How to connect an alternator to my vans solar system

Are you going to have two different battery banks (one to start the van, a second for the "house" power)?

The typical method is to get a relay (or electronic relay/diode battery isolator) that only connects the two battery banks together when the alternator is charging:

http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias=automotive&field-keywords=battery+isolator&rh=n:15684181,k:battery+isolator

There are also various DC to DC battery charger options... Here is one:

http://www.xantrex.com/power-products/power-accessories/auxiliary-battery-charger.aspx

There are pluses minuses with each type.

-Bill

The isolator is simply connected (with the correct size wiring) between your two battery banks. The simple version is just a heavy electrical relay that "turns on" at ~13.x volst and turns off at ~12. volts.

When the alternator is charging, both battery banks are connected together (in parallel). Note that (especially) for 12 volt battery systems, you need heavy wiring to carry the current and keep the voltage drop low. Ideally, you want about 0.05 to 0.10 volt drop because of the copper wiring. And that is one weakness--Heavy/expensive copper cable + long(er) wiring run from the vehicle battery to the house battery bank--Of course, in a van, hopefully that is not a very long run.

Another issue--Most car type alternators while rated for >100 Amps--Typically get hot pretty quickly when supplying high current, and frequently will drop down to much less than 50 Amps (guessing) when charging. So--Using the stock vehicle alternator setup may supply less than expected charging capabilities. And idling the vehicle engine can use a lot of fuel and exhaust fumes can be dangerous (if you are sleeping in the vehicle).

If you are driving a lot (every few days)--The vehicle alternator can be used to supply a significant amount of your house power... However, if you drive 20 minutes and park for 2 weeks--Then the alternator becomes less useful (in general). And you need to look at other options (lots of solar panels, Honda or Yamaha 1,000-2,000 Watt genset, etc.).

My suggestion is to start with your loads (how many watts * hours per day of usage), How many days of dry camping at a time. Seasons of use, Approximate location, etc.

Most RV solar applications start with plastering the roof with solar panels (what will fit). Then design the battery+inverter+etc. system around the amount of power the panels can supply. In some cases, RV's are battery limited--weight and space--And that is where we start the design. Then--Whatever power the solar system can supply is what you get. Make up any extra power needs with running the vehicle engine and/or AC genset.

in the end, solar panels and batteries usually supply much less power than most people would expect to use (charging laptop computer, lights, fan, etc.). Until you know your loads and energy usage--It is very difficult to design an off grid power system to support your needs. We are just guessing.

-Bill

We can do the basics, without you spending any money.

Look up some solar panels and see how many you want to fit on your rv. Then we can size your battery bank and predict the basic loads the system can supply.

There are Vmp~18 volt panels which can change 12 or 24 volt battery bank's with inexpensive PWM type solar controllers. Vmp~18 volt panels are usually smaller and may fit your roof space better.

If you go with Vmp~30 volt or other panels, you typically more expensive MPPT type solar charge controllers. Vmp~30 volt panels can be much cheaper. So, it can be a balancing act.

Do the paper design first. You can save lots of expensive mistakes.

-Bill

Mini fridge can be the killer. They can use a lot of electricity. Why many people use propane refrigerators.

-Bill

And, in general, it is pretty difficult to pull large amounts of current (100 amps+) vs the 10-20 amps or so that the long cable run at 12 volts generally supports (voltage drop from long cable runs) wnen batteries are mounted in a towed vehicle.

-Bill.

Balmar and possibly some others (as I recall) also can have remote voltage sense leads. Attach the sense leads to the battery and the alternator will output higher voltage to make up for the voltage drop in the wiring--But that is two extra wires that need to run back to the alternator/charge controller.

-Bill