You can actually plug that question into AI. I have no clue of the answer. But I do know how to plugin a question to AI
Is the AC going to run 24/7 on a hot day?
I have some knowledge, but will not ever claim to be “an expert “. Further, I fully expect others to be more knowledgeable.
But. What is your highest load, expected average load, and minimum load. What frequency AC and voltage to be delivered? Automatic and continuous service? Or irregular with you turning switches and breakers on and off - as at a vacation house or disconnected work shed away from the grid?
DIY Solar Power with Will Prowse
I bought the book in the third link and used it to set up an emergency solar system for our house.
They have a marine forum...might be helpful for non-solar applications/questions too...???
You need to add up all of the watts of the things you are running. Then multiply by the hours you will be using them. That gives you the watts/hr.
Trying to keep batteries charged to power that stuff is going to go through a ton of cycles. That wears out traditional batteries.
You will need deep cycle batteries or those used on solar applications.
Your issue is going to be in trying to keep those batteries charged. Depending on your location, it might actually be a decent case for a small solar set up.
Wattage is voltage times amperage. If you need 1000 watts at 120 volts, your current demand is 8.3 amps on the 120V side. You will require 1180 watts on the battery side. With a 12V input that requires 98 amperes. A 24V input would require 50 amperes. Scaling to higher wattage is linear.
One thing I did learn from Will Prowse is that the higher voltage battery you use the lighter the copper wire you need to use, and copper wire can be expensive. I wound up with 48 volt batteries.
You need to first start by determining the running watts of each of your electricity usages. Then determine the number of hours that each of them will run each day. Add all the watt-hours together to find out how many watt-hours of battery you will need. remember that batteries generally can be charged to only 80 percent of capacity and shouldn’t ever be discharged below 20 %. This means that your batteries need to have 40 % more capacity than you use.
Lithium iron (not ion) batteries last far better than lead acid for long term use. If you can run your boat off the generator while you are charging the batteries, you can subtract off the hours that the batteries are charging.
Food luck
It’s all about input versus output.
I would use AGM batteries because they provide high current output for extended periods and don’t require maintenance.
I use them all the time for battery backups.
Freepmail me if you would like some equipment suggestions.
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!
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.
Don’t a.ways agree with him on the issues, but genxpolymath knows charging and batteries.
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.
hmmm, I solar powered my well because it was well over $100K to bring power to it, I also got fed up with all the APU’s they sell for computers, none work for much more than an hour and of course the software NEVER worked with server 19, I had 2 dns and 1 mail server.
Well
1 Magnum MS4024PAE 240 grid tie volt Inverter
8 225 AmpHr 6 volt golf cart batteries
8 350 watt solar panels
1 MPPT Solar Charge COntroller/
this setup runs wy well for up to 2 hours a day flawlessly using less than 20% of storage, actually only runs 1 hour every other day on average, works absolutely great and was well worth the $5000 it cost me to build.
Server Backup for 3 servers
1 Magnum 120 volt/24 volt grid tie inverter(dont remember model)
4 225 amphr 6 volt golf cart batteries
wired to wall socket to keep batteries fully charged.
this will keep all 3 servers running for over 24 hours without a hitch and switchover is fast enough to not even cause a glitch in computers, ready for solar panels if wanted or needed, but grid tie works where I have it just fine.
Solar Power is NOT a panacea, but depending on what you are looking for, it can be a godsend.
Here is what Grok AI said about your post;
Step 4: Inverter Sizing and TypeThe inverter converts 12V DC battery power to 120V AC for microwave, TV, computer, and AC unit. Size for surge (startup draw, 2-3x running watts for motors like AC compressor).Peak Load: Microwave (1,000W running, ~1,500W surge) + TV/Computer (150W) + AC (960W running, ~2,000-3,000W surge if compressor starts). Worst-case simultaneous: ~3,000-4,000W surge.
Continuous: ~1,500-2,000W (e.g., AC + TV).
Formula: Inverter Watts = (Highest Surge Load / 0.85 Efficiency). Aim 20% larger than max continuous for safety.
Recommendation: 2,000-3,000W pure sine wave inverter (e.g., Victron MultiPlus or Xantrex Freedom). Pure sine is essential for sensitive electronics (TV/computer) and efficient AC/microwave operation—modified sine can cause humming/overheating. 2,000W handles most; 3,000W if AC surges high.
Include a transfer switch for seamless generator/shore power integration.
DC draw: A 2,000W inverter pulls ~170A from 12V batteries (use 2/0 AWG cables, fused at 250A).
Step 5: Charger Type and SizingYou’ll charge batteries daily via generator (AC output to charger). Use a smart multi-stage charger for safe, efficient charging (bulk/absorption/float stages).Sizing: Match to battery bank (C/8 rate, where C = Ah capacity). For 300Ah bank: ~40A charger. Generator must support charger + loads (e.g., if charging at 40A while running AC, total ~1,500W+).
Type: Inverter/Charger Combo (e.g., Victron MultiPlus): Best—one unit inverts and charges (80-120A models). Auto-starts generator on low battery.
Standalone AC-DC Charger: Simpler/cheaper (e.g., Progressive Dynamics 40A, $200-400). Lithium needs a dedicated profile (no equalization stage).
Daily Runtime: For lead-acid, 4-6 hours at 40A to recharge 50% DoD (full charge takes longer). Lithium: 2-4 hours. Run generator at 50-75% load for efficiency (quietest/fuel-saving).
Generator Note: Size 2x inverter continuous rating (e.g., 3,000-5,000W Honda EU series). Quiet marine models (e.g., 3,000W) suffice; add auto-start if using inverter/charger combo.Step 6: Overall System TipsTotal Cost Estimate (Basic 12V Setup): $1,500-3,000 (200Ah lead-acid bank + 2,000W inverter/charger + wiring/fuses). Lithium: +$500-1,000.
Wiring/Safety: Use marine-grade tinned copper wire (e.g., 4/0 AWG for battery-inverter). Install fuses/breakers (e.g., 300A ANL), battery isolator, and low-voltage disconnect (12V). Ground chassis to boat bonding system.
Add-Ons: Battery monitor ($100-200). If space allows, add 200-400W solar panels (~$300) for partial daytime charging, reducing generator hours.
Testing: Start small—install and monitor for a week. Adjust based on real data.
Professional Help: Consult a marine electrician for install (vibration/moisture risks). Check local codes for houseboats.
This setup should give you reliable power with 2-4 hours generator runtime daily. If your AC is DC-native or usage changes, recalculate. For specifics, provide exact appliance models!
On my 43’ sportsfisher, I consume about 10 KW per day. My house bank consists of 3 lithium iron phosphate batteries, each 460 AH at 12V for a total of 16560 KW capacity. My inverter charger is a Victron Multiplus 3000.
AC requires a lot of amps when it starts, unless you add a soft start device. I have never tried to run it on the inverter.
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.
To power a houseboat with battery storage and an inverter for AC appliances using daily generator charging, the most important factors to decide are battery capacity, inverter size, charger type, and whether to use lead-acid or lithium batteries. Lead-acid batteries can work for simple setups, but lithium batteries offer significant efficiency and lifespan advantages for marine use.
Core Components and Sizing
Battery Storage Size
For lead-acid batteries, only about 50% of their stated capacity can actually be used (Depth of Discharge, DoD), so you need double the storage for your daily energy demand.
Example Calculation: If your daily usage is about 3,000Wh (microwave, TV, monitor, computer, small A/C), you’ll need batteries with a minimum rating of around 6,000Wh (or 500Ah at 12V).
For lithium batteries, you can use up to 80-100% of their rated capacity, so you’ll need less overall battery (e.g. 3000-3500Wh for the same usage).
Inverter Size
The microwave is typically the largest load, requiring an inverter rated at 1800-2000W (pure sine wave type).
TV, monitor, and computer can be run off smaller inverters, but if combined with the microwave, the total inverter size should meet or exceed the microwave’s surge requirement. For a standard 1000W microwave, a 2000W pure sine wave inverter is usually necessary for safety.
A/C units that pull 8 amps at 120VAC = 960W; check their startup surge rating before sizing inverter.
Charger Type (for Generator Charging)
Use a smart charger or inverter/charger sized for the capacity of your battery bank. Match the maximum charging rate allowed by the batteries so you can charge efficiently in a few hours.
Lead-acid batteries accept lower charge rates; lithium batteries can accept higher currents and charge faster.
Lead-Acid vs. Lithium Batteries
Feature Lead Acid Lithium (LiFePO4)
Cycle Life 300-500 cycles 3,000–15,000 cycles
Usable Capacity (%) 50% 80–100%
Weight (100Ah) ~30 kg 10–13 kg
Maintenance High Low
Charging Speed Slow Fast
Cost Low Initial Higher Initial
Lead-acid is budget-friendly for basic setups with low cycle demands. Lithium (LiFePO4) batteries are recommended for longer lifespan, lighter weight, deeper discharge, and faster charging, especially for frequent use or higher daily energy loads.
Quick Recommendations
Battery Bank: 500Ah (12V) for lead-acid, 250–300Ah (12V) for lithium, based on 3–3.5kWh day usage.
Inverter: 2000W pure sine wave inverter, minimum, capable of surge demands of microwave and A/C.
Charger: Match battery bank and generator output. Smart charger with proper amps for lithium or lead-acid type.
Microwave Use: For brief microwave use (1000W) and AC appliances, the inverter and battery bank as above are sufficient.
Practical Notes
Always size your system for worst-case peak power (e.g. A/C + microwave running briefly together).
Use fused wiring and marine-grade cables for safety.
Lithium batteries require compatible chargers/inverter settings and are initially more expensive but offer clear benefits long-term.
For occasional generator charging (daily or every few days), size for full recharge in 3–4 hours.
Lithium batteries (LiFePO4) are strongly recommended for a houseboat setup where weight, longevity, and recharge speed are important, but lead-acid can work for basic or budget builds.
A setup with a 2000W pure sine wave inverter and 250Ah lithium battery bank (or 500Ah lead-acid) will cover your described loads, allowing daily generator charging for AC power on your houseboat.