Battery isolator installation
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Fleet Mechanic
Joined: Nov 2008
Posts: 1,573
Likes: 4
From: Seattle
Battery isolator installation
I have plans to put a deep cycle battery in the bed, fed by a 120 amp isolator which I hope to mount somewhere on a fenderwell. I also have a 1200 watt inverter I will mount in the tool box.
Having a battery in the bed serves me better since my fueling station cart is 12v, along with my wvo pick up pump, light duty in-bed winch, and other items.
My question is, will this put too much additional strain on the charging system? Perhaps pushing the alternator or other parts of the system beyond its limits?
Any input would be greatly appreciated.
Having a battery in the bed serves me better since my fueling station cart is 12v, along with my wvo pick up pump, light duty in-bed winch, and other items.
My question is, will this put too much additional strain on the charging system? Perhaps pushing the alternator or other parts of the system beyond its limits?
Any input would be greatly appreciated.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,111
From: Rio Rico, AZ.
I hate those diode based isolators, they tend to drop the charge voltage for the entire vehicle.
What I use when installing an isolator system is to use a continuous duty relay that closes when start the engine.
Also in the charge circuit I install one of those little 50A circuit breakers so that the alternator won't fry itself trying to charge up a dead battery.
I'll go try and find the part number at NAPA for the ones that I use.
What I use when installing an isolator system is to use a continuous duty relay that closes when start the engine.
Also in the charge circuit I install one of those little 50A circuit breakers so that the alternator won't fry itself trying to charge up a dead battery.
I'll go try and find the part number at NAPA for the ones that I use.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,111
From: Rio Rico, AZ.
The relay.
http://www.napaonline.com/NOLPPSE/(S...402_0172436509
50 Amp circuit breaker. It auto resets itself, so it basically slows down the charge rate for the auxiliary battery to 50 amps max, saving the diodes in your alternator from overheating.
You can get them as low as 20 amps if you are driving a big stereo or something and need to be careful of the load that you are placing on the alternator.
http://www.napaonline.com/NOLPPSE/(S...001_0244704737
http://www.napaonline.com/NOLPPSE/(S...402_0172436509
50 Amp circuit breaker. It auto resets itself, so it basically slows down the charge rate for the auxiliary battery to 50 amps max, saving the diodes in your alternator from overheating.
You can get them as low as 20 amps if you are driving a big stereo or something and need to be careful of the load that you are placing on the alternator.
http://www.napaonline.com/NOLPPSE/(S...001_0244704737
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,111
From: Rio Rico, AZ.
You can get fancy if you want and run a small load reduction relay to power the large relay.
The small relay is driven by the exciter lead on the alternator so that the large relay won't close until the engine is running and the alternator is charging.
VW did it that way for 20 years on thier Westfalia campers. It was a very slick system.
They used a standard Bosch X-contact relay.
Terminal 86 goes to D+, the exciter lead.
Terminal 85 goes to the starter solinoid wire. Not the big main power wire, but the smaller wire that tells the starter to operate.
Terminal 30 goes to B+, the output post on the alternator.
Terminal 87 goes to the positive post of the aux battery, or in this case the energizer post of the isolator relay.
Using this system it will never come on until the engine is started and the alternator is charging.
The small relay is driven by the exciter lead on the alternator so that the large relay won't close until the engine is running and the alternator is charging.
VW did it that way for 20 years on thier Westfalia campers. It was a very slick system.
They used a standard Bosch X-contact relay.
Terminal 86 goes to D+, the exciter lead.
Terminal 85 goes to the starter solinoid wire. Not the big main power wire, but the smaller wire that tells the starter to operate.
Terminal 30 goes to B+, the output post on the alternator.
Terminal 87 goes to the positive post of the aux battery, or in this case the energizer post of the isolator relay.
Using this system it will never come on until the engine is started and the alternator is charging.
Thread Starter
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Fleet Mechanic
Joined: Nov 2008
Posts: 1,573
Likes: 4
From: Seattle
Much appreciated. I really don't want to disrupt any balance which exists in the charging system. I'm pretty inept and uncomfortable when it comes to automotive wiring as it is.
I'll read up more on the set up you describe. That makes more sense to me. I foresee putting some heavy, extended loads on the auxilliary deep cycle battery at times, and that would definitely put additional strain on the alternator.
Thanks Dan. Reps sent.
I'll read up more on the set up you describe. That makes more sense to me. I foresee putting some heavy, extended loads on the auxilliary deep cycle battery at times, and that would definitely put additional strain on the alternator.
Thanks Dan. Reps sent.
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