Battery and converter size questions

Hey everyone! First off I’m new here so hello all!

My set up right now is wired for shore power. I have an AC/heat unit that pulls about 1200 watts 10amps and a mini fridge pulling around 65 watts if I remember correctly. I also have some 12v lighting and our water pump that run off an ac to dc inverter/charger. Charger isn’t connected to any batteries yet.

My plan is to get some agm batteries and rewire my system so when I’m in transit I can use my fridge and potentially the AC off the batteries then when I park I can connect to shore power and charge back up. Most of our trips run around 6 hours between shore power.

My question is, what size DC to AC converter Would you buy given my two appliances and second question is how many 100ah batteries would you use considering my average trip time between charges.

I am curious on the ac/heat unit that only pulls 1200 watts, what brand/model is it as most I’ve seen are considerably higher.

If you took the AC unit out of the equation one 100 amp hour battery would be fine. I honestly do not know if the AC unit would be doable as the math around the conversion DC to AC is beyond me. It is not efficient and power is lost there. Remember with two non lithium 100ah (200ah total) batteries you still only have 100ah of usable power before you start damaging the cells, reducing life and capacity.

My guess would be at least a 2k watt inverter and a pile of batteries. In our travels the only people running AC units are doing so with generators if they don’t have shore power.

Thanks for the quick reply!

So the unit is a Black an decker 12,000btu heat pump. Amazon purchase. Runs great on shore power. I found the readings off the listing on amazon cause I’ve long gone thrown away the box and it’s been installed in my rig so not the easiest to see the back or bottom where the placard is.

I do know of only draining half of the battery so I was planning on having a few. I also know to get an inverter that is at least double my surge draw. I was thinking 3500watt with surge of 7000watt.

Running the fridge is our biggest thing. That’s our newest addition. We’ve been dealing with no AC between stops but I was thinking the fridge would be useless if I can’t keep it cold from place to place. Lastly I was thinking we could do more “off grid” type camping is I could get everything to be powered off batteries.

This is just a weekend hobby so not necessarily “van life” so not having AC is ok and not spending a fortune on batteries and massive inverters is even better but I still think it would be cool if I could do it on a slight budget.


I paid $99 for my no name 3500w inverter generator that will run for ~8 hours on a gallon of gas. I added an $18 scooter muffler to make it extremely quiet. On a hitch rack, you could run it while driving to power everything, and even charge house or starting batteries if needed.

Even though I rarely use my generator at present, it is one of my very prized backup plans. If I’ve got gas, I’ve got power… with no sun or batteries needed, but I can also charge batteries if needed with my battery charger.


"Always avoid expensive solutions to cheap problems." ~ OffGrid

That right there is a very clever idea! I was just talking to a family member last night about this topic and he also agreed it’s just so much money for something I’ll be using so little. I love the generator idea. I mean hell the vehicle is running anyways so a little generator isn’t going to add much more noise. Thanks for your input. That’s the top of my list on solutions right now!


Always glad to help when I can. :smiley:


"Always avoid expensive solutions to cheap problems." ~ OffGrid