Solar 12v assist

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Before you buy anything ask questions on the forum or the northern AZ wind-sun forum. The most common mistake people make is they start out by buying garbage charge controllers, inverters or solar panels. The on line solar market is being flooded with cheap Chinese imitation solar hardware.

Helpful for cars with older batteries, or cars that sit for extended periods (batteries experience slow self-discharge when sitting). Can keep your battery topped off during the day to counter small electrical loads. Can reduce the amount of output needed from your alternator (and therefore fuel burned) by a very small amount.

Only small gains should be expected. A full alternator delete was shown to cause a 10% mpg gain therefore the low power supplied by a solar panel would only provide a small fraction of this saving. Adding a solar panel could increase the aerodynamic drag which could cause efficiency to decrease overall.

Note: To keep solar panel running at peak efficiency ensure the panel is clean and avoid parking under trees if charging is required.

Instructions for mod

Bolt solar panel to top of car.
Or glue low profile panels to the roof with RTV.
Low profile flexible stick on panels or small ridged fiberglass backed panels are highly recommended for vehicles that will be driven at highway speeds.
If low speeds will be the norm and aero dynamics are not of concern then just racking a ridged glass topped panel to an existing roof rack will work fine.

Connect the solar panel to a battery charging regulator and connect the regulator to the battery.

Modern charge regulators in a nut shell

First and foremost you get what you pay for.
In the world of solar, an input of 1 going in never equals an output of 1 by the time it gets to where its going.
If you put 100 watts worth of solar panels on top of your vehicle don't expect to get more than an average of 65 watts for more than 4 or 5 hour a day while the sun is at its highest. During winter expect to see under half the panels rated power coming out of them.
PWM, A Pulse Width Modulation charge controller gives you the solar panel's amps but anything above 12 to 13 volts, you know all those volts that make up the watts you thought you were going to get are actually just wasted. (sorry)
This is why PWM controllers are typically around 60% to 70% efficient.
MPPT, Maximum Point Power Tracking charge controller.
If you want any chance at getting anywhere near your solar panels rated out put going to your vehicle electrical system you need one of these.
Or you could just add more solar panels, spend more money and get less fuel economy.
A good MPPT controller is up to 97% to 99% efficient.
This charge controller can take all the useable watts, even with the solar panel producing as little as 8v to 9v and actually push that power onto a vehicles 12v electrical system, an impossible feat for a PWM controller. This is the solar charge controller holey grail. And yes, they are expensive. And no, there is no such thing as a cheap MPPT charge controller. If you find a cheap MPPT charge controller its likely a mislabeled overpriced cheap copy of some name brand PWM controller. If you think you are smart because you have found a $20 Chinese MPPT controler, guess what, it's not MPPT. It's the same as the $15 PWM controller that looks exactly like the MPPT. This fake chinese MPPT garbage is flooding the market.

Current available charge controllers

The smallest high quality MPPT charger on the market at this time are the genasun 14.2v 5amp chargers for lithium batteries. The 14.2v charger will work with both LiFePO4 and lead acid AGM batteries. Cost: about $100 form batteryspace dot com. I believe most people will only want to install 65 watts or less of solar panels on top of their car.
If 65 watts isn't enough for your vehicle borne solar aspirations, next up from that is the 10 amp genasun 14.2v, about $180 for LiFePO4 and AGM. Realistically few cars will fit 140 watts of solar panels on their roofs.
If you have a caravan or just a van that you want to solar the roof of, then you move up to 15 amps and higher MPPT charge controllers.
Starting price on 15 amp MPPT charge controllers is around $200.

User experiences

Please enter your user name and any relevant data in the table

User data
User Name Car Make, Model, Year Cost of Mod Time to Perform Mod MPG Before Mod MPG After Mod MPG improvement guess Instruction Link
Example Data Saand Example Data Mazda, 626, 1991 Example Data $5 USD Example Data 1 Hour Example Data 27.2 Example Data 29.8 User mod detail or measurement detailed data

Problems / Consequences of mod

- Increased aerodynamic drag which could cause an overall reduction in efficiency.
- WARNING: A typical "12 volt solar panel" by its self typically generates up to between 17 and 21 volts, with out a charge regulator you will fry the vehicle battery and possibly damage other electronics.


Forum thread links

Civic VX mpg project: delete alt, install solar
Solar assist: vehicle roof top solar panels
Ambulance with solar panel roof
VW short bus with huge solar panel roof
Flexible solar panels 2
No alternator solar charging
flexible solar panels
solar panel to lighten alternator load
solar panels auto applications
replace alternator with solar panel array
solar disappointment
solar roof

Forum thread links where an ecomodder (here) actually attached a solar panel to a vehicle

The good, bad and ugly; we show it all:
Civic VX mpg project: delete alt, install solar
Solar assist: vehicle roof top solar panels
Vehicle solar to grid
solar disappointment
solar roof
Alt delete, solar panel bed cover

External links

Solar panel install on a camper

Legit External links for buying high end charge controllers

If you are not buying a name brand charge controller like Outback, Genasun, Morningstar, Midnight, Solar Converter inc., Blue Sky, Renogy its likely to be a very cheap knock off of one of these.

Northern Arizona Wind and Sun
Batteryspace charge controllers

External links to battery suppliers

Related or complementary mods