Power ideas

[Shamu1999]

I have purchased a gutted mini school bus, going to use it almost exclusively off grid. My thoughts are, generator for small a/c and the water pump. Propane for the water heater, heater, and refridge. Then solar for the outlets, tv/radio and any other minor items.

What are everyone thoughts. Also this might be a dumb question, but on rainy days, is the generator a good way to charge the batteries. Also if I am completely forgetting anything let me know.

Since it’s only me and my pup, I was thinking of a portable toilet, to avoid the black water tank.

Evan

[TheHubbardBus]

A few thoughts regarding off-grid concerns:

1) Anything you can power off DC you should, as there will be no conversion losses from DC to AC, and many DC appliances are designed with extreme energy-efficiency in mind. So AC for your A/C makes sense. But AC for your water pump does not.

2) Don't think of 'solar' as a system. Your house system is a battery bank. Solar is one way to charge that bank. Other options to charge that same bank include your generator (via an AC-DC charger), shore power (via an AC-DC charger), and/or alternator (via a DC-DC charger or other means of isolation). So no - using a generator is not a dumb idea to charge your batteries. It's a smart idea.

3) I'd rethink the propane fridge, if I were you. I like DC-only, or AC/DC versions much better. All kinds of issues w/ propane fridges in general, including inefficiency, safety concerns, and the requirement to be level.

4) Again - terminology - but it's important. You're not powering anything with 'solar'. You're using an inverter to turn DC (from your battery bank) into AC. And again, it comes with a cost, so anything you can not power with AC, is energy saved.

[Shamu1999]

Wow thanks, so #1 is make sure for a dual source refridge, not just propane. Do you have a suggestion for a specific suggestions for the water pump, remember it’s a small skoolie with only one guy using it. Also how many deep cycle batteries in my situation do you think I would need, I’m pretty sure having less than 100 sq feet, a 5,000 btu a/c will be plenty. Besides that my tv will probably be my greatest escape. Do you think 200 amp will be enough?

[flattracker]

I agree with HubbardBus. I don't know your budget for the generator setup, but a suggestion there would be to build in the generator under the bus, buy one that uses the same fuel as your bus engine and run a separate fuel/gas tank for the generator. I used a 20 gallon tank in the "new Crown" and in the "old Crown" around 15 gallons. Their are a number of good brands of generator out there. I used Onan generators in both cases. If you use a generator that uses the same fuel/gas that your bus uses, and build a fuel transfer system, you can save a trip to the gas station if one tank or another runs low. Onan makes good stuff. If you look around you can find them at a reasonable price.
I considered using LiFePo4 batteries but decided on deep cycle lead acid based on difficulty in charging them correctly. In my case I have a second alternator installed to supply RV power going down the road. I am also installing a 1 kw solar array on the roof. If you are boondocking a lot you could carry additional solar panels and set them out on the ground to provide even more power.


If you intend to have built in water supply, you will still need to have some form of water storage both fresh and waste.

[HamSkoolie]

MAX out your solar on the roof, don't waste time with tilt mechanisms because you won't tilt them.
Use the solar to charge a lithium battery bank. They are smaller, lighter, provide more usable power, require no maintenance. Make the bank large enough to provide a full day and night of power needs to reduce generator use.

Use a small generator to run a battery charger when there is insufficient solar. Best to use the same fuel for the generator as the vehicle but diesel generators can be expensive. Your budget will determine which you get.
Run lights, USB chargers, TV, etc. on DC. Buy USB chargers that have built in off switches to minimize parasitic losses when not being used (USB chargers convert 12vdc or 120ac to 5vdc with a transformer which draws power whether a device is plugged in or not.
Your fridge can be 12vdc or 120ac depending upon the build. I prefer 120ac but am building a 40' bus and there will be two of us going off grid for up to a month. We're willing to accept the loss as our inverter will also be running AC, microwave, washing machine, and even an inductive cook plate and more. (our system is 2500+ watts solar and 10.24kWh of lithium)


You should write down all your NEEDS and WANTS as far as electrical devices. Calculate the wattage requirements to run each for the amount of time each day that you will use them in a worst case scenario, then size your solar, batteries, inverter, etc. to meet the requirement. You'll probably start pulling the wants out or reducing them but that's how you get a system that works for YOUR mission.