Need advice for RV setup

joseph
joseph Registered Users Posts: 1
I'm converting a cargo van into an RV and need some advice on powering the electrical systems. I've been doing a ton of research over the past year but I am having a bit of trouble pulling the system design together. I'm really glad I stumbled on this forum and I'd appreciate a gentle nudge in the right direction :)

Here's what I want to power:

Portable air conditioner (120v/900w/7.5a)
LED strip lights
fan(s) (dc or ac)
compact refrigerator
compact microwave
blender
laptop/tablet
small heater

Everything but refrigerator will obviously run only during certain times and never all the components at once. I've found a specific a/c unit I like so that's why I've included the w/v/a for it. Everything else is still up in the air as far as the actual unit I'll obtain and their respective load requirements.

Here's my dilemma

It seems that there is two ways I can look at my plans. A) Determine what I need to power and calculate and design the system to do it. B) design a system that produces maximum output and determine what I can power based on the results. I prefer option A, but option B seems more realistic. Money isn't really a problem, but at the same time the system has to be reasonably profitable down the road.

I want to install a battery bank with two trojan 6v T-105's hooked up in series to provide 12v @ 225ah connected to a 1100 watt true sine wave inverter to power a/c components. The van dashboard is huge so I'd like to use that space to install a renogy 100w/12v panel to charge the batteries during the day (texas sun). Conservative reports of those panels show they produce 5.5amps so it's obvious that I'm not going to be able to charge a battery bank in a single day that's been 50% discharged during the previous 24 hours. I know I'll need a charge controller to prevent damage to the batteries and enable a complete top off to charge them. I also know I'll need a system to monitor battery bank to ensure I don't drain it beyond 50%.

The van currently has no insulation so ambient temperature is usually the current outside temp. I plan to insulate the entire cab to reduce thermal radiation as much as possible. Cold weather is usually not a problem for me but the insulation will help this too.

By increasing the delta between ambient and outside temperatures, I can reduce power requirements for the a/c, refrigerator, and heater. I've also considered putting the refridgerator on a timer so I can reduce consumption even further. but I'm still going to be significantly over the amount of power I can draw daily from the bank and recharge it on solar power alone. I've considered connecting the battery bank to the alternator as well to have two sources of charge but I've yet to determine if that's possible.

I guess I have two questions here: 1. Is my plan to power the above system and recharge without connecting to the grid reasonable? and 2. If yes to Q1, What would be the best way to do it?

Thanks in advance for any advice!

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need advice for RV setup

    Welcome to the forum.

    Okay item #1: 900 Watts of A/C.
    That would be a huge load even for a fixed location off-grid system. They have big start-up demands and since they run via thermostat it becomes difficult to predict how many Watt hours they will actually use. But suppose the duty cycle was 1/3 of 24 hours: at 900 Watts that's (900 * 8) 7.2 kW hours just for the A/C. My whole cabin uses 2.4 kW hours. See what I mean? Monster power user.

    A microwave will suck down 1kW+, but doesn't operate for very long. So you need an inverter & battery bank capable of taking the 'hit', but not a huge amount of stored capacity.

    Small heater = another big power user. Electricity is not a good way to heat things when you're off-grid.

    The refrigerator is likely to be a considerable load as well.

    So what you need here is a plan, and a back-up plan; what would happen if the battery-based system failed? If the answer to that can be "start the small inverter-generator" you're in luck; nothing like having compact power available on an as-needed basis. If the answer is "start the truck" you need a different plan, as the alternator driven by the engine is going to be a poor power producer in terms of fuel in vs. electric out.

    So, have you room on board for a Honda EU2000i? That could run the big stuff "as needed" and provide some charging for batteries, meaning you can make the inverter system smaller. Remember you've only got so much 'roof real estate' for placing panels on too (although this can be supplemented with moveable panels sometimes). One 100 Watt panel isn't going to do anything for recharging 225 Amp hours @ 12 Volts worth of battery. You need about four times that much.