Electricity to my Ice-cream van from 12v alternator by using mppt charger

Hi everyone,
I hope anyone can help me in my problem.

I am new in solar technology.
I created my an ice-cream van that I struggled to supply it with low cost electricity. My van needs 7000w, and I am looking to do my handmade electricity supply by connect the van's 12v alternator to mppt charger.
My question is, how can I use the van's alternator to supply electricity to the MPPT charger ?


  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,147 ✭✭✭✭
    edited August 2016 #2
    You cannot do this at a low cost. 7000 watts on a 12v system is extremely difficult, very complex and super costly to do. You would have to divide it into multiple systems. While not technically impossible, this is darn close to it.

    Example: Your alternator is likely rated for 1400-2000 watts peak. It was not designed to do that continuously, so it would burn out prematurely if forced to do so.

    Note how far apart 7000 and 2000 are!

    Are you sure that your load is 7000 watts?

    I always have more questions than answers. That's the nature of life.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,533 admin
    Let us know more about your installation/needs...

    7,000 Watts is like 4x electric room heaters on full. Is it you are using 7,000 Watt*Hours per day (say 10 hour driving/delivering)?
    • 7,000 Watt*Hours per day / 10 hours on road =  700 Watt average load
    That would still be a large system, but much better at 700 Watts vs 7,000 Watt load...

    Watts is a "rate" like miles per hour.

    Watt*Hours is an "amount" like miles driven.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Johann
    Johann Solar Expert Posts: 245 ✭✭✭
    If your van is a 12 volt system already, your alternator will put out about 14 volt of regulated power to charge the 12 volt starter battery of your van. No charge controller is needed to charge your starter battery. If you have extra batteries, the alternator can supply power to the extra batteries also and there are different ways to do it.
    Do you know how many amps your alternator can put out?
    A alternator for cars can range from 40 amps to about 60 amps and 80 amps to 120 amps for trucks and vans. And there is always a special alternator that may have different voltages and amps.
    A 80 amp alternator will give you 1120 watts an hour at 14 volts, but the vehicle itself  will use/need  about 20 amps to 30 amps so it can operate and run,  so your available power  that you can use from the alternator will be even less for other things.

    There are pricey alternators on the market that put out a lot of amps and may even fit your van without major modifications. Those alternators may come in different voltages and there are some where the alternator output amps and volts can be adjusted. BUT you got to have a ICE (internal combustion engine) big enough  that can supply the power needed.
  • DRickey
    DRickey Registered Users Posts: 22 ✭✭
    As far as I know, the biggest 12v alternator made does 250 amps (max output 3.5kw), so you'd need two of them. There is also a 24V version (which could do it with one), and if you want to get really insane there's a 450 amp 24v alternator. None of those are designed to put out full power at an idle, they generally peak at 3000 RPM. Although you could finesse that with non-stock pulley ratios, the typical engine probably could not maintain an idle under that much load without some special tuning.

    All of which begs the question of what kind of cryogenic-grade ice cream freezer needs 7 freaking kilowatts? At even 10 EER, that is 70K+ BTU, enough to cool a small office building (say, 10,000 square feet), or an industrial freezer about half that size. 700 watts I would believe for a small chest-type ice cream dipping station, around 7-8 cubic feet. That you could run off of a vehicle alternator, easily, but what you want is not a charge controller, but an inverter.