Posted on 09/12/2025 4:36:17 PM PDT by eastforker
Trying to figure out how much battery storage, inverter size, type of charger and what have you to power my houseboat. My plan is to have enough battery storage to run everything using an inverter for AC power using batteries and by charging those batteries daily using a generator for a few hours. The biggest draw would be an occasional few minutes of a microwave to heat food, and also run a tv/monitor along with computer. everything else runs on DC current for short periods of time like fresh water pump. I do have a small a/c air conditioner that pulls maybe 8 amps. Pretty simple setup but also need to know if lead acid batteries are sufficient or do I need special batteris. Any help would be great.
You have a link to that?
Myself, I find that I can get by a lot of times with just a window fan on many nights. The air conditioner is going to be your biggest power hog.
I was giving ballpark back of envelope figures to get you thinking. Talk with some local folks and get their input.
You'll be running a generator all day or carrying 1,000 lbs of battery which would take all day/night to charge. I would go with a Honda inverter gennie to run things by day and keep a battery bank charged for night use of the small loads. A fridge is likely not a small load though unless it's something meant for off grid.
We lived off grid for 4 years on a 500 watt 12vdc solar panel system using four golf cart batteries with a chinese Enkle knockoff 12 vdc fridge. Did ok with it but AC without a huge battery bank or gennie running ain't gonna happen.
I would give you a link to a calculator for this sort of thing but we searches have become 100% useless in recent years.
“and a 2K watt inverter.”
Kws:
A/C 1.0
Microwave 1.0
TV .3
Computer .3
...
Hello,
For what its worth, I would offer this:
Definitely look into getting a “Kill-A-Watt”-type meter that can show you power and energy usage. It should be under $100 and could save a lot of headaches. Power and energy usage are usually horribly labeled on devices. I have manual-defrost deep freezers that are misers with both and a frost-free house refrigerator that is an electrical beast. The labels say the opposite.
Your 8-Amp air conditioner is more like 80-Amps at 12 Volts. It will suck batteries dry pretty quickly.
40 Watts continuous is about 1kWH a day, so your TV and computer may each be more than 1 freezer, for me. A powerful inverter may draw about this much.
I have only 800 Watts of fixed solar panels, but they easily generate more energy than my 5kW generator running for an hour and a half. I wish I was on a boat, then I would follow the sun and get more energy. A gasoline generator seems great for emergencies or periods of no sun, but the gasoline is expensive.
I am using deep cycle RV lead-acid batteries. The jury is out on how long they will last, but I keep them close to full charge daily.
Good luck to you!
The thing to remember is that rarely are all of them running at once.
Using a laptop is an excellent way to ration power. Cook with propane. Microwave only runs for 3 or 4 minutes at a pop. Heat with kerosene. AC is the power hog. Running a window fan after midnight can cool pretty well. Use LED lights designed for RVs to run directly off the battery power.
Lead acid is no longer the sensible option from both a cost, life and weight perspective. The Li po 4 battery is the way to go now I believe. Well at least if you can keep them dry.
With reports of ocean-crossing cargo ships with EV cars and such catching fire, I'd worry about having lithium ion batteries anywhere near salt water, including on a houseboat.
-PJ
I have been living off grid on wind and solar for 25 years. And I agree with Pollard, the A/C is a problem child. Everything else you can get away with a minimal set up, but not the A/C. It would require too many panels and too many batteries to use one. And even then an AC fridge would be a problem, propane fridge is more practical on a self contained system like that.
I have a 12 volt fridge in my camper and it will runn 24 hours on one 12 volt battery with no problem.
Don’t a.ways agree with him on the issues, but genxpolymath knows charging and batteries.
“I am using deep cycle RV lead-acid batteries.”
I get about five years out of mine the same. But I rotate them a couple times a year so that some do not get more primary input charging than others. If you leave them in one configuration the first couple batteries closest to the charge coming in cook more than the rest. So rotating them helps this issue and extends the lifespan.
I could go with a propane fridge, no problem there.
Yes, having a 12v fridge helps greatly! Mine is three way. 120, 12v, and propane. It takes awhile to cool new stuff on 12v but it will maintain cold fine once everything is cold.
“Microwave only runs for 3 or 4 minutes at a pop. “
True, but if comes on while AC, TV, Computer and AC are own ...
Thank you!
I sure hope I get more out of mine than that, but that is about what I get in a vehicle. The batteries are easily the most expensive part of a system.
I had an Edgestar freezer/fridge that iirc, pulled 5 amps @ 12 vdc. Our 500 watts of panels were minuscule but managed. The golf cart batteries were 6 vdc wired in both parallel and series and each was 220 amp hour.
TV and DVD player didn’t take much. A laptop or even better, a tablet would be better than a desktop.
I thought about that and was thinking I could turn off the AC if I needed the microwave for a few minutes.That 2.2 k generator only uses about a gallon every 5 hours so thats not so bad, I could run that in the hottest part of the day if need and would also be charging batteries during that time.
Lead-acid is actually an excellent technology, a mature technology. Over a hundred years old in fact. There are no tricks or magic hashed out, it’s all extremely well documented. The final proof testing was done by American diesel boat crews, who learned what batteries could really do compared to the “book”. Their lives depended on it.
First, forget about charging for “a few hours” with any sort of moderate or heavy use. One down side to lead-acid is the charging rate for large high amp hour batts is glacial. And as the temperature goes down, the internal resistance rises, slowing the process further.
The charging voltages are not fixed, it is based on temperature. Charging tables are based on a 77°F standard temperature. Most chargers are not temperature compensated. If you want a usable bank you’re probably looking at large “golf cart” batteries, 6 volt, wired in series and parallel. In order to maximize service life and performance you’ll need to monitor charging voltage against the battery temperature.
Keep in mind a 65 pound chunk of lead will lead and lag ambient air temperature by quite a lot. It might be 70°F ambient air temp, but the battery is not, it’s still at 47°F, this is important to understand. There is about a 36 hour time lag for the battery core temperature to reach ambient.
Rolls Royce has an excellent web page or .PDF on deep cycle or marine lead acid battery care and maintenance. I use a Honda generator for charging my RV battery, and deep cycles will start to choke after about a week of partial recharges or so. In fact Rolls recommends an Equalization charge every 7 to 10 days, my experience has been you have to do this, the battery demands it on its own. A voltmeter and thermometer are your friends, the “smart” chargers are good, but there is no substitute for a good old “dumb” charger too. You’ll need to let it cook at 16+ volts every so often to keep all the cells equalized. Be sure to purchase a charger that is capable of supplying sufficient current, roughly 20% of the ampere-hour capacity. A 100 amp battery bank wants a 20 amp charger. Even larger would be nice now and then.
We take charge times for granted when we can plug into the wall current. Generators mean noise and time and fuel, make it count.
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