Help with solar system for campervan that will be UK winter proof.

[Pedroz]

Hi there!

As a word of introduction my name is Peter and I'm living full time in self converted campervan for last 4-5 months. My camper has 230/12v installation with power controller and two batteries van and leisure 110Ah lead acid. On the beginning I was nearly every second day hooked up to mains allowing my leisure battery to be fully charged and rarely drained it more then 50%.

Now due to circumstances I'm going to be off grid permanently. I also drive/run engine very little ( aprox 20min a day) consequently running out of energy.
Commonly I'm using only 12v installation and trying to be as humble with power consumption as i can. Typically I'm using around 2hours of lighting (LED), 1-2 cycles of laptop charging, 1 cycle for mobile phone, water pump, and gas heater with air blower... I'm estimating my average daily use at about 300Wh.

My question is will I be able to get away and getting through winter by installing 250W solar panel? If so what is best way of doing it?

I've read that efficiency in winter gets down to average 20% and sun cycles are short..
Therefor I take that in bad day I can get 250Wh, but I take that there are some good sunny days where I could get more plus I do drive now and again and hope that in longer run it should balance out. I'm aware of losses but not sure of how ratio of good vs bad days really is. Please let me know if this seems to make sense?

I do not want to add another bank battery as I'm out of space.

If above make sense could you advise me of what type of controller I should go for? I do like the idea of "dual" controllers that send 10% to van battery as this would allow me to dump my van for longer periods without worrying about batteries to discharge.

Also considering above scenario, should I go for flat mount or should i use one of those adjustable brackets?

Thanks for reading!
Peter

[jony101]

all I can comment is definitely get the 250 watt panel. I have a 240 watt solar panel on the roof of my astrovan and it's definitely an improvement over the 120 watt panel I use to have. I have it mounted flat on the roof and get at max 12 amps when the sun is overhead. My house battery(145 ah agm) is 100 percent solar, never connected to shorepower/engine alternator. its very possible to be offgrid especially with such a large panel. Even with a 120 watt panel and 75 ah battery I was 100 percent off grid but barely, a couple of cloudy days and my battery was low.

My main power use is the 12 volt swamp cooler I run in the day to keep cool, but I also charge my laptops and I still use flourescent lights but nothing my system cant handle. I produce more power than I use. The only reason I dont get a larger battery is because I dont have the room and in my situation I dont need it.

For charge controller you need MPPT for such a large panel. With my 240 watt panel for example with a PWM controller I get a max of 7 amps, with MPPT I get 12 amps, definitely worth the added cost. I use a cheap 20 amp ecoworthy MPPT that cost me 102 US dollars. It prove very reliable in almost 2 years of 24/7 use. The bluesky MPPT controller can actually do what you want charge an auxillary/engine battery at 2 amps, but that controller is more expensive. But worst case scenario which has happen to me when I left the lights on, I was able to connect my MPPT controller to charge the engine start battery, in 3 hours I was able to crank the engine over. But you also connect a trickle charger to an inverter and run it to your engine battery.

The good thing about a large panel is that even in cloudy weather you still get usable power.

[russ]

Pedro - Some one else will chime in I expect - jony spreads BS a bit thick at times.

[Sunking]

Now due to circumstances I'm going to be off grid permanently. I also drive/run engine very little ( aprox 20min a day) consequently running out of energy.

Well Peter if you run the engine 20 minutes per day, depending on the size of the alternator, assuming 100 amps, generates roughly 500 watt hours of power that you are NOT tapping into, or slightly more than a single 150 watt solar panel can generate in a summer day. In England where you have terrible solar isolation from late September to early April it would take a 500 watt panel to generate as much energy as your engine alternator in 20 minutes. If I were you I would be tapping your engine alternator before I even thought about solar as that only cost less then $100.

[Pedroz]

Well Peter if you run the engine 20 minutes per day, depending on the size of the alternator, assuming 100 amps, generates roughly 500 watt hours of power that you are NOT tapping into, or slightly more than a single 150 watt solar panel can generate in a summer day. In England where you have terrible solar isolation from late September to early April it would take a 500 watt panel to generate as much energy as your engine alternator in 20 minutes. If I were you I would be tapping your engine alternator before I even thought about solar as that only cost less then $100.

Thanks Sunking for your answear. Ok I'm lacking a knowledge here but how i can transform 20 minutes of running 100amp in 500Wh? My leisure battery is connected to alternator via some split charging system. I honestly don't know at what amp and voltage it's getting charged but surly it can just bank 500Wh in 20 minutes?!


@jony101 Thanks for your respond!

[inetdog]

how i can transform 20 minutes of running 100amp in 500Wh? My leisure battery is connected to alternator via some split charging system. I honestly don't know at what amp and voltage it's getting charged but surly it can just bank 500Wh in 20 minutes?!


@jony101 Thanks for your respond!

You can approximate the charging voltage at 12V (for a nominal 12V system). So 100A for one hour would be 100AH, and 1,200 Watt-hour.
1/3 of that, corresponding to 20 minutes, would be 400Wh.
The problem is that an FLA battery will not be happy with a charge rate much greater than C/8, while an AGM might tolerate twice that or more.
For a 200AH battery, C/8 is 25A. Charging at 100A would be very ungood.
For a 200AH AGM battery with very low internal resistance C/2 would be 100A, and you might survive regular charging at the 100A rate as long as voltage and temperature are carefully monitored, so that the current can be reduced when necessary.

[Sunking]

For mobile applications AGM is the preferred choice for obvious reasons.

[Pedroz]

For mobile applications AGM is the preferred choice for obvious reasons.

ok, I've done a little bit of research and my conclusions are as follow. If I would like to take advantage of fast/full charge from vans alternator I would have to get AGM battery and "tap in". Considering that i don't have a clue how to tap in except the fact that i take you have tap in before regulator and use seperate regulator to charge battery the whole thing sounds like 250£+ and leave me depend on runing diesel.

I still think that going solar panel would be better choice. I nderstand that UK especially in winter gets little radiation but my needs are also limited. Therfor basing on what I read 250wat with decent MPPT regulator and my LA110ah battery should be enough? I feel I would like to go ahead with this setup. Any words of precations?

Thanks,
Peter

[Sunking]

Peter you use an Electronic Battery Isolator.

[Mike90250]

As a word of introduction my name is Peter and I'm living full time in self converted campervan for last 4-5 months. My camper has 230/12v installation with power controller and two batteries van and leisure 110Ah lead acid. On the beginning I was nearly every second day hooked up to mains allowing my leisure battery to be fully charged and rarely drained it more then 50%.

So you were consuming about 110ah @ 12V . (50% of 220 ah)

That's 1320wh you use, and to replace it, you need about 1848wh harvested!! Even if you cut your winter loads to half that of your summer load, thats 600wh you have to harvest in maybe an hour of sun. (or less!) A 250w panel will be better than nothing, but I would consider a small generator and battery charger to top off the batteries at least every other day. Cheaper to fuel then the diesel camper engine.

[Pedroz]

Ok, I've made decision of going down solar panel route. I'd like to get ONE 250W panel (less hassle to mount). However I've notice that at this segment of panels nearly all of them being 24V. My battery and installation is 12V. So here is my question. Are these panels user configurable to 12V (I've read about junction boxes to rearrange cells to output in 12V). If not all panels are like that would you advise which one are/to buy (I'll be hard fixing it flat on the roof. )
If all above isn't true I'll be getting mppt regulator. Can it take care of voltage conversion ? Is this conversion happen at the cost of significant power loss? I've learn that higher voltage equals lower voltage drop on transmission. I'm curious what's better outcome 2x125W @12v panels or 1x250W@24v. Is greater loss happens at transition or conversion (as despite not having answer for above question I take any conversion will happen at some cost ).
Please let me know if all that make sense? Thanks!

[paulcheung]

1x250watts panel and a 20 amps MPPT charge controller would be better and use the alternator to help charge the battery when ever you turn on the engine.

[inetdog]

1x250watts panel and a 20 amps MPPT charge controller would be better and use the alternator to help charge the battery when ever you turn on the engine.

Which requires a battery isolator separating the house battery from the engine battery as part of good design.

[paulcheung]

Thanks Sunking for your answear. Ok I'm lacking a knowledge here but how i can transform 20 minutes of running 100amp in 500Wh? My leisure battery is connected to alternator via some split charging system. I honestly don't know at what amp and voltage it's getting charged but surly it can just bank 500Wh in 20 minutes?!


@jony101 Thanks for your respond!

I think he might already has the isolator.