What improvement will a MPPT charger provide in my system

[guymadison]

Currently I have a 240 Watt solar panel with a PWM charge controller and a 800 ah 12v battery bank, I see charge rates of about 6 amps on the sunniest of days will I get better performance with a SCCM10-100? Ideally if it's not connected to the 12v battery rail it should benefit but I am not sure I understand if the SCCM10-100 isolates the battery from the solar panels which produce most of their power at 30 V.

[hendrik krijt]

Hi

Currently you have 6A coming to your battery at 12 volts, that gives you about 70Watts, A mppt charge controller will draw power from your panel at its max powerpoint of 30volts. Depending on the amount of sunshine and the temperature and the angle of incidence of the sun onto the panels and atmospheric conditions, you may see upto the 240watts going to the batteries. you might see upto 20 Amps into your batteries. I will try to post a photo of what my mppt charger is currently doing. 70v at 6.3A coming from panels, 29.5v at 14A. that 441watts coming from panels, 413watts going to batteries. thecharge controller uses some power, but you will win big time.

Lots of South African Southern sunshine to you all!
Hendrik Krijt

[billi]

Please provide the specs of your PV panel , hard to believe for me that a 240 watt panel is ideal for 12 volt charging without an Mppt charger

[guymadison]

Oh I knew it wasn't ideal, but based on the sun we get here in Seattle it's been quite impressive. On a bright sunny day I did some experiments under load with an adjustable switching power supply and I found I was able to get about 8-10 amps as I drove the max current / voltage up to the peak output of 30V for the panel.. since I already had a PWM controller it just didn't seem worth the extra cost to install a MPPT controller which is pretty much a switching power supply on using the inductance of a toroidal coil to isolate the voltage between the batter and the panel.

It's a big panel at 240 Watts with a peak output of 8 amps at 30 volts, the curve is pretty static until it hits that point and drops off like most panels.

But Hendrik is getting good results, I ordered a OB MPPT controller just to see if there is a noticeable difference.

I will probably add another 240 Watt panel on the back of my sailboat which will give me plenty of power for long anchorages.

[billi]

...... so your battery is 12 volt or when charging around 14V and a 8 A panel then gives you 14Vx8 A= 112 watt only so you waste half of the panel without an Mppt controller

[guymadison]

In Seattle we don't see the same amount of sun as say South Africa, so that was one of the considerations when purchasing a solar panel and the fact that most all panels are the same size. If you think of a solar panel as a large capacitor powered by light knocking electrons free the bigger the better. My expected use was from May - Oct for solar and even at the lower wattage it keeps up with my daily use. The average radiation in kW/m^2 is around 3 for Seattle.

I found a white paper from the Texas Instruments site that states a MPPT controller is about 20-30% better than a PWM, even with that my expected output will be around 10 amps. But I would need more like 16-20 amps to make a significant difference and I am not sure a MPPT controller will provide a 100% increase when loaded down with a 14v charge on a battery.

But I will find out once the sun shows up...

[billi]

Hi, it does not matter how much sun u have in Seattle , all i am saying is that a 30 volt PV panel is not ideal to charge a 12 volt battery !!!!!

[guymadison]

No it should work fine, a MPPT is just a DC-DC converter (some sort of buck converter). The power across the output inductor will remain constant, I(in)V(in) = I(out)V(out).

The max current from a panel is defined by your latitude as this defines your average W/m^2 of solar radiation, which is constant for any panel Voltage (see IV curves in pdf).

https://www.wholesalesolar.com/cms/specs-2801912752.pdf

The efficiency is defined by how well the MPPT can convert from 30V to 14V, that's the question.

[EMCF]

Don't underestimate the Washington state sunshine On a good sunny day, you can get around 15A from your 240W solar panel using an MPPT charge controller. And say, the voltage is the same 14V, you have 210 watts there.

[guymadison]

EMCF.. that's good news!

I have spent a lot of days like this on the water, but there are plenty of sunny ones also.

(https://drive.google.com/file/d/0B_BQKz ... sp=sharing)

Hence the big panel.. after my alternator blew on two separate trips I decided to go solar.

[billi]

.... I sometimes get more as the rated watt of my panels (66 Vmp connected to 24 volt battery via FM 80 ) and Ian in Ireland , with a non mppt controller it would be about half the watts

[cyrax]

Dear All,

How effective are PV Maximizers? especially the one from solaredge and tigo
read online they use MPPT technology.

Please help