MPPT Solar Controllers

**101RRS** · 20th September 2014, 10:07 AM

I have had a 120w 12v folding solar panel for some time. It has the standard el-cheapo controller mounted on the back of the panels.

I bought a 30amp MPPT controller to be mounted near the battery and decommissioned the controller on the panels. I also have a couple of Watt meters that show Volts, amps, Ah, Watts etc.

I connected it all up this morning and the panels are in full sun. It is showing battery volts as 13 and is only charging at 1 amp.

So I take it that at 13v the battery is basically charged.

Does a MPPT controller act like a smart charger and throttles back charging when the battery is getting full - hence only 1 amp going into the battery so is like a float charge.

If the battery was down would I see the expected 7-10 amps in full sun on the meter.

Thanks

Garry

**PhilipA** · 20th September 2014, 10:12 AM

Yes it acts as a smart charger.
I only get 6.1 amps or so , but that is with batteries at 12.6 volts to start with.
My MPPT is a 10 amp one OZ made with 20 metres marine 8 Gauge cable and the panels in series not parallel , and the MPPT is next to the battery.

What happens with mine is that it appears to sample every 5 minutes and then decides what to charge.
Regards Philip A

**p38arover** · 20th September 2014, 10:22 AM

What brand, Philip? I'm a bit suspicious of many of the controllers on eBay. Are they really MPPT?

**Graeme** · 20th September 2014, 11:16 AM

I was told that MPPT charges work most efficiently close to their rated output, which makes me wonder if the 30A charger isn't the right choice for a 120W panel.

**101RRS** · 20th September 2014, 12:18 PM

I have heard that too but not according to the information with the controller - the 30amp side is its max deliverable current but indicates it works fines at low power levels.

**spudboy** · 20th September 2014, 01:18 PM

A 30A MPPT for a 120W panel is sort of overkill. I am running 6 100W panels through a GSL 30A MPPT controller, and that is comfortable.

If you want a true MPPT controller, look at these guys: GSL MPPT

Industrial quality and made in Australia. They do 12A 20A 30 & 60A models.

I am using 2 of them in my MAN:

HTH
David

Doc130 · 20th September 2014, 01:43 PM

You will never see anywhere near 30 amps out of 120 watt solar panel, depending on quality you won't even see 10amps

Doc130 · 20th September 2014, 01:44 PM

..... No matter what charge is in the battery

**PhilipA** · 20th September 2014, 03:32 PM

What brand, Philip? I'm a bit suspicious of many of the controllers on eBay.
Are they really MPPT?

This is the one I have, and seems to be fine, and can recognise battery voltage and panels in series so must be MPPT .(LOL)
Do a google search to their site and it will give info.

GSL Electronics : MPPT 12-1 / MPPT 12-2

Regard s Philip A

**Fluids** · 20th September 2014, 06:27 PM

I bought a 120w folding with 10a MPPT controller mounted on the back of the panels. It was only around $170 delivered.

Using a clamp meter, best I have seen in full sun was between 6.8-7.2A.

I set it up facing east before we go to bed so it starts charging as soon as the sun pops up. Easily charges an Optima D31 & D34 back to full from the previous days use (47L fridge, lighting, D2 stereo use, camera, air bed pump, phones, iPads, etc).

I believe the MPPT feature doesn't come into play until you've passed the bulk charge phase.

I'm surprised at just how well it works for a cheapy !

Sent from my iPad using Braille

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