Solar power for camping/overlanding trips installed 6 27 2009

[george_tlc]

Bogo, you have some errors in your description of PWM and MPPT.

PWM controllers just turn on/off the circuit between the panel and the battery varying frequency and duty cycle as needed to taper off the charge to the battery as the battery approaches full charge and then transistions to float charge. It does NOT use a switching converter to change input voltage to output voltage. Basically it is controlling the duration of current pulses to the battery.

MPPT controllers use a switching controller to transfer maximum power to the battery. They do this by tracking the product of solar panel voltage X solar panel current and ensuring that the voltage X current is the maximum. A solar cell has an 'interesting' voltage versus current curve that has a very distinct point where maximum power can be extracted. An algorithm in the MPPT controller calculates the power being drawn from the solar panel and adjusts the output voltage/current to ensure that it continues to draw maximum power from the panel.

The MPPT controller uses a buck driver to step the solar panel voltage DOWN to the battery voltage. Panels are sized to produce higher open circuit voltage than the desired battery voltage, most "12V" panels produce around 18V (even under VERY heavy cloud cover). Thus the switcher only needs to step the voltage down, obviously under heavy cloud cover there isn't much current that can be drawn before that voltage drops too low, but that's the job of the MPPT to track the maximum power and draw only enough current to maximize the voltage X current (power) output.

MPPT controllers obviously cost more, but can extract more power from a panel than a PWM controller, especially in less than optimal cloudy/shaded conditions.

Both PWM and MPPT controllers will work to prevent battery overcharge and usually will follow the recommended float charge protocol when the battery is fully charged. They also ensure that during dark periods the battery does not discharge back into the controller/panel.

cheers,
george.

 

[VTCDN]

Cheers George !

There are Panels and panels , same as tools and a real Tool .

Here is MAJOR reading for those. Im a mod there.

It's an open site , Be polite , Most know more than I ever will (age thing older ya forget) .

MPPT controllers like higher voltage . Give the above link a real good read.
Im not typing a short form.

I run two 125 watt panels through a MPPT controller for house battery , and a pure sine wave inverter. It runs my fridge, LED TV entertainment system , sound system,cell chargers, computers , satellite radio / internet /phone .

Over build on the worst day & keep the truck / boat (as in both of my toys) battery out of the power / system..

That way when poo meets fan , turn key and Diesel clacks .

My Pecos ,

VT

 

[Nick9000]

Nice set up. Thanks for sharing, I recently purchased four 15 watt panels from Goalzero. I plan on using them to help charge my motorhome battery while desert camping. I also bought a Goalzero Escape 150 battery for all my electronic gizmos. I'm hoping solar will help me lessen my generator use(if it gets hot, the generator and a/c will be running). I hope to test out my array during my next trip in January. Merry Christmas. Nick.

 

[Corey]

Merry Christmas Nick, or is that Saint Nick

Yes, I really like my Goal Zero stuff.
Comes in handy too at home in case that power goes out.
Five of those LED lanterns hooked up to the Ranger 350 battery put out quite a bit of light inside my place.