Battery isolator installation?

zuren

Adventurer
Maybe the original installer wasn't planning to run enough stuff off the inverter to need a bigger breaker so maybe that's why the 120a.

Fuses/breakers are to protect the wire, so the biggest you can use is however many amps the wire is rated to handle.

Even if the inverter could do 6000w, that'd be more than the wire is rated for, so you don't size the breaker based on the inverter's rating, but only based on the wire size.

I had continued to research and forgot to update my post with my wire ratings and what I was finding. What I'm gathering is that 2/0 awg wire (aka "00" wire) with a 105*C insulation rating for a 25' length can handle somewhere in the neighborhood of 195A. I've found other sites that claim it can handle up to 300-400A but the majority of info I'm finding is in the 200A range. I need to pull all of the info off of the wire to see if I can pin this down more. It definitely looks like 2/0 awg industrial welding cable.

http://www.powerstream.com/Wire_Size.htm

http://en.wikipedia.org/wiki/American_wire_gauge

Then I found this link that is more specific to 12v systems and it claims 100-150A:

http://www.alternatorparts.com/wire_size_chart.htm

I'm thinking 150A breakers throughout the system is probably the biggest I can go.
 
Last edited:

dwh

Tail-End Charlie
Yea. On that Powerstream table "chassis wiring" means "inside of a metal box" (or inside of a machine like a mill or lathe or welder or whatever). You are doing power transmission. You could go up to a 175a breaker on that normally. If the wire is rated to 105c and in "open air" - i.e. not in conduit, I wouldn't feel bad going to 200a on the breaker.
 

zuren

Adventurer

Thanks for the link! I was able to get my 150A breakers through Amazon. I also found this site: http://www.wiringproducts.com/contents/en-us/d195.html

I still haven't decided on what isolator I want to use. Does anyone use something like a manual boat battery switch like this?

51JiSnLgmqL._SL500_AA300_.jpg

http://www.amazon.com/Perko-9601DP-Marine-Battery-Disconnect/dp/B00144BF9Q/ref=pd_sbs_sg_1

I'm just considering all potential options. I know it's manual therefore a reduced convenience factor but it would be reliable. I may also have a small solar setup in the future, so I'm not certain how that may figure into my setup.

For the rest of the system connections (to the "house" fuse panel and inverter from the house battery) does 2 gauge welding cable sound heavy enough?

Thanks!
 

dwh

Tail-End Charlie
That battery switch in the pic is just an on/off. It would work...the drawback is forgetting to turn it off and running both batteries dead.

I think most people use the A/B/A+B/OFF type. With that type, there are two sub-types: Break before Make, and Make before Break.

Make before break means that it will connect the loads to B before it opens the connection to A. That's useful if you don't want to lose the programming to the microwave or the DVD player or whatever.


You probably don't need #2 wire to the fuse box, and depending on the inverter, #2 might not be big enough. You need to size those wires according to the load they'll need to carry.
 

zuren

Adventurer
National Luna is a good looking bit of kit. Expensive though. My camper van just has a simple split-charge relay. Like this:

http://www.amazon.com/SOLENOID-GOLF..._2?s=automotive&ie=UTF8&qid=1311617329&sr=1-2

Wire it to tie the batteries when the key is on "run" (not accessory) and forget about it. That's about as simple, bulletproof, cheap and reliable as it gets.

dwh - Now I'm looking into your idea of using a solenoid like this. How did you wire it to connect the 2 batteries when the engine is running? Is one of those terminals a signal connection?

I keep hemming and hawwing being overwhelmed by the number of options out there and wanting to understand each one. I just need to pick a solution, place an order and get this portion of the build going!
 

wrcsixeight

Adventurer
I've been using a 1/2/both off/ make before break battery switch for 9 years now. Mine is the Guest brand.

The break before make types, which I was not aware of, might lead to alternator issues if switched while the engine is running.

I know if I were to switch mine to off with the engine running, not only will my engine stall, but the alternator might briefly send a voltage spike through the system destroying things.

Mine has 2 extra contacts on the inside for rerouting the alternator field wires through the switch, so if turned off it would prevent alternator load dump.

I do not use these, but just have my switch inside a cabinet and instruct any fellow travelers never to ever touch it on pain of death.

Turning the switch to off, and locking my cabinet adds another level of vehicle anti theft. I used 2 awg wiring between the switch and batteries.
 

dwh

Tail-End Charlie
dwh - Now I'm looking into your idea of using a solenoid like this. How did you wire it to connect the 2 batteries when the engine is running? Is one of those terminals a signal connection?

Not a signal per se...

There are two large terminals. There is an electromagnet inside. When the electromagnet is energized, it pulls the contacts into position which connects the two large terminals together.

Then there are two small terminals. These are the positive and negative to energize the electromagnet. One goes to negative or "ground", the other needs to get power from positive.

The normal setup would be to tap an ignition hot wire (not an accessory hot wire) and use that to energize the electromagnet when the key is turned to RUN. By not tapping an accessory circuit, you can turn the key to ACC and listen to the radio or whatever but not have the batteries tied. They are only tied when the key is in the RUN position.

There are also the same thing, but with only three terminals - the two large, but only one small. On those, the case of the unit is grounded, so when it is bolted to metal - like a firewall or inner fenderwell - it is grounded. For those you only need to run the hot from the ignition.

The reason for the 4 terminal type, is so you can mount it to something that isn't grounded - like a fiberglass boat hull or camper hull.
 

Forum statistics

Threads
185,527
Messages
2,875,533
Members
224,922
Latest member
Randy Towles
Top