Anyone installed an inverter on the second battery?

[patracy]

I've got a large 12v to 120v inverter I was thinking about installing into my CUCV. Since the #1 battery gets hammered on so much and the second battery/alt isn't used all that much, can't I just tap off it? The inverter has isolated leads in for positive and negative. I've gotta get my listeroid genset up and running, but in the mean time I could use this to power up the lights around the house the next power outage we have.

 

[319]

Yes you can, but if I recall, in an earlier thread it was discussed that you cannot connect a ground from the inverter case to the vehicle. The unit has to be grounded to the battery.

 

[doghead]

If your only using it as a "generator" for power failures and your truck is just running at idle, the only power being drawn is your shutoff soleniod.

 

[mistaken1]

The negative post of the second battery 'floats' 12V above the vehicle chassis. If your inverter has the case internally grounded to the negative input it too will float 12V above the vehicle chassis meaning if you bolt it to the chassis there will be a dead short from the front battery positive (same point electrically as the back battery negative) through your inverter to the chassis.

If you isolate the inverters metal case from the vehicle chassis then it will not be a dead short but anything that contacts the metal parts of the inverter case and the metal parts of the vehicle chassis will be a path for that dead short. How much current flows will be a function of the resistance of the connection between the two, wet skin has a low resistance.

While laying on a wooden workbench check for continuity on the inverter between the negative input and any metal components on the inverter case (like a metal heat sink). You need to use a sharp tester probe to penetrate any paint or other coatings on the inverter. If you have continuity then the inverter has an internal bond between it's chassis and it's negative input.

Just to be safe connect your inverter to the front battery only.

 

[Barrman]

Yes, you can do it. However, as pointed out in several post above. It would be better to use the front battery. Being someone who used to mess with positive ground British cars. I can tell you having something in the vehicle "floating" seperate from the vehicle is just a short waiting to happen. Like installing a negative ground radio in a positive ground car. It works until your wet from the rain hand touches the case and the car body at the same time.

 

[patracy]

Did the military use any 24v to 110v inverters? Anyone know of any numbers for them?

I've found a lot of chainable 220v and 110v inverters online from china, but I'd rather find something like an old rotary inverter or mil-spec solid state inverter.

 

[patracy]

In my typical luck, got the inverter installed and tried to power it up. Nada. Fans come on, power light never comes on. 0v on the AC side. Guess I'll just look for a 24v inverter now.

 

[notsosanestan]

i hooked up my inverter to the buss bar in the back for the radio grounded it there too.

 

[Mohawk Dave]

The negative post of the second battery 'floats' 12V above the vehicle chassis. If your inverter has the case internally grounded to the negative input it too will float 12V above the vehicle chassis meaning if you bolt it to the chassis there will be a dead short from the front battery positive (same point electrically as the back battery negative) through your inverter to the chassis.

If you isolate the inverters metal case from the vehicle chassis then it will not be a dead short but anything that contacts the metal parts of the inverter case and the metal parts of the vehicle chassis will be a path for that dead short. How much current flows will be a function of the resistance of the connection between the two, wet skin has a low resistance.

While laying on a wooden workbench check for continuity on the inverter between the negative input and any metal components on the inverter case (like a metal heat sink). You need to use a sharp tester probe to penetrate any paint or other coatings on the inverter. If you have continuity then the inverter has an internal bond between it's chassis and it's negative input.

Just to be safe connect your inverter to the front battery only.

Mistaken1,

I've read and re-read this post many times, and yet I am still uncertain. For my set up I have a 4 gauge coming off the front battery and running to my fuse blocks, pictured below. The fuse blocks are grounded as seen to the body. I am running a slew of items off of these and have had no problems with them or the charging.

Am I supposed to have my ground running back to the first battery?

Thanks for your time,

Also, to the OP, I run a 400/800 max inverter from my fuse block with 8 gauge and we use our laptops etc on it all the time. But I think you are talking about a much larger inverter, so this may be moot.

Dave

 

[quickfarms]

Get out the ohmeter and voltmeter.

Check to see if the case is grounded to the negative terminal of the inverter using the ohmeter. If it is, isolate it

Check the incoming voltage

check the fuses and circuit breaker.

if all else fails wire it up to amother vehicle to make sure that the inverter works.

 

[Recovry4x4]

There was a guy on the mailing list back in the 90s that had some surplus inverters. These were basically a 28V motor coupled to a 120 genset head. They were milsurp for sure. I don't recall the amperage at all but remember it was quite unique.

 

[mistaken1]

Mistaken1,

I've read and re-read this post many times, and yet I am still uncertain. For my set up I have a 4 gauge coming off the front battery and running to my fuse blocks, pictured below. The fuse blocks are grounded as seen to the body. I am running a slew of items off of these and have had no problems with them or the charging.

Am I supposed to have my ground running back to the first battery?

Thanks for your time,

Also, to the OP, I run a 400/800 max inverter from my fuse block with 8 gauge and we use our laptops etc on it all the time. But I think you are talking about a much larger inverter, so this may be moot.

Dave

If I understand you correctly your positive fuse block is connected to the positive of the front battery (same point electrically as the negative of the back battery) and your negative fuse block is bonded to the vehicle chassis.

If so that is the same as most of the original factory 12V electrical components in in the vehicle.

If you are using a high amperage device then you should run a wire to negative post of the front battery (same size as your positive wire).

The problem is when you try to use the positive post of the BACK battery. That post is only 12V above the negative post of the BACK battery but is 24V above the negative post of the FRONT battery and the vehicle chassis (because the front battery negative post is bonded to the chassis to make the factory original 12V electrical components work {lights for example}). It is when using the BACK battery that you need a separate wire to the back battery negative and must isolate the component case from the vehicle chassis.

What that would mean is that if you connected something to the BACK battery with separate wires and kept it isolated from the vehicle chassis you could then take your volt meter and measure 12V between your isolated case and the vehicle chassis. IOW your isolated case would be 'hot' with respect to the vehicle chassis just as if it was a wire tied directly to the front battery positive post (which electrically it is).