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Jumpstarting from battery isolator


Bikemike

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Yes you can but do not expect instant results it might take a bit to "recharge" the truck battery from the coach battery it's not like jumper cables. A small jumper with clips would do it with a #10 or greater wire with out having to disconnect any thing. It's fairly common to see switches on Motor homes that will do just that by turning on the isolator relay the same thing can be done with the solid state ones but with diminished results.

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I had a problem on my recent vacation with the RV stalling out due to no connection from the alternator and truck battery.  I pulled the coach battery and exchanged it for the truck battery.  It turns out that I had a bad connection under the hood which I got around by installing a #4 cable from the isolator straight to the positive post on the truck battery.  Changing the batteries took about 10 minutes and got me on the road again.

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yes you can jump the isolator and give it time to charge. And, with most isolators, you should actually just be able to turn the ignition key and it will charge the truck battery from the coach battery

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2 hours ago, bicoastal eric said:

yes you can jump the isolator and give it time to charge. And, with most isolators, you should actually just be able to turn the ignition key and it will charge the truck battery from the coach battery

True but doing so will also turn all of your trucks ign. related electrical stuff. A jumper or a dedicated switch would give the best results.

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on my winnebago warrior, U can daisy chain my 2 jumper cables and reach from the positive terminal of the house battery to the positive terminal of engine battery.

 

Note that hot wiring the positive contact of the isolater would connect the 2 batteries, but (at least on my camper) the wiring between the batteries is not nearly big enough to handle the starter's draw.

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It is always best that you make the initial connection the allow the starting battery to soak up some charge before attempting to start. A long 10 gauge wire really is not big enough to supply starting amps especially if you have to crank it for awhile. A 10ga wire will get hot even to the point of damaging it's sheathing maybe even melting and shorting to ground somewhere. 

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Yeah you will be able to... as long as you have a solenoid type isolator. Don't think it's possible with a solid state without disconnecting some wires. 

I've seen a 3 way switch wired under the hood that will let you select start or house bank for cranking. 

If you are looking to replace your unit 12vguy.com makes a really slick set up with either winch controls or extra accessory switches wired up that bolts into the ash tray or coin tray of all types of toyota interiors. I have one of his units in my 1990 3.0 and you can select whatever battery you want to start off of with out even popping the hood... plus there's more cool looking switches and little led indicator lights to really make it feel like a space ship inside ?

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You do not need a long wire 6" and two clips is all you need. Jump across the two large terminals on a relay type jump terminals1 and 2 on a solid state isolator both under the hood. Boat battery switch's could be used but it's a long run to the rear battery the cables would cost more than the switch. No matter how you do it it is not like jumper cables it would be like a trickle charger the good battery charging the weak one it does work but it takes awhile.

Edited by Maineah
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If you have a solenoid isolator just turn the key on. If your worried about the auto systems draining things, just use a short wire with clips between the house battery (big cable) and the 12v switch in (small wire). This will make a high amp connection.  

Desperate times,  just connect all 3 big wires to the same terminal, works with any isolator. This will also work when your alternator cr*ps out in Baker Ca. at 03:00 :angry:. You would be surprised how long a 100AH battery will run the engine and lights.

Edited by WME
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