Design for a 3,000 W inverter install.

[GOOSE]

I am designing a system to utilize a 3,000W inverter. Here is a picture of my design. Two group 27 deep cycle batteries so you don't have to rely on the trucks batteries. Solar charging capabilities backed up with a keyed on continuous duty solenoid to tap into the trucks charging system only while the truck is running. Anyone install a system like this? Is there something I'm missing? Tell me what you think.....

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[laserjock]

I spent a lot of time thinking about this. I guess it depends on why you are doing it. If you want to run power tools etc. for short periods that’s probably enough capacity but you may need to look at starting marine batteries instead of deep cycle if you need all 3000W. That’s ~250 amps. Deep cycle bats are not designed for high current loads so the peak output is lower but the capacity is usually higher. If you are thinking AC on the camper, you will blow through your batteries pretty quick even with the truck boosting. The capacity is just not there to sustain it very long. Group 27’s are what like 80-100 amp-hr so 200 for a pair to make the math easy? If you are pulling 2kw that’s that’s 166 amps so you’ve got a little over an hour assuming the low voltage doesn’t get you. May only get about 80% of rated capacity. So realistically you’d get an hour. You could stretch it with the truck but it’s not a sustainable source that way. Same with the solar panels. Another note, if you do solar panels, make sure you either put in a voltage regulator for them or get the ones that are “smart” battery chargers so you don’t cook the batteries charging them.


Edit: your got the regulator! [emoji1303]

 

[GOOSE]

This is going on a work truck to have on site power. Charging batteries, maybe running a porta band saw. The underlying idea is to put a mini frig, microwave, coffee maker and toaster oven in the truck. I'd have 1,000-2,000 watts of usage for a couple minutes at most and the low demand of a mini frig.

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[laserjock]

In that scenario, I think you’re golden. I don’t know what minifridges pull these days. If you do a thermoelectric they don’t pull much. No compressor to run.

 

[BeastMaster]

I guess those are 6 volt batteries you are connecting in series.

Amp Hours does not add for series connected cells, but voltage ( and watt-hours ) do.

That is two 6V 100AH batteries in series will net you 12V, 100AH. Or, in parallel you will get 6V, 200 AH. 1200 Watt Hours either way.

Be sure you can shut the inverter down completely when not in use, as some draw substantial power even in standby.

 

[Macrobb]

In that scenario, I think you’re golden. I don’t know what minifridges pull these days. If you do a thermoelectric they don’t pull much. No compressor to run.

Exactly opposite - thermoelectrics are *very* ineffecient for the amount of cooling they do. Tons of waste heat(and therefor waste power), especially to get any reasonable temperature differential. So keeping beer at 40 degrees when it's 70 out? Sure. Keeping a freezer compartment below 20F when it's 100F out? Really hard to make that happen.

A compressor-driven unit is actually a lot more efficient(for the BTUs moved); the best case would be if you could get your hands on a DC compressor refrigerator*, but even with the losses from the inverter you are probably still better off.

(*Danfoss makes these really cool brushless DC compressors for use in 12-24V applications. Kind of expensive, though. I accumulated a custom "minifridge" at auction out of a fire engine of some sort using said compressor. The thing takes 60W/5A to run, and can keep the "minifridge" at 30F while only running about 20% of the time.
It's been great to use while on vacation keeping the batteries charged via solar).

 

[ClifFord]

I'd put a inline fuse, or breaker between the isolator and the system. Also imo it's always good to build a terminal box to keep things organized, and not just everything hardwired with ring terminals. And also a battery off / kill switch from the battery bank to the inverter.

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[Oledirtypearl86]

The 27's will work for a bit on the service truck I switched to 4d Batts and it will run our 5k watt generator pretty well and hold a charge longer also they seem to come back up fairly fast when I start it back up

 

[u2slow]

I ran an 1800W inverter with a single group 31 gel in my van for a while.

I used an auto-charge relay (ACR) to keep it topped up, and a separate on/off switch for bridging with the cranking battery - in case something completely died.

Make sure you put disconnects and overcurrent protection in the appropriate places.

 

[saburai]

Macrobb is correct. We live off grid. We've got a Nova cool RFU 9000 in the house
http://novakool.com/products/two_doors/rfu6200_6800_8000_9000.htm
I believe that they make a smaller truck fridge.


We have a expo style Jeep XJ with the 43qt. version of this edgestar Danfoss swing compressor fridge. Two AGM 1100 CCA batteries, an isolator, small charge controller and a 62W soft folding solar panel tha I throw on top of the rooftop tent. It's been in service for about ten years. I had to replace the control board about five years ago otherwise it's been fine. Doesn't look like they make the 43 quart any longer
https://www.compactappliance.com/fp630-spacious-edgestar-portable-refrigerator-freezer/FP630.html