dual batteries and solar setup in a van

Re: dual batteries and solar setup in a van

Welcome to the forum.

What a coincidence: I have a '92 E250 (fuel-sucking monstrosity that it is). Mine is a work van, though, not a camper.

First of all, you won't find a 10 Amp MPPT controller. The closest you're likely to get is Morningstar's 15 Amp unit: http://www.solar-electric.com/mosumpsochco.html

Second, you probably do want to run those panels in series because their Vmp @ 16.5 is a tad on the low side for a 12 Volt system.

Third, you don't want to use a Morningstar duo on the alternator output. An ordinary battery isolator would do. If you need to boost the starting battery from solar, mechanically connecting it only when needed is the way to go. Otherwise it remains separate from the "house" battery at all times. Having the alternator feed some current to the "house" battery when the engine is running is not a bad idea, though. Personally I'd prefer to keep the systems as independent as possible to minimize the problem of running down the starting battery with camping loads.

Which is where we come to the calculations. From two 68 Watt panels you can expect enough charge current (about 8 Amps) to properly charge maybe a 100 Amp hour 12 Volt battery. That isn't very much. Are you sure you want those panels? Were it me I'd be looking at a single monocrystaline panel of 230 Watts or so and some solid roof mounting (the van can take it). That would maximize the 15 Amp charge controller and give you enough to handle twice as much battery with a little management.

Another option would be a PWM type controller around 20-30 Amps and three 130 Watt polycrystaline panels: http://www.solar-electric.com/ps-30.html and http://www.solar-electric.com/solartech-spm130p-s-n-130-watt-multicrystalline-solar-module.html This would provide enough to keep a pair of 220 Amp hour 6 Volt GC2 batteries wired in series happy.

Otherwise you may find yourself running a generator to keep the batteries up, or worse the engine.

Just trying to offer some options.

Re: dual batteries and solar setup in a van

verdigo wrote: »

I have a 71 VW Bus that I have been installing some Westfailia camper interior parts into I found in the shop attic. It probably uses as much fuel as the Ford.

There must be something wrong with it. You're not trying to drive it uphill are you?
Seriously the Ford does okay at highway speeds considering how big it is. In town? Ugh.
Former girlfriend of mine had a '71 Bus (it wasn't old then you understand) and it was great on mileage. Especially after I fixed the stuck-on rear brakes. The dealership kept selling her tune-ups. :roll:

Re: dual batteries and solar setup in a van

preposterous4 wrote: »

Thanks for the straight forward reply cariboocoot!

Doesn't this qualify as a 10 amp MPPT?

http://www.solar-electric.com/12vo10ampmpc.html

Well that's a new one. And unlike some of the other "MPPT" controllers it appears to work properly (35 Vmp panels to a 12 Volt system as opposed to those who limit input Voltage or output current based on output Voltage). Not much flexibility to it though, and the charging Voltage seems to be only 14.1 which means it is really too low for deep cycle batteries. It seems to be more of a battery maintainer than a charge controller as I read the specs. No indication of Bulk/Absorb cycle functions, just "charging" and "floating". I wonder how long it maintains 14.1 V? I also wonder how many of them they've sold and what feedback they've got.

Going to keep my eye on that one.

Also if I drive it short distances daily can't I keep a larger battery topped off?....I am still wondering though if running the solar and the alternator to one battery at the same time might cause some problems.

The solar and alternator will not interfere with each other. There will be a Voltage discrepancy as alternators do not charge to the same profile as solar.

Ordinarily I'd say use the SunSaver duo with the panels in parallel: one output to the house battery the other to the starter battery. But the Vmp on those Unisolar panels is less than 17 so there may not be enough Voltage left after the wire run to actually achieve charging Voltage (especially with hot panels). Any idea how long the wire runs would be from panels to batteries? Less than 20 feet and you could probably get away with it.

Re: dual batteries and solar setup in a van

preposterous4 wrote: »

The panels are nearly 10 feet so I will run to the battery(s) either in front or back. Definately less than 20 ft.... Is there a method for 2 house batteries, one alternator, one solar, and have them both feed a UPS or something with 12v outputs.... without them communicating with each other? I am getting vertigo up here walking the noob tightrope

The only way to share two batteries with one inverter without also sharing charge sources is to use a manual battery switch http://www.solar-electric.com/basw1300amp.html to change between them. Note that particular one has a "BOTH" setting wherein the load can draw from the two simultaneously. If placed in that position the two batteries will share charge sources as well.

Yes, it's complicated stuff. That's largely because there's always more than one way to do the job. Choosing which one would work best for a particular application tends to come down to a judgment call that only the end user can make.

Re: dual batteries and solar setup in a van

preposterous4 wrote: »

I won't be needing a converter, but maybe I should go with 3 panels, I think I can fit 3, with the 15 amp mppt.

If you go with three panels you can still put them in series: the MS 15 MPPT has an upper limit of 75 Volts (for Voc which ought to be about 21 for those panels * 3). That would give you 204 Watts and should work just fine (about 13 Amps peak output).

So then should I just keep 2 power stations seperately?

My personal preference is to keep the two power systems separate but have a method of connecting them so that you can either "borrow" solar charging for the starting battery or alternator charging for the house battery. If they're close enough to hook a heavy line between the two you can give your starting battery a jump from the house battery if need be.

Do I need anything post battery(s) to protect the laptop?

That depends on the laptop and what its input is. Check the VDC input range and see what it requires. Fusing the line against over-current is always recommended.

Yes and how to get better MPG in that damn E250, man what a pig!

Push it downhill with the motor off.
I haven't figured out how to improve the uphill mileage yet.

Re: dual batteries and solar setup in a van

The only problems with connecting the two systems together are the different charging profiles between starting and house batteries (not critical) and the inadvertent draw of power from one to the other. A battery isolator can be made use of here. Some of the guys on this forum who have done it say they prefer the mechanical isolators to the electronic ones (less power loss).

Usually two 6 Volts in series works out better than two 12 Volts in parallel, but not always. Check prices on whatever you can get that will fit in the space available. GC2 (6V 220 Ah) tend to be power bargains.

If going up hill attach a grappling hook to the vehicle in front of you. How about that?