Thread: Reliable Budget MPPT controller req'd

I've often wondered if the MPPT controllers on ebay are really PWM. They seem too cheap to be MPPT.

I built an MPPT controller a while back (Jaycar kit from Silicon Chip design I picked up at 75% off) but haven't got around to doing a comparison with the PWM controller on my camping solar panels.

The camping panels I have comprise two that unfold. I'm thinking of connecting the PWM to one half and the MPPT to the other. They will receive the same level of sunlight as they will be side by side and I can can record the voltage and current with a 4 channel digital recorder (I wondered for years about a use for it. )

One day.

Most of the cheapies are PWM Ron even though labeled as MPPT.

For a 40watt panel a cheapie PWM should work fine, from my experience, with little to gain from going to a more expensive MPPT.
It will probably be rated to 15A and a 40 watt panel is unlikely to ever make more than half that anyway, so no problems. I've never seen more than about 10A from a 160watt panel.

Originally Posted by DiscoMick

I've never seen more than about 10A from a 160watt panel.

I've never seen more than 7.5A from the alleged 160 watt panels that I have. I think one might need to take the panel specs with a grain of salt.

I bought a supposed MPPT 15 amp on ebay for $25 as I was concerned my 12 amp Good quality MPPT would be too light for my new 240Watt (ha ha ) panel.

It gave a good output but about 1 amp less than my good MPPT.
Regards PhilipA

Originally Posted by PhilipA

I bought a supposed MPPT 15 amp on ebay for $25 as I was concerned my 12 amp Good quality MPPT would be too light for my new 240Watt (ha ha ) panel.

It gave a good output but about 1 amp less than my good MPPT.
Regards PhilipA

If my number are correct a 15amp controller is on the small side, I’d probably get a 20amp controller

I use the following to size a controller

240w x .85 (85% efficiency) = 204w

204w / 12v (although some say you should use 13v) = 17amp on a good day.

Do we ever get perfect conditions and angle to the sun, not sure.

Originally Posted by p38arover

I've never seen more than 7.5A from the alleged 160 watt panels that I have. I think one might need to take the panel specs with a grain of salt.

That and the fact panel output is rated at constant temperature (25C I think) and incident radiation equal to levels you might achieve at midday on the equator both of which aren't achieved locally.

Originally Posted by p38arover

I've never seen more than 7.5A from the alleged 160 watt panels that I have. I think one might need to take the panel specs with a grain of salt.

This thread is going to turn into the AULRO great solar debate
Here is what I remember from years ago, it may not be 100% but like I said it’s what I remember from years ago


Solar panels specs are rated to a standard test condition
And there are so many variables
If I recall it’s 1000 watts per metre square at 25 degrees Celsius
If your panel isn’t facing the sun directly you won’t be receiving full solar irradiance
In summer, If your in Tasmania you will only get at most about 800 watts per metre square
If In FNQ you will get 1200 watts per metre square
But your panel is going to be more than 25 degrees and in tassie your panel will be less than 25
So you could end up with about the same power produced
Then there’s dirt
If you clean your panels expect 5-10% better output
Until they get dirty again
How old are your panels, the cells deteriorate

I’ve got 1520 watts of panels at the farm house on an inverter with 94% efficiency

I’ve seen 2110 watts of output on a cool
Spring afternoon after cleaning them

Anyways back to the original post
For what you are trying to do Don try this little sucker from Jaycar

Miniature 12V 3A PWM Solar Charge Controller | Jaycar Electronics

I’ve had a few running for a couple of years on electric fences
Compact and reliable

Gav