Solar van for boondocking

MikeCMikeC Registered Users Posts: 3
I'm putting together a van for dry camping/boondocking and wanted to run this by those of you more experienced in these matters.

Power usage: probably around 65 - 75AH daily on the high side.

An ARB fridge (25AH),

Fantastic Fan (25AH, if run 24/7. Not a likely scenario),

Lighting(AH currently unknown, I plan on minimal LED lighting).

Occasional LED TV and computer use. TV is 12 volt and would double as computer monitor, I don't have power draw stats, but it's very low. Computer (Mac Mini) draws 10-85 watts depending on what it's doing, Browser use + email would probably run on the lower end of it's power range. I'm not going to be doing any CPU intensive stuff that would draw lots of power. The computer would be powered by a Suresine 300 inverter, and would probably not be used on a daily basis.

So far I'm thinking a couple of Trojan 105's, Morningstar MPPT 15 w/temp sensor, Trimetric 2025RV.

Panels.... well, here's where I'm a little stumped.

I'd originally considered a couple of Kyocera KD140SX panels. Then got to thinking about just one big high power panel 200-250 watts to save space.

I guess I'm confused about which direction to take to get the best performance. Two Kyoceras wired in series? Parallel? A big high voltage panel rated at lower amps?

Am I on the right track with this combination of equipment, given my needs?

Any tips, hints, clues, and recommendations gladly accepted.




  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Solar van for boondocking

    Welcome to the forum.

    Well let's see. A couple of T105's would be 225 Amp hours @ 12 Volts. If you do keep your usage to 75 Amp hours per day that would be less than 50% DOD so it should work. The Trimetric is a really good idea here as you're doing quite a bit of guess work about loads, and don't forget that any inverter used will consume some too (the MS 300 is really low power though).

    Now the ol' rule-of-thumb for sizing the array (since I just did this calc in another post) puts your panel Wattage around 350 or so. A couple of 140's would be a tad on the light side.

    The higher Wattage GT panels may prove to be a bargain, especially if you were going with an MPPT controller anyway, but the MS 15 Amp controller will limit you to 15 Amps no matter what's on the input. What you really want here is a bit more than that, as 15 Amps is only 6% on 225 Amp hours.

    This is where we need that new Rogue 30 Amp controller (ready to ship in April, I think he said last) or the rumoured MidNite 30 Amp controller (no date set).

    Trying to make up for small space means shifting from polycrystaline to monocrystaline; they are more efficient and can deliver the same Watts in less area. Keep in mind that larger panels are still larger, and finding some that will deliver the needed power and fit in the available space means you're going to have to look at a lot of panel spec sheets and do a lot of calculations.
  • MikeCMikeC Registered Users Posts: 3
    Re: Solar van for boondocking

    Thanks Cariboocoot!

    I was wondering myself if the 15 amp controller would be enough.

    Seems there's a lack of 20-25 amp MPPT controllers on the market.

    For a system this small would not a PVM controller work almost just as well?

    I was just looking at the Morningstar PS-30 as a possibility.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Solar van for boondocking

    Yes, a PWM type controller would work fine. Provided you check that the Imp of the panels will give you the peak charge current you seek and that the Vmp is proper for the system Voltage (no down-converting of higher Voltage available). This means most of the higher Watt panels are out, because they tend to have Vmp around 30. For a 12 Volt system you want a Vmp around 17-18.

    Now here's the interesting bit. You're after about 350 Watts for a 12 Volt system, or more accurately 22 Amps peak current. So with a PWM controller:

    Three 130 Watt panels (7.3 Imp: 21.9 total) @ $244 each = $732 plus ProStar 30 @ $115.
    Total: $847

    Two 215 Watt panels @ $246 each = $492, leaving $355 for an MPPT type controller (about the range the Rogue used to sell for). Nor are those the cheapest "big" panels available. Two Conergy 245 would be $446

    Around 400 Watts is just the point where the GT panel + MPPT controller starts to make sense financially (but we do need those good 30 Amp controllers!)

    With space considerations you may well want monocrystaline, but that limits your choices more. I don't think there are any mono "12 Volt" panels in higher capacity (>100 Watts) and of course any of the larger Wattage panels are going to be physically big.

    Sorry, but I'm not going to look up all the spec sheets and calculate size/Watt/price & output for you. :p
  • MikeCMikeC Registered Users Posts: 3
    Re: Solar van for boondocking

    Thanks again!

    That gives me a much clearer picture about how the components work together and what specs I need to take into consideration.
  • westendwestend Solar Expert Posts: 46
    Re: Solar van for boondocking

    I'm doing something similar--Solar charging on Starcraft travel trailer. My use is around 60-80 ah/day. I will have two banks totaling 320 ah (just worked out that way). I went with an MX-Solar 235w module, Morningstar MPPT-15 controller, and a Samlex 600w puresine inverter. Currently, I am powering a 120 vac dorm fridge through the inverter. The MX-Solar module puts me at the absolute peak when conditions are perfect for harvesting, re: MPPT-15. Since I may upgrade panel watts in the future, I'll be looking at buying a different controller. If Rogue would have had a specific roll-out date for their new model, I would have waited for it.

    What makes the Morningstar 15 amp controller really useful is that it can interface with a PC through the MS software. User can datalog, change voltage setpoints and durations of charge levels, program an equalization schedule. This is about the same functionality of the Trimetric but, of course, isn't as easy as a standalone monitor and battery storage amounts may not be as accurate. It does offer a less expensive solution than some and has a good bit of functionality. I got around the monitor's visual aspect by mounting some analog gauges that let me see the system status at a glance (if I have them on).

    I'm waiting for weather to clear to mount the module so don't have any real-world numbers to give. Those should be on my hard drive by the weekend.
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