Solar system for expedition van... Need review of diagram

Kiomon · July 2012

Hi all,

We are preparing to live and work out of a camper van for the next year+ owing for a non-profit to tell the stories of other non-profits across Europe and Africa. I am trying to deismg a solar and battery set-up for our van. I am new to solar and electric so I have been reading and studying others work

For background, we will roof mount the main panel. Trying to potentially move up to a 315 watt panel. Waiting to confirm measurements. We want to be able to charge via alternator, solar, and shore power..

Would love your feedback on the diagram below.

1. Can I move all of my positive connections to my positive bus bar, with the exception of my "sensor" wires? I would have a positive bus bar for each battery.
2. Have I connects all of this correctly?
3 I am thinking of adding a solar combiner and have a MC "port" that I can connect a flexible foldable panel too when we are parked. Is the anything wrong with that idea if there isn't a panel connectd to that second port 90% of the time.

Love any feedback, we are looking to order it all on Monday!

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Cariboocoot · July 2012

Re: Solar system for expedition van... Need review of diagram

Welcome to the forum.

Now, slow down, stop, put the brakes on before you spend any money.
You're going about it the wrong way.

It is essential that you come up with a number for how much and what type power you need to supply each day. Design the system around that.

What you've got is a collection of equipment that may or may not be suitable. For instance a 258 Amp hour battery is going to need more than 300 Watts solar to charge it. It will not "play well" with a 55 Amp hour battery. Mostly you may find when you measure the roof that there isn't room for one big panel and you'll have to use several little panels instead.

You'll want to keep your starting battery isolated from the other power system. It's okay to use the vehicle alternator to boost up if needed (or vice-versa) but you would be better off without an automatic connection here.

I'm sure others will have some additional suggestions as well.

Kiomon · July 2012

Re: Solar system for expedition van... Need review of diagram

Oh good, point, I didn't put enough background. We are a bit constrained on the amount of battery power we can carry based on space. But here is some more info.

1. Load / Usage
- we used the spreadsheet here and calculated we will use 3000 watt hours a day, about 50/50 DC/AC

2. Generator
- we will have a 2000 watt Honda generator to serve as shore power as needed during the night. We are planning to carry a separate 10 gallons of gas for the generator to give us some "range"

3. Alternator
- we will drive early AM's for about 3-4 hrs per day, with every 5-7th day (on a 10 day cycle) we will have 8 Hrs of driving. The alternator is a 120amp model

4. Load and appliances
No AC unit (sigh), battery charges for professional cameras are the biggest draws when connected at 400watts

5. Optima Battery
I wanted to think of this an aux/ back-up / emergency battery. I was going to wire a separate st of DC plugs that could b usd in the event that the main battery goes down and need to ensure the basic still work. E.g. Cell phones, sat data, etc.

6. Roof size
JUST confirmed, 58" wide by 99 inches long

Does that help?

Cariboocoot · July 2012

Re: Solar system for expedition van... Need review of diagram

Yes indeed; the devil is in the details. Didn't mean to jump on you so hard, but about 60% of the inquires we get here are of the "I've bought this stuff, now how do I get it to do what I want?" variety. :roll:

3kW hours per day is substantial. You will not get it from one panel (not even 315 Watts). This means you either add more panel, or more likely depend on the generator. Basically: 315 Watts * 4 hours of good sun (a problem with a mobile application where you don't get ideal insolation most of the time) would be 1260 Watt hours. Over-all system efficiency will eat up about half that (even with some of the loads being DC), so you see you will fall far short of supply the total power need from panel.

This is one of the reasons I say for mobile apps you should put as much panel on the roof as you can fit.

Another issue on the same line is the main battery: 258 Amp hours @ 12 Volts is 3096 Watt hours total, but since you need to keep the SOC above 50% to avoid killing the battery prematurely you'd only get half that at best: 1500 Watt hours (DC). No room for more battery?

At the very least I'd say you want to try for over 400 Watts of array, based on the standard formula for recharging a battery that size: 25.8 Amps * 12 Volts = 309 Watts / 0.75 = 412 Watt array. Any chance you can get two 235 Watt Kyocera panels up there? They're pretty cheap per Watt and measure about 65 x 40 inches.

To get the full 3kW hours from panel you'd need about 1kW of array. What about the possibility of adding "mobile" panels that you can set out in the full sun during the day when you're not moving?

The back-up DC system is a good idea. You should look at getting some Blue Sea battery switches so that the different batteries can be switched in/out as needed. You don't want to batteries that are vastly different in capacity connected together at any time.

I think you're going to become expert at load shifting.

Having to run even a EU2000i for 1/2 your power needs is going to be a pain, especially when on the move through foreign lands.

Kiomon · July 2012

Re: Solar system for expedition van... Need review of diagram

Thanks man for the feedback, and no worries on the direct answer. I know how it goes, as i moderate some other forums myself

Thanks for the help on the math and thinking all of this through, so we need more storage and arrays.

What about the idea of a solar port on the exterior of the van? I am attaching a new diagram below, as i have cleaned up some stuff, and added this idea of a port that i could run to enable me to set out other panels when parked. I have been looking at solar diagrams showing how they combine several panels into larger arrays, and it got me thinking. From the looks of it, you can combine panels using these branching connectors. Thats what the diamond with a "B" in it means.

http://www.solar-electric.com/mumc4colam.html

The issue is that the other panels i would tie in would not be the same size as whats mounted on the van. Would this be a problem. The bummer news is that the 315 won't fit, so I have to go with a a 250 Watt Samsung. But i am hoping i could cary two smaller 60WATT panels that i could connect together and then attach to my solar "port". So then i would be at 370 Watts. Not quite 400, but better/ closer. Would this work? The external panels would be identical.

I have color coded anything that i changed yellow, so you can better see it. A "S" in a diamond, stands for switch, and a "B" refers to the branch connectors i link to above.

Thank for the help!
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vtmaps · July 2012

Re: Solar system for expedition van... Need review of diagram

There are a lot of issues for you to learn about if you want to mix and match solar panels. You need to sort that all out before you start spending. You may want to have two charge controllers, one controller for each type of panel or each group of panels.

I presume that your portable panels will not have shading issues (you put them in full sun). The panel on your roof is a different story. Do you have anything sticking up from your roof that could cast a shadow? Even the shadow of a whip antenna can cut that power in half. Depending on how you configure your panels, that shadow on the roof could even cut the power from your portable panels that are in full sun. If you do have roof shadows, you might be better off with several small panels on the roof, configured in parallel. The portable panels may work out better in series, through an MPPT type controller.

--vtMaps

Kiomon · July 2012

Re: Solar system for expedition van... Need review of diagram

Yeah, I read a ton about the shading issues. Nothing shades the panel on the roof. The main controller I have speced is a mppt controller.

Now on the different types of panels and the need for separate controllers, is there a place you could point me to learn more? So if I want to tie in different panels they need their own controller?

icarus · July 2012

Re: Solar system for expedition van... Need review of diagram

Nothing shades the panels, except trees, wires, buildings, clouds etc.

The first rule of solar is that loads always grow with time, and the second is relevant here, people tend to over estimate thier solar potential in the net, while at the same time underestimating thier loads.

Tony

Cariboocoot · July 2012

Re: Solar system for expedition van... Need review of diagram

As far as mixing panels on one controller is concerned it's pretty straight forward:
For parallel connections you want the Vmp of the panels to be very close (less than 5% difference is best).
For serial connections you want the Imp of the panels to be very close (less than 5% difference is best).

You are not going to be able to meet those criteria using a 250 Watt panel and a couple of 60 Watt panels. The first will have a Vmp around 30 and the others will be more like 17, nor is it likely the Imp ratings will be compatible.

What's more; even if they were close on the panel specs since one is on the roof and the others will be on the ground they will have different insolation, which can lead to problems with an MPPT controller picking the right power point.

For this situation using two separate controllers (the second a less-expensive PWM type) would probably be best.

Disclaimer: spent most of today in the ER so I may be talking nonsense here.

Kiomon · July 2012

Re: Solar system for expedition van... Need review of diagram

@cariboocoot bummer you went to the er. I hope everything is ok. Thanks for the knowledge on mixing the panels. I had done some reading since my last post and now this makes a lot more sense to me. I will update my diagram later this morning to show what I am now thinking. I really like the idea of being able to get more wattage by carrying some folding panels. Get better

mike95490 · July 2012

Re: Solar system for expedition van... Need review of diagram

Often roof top panels are NOT at the best angle for solar harvest, so you loose more power there.

Having external, portable panels would be a boon, Anderson connectors would make it easier to connect/disconnect/panels walk away by themselves.

My suggestion: since you will be driving nearly every day, look into installing a) an additional alternator with it's own regulator for deep cycle charging. b) upgrading existing alternator to high output model, and adding a dual regulator, one for starter, one for deep cycle. That will, in a couple hours, give the battery a BIG boost, and the solar may be able to top it off later.

Consider just keeping the 1 battery, and running it to death, a quality battery should be good for a couple hundred deep cycles, and then you go get a new one. (the house battery, not your starter battery)

Fire up the generator (is it a standard generator, or an Auto Throttle Inverter Generator)? in the evening, to meet your power needs, and to top off the battery. 5 gal of fuel should last you 6 days at least.

You are NOT cooking with electric are you ? How do you consume 3KWh daily ?

Kiomon · July 2012

Re: Solar system for expedition van... Need review of diagram

no we aren't cooking with electric, we have a multi fuel stove for that, and a propane tank system installed as well. The power draw is based on the film production gear we use. We are a production company basically, so we have to charge our film gear. And thats a big drain on the system, and also communication equipment. It looks like we have some BGAN satellite gear donated, so we want and need to be able to keep that powered up. It really adds up.

@mike90045 Love the idea of another alternator as well. We will look into that today. Also, if we had to buy a new battery at the end of this year's trip, it may just have to be something we plan for. HOw deep could we push it and how many cycles do you think we can pull off? We have limited weight we can carry and be legal on vehicle weight, so not sure we can fit more batteries. The generator we are looking to bring is this one:

http://powerequipment.honda.com/generators/models/eu2000i

It's no a RV generator perse, but its light weight and we can pack it with us fairly easily.

I have updated the diagram to factor in the need for another controller for the external panels. Also i want to separate the battery gauge from the inverter because the goal will be to keep the inverter shut down as much as possible. We really are working hard to get DC supplies for as many of our loads as possible.

I'm still trying to figure out the best connector to have for the external solar "port". I wrote a manufacturer and they were concerned about the MC4 connectors being connected and disconnected frequently. Some have suggested a ruggedized standard auto plug. Any ideas?

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BB. · July 2012

Re: Solar system for expedition van... Need review of diagram

For the Honda eu2000i, here is some information to help picking the "optimum" AC to DC battery charger (and why it matters):

Question about battery charger selection with EU2000 generator.

-Bill

mike95490 · July 2012

Re: Solar system for expedition van... Need review of diagram

here's a battery life vs cycle depth chart.

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So, even with pretty deep discharges, as long as you are quick to recharge, you should get a years worth out of it.

To squeeze out the last bits of efficiency, you may have to compare mains style chargers vs. 12V mobile chargers for your gear.

Solar system for expedition van... Need review of diagram

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