I have had solar panels on my suburban since 2011. Only about 10 or 15 watts worth. That was enough to float charge the large flooded lead acid starting batteries I had at the time on a cold day.
Then when I switched over to LiFePO4 batteries I found that the tiny amount of solar I had added could easily over charge the LiFePO4 batteries. So the switch they were wired through stayed off pretty much all the time.
Well now I would like to do an alternator delete and the obvious choice to help the alt delete along is to add solar. I knew there were charge controllers for lead acid batteries and none for lithium.
Not too terribly long ago I was reading that there were no solar charge controllers for LiFePO4 on the market and none in the foreseeable future and the solution people at that time were using was non temperature compensated controllers with a gel battery setting (you don't equalize gel batteries or you will fry them).
It works, but not ideal.
With help from the wind-sun forum I found this.
They do exist.
A 10 amp LiFePO4 specific Maximum Point Power Tracking solar charger.
MPPT chargers like this can take up to 75 volts (a genasun charger can't do 75 volts but others can), use all the wattage, step it down like an AC transformer and use all of the power to charge the battery.
Unlike a PWM charger. Sure you can hook up a PWM charger to 24 volt panel and a 12 volt battery if you have the right one, but you will only ever get the panels rated amperage and not the total wattage the panel makes for battery charging.
With PWM you want to match your panel to the battery to get max amps going into the battery. Then if its overcast, you are screwed.
With MPPT you are more likely to get at least some usable power in less than ideal conditions. IMO "Less than ideal conditions" very accurately describes any application where you have solar panels laying almost flat on the top of a vehicle.
And yes they do make MPPT charge controllers for lead acid batteries, they have been around for years, but most of them are 15 amps, $200 and up.
I figure 10 amps for battery charging is plenty.
A 140 watt panel should cover an area of roughly 2 feet wide and 5 feet long if it were a more efficient single mono crystalline panel. I will likely use less efficient, more flexible poly crystalline.
That is a lot of solar panel coverage, about the maximum amount I can foresee using.
This line of charge controller also works very well with lead acid AGM batteries.
The fixed 14.2v this charge controller put out is perfect for AGM. The only thing this charge controller is missing for use on lead acid is equalization, which can be done with a digital inverter based stand alone battery charger and temperature compensation, which you really don't have to have.
I did some searching around and I can not find a high quality low amp MPPT lead acid MPPT charge controller.
The only one I can find is the genasun 5 amp MPPT for LiFePO4.
So if you really want a high quality low amp name brand MPPT controller, at this time it looks like your best option is to get a AGM or LiFePO4 battery in your vehicle, a 5 amp genasun MPPT and start sticking solar panels on your roof.
If you wanted to throw down some money and get a heavy duty 15 amp MPPT charger you could get a Morningstar sunsaver tristar MPPT set it up for Gel batteries (14v even) you could go with the AGM setting and get 14.3v with LiFePO4 I say less is more as far as max charging volts go. Then set the higher voltage cut out dip switch "on" so it cuts off load power at 11.5 volt, which is not good at all for lithium, no equalize so dip switch 3 "off", then install a resistor in the "remote temperature sense" terminals to trick the charge controller into putting out stabile voltage all the time.
At this time I do not know what the value of this resistor would be.
I have seen the built in temperature sensor and judging by the application and actual size of the sensing element I can only surmise its a thermistor.