12V A/C anyone?

I looked at LifePo batteries. Mine are about a year old and can start my 14.7L 893ci engine with ease. I didn't see a LifePo with a higher ah.

 

3,000 watts WHEN the truck is running...

When the truck is not running the invertor is relying on just the batteries for power and the the batteries don't have that much power...

 

You need to get your system off the chassis batteries, the best solution is to use a maxwell starter module for starting the truck, reduce the number of flooded batteries to two, and to install three or four LiFePo 100 ah batteries OR 2 200ah batteries.

your batteries have when new a real capacity of 88 ah each, this goes down with time.

 

You've gotten some good feedback so far. I'll offer my take.

TLDR: There's a lot of room for improvement. However, insufficiently sized cables connecting the batteries to the inverter are likely the main problem causing the inverter to die when the a/c starts.

"Duracell" group 31 batteries are run of the mill AGM, made by Deka. They are not ideal to begin with.

950cca tells me they're start batteries, not deep cycle or hybrid. Even worse for use as "house" batteries. They aren't going to tolerate deep discharge cycles well. The difference is with the construction of the plates inside. Higher cca rating does not equal greater capacity. Lots of tech articles on the internet to explain that, so I won't.

Using truck batteries for house loads, you cannot deplete them much more than 50% and still start the truck without a jump. On my truck that's about when the battery voltage drops to about 11.8V. Those Duracells are more like 80Ah so four gives you 320Ah capacity, of which you can only use about half, or 160Ah. Worst case your a/c is going to be pulling 40-45A off the batteries (explained later). 160Ah gives you about 4 hours of run time before you have to start the truck to recharge.

LiFePO can be depleted 100%, and since they aren't (can't be) used to start the truck you won't be late to your delivery dealing with dead batteries, should you fall asleep with the a/c running. If the wattage on your a/c is right, 200Ah would be the bare minimum, more would be better since you no doubt have other things on too.

If they were wired in series, you'd smoke the inverter with 48V. Probably wired in parallel, as usual for 12V output. That is, all the negative terminals bridged together, the positives likewise. It may seem like grammar police, but the difference between the two is substantial enough to mention.

If you're insisting on using the truck batteries, versus dedicated house LiFePO batteries to power a/c and other bunk devices as @Ridgeline suggests, at least get some premium hybrid gel batteries. That would be Northstar aka Batteries Plus X2Power or Odyssey. They are not cheap, really not much less than LiFePO if you don't count the extras (cabling, charger/isolator, etc) needed to set up a house battery bank. They will give you 25% more capacity and survive deep cycling much better, by years not months.

Power Drive is another sub-optimal choice. First, it's a modified sine wave inverter. A better choice would be a pure sine wave inverter. You can search and see why. Xantrex is a good brand, there are a few others. Beware of the Chinesium brands on Amazon and the like - they're cheap for a reason.

If you hooked it up to your batteries using the cables it came with, that's probably most of your problem. 3000W at 12V = 250A. If you've been running stuff all night and your batteries are down to 11V, a 3000W load would pull 273A. Find a web calculator and put your wiring run length and 300A in to see what size wire you need to the batteries. Off the top of my head, if you aren't using at least 2/0 cable it's not enough. Look it up to be sure. I'd be surprised if the included cables were any bigger than 0 or 1AWG. I don't see a 300A fuse and holder in the product description either. You should have one on your battery leads.

When your a/c hits that inverter with a start up load, the small wire gauge causes the voltage to sag enough that the inverter shuts off. Fortunately for you, the protection shut down prevents the small wire from overheating and possibly burning your truck down.

Very important: whatever inverter you buy, get one with line outputs for 120V. The one you have likely uses a floating neutral, ones with line outputs typically have a bonded neutral. Bonded neutral is what you need when running household loads like a window a/c, versus a small tv or laptop/phone chargers. The risk is: if you have a short from hot to neutral, it can energize the case of an a/c unit which would be no bueno if you touched it in such a state. I'm no electrical engineer so not gonna try explaining that. Look it up on RV sites and you'll see.

It's a small error, but 4.1A at 120V is 492W. At 12V that's 41A. At 11V it's 45A. As mentioned, running not starting up. Starting is 2-3X that.

A more efficient a/c unit would extend your battery life, a lot. SEER 20 or better.

Find, buy, and install a "soft start" on the a/c unit. It's smarter than a capacitor and will do what you need. That is, reduce the momentary burst of power needed to get the compressor running. I already covered why I think your inverter is taking a dump when the a/c kicks on. This would help, but my gut feeling is your battery cables to the inverter are the main problem here. Fix the cables first to eliminate a serious fire risk.

 

Great detail here. A person should learn a lot just by paying attention to these kind of post.

 

Another post that makes me wish that TTR had more buttons than "thanks"!

 

RedForeman, thank you for the explanation. Now I have something I can use to research. I know it was a lot of your time to put all that knowledge into print, but I do sincerely appreciate everything you have given me.

Bean Jr. & Siinman, you are both correct. People throwing half ### responses out there at best accomplishes nothing. Thats why I rarely make recommendations. Especially ones that would cost someone thousands of dollars. I had an experience 30 years ago with bass amps and misleading salesmen.

 

No doubt. It does not do it justice.

 

Close to same unit on my 2nd truck

I have examined the unit and outdoor unit could be placed on the frame if desired.

I opted for stripping back the interior wall, silliconing the holes and putting longer ss through bolts to mount the outdoor unit.