# Inverters,And Batteries



## james dilley (Mar 21, 2004)

Any ideas on wiring A 1200watt inverter into A semi.??I want to use it with 2 deep cycle batteries so as not to run the main ones down,, Any thoughts??? thanks


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## Guy_Incognito (Jul 4, 2006)

Quickest way - get one of these :
http://www.redarc.com.au/smart-start.htm 

Automatic, all you need to do is hook your new set in parallel with your main set, with that gadget in the middle. It automatically closes it's relay when the alternator's charging and drops out when the engine's off.

A little pricey, but saves a lot of fiddling.


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## james dilley (Mar 21, 2004)

I used to have A M/H that used A ford starter relay to keep the extra batteries from draining the main, Thats what I was thinking of.


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## Guy_Incognito (Jul 4, 2006)

That gadget's the same deal, just with more smarts in it.

Basically, you'd want a relay to kick in only when the engine's running. 
When I did my time as a "car" auto electrician, I used to run them off an oil pressure switch - or via a smaller relay run from D+ on the back of the alternator. Or in some cases, just from the "accessories" position on the key - as that dropped off when cranking, it avoided surge currents from your backup set. After I while, I figured out that getting another oil pressure switch and plumbing it in and running the wires,etc took longer in labour costs than for me to just go and get one of those smart relays.


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## Jim-mi (May 15, 2002)

Go to a RV place or auto store and get a simple battery isolator. Just a pair of hefty diodes on a big heat sink.


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## Guy_Incognito (Jul 4, 2006)

Jim-mi said:


> Go to a RV place or auto store and get a simple battery isolator. Just a pair of hefty diodes on a big heat sink.


You know, I completely forgot about those!

Never did really like them - you lose a bit of voltage across those diodes (well, that's what the big heatsink's for...) and consquently you never get your batteries up to full charge. And you can't start your flat vehicle from the other set of charged batteries if you have one of those, whereas with the (correctly-rated) relay, it's just a push of an override button.

Which is probably why I forgot about them


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## patarini (Nov 19, 2004)

I just hooked direcct to batteries with a pair of 300 amp fuses in the circuit for my 3000 watt inverter works great. Only thing is when I use my convection oven it helps to be driving, will draw power down to 13.2or a bit less. With my normal load -- 4.2 cu ft fridge and a big hamilton beach electric grill I never have a prob. I did use speaker cable because it can handle a bigger power draw, ran me 2 a foot for my 2000 watt and 5 a foot for my 3000 but that is 00 cable. I have never run my batteries down, but i do run all 4 deep cycle extra heavy duty types! Shouldnt drain you over a weekend with just fridge on, and if you are running big draws(lathe, grill, oven) IDLE! LOL


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