New member with an van electrical problem

Hello Everyone,

My name is Herve and I leave in Bay Area, California. Yes, we have a lots of crazy fires right now. Hopefully the situation will get better.

I just signed up to this forum and I hope to find help on my electrical issue in my van we are building (DIY) .

So here is the general question : what wire size do I need to support a 1440 watts device (water heater) on a 12v battery bank ?

I designed the system with a 2/0 AWG wire running from my inverter to the battery.

Once I turned on my water heater , the 2/0 wire from the inverter got very hot.

Here is the system configuration:
Water heater Bosch ES4 - 1440 watts
Pure Sine Inverter 3000 watts
2/0 awg between inverter and battery. This wire is protected with a 250amp fuse. A 2/0 should handle 1000+ watts.

So what could cause a wire to get hot knowing it can handle 1440 watts.

Please note, Only the water heater was running in the system.

Thanks for any help.


Any additional resistance in a system will cause heat. A loose, insecure, or corroded connection will cause the connection to heat up, and could start a fire.

I would not try to run a water heater using battery power. Get something that runs on propane and have it properly installed - far fewer problems, and less chance of a fire in my opinion.

Also, what’s the length of wire between the battery bank and the inverter?

With that size inverter you should be using wire LARGER than 3/0 AWG, probably 4/0 AWG for anything up to 20 ft (not 4 AWG, …4/0 AWG). Longer than that and the wire size even gets bigger. (3000 watts/12 volts = 250 amps!)

1 Like

Also, what size is your battery bank, and how are you charging it?


Thank you for your response. Here are some info:

  1. My battery bank is 400amph (4 lithium battery of 100 amph).
    2 The battery is charged by 400 watts solar panel .
  2. Length of wire between the battery bank and the inverter is less than 2 feet.

During the test the battery voltage was 13.26 volts. No others devices were using the inverter.

You made an interesting point : Does a 3000 inverter needs a 3/0 awg or 4/0 awg wire EVEN if the load is lower than 2000 watts (1440 watts exactly)? If yes, I might need to downsize my inverter to 2000 watts else I have to upgrade my system to 4/0 wire.

I just don’t think it’s wise to use wire that’s smaller than needed for the inverter’s capacity. Always good to be conservative with it. More of a safety issue for if you sell the van, or someone inadvertently plugs something in that matches the inverter’s capacity.

Greetings & Welcome!

I think you have multiple problems here. A 3kwh inverter is going to draw 300+ amps with inefficiencies.

Odds are your 4x 100amp lithium batteries are only 3.6 volts, so it takes 4 of them for a 12v system wired in series. When wired in series, it ups the voltage but not the amps. Meaning that you only have a 100 amp battery bank that you’re trying to draw 300+ amps out of. Thus your wiring gets hot because your fuse is way too big for a 100 amp system, so it isn’t blowing it as it should.

If the batteries were wired in parallel, you’d have 400 amps but only 3.6 volts. In either case, you’re screwed, not even mentioning that a 3kw inverter is going to draw that many watts from the battery regardless of the load on it.

Electricity in a camper is precious and hard to come by, solar panels aren’t magic, they’re just a very inefficient battery charger, and battery power isn’t well suited for heating, cooking, hot water, microwaves, hair dryers, refrigeration, air conditioning etc. These types of things are best powered by either some type of fuel, or with a generator or shore power.

I either heat my water via solar (set a black container full of water in the sun) or on my camp stove in a pot. If I need more, I use a fire coil on my stove or in a campfire to supply unlimited hot water just like a tankless hot water heater. I’m just using my more energy efficient camp stove instead of electricity.

Save your battery power for your laptop & phone, and get car cords for them so you can eliminate the inverter all together. If you want to run household type stuff use a generator or shore power, not an inverter.

You’re also going to want to charge your house batteries via an isolator when you’re driving, which is much more efficient and reliable than solar. I skipped solar in favor of a cheap generator & a cheap battery charger. Total cost of $129 and totally reliable. 99% of the time, simply driving keeps my house battery charged, and the other 1% of the time uses only a couple gallons of gas per year for the generator, and if I need to run something that requires household power, the generator will happily supply it.

There’s a decent chance that you’ve ruined those lithium batteries. If you have, replace them with normal lead acid deep cycle batteries from a junkyard for cheap. Don’t waste your money on new batteries, lithium batteries, or AGM batteries. My junkyard batteries typically last for 5-7 years and cost under $20 each.

A good, efficient, reliable, and comfortable conversion should cost hundreds, not thousands of dollars. The promoters are not your friends, they’re only after your money, whether or not it’s obvious. A non factory camper is a metal tent, not an RV. If you want the comfort and conveniences of an RV then your money is better spent buying a factory RV. I’ve owned many great motorhomes for under $2500, and at that price you can drive them for years and they’re still worth what you paid for them if you keep them stock and don’t do anything stupid like modifying them. Modifications lower their value dramatically. Example: If you add solar, your rig is worth thousands less. People don’t want the hassles or risks involved in solar or any other non factory modifications.

A friend added solar to his factory camper, he had a flare up while cooking, (not related to the solar), and it caught fire. His insurance company denied his claim because his camper had been owner modified. You want to keep everything as cheap as possible, easily replaceable, and never count on insurance to pay you anything. Your real insurance should be an emergency fund large enough to repair/replace everything, plus at least a years worth of living expenses. For me that’s a minimum of $10k. which includes replacing everything, and a years worth of living expenses, mine does not include the money for rent if I needed to rent somewhere, but I also have a large retirement fund if I need it.

It is much harder for someone to be a successful nomad than it is for someone with a stable job & housing.


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

Hello Van_dweller,

Thank your for your long response.

I would not say that your insights really comforts me in my journey to #vanlife :slight_smile:

I still believe that having an inverter is a not that a big risk. Most of #vanlife community people have installed. They do run their 1800 watts induction stove, water heater appliance, charge laptop, …

My inverter wire overheat problem is probably due a to loose connection with busbar.

Now I have 2 options to fix this

Option 1 :

  • I keep the 3000 inverter and upgrade any 2/0 wire to 4/0. between the batteries, from the batteries to busbar, and from busbar to Inverter. Too costly.

Option 2:

  • I return the 3000 inverter and replace with a 2000. Therefore no need to upgrade any wire. Get money back. Less costly.
  • Just need to explain my wife to NOT take a hot shower while cooking on the induction stove :slight_smile:

It would have been better to hire a van conversion company to build our van based on our requirements. We chose the DIY road. IT is much more cheaper and also an opportunity to acquire new skills.

We chose Van versus RV for the main reason to be able( as much as possible) to park anywhere.


Here in the USA, lower numbers mean a larger capacity for wires, not higher numbers.

I’ve parked motorhomes on city streets with no problems ever, the same with obvious camper vans, and shuttle bus’s. Cargo vans were a totally different story though, they weren’t welcome anywhere. People who try to hide are suspicious, and cargo vans have a terrible reputation. It sounds to me like the people you have been following are promoters, not real vandwellers.

“It would have been better to hire a van conversion company to build our van based on our requirements. We chose the DIY road. IT is much more cheaper and also an opportunity to acquire new skills.”

The only time DIY is ever cheaper is if you already have the skills, equipment, knowledge, and experience. Even then, it is very difficult to do a DIY cheaper than a used factory unit which will be better in a thousand ways.

Let’s start here and try to figure things out. Are your 4 batteries wired in parallel or series? What brand and model are they? We need to figure out exactly how many amp hours you have available before we can really figure out anything else. WE CAN FIGURE THIS OUT, AND IT DOESN’T HAVE TO BE EXPENSIVE!

The real people doing what you want to do usually use generators, even if they have much bigger solar systems and battery banks than you, they’re still relying heavily on a generator. One person I know who’s loads are similar to yours has 1800 watts of solar, and 1200 amps of battery power, and he still runs his generator 6-8 hours per day. He’s a real RV dweller, not a promoter. He has 40 feet of roof covered in solar panels and curses them regularly.

In short the promoters have no real life experience, and they’re just after your money. In contrast, I’m a certified tech with over 40 years real life experience. Wanting all the amenities of an RV is okay, but your power system then has to match that of an RV, and your amenities should match that of an RV. Shortcuts lead to catastrophes.


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

You might be able to get some more 2/0 wire to double it up to match the capacity of the 4/0. Just make sure the connections are nice and tight with no chance of becoming loose or becoming corroded.

With your solar array at 400 watts, that’s 33 amp-hours times the number of hours they’re exposed to full sunlight. If they’re flat on the roof you’ll lose some efficiency, if it’s cloudy you’ll lose more, if you’re parked in the shade you’ll lose a lot, and don’t forget that charge controllers are never 100% efficient. As an average I’d count on maybe 75% of the capacity, meaning 300 watts. 300 watts/12 volts = 25 amps. Multiply that by say 6 good hours in the summer on a sunny day and you get 150 amps plus or minus. Might work okay if you’re not heating the water for too long. It would be good to install a timer that shuts it off when it’s not needed. Is this a tank water heater or tankless?


setup is 4 battleborn lithium battery of 100 amph each. They are mounted in parallel.

We do not follow any promoter. There are plenty of youtubers that share their vanlife journey. We have learned a lot from those people. how they build their van. The pros and cons…and very few have generators. They rely on solar, shore power and vehicle alternator charging.

Agreed. DIY is not that cheaper. But the reward to learn new skills in priceless.

We do not plan to be full time van-lifers anytime soon. But my wife and I are not materialist and we are attracted to this nomadic life. Travelling and meet people. Life is too short to be spend in the same spot. We don’t see ourselves continuing living/renting an expensive house. We feel safer to build & own a camper van just in case if tomorrow we lose our job, house…

1 Like


Okay, that helps, you do have a legitimate 400 amps of battery power, so these batteries are rated at a 20 hour discharge rate, so 400ah/20 = a 20 amp discharge rate max per hour is where they’ll be happiest at. 20a x 12v = 240 watts per hour. This can go higher very briefly, but not sustainably. Not long enough to heat your water, or run your induction cooker or microwave. Not enough to support a large inverter either. Even adding in your full solar, you’re still only up to 640 watts…

Nobody does what you’re attempting to do for good reason, it’s not a reasonable choice.

Your expectations are wrong, and you’re looking at a $10k+ investment to be able to accomplish your expectations, and even then it wouldn’t be the best or safest practice. Even people running tesla electric car batteries aren’t using it for heating, cooking, or water heating.

If it was as simple as you envision it, EVERYBODY would be doing it, including myself, but unfortunately reality can be harsh. A generator or shore power is going to be the cheapest and most efficient way to run what you want, without using much more efficient fuel powered amenities.

In my RV’s, I frequently used all electric, but everything over 10 amps @ 12vdc was run by the generator, not batteries. In my camper van, I rarely use over 10 amps per day, and the average is probably closer to 5 amps. All my high power amenities are powered by fuel, not batteries, which is a much better and the most common option. Most of us try to eliminate the use of inverters entirely.


"It is always cheaper and easier to conserve power than it is to make it." ~ Road Warrior


Thank your for your info about solar metrics.

This is a mini tank water heater [Bosch 4 gal., 120VAC, 12 Amps, 1440 watts, Mini Tank Water Heater]

We plan to use it only for our shower. So we run it for 5-10mn. Not everyday of course and be unplugged when not needed.

We dont have shore power in our van. Our inverter is not even an inverter charger.

The reason is that we don’t plan to be at camping site with RVs. Van is designed to be stealth. Our project in the future is to live full time in a van. Hopefully gym center will reopen in order to access showers :slight_smile:

Having said that, lot of Vanlifers uses off grid devices such as Instant Pot (1000 watths), induction stove (1800 watts), micro wave (1200 watts)…

Anyway, I really do appreciated all your feedback. it benefits anyone who reads it.

1 Like


I think I’m going to drop out on this, but if you get it working LONG TERM, please post an in depth tutorial. because there’s thousands of people who would love this information.

Meanwhile, I’ll just keep doing what I learned the hard and expensive way, and keep it cheap, simple, & reliable.


"It is always cheaper and easier to conserve power than it is to make it." ~ Road Warrior

I assume that your batteries are LiFePO4 chemistry, and that they have built-in battery management systems (BMS)?

Also, be absolutely sure that: there is over-current protection very close (within a few inches) to the positive terminal of the batteries (fuse or circuit breaker), and that there is absolutely no chance that any positive terminal or unfused lead can come in contact with anything that is grounded such as the frame, body, or any other metal parts of the van, even in a rollover accident. The batteries must be securely bolted or strapped down, and the positive terminals should have some kind of electrical insulating material covering them.

I knew I saw this somewhere…

I ran across some extremely simple tip how to deal with a water heater like that. Start it when you are 30 minutes away from your destination. When you arrive, you will have hot water that will stay hot for some time. Let the van’s engine/alternator do the job instead of your battery bank.

Of course this works best when you travel daily from place to place.

Did you end up solving this? Also working on a similar set up but running into issues, I believe related to the amperage draw from the batteries.

Greetings & Welcome!

The only solution to this is a better plan. Inverters are terribly inefficient, and should be avoided if at all possible. Cooking, heating, cooling, refrigeration, water heating, etc. are best accomplished using fuel instead of electrical power. Solar & batteries are best suited for very minimal loads, not power hungry ones. I do have a cheap generator ($99) and a battery charger ($29) for a backup, or on the rare occasion that I need shore power but normally I just charge my house battery while driving. I ditched solar long ago.

I heat my water in the sun, on my stove, or with a fire coil on either my stove or a campfire for unlimited hot water with no electrical or battery power required.

My choice is simple, whatever battery capacity I have must last at least a week between chargings. So I have a 100ah deep cycle battery, that’s 50 amps usable PER WEEK! Anything that is going to break that plan must be fuel powered, not battery powered. That doesn’t mean I do without anything I want or need, I just do them differently, so they don’t require battery power.

Expensive batteries aren’t the answer either. Today I purchase used deep cycle batteries from junk yards for under $20, and they’ll last me 5-7 years since I eliminated the solar that would kill them prematurely, usually within about a year.

In many campers older than the 1970’s, they didn’t even have batteries, everything including the lights were fuel powered. With fuel, you could live off the grid indefinitely, and they didn’t use much fuel either. Today, with laptops, cell phones, & the internet, we need power more than we did back then, but if we restrict our power usage to a minimum, we can enjoy more and it will cost less.

I’ve been living as a nomad since before house batteries, solar panels, 12v fridges, microwaves, computers, cell phones, or the internet, yet I had every comfort I wanted or needed. Today, people want to complicate the simple & easy, not because it’s better, but because they want your hard earned money. There’s a lot to be said for cheap, simple, easy, convenient, reliable, eco-friendly, and sustainable. All things that the newer generations have forgotten or just never learned to begin with. The prepper’s & survivalist’s are embracing many of the old ways for good reason, and the happiest nomads like myself are doing it as well.

It’s not about doing without, it’s about using the best technologies available for the task, using what’s readily available. We have to create our own power, so it is not readily available. Then we have to store it, and batteries can and do go dead, and much more often than a generator that only requires fuel.

Newer cars don’t have fresh air vents or wing windows, yet they claim newer is better. According to who??? The people who are after your money, that’s who.

KISS (Keep It Stupidly Simple) is quite simply THE best advice available. Spend your money on your adventures, not expensive or complicated builds, systems, or gadgets. Your camper can be stolen or totaled in an instant, and you can’t count on your insurance to make it right.


"Be a credit to the human race, and make the world a better place." ~ Off Grid