Help... Lots of questions - Solar recommendations for my camper van build.

rusty78906

I picked up a super hightop van from a government surplus auction, I'm converting to a camper van, now I'm thinking about adding solar, I need help on what size system.

Budget $2k+. Wish list on what I would like to run. 5,000btu a/c w/ soft start, 2x max air or fantastic vent fans (12v) small refrigerator (12v) flat screen smart tv up 32", most lighting will be LED. Also as backup power source for power outages to run my freezer and refrigerator inside my house I need.

should I go with flexible panel?

Watts available per panel 100w, 200w, some odd numbers in between?

Total watts? 400, 500, 600 or more? 

Inverter, brand / model, pure sine wave 1k, 2k 3k, 4K? 

controller, mppt? How many amps and brand / model recommended?

I'm not opposed to running 2 systems, 12v for 12v lower usage items, 24v for bigger draw items.

batteries recommended, I would think a type of agm, 12v, close 200ah, how many? 

I could ask more questions but this should get me started;) thank you for this great forum and helping.


http://i600.photobucket.com/albums/tt84/rick2106/image_zpspp2koade.jpeg

bill von novak

rusty78906 said:

I picked up a super hightop van from a government surplus auction, I'm converting to a camper van, now I'm thinking about adding solar, I need help on what size system.

Budget $2k+. Wish list on what I would like to run. 5,000btu a/c w/ soft start, 2x max air or fantastic vent fans (12v) small refrigerator (12v) flat screen smart tv up 32", most lighting will be LED. Also as backup power source for power outages to run my freezer and refrigerator inside my house I need.

should I go with flexible panel?

Watts available per panel 100w, 200w, some odd numbers in between?

Total watts? 400, 500, 600 or more? 

Inverter, brand / model, pure sine wave 1k, 2k 3k, 4K? 

controller, mppt? How many amps and brand / model recommended?

I'm not opposed to running 2 systems, 12v for 12v lower usage items, 24v for bigger draw items.

batteries recommended, I would think a type of agm, 12v, close 200ah, how many? 

I could ask more questions but this should get me started;) thank you for this great forum and helping.


http://i600.photobucket.com/albums/tt84/rick2106/image_zpspp2koade.jpeg

First off get a value (in kilowatt-hours a day) for how much power you need.  You may have to estimate based on measuring the A/C and fridge during operation (those will be the big draws)

You are generally going to make the panel decision based on mounting considerations - what sort of mounts the panels will accept, and what will work with the van roof.  Smaller flexible panels work OK (specifically the sort that use laminated crystalline cells on a semirigid backing) but they are far more expensive than larger grid tie panels.  If cost is a big deal go with the larger/cheaper panels.  If aerodynamics/weight is a big deal AND you can figure out a decent mounting method then the smaller flexible panels may work.

MPPT is a given here.

You will want pure sine, and if you are running an A/C 1000 watts is going to be a bare minimum due to starting surges.  2000 watts is more likely.

You can do this all at 12V but you are going to be pushing the limits of cabling and fusing.  The big advantage to 12V is that you can charge from the alternator, which if you are doing any RVing will be your primary source of energy.  24/48V is much better from an efficiency/reliability standpoint but you'll need boost/buck converters and/or a new alternator.

If you have a space to mount them I'd go with T105's (flooded) if at all possible.  Cheap and it's a given that you will break them quickly - so that means not as much money lost.  A 2x2 T105 setup will give you ~3kwhr of usable storage, which may be enough to get you through the night without running the vehicle.

If money is no object there are plenty of good 12V LiFePO4 solutions out there now.

Estragon

Normally, we start with loads, but with a mobile application there is a limit to space available for panels. PV will generate ~100-150 watts per square metre (10-15w/sq.ft) of mounting space. You might want to start with how and where you can mount panels.

AC can be a problem load even with unlimited space for pv. With limited space, you will likely want to consider some combination of using a generator or shore power, insulating well, and making do with fans.

In general, I'd stay away from flex panels. They tend to be less space efficient and not last long. In some applications, they may be the only choice, but I'd avoid them if possible. I'd also avoid multiple voltages in a mobile application.

AGM batteries have advantages, especially in mobile applications, but can be more expensive and depending on the application, may not be worth the cost. They generally charge faster, and if gassing is a concern (tight spaces) AGMs don't normally gas, so if that's worth roughly 2x the cost, they may be worth it. I have flooded in a smallish box under the transom stairs on my boat, and don't worry about having a cigar in the transom. YMMV.

Ideally, you want to end up with a single battery (or series string of batteries) that has the capacity you want. More than a couple of batteries (or strings) can be a problem.

Just a few things to start thinking about.

rusty78906

 Thank you, Bill Von Novak & Estragon, great information, I'm getting closer:) I do think think I could get 4x 100watt panels on the top of the van, I have found Trojan T-105 agm (reliant I think) $250 each, buy 2 of those, I have my 12v and 200ah, 400watts of solar panels with the 2x T-105, would there be a benefit or hassle using 4x T-105? 2x 6v series other 2x 6v series. What size mppt controller? 20amp, 40amp, 60amp? Seems to be 2x-3x increase in price from 40a - 60a controller, what I've priced, $200-$250 40a, $500 & up for 60a.
 The inverter. I'm looking at 3kw, I'm not sure 2kw will do I think I'm going to do, if bigger is better in this case, inverter I'm thinking does not need to be Built in charger model like the aims inverters, if I charge from my alternator. Most attractive inverter so far for me is a PowerTech AT 3k - 6k peak $350 on Amazon.  Thanks again...

Estragon

With 400w of pv, that's 400÷~18v charging =~22a. Something like a Midnite Kid 30a mppt controller would do nicely.

A 3kw inverter is pretty big for ~200ah of battery, and for any size bank at 12v. 3000÷12=250a (double that for surge capacity). 200ah is the capacity discharging at 5%/hr (20hr total discharge). Discharging at a 1hr rate reduces the apparent capacity a lot. Voltage will sag (and current will increase) a fair bit under that load as well. Depending on the inverter, you may find it takes 30-40w just being on, so it could cost you close to 1kw/day just keeping the inverter lit. I have a 2kw inverter on my boat, but I only turn it on to run a small microwave for short times. You might want to consider a two inverter system, with something like a 300w Morningstar PSW inverter running small loads that run for longer periods (light, TV etc.).

There isn't a lot of difference between running 2x12v deep cycles vs running 2 strings of 6v in terms of keeping things balanced. It gets tricky with 3 or more in parallel. Doing 2 strings of 6vGC size batteries would give you ~450ah@12v