual switch, but you'd have to remember to switch it on and off all the time.

 

[TubeTruck]

This is the one I bought: Amazon.com: NVX Microprocessor-Controlled 200 Amp, Dual Sensing Smart Relay Battery Isolator: Car Electronics

Their site was down but here is the manufacturers website: https://nvx.com/nvx-xsbi200.html

If I'm reading the description correct I believe this isolator will use the main battery to start, charge it back up to 13.3v, then switch to the Aux battery and run off that, and switch back when it drops below 12.7v. Here's my school of thought, and correct me if I am wrong. The main battery is used for vehicle starting, keeping the PCM wired to this battery ensures I will be able to start the truck even if I drain the Aux battery. The aux battery will run stuff like the lights, radio, and any extras (fridge, winch, etc.).

My misunderstanding of how this is wired lies with the wiring to the starter. If I run a cable from the Main battery to the main post on the isolator, then from the main post on the isolator to the starter, it would always be charging the main battery, even if the isolator switched to the Aux battery, at which pint it would be charging both?

 

[TubeTruck]

I think what I wrote was correct. Just took a bunch of times reading the description. For some reason I couldn't wrap my head around it, but I think my last post is correct.

 

[bucket]

If I'm thinking about it correctly, you will have to isolate the complete starter circuit from the rest of the truck. Ignition switch, park/neutral switch and everything receive power from the part of the truck that you want to run off the AUX battery. Lights, radio, etc.

 

[theblindchicken]

This is the one I bought: Amazon.com: NVX Microprocessor-Controlled 200 Amp, Dual Sensing Smart Relay Battery Isolator: Car Electronics

Their site was down but here is the manufacturers website: https://nvx.com/nvx-xsbi200.html

If I'm reading the description correct I believe this isolator will use the main battery to start, charge it back up to 13.3v, then switch to the Aux battery and run off that, and switch back when it drops below 12.7v. Here's my school of thought, and correct me if I am wrong. The main battery is used for vehicle starting, keeping the PCM wired to this battery ensures I will be able to start the truck even if I drain the Aux battery. The aux battery will run stuff like the lights, radio, and any extras (fridge, winch, etc.).

My misunderstanding of how this is wired lies with the wiring to the starter. If I run a cable from the Main battery to the main post on the isolator, then from the main post on the isolator to the starter, it would always be charging the main battery, even if the isolator switched to the Aux battery, at which pint it would be charging both?

You have two batteries: the Main/Starter battery and the AUX battery.

The isolator you ordered connects the two batteries in parallel (pos to pos, neg to neg) when it reads a minimum of 13.2v on the main battery, then disconnects when it reads below 12.7v. When they're connected, the alternator is charging both batteries, but when they're disconnected they're two completely different circuits. The alternator will always be charging the main/starter battery and is wired directly to it in the usual configuration.

You'd wire the PCM and the rest of the truck wiring to the main/starter battery. All the additional accessories would be wired to the AUX battery to minimize the draw on the starter battery.


For the batteries wiring:

Main/Starter:
Pos (+) -> Starter (which goes to the alternator)
Pos (+) -> Isolator
Ground (-) Chassis
Ground (-) Alternator/Alternator bracket
Ground (-) To AUX Battery (-)

AUX Battery:
Pos (+) -> Isolator
Ground (-) Chassis
Ground (-) To Main/Starter Battery (-)

Isolator:
Pos_1 (+) -> Main/Starter Pos (+)
Pos_2 (+) -> AUX Battery Pos (+)
Ground (-) -> Chassis
Override Switch -> Cab to manually engage the isolator

So it'd be almost like wiring the batteries directly together in parallel (pos to pos, neg to neg), but you're placing the isolator in the middle of the positive cable (Main pos to isolator to Aux pos). Adding a ground cable between the two battery negatives allows for maximum charging capacity and reduces any voltage drop.

I can draw a basic wiring diagram a bit later if you'd like.


Hope that helps.

 

[fast68chevy]

you can buy a basic isolator for dirt cheap, its a finned box with three threaded studs on it.,., one for the alternor charging output cable and the other two for each battery charge wire.., really simple.
i have one i took from an old motor home i cut up., thats all you need.
and theyre only like 20 bucks new. one battery for starting system and the other one for everything else including the fuse block