# how to check the performance of an MPPT charge controller

Registered Users Posts: 8
hi

i bought a 30 watt solar PV panel and one MPPT charge controller (http://www.eco20-20.com/mppt-solar-charge-controller-tracer1210.html). i have one 12 volt 18AH lead acid battery and a 10 watt LED light DC load. I am interested in analyzing the performance of the system after adding MPPT charge controller. can any one help me how can i performance this task with above mentioned experimental setup?

Re: how to check the performance of an MPPT charge controller

In general, we have not seen very many true MPPT charge controllers out of China--Especially small/inexpensive ones.

To test the controller, a 30 watt panel is a bit on the small side, and you should really have at least two 30 watt panels you can put in series (assuming each is Vmp~17.5 volts and Imp~1.7 amps).

You would connect the two panels in series to make an Array with Pmp=30 watts; Vmp~35 volts; and Imp~1.71 amps).

With a discharged battery (to keep the charging voltage low), you would connect a DC current clamp meter or Shunt Resistor to measure the charging current into the battery.

If the panels are in full noon time sun, the charge controller is a true MPPT controller, and it is in MPPT mode (discharged battery), you will get roughly:
• 60 watts * 0.77 typical solar panel+charge controller derating * 1/14.5 volts charging = 3.2 amps or so into the battery bank
Note, a true MPPT charge controller takes high voltage/low current from the solar array and efficiently down converts it to low voltage/high current needed to recharge the battery bank.

If you measure Ibatt current >> Ipanel current, then you have a working MPPT charge controller (assuming Vmp-array~35 volts and Vcharge-batt~14.5 volts or less).

If Ibatt = Iarray; then the MPPT controller is operating in PWM mode (battery relatively charged) or it is not a MPPT charge controller but just the cheaper PWM controller all done up with pretty markings.

Many times, you can open the charge controller and see inside. If you do not see large inductors/transformers/toroids of some sort, but just transistors and a few capacitors, then it is most likely a PWM charge controller.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 3,009 ✭✭✭✭
Re: how to check the performance of an MPPT charge controller

On my micro-micro hydro feeding my Morningstar TS-MPPT-60 controller, I have both a volt meter and an amp meter in the line between the turbine and the controller. It's very easy to multiply the voltage by the amps to get watts coming up from the turbine, then compare it with the watts going into the batteries from the controller.
At this moment the Fall season has begun and the leaves are beginning to drop from the trees, floating on and in the brook, and have the filter screen partly clogged, so output is down a bit till I clean it out. Meanwhile I have non stop, 27.5 volts and 6.1 amps coming to the controller, which is 167.75 watts. What's coming out of the controller is 12.4 amps and the battery voltage is 13.3, which is 164.9 watts. So what am I loosing in the conversion process within the controller? 2.85 watts, and I consider that to be very good.
By the way, as daylight arrives, solar will drive up the battery voltage, topping them off for the day.
• Registered Users Posts: 8
Re: how to check the performance of an MPPT charge controller

dear bill thanks for your kind guidance

i have taken one more 30 watt panel. and analyzed the results with the method you have guided. i also opened the MPPT controller. It has one big inductor in it and capacitors as well as few transistors.

now my interest has been developed in analyzing the mppt performance with two 30 watt panels connected in series and parllel and also the MPPT performance with one single 60 watt panel. what will you suggest? obviously the low voltage configurations (i.e 17.2 V in case of two 30 watt panels parallel connection and also for single 60 watt panel) will be not so efficient but is there any trade off? what experience do you have in this regard? and my 2nd question is that if i incorporate a sun tracking system with this; will it be a good deal?
Re: how to check the performance of an MPPT charge controller

My own system is Grid Tied--And my experience is as a "systems engineer" (mix of electrical/computer/software + mechanical engineering). So, I am not the guy that has been in the lab with solar charge controllers--So my suggestions are from my other experiences/reading here.

The "big issues" typically with placing solar panels in series is the maximum input voltage (can cause the switching FETs/Transistors/Diodes/Capacitors to fail) and the extra wasted energy from capacitive charging/discharging of the switching transistors (wasted as heat).

Basically, you never want to operate the charge controller over its rated input voltage (whatever that may be).

Regarding input/output current, if the MPPT controller is properly designed, it should automatically (and safely) adjust itself to limit current to its maximum rated output (switching power supplies/down-converters can adjust the current/power flow to the controller's limits. PWM controllers do not have the capability).

Also, when measuring current and voltage, your readings may get a little confused at times. Digital Meters "sample" the voltage readings and depending on the meter and the controller's operating frequencies, it is possible for them to "beat" on each other and you get odd readings (meter/controller near same frequency/multiple of frequency--meter may read all "low voltage" or all "high voltage" of wave form if all in sync).

Also, if you use the meter to measure current, the leads + meter internal resistance can add enough impedance (resistance and inductance) to the circuits to cause the charge controller to adjust its operation--so you may end up with less than normal charging current or other issues.

If you can get a DC Current Clamp Meter (this is a functional DC Current Clamp meter for not too much money--if you were in the US), it will do a better job of measuring current flow.

Also, MPPT charge controllers have more fixed internal losses that can become significant with a small array on a "large" charge controller. So, do not be surprised with a "small array" that you get less than 95% efficiency, especially in morning/evening testing.

Keep charge controller lead to battery bank wiring short and heavy, I would suggest that you design your system to have less than ~0.05 to ~0.10 maximum voltage drop for a 12 volt battery system.

Wiring resistance on the input to the charge controller is less important, but still worthwhile to keep the input voltage drop to a maximum of 3% or less so as to not waste too much power from your solar array (if you can place the two panels in series, that allows you to use much thinner wire because of the higher Vmp-array voltage--Double voltage means 1/2 the current so you can use 1/4 to 1/6th or smaller gauge wiring).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 8
Re: how to check the performance of an MPPT charge controller

bill you have a very right reading experience i am facing the same problem. when i check the current flowing in the battery (with MPPT controller) it shows less current compared with the direct connection of panel and battery. have a look at the battery current graphs of the four systems 1) with out any tracker 2) with MPPT only 3) with sun tracker only 4) with MPPT + SUN tracker

thanks
Re: how to check the performance of an MPPT charge controller

First, what do you mean by "sun tracker"? I assume a moving array (one or two axis) that follows the sun?

In the end, tracker vs more panels is usually a financial question... Is it cheaper to buy a tracker or more solar panels. In the old days, when panels cost \$10 per watt, the cost of a tracker (plus maintenance) was worth the trouble. For smaller systems and with lower cost solar panels, trackers make less sense.

Regarding your chart--It appears that the MPPT controller may be functioning correctly.

The declining power output appears to be the difference between having a charge controller or not connected to the battery bank.

Basically, the MPPT controller will cut down the current into the battery as the battery approaches 100% state of charge.

If you connect the solar panels directly to the battery bank, when the battery is fully charged, the excess energy is simply used to "electrolyze" the water into hydrogen and oxygen. This is overcharging the battery and will cause the batteries to fail fairly quickly with plate erosion and positive plate/grid corrosion (oxygen from electrolysis oxygenating the battery positive plate).

This is a problem with measuring output from solar charge controllers--Batteries are not ideal loads and your system will have varying performance depending on how discharged (and/or what loads you are running) while doing the testing.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 8
Re: how to check the performance of an MPPT charge controller

thanks bill for constantly providing me the good sense and guidance to go through my investigations of solar systems.

I have a single axes solar tracking system which i am using for the analysis. but from graph i am confused that only the sun tracking have greatest performance regardless the issue of over charging the batteries. when i looked through different MPPT performances videos on u tube they compared MPPT performance with PWM controller rather than making direct connections. i think i have to buy a PWN controller to compare the performance again :-(. In conclusion will it not be better if i just develop battery overcharged circuitry and place this sensor in the directly connected solar and battery system so that when overcharging will start it will disconnect the batteries form the solar PV panels?

The "big issues" typically with placing solar panels in series is the maximum input voltage (can cause the switching FETs/Transistors/Diodes/Capacitors to fail) and the extra wasted energy from capacitive charging/discharging of the switching transistors (wasted as heat).

Why this happens?

Thanks
Re: how to check the performance of an MPPT charge controller

I am not quite sure I understand all of your questions/statements... But will give it a go.

A charge controller basically does disconnect the solar charge controller from the battery bank as it approaches full charge. So the output of any charge controller is limited by the battery capacity/state of charge/connected loads. If the battery bank is full before the sun goes down, you will get less than the 100% power that a charge controller/solar array is capable of.

Connecting a solar array hard to the battery bank simple takes regulation out of the equation. At the expense of overcharging the battery bank.

That is why comparing long term power output of a solar charge controller is difficult to standardize.

With a grid tied inverter, those output 100% of the power to the grid--so it is easy to see what different controllers/brands/mounting/weather/etc. does to the overall output.

You could install a diversion controller and set it to a lower voltage (13.5 volts or so) and "dump" the excess current to a resistive load for measurement purposes.

If you want to better understand solar MPPT charge controllers, look up switching power supplies--specifically "buck mode" type. That is the type typically used in MPPT solar charge controllers. The difference is there is a computer that "adjusts" the duty cycle of the buck converter to optimize loading on the solar array (when the battery is less than ~80-90% state of charge).

Buck converter
Switched-mode power supply

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 8
Re: how to check the performance of an MPPT charge controller

i have read the links that you provided me and now feeling quite comfortable. thanks for your help one thing which is a creating a problem for me is that while taking four reading (without any tracker, with sun tracker only, with MPPT tracker only, with MPPT + sun tracker) for my three experimental setups (two 30 watt parallel connected panels, two 30 watt series connected panels, one 60 watt panel), the intensity of light and temperature changes significantly during reading. where as my objective is to investigate all the above three system characteristics for four options at same intensity and temperature level. can you suggest me any method to take these reading with very minimum change in insolation and temperature? thanks
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: how to check the performance of an MPPT charge controller
BB. wrote: »
In general, we have not seen very many true MPPT charge controllers out of China--Especially small/inexpensive ones.

To test the controller, a 30 watt panel is a bit on the small side, and you should really have at least two 30 watt panels you can put in series (assuming each is Vmp~17.5 volts and Imp~1.7 amps).

You would connect the two panels in series to make an Array with Pmp=30 watts; Vmp~35 volts; and Imp~1.71 amps).

With a discharged battery (to keep the charging voltage low), you would connect a DC current clamp meter or Shunt Resistor to measure the charging current into the battery.

If the panels are in full noon time sun, the charge controller is a true MPPT controller, and it is in MPPT mode (discharged battery), you will get roughly:
• 60 watts * 0.77 typical solar panel+charge controller derating * 1/14.5 volts charging = 3.2 amps or so into the battery bank
Note, a true MPPT charge controller takes high voltage/low current from the solar array and efficiently down converts it to low voltage/high current needed to recharge the battery bank.

If you measure Ibatt current >> Ipanel current, then you have a working MPPT charge controller (assuming Vmp-array~35 volts and Vcharge-batt~14.5 volts or less).

If Ibatt = Iarray; then the MPPT controller is operating in PWM mode (battery relatively charged) or it is not a MPPT charge controller but just the cheaper PWM controller all done up with pretty markings.

Many times, you can open the charge controller and see inside. If you do not see large inductors/transformers/toroids of some sort, but just transistors and a few capacitors, then it is most likely a PWM charge controller.

-Bill
hello Bill. Could you please tell me how many solar charge controlers are made in the USA. Not too many. Now next,. to make these charge controllers , ALL the parts are bought from china.. Next so you ONLY think that usa people are smart.Next who's Fault IS it that most of the stuff is made in china. Next seeing you don't like china made stuff, HOW MUCH STUFF IN YOUR HOUSE IS MADE IN CHINA.
I have to admit. i bought a 40 mppt solar controller from china for \$80.00. also it WORKS. I was going to buy a ruge, but he wanted over 3 hundread dollars..
please, everyone has to stop with this stuff, and MAKE it so we have to buy AMERICAN. Also this will bring back all the jobs. oh I guess we will have to hold back the Unions, from RASING all the pays and benifits.
I fought in Viet nam 68-71 for all of us.
Re: how to check the performance of an MPPT charge controller

Just to be clear, many of the "US" manufacturers are making their product in, and buying components from, China as well...

I was attempting to clarify that we have seen quite a few China Direct "MMPT" charge controllers (and "inexpensive MPPT" charge controllers sold by US retailers too) that claim to be MPPT and are not.

I am not trying to say that everything coming from country XY&Z is bad or good... I am trying to education people how they can look past slick marketing literature (® USA) and examine/test the product to see if it meets the claims or not.

I am not going to get drawn into trade wars--A new Smoot Hawley tariff act is probably going to start a whole new set of trade wars and deepen the economic problems that much of the world is in right now.

My wife is Chinese, and my kids are 1/2 Chinese. That much of the western world has moved major portions of their production to Asia is a fact of life.

I tried very hard to address issues in terms of engineering specifications and testing.

This forum is, more or less, non political and attempts to be a technical support discussion board provided to anyone whom cares to post, either questions or answers.

If you have found a good \$80 MPPT controller--You are welcome to start a thread (or continue in this thread) with pictures and specifications/test results that show it working well.

We (I) have been equally hard on USA equipment too:

mppt charge controller (BZ)
opinions about the ecostar mppt charge controllers

And many other issues that have been found over the years.

I have posted links/pictures of Chinese controllers that are both MPPT and PWM (but claim to be MPPT).

--Plus we have always attempted to be practical and not waste people's money telling them to purchase expensive MPPT charge controllers... We give suggestions on which installations would work with MPPT and which would work just fine with PWM.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 125 ✭✭✭✭✭
Re: how to check the performance of an MPPT charge controller

Hello BB. i forgot if i mentioned that I have my zlpower SL-40A hooked up finally and with my panels that I made a few months ago 8 in all so far which are 36 x 3x6 cells , having 2 panels wired in series and then tied together are putting out 35.8volts to the INput of the solar charger which now goes to one small Optima 55AH 12volt battery.My computer that im useing now off this is drawind .63 amp or 50watts, My next step will be more and larger batteries. I want to use common size batteries so that replacements wont be hard to get and local.
When i first hooked it up to the battery the batter was 10.2 volts and from the morring to about 9;30 it was charged. thats when I got up ha ha ha So i guess thats good. Don't know for sure.
John
So far Im happy with my first solar controller
Re: how to check the performance of an MPPT charge controller

conntaxman,

Glad to hear that everything is working well for you... That is why we are here.

And that controller does look like it can very well be a MPPT type charger (from external packaging and specifications). That was one that I used a picture of earlier showing what a true MPPT type controller should look like inside.

Specs are a bit "optimistic" and confused (my specs. in Chinese would not be near as good )--But you already have had some discussions with others on SolarPanelTalk.

Detailed and accurate testing of MPPT charge controller systems is difficult and can require some pretty expensive equipment to properly perform measurements.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset