testing MPPT controller

[tonys681]

Could someone please outline the steps to test if my solar controller is a genuine MPPT controller, I have placed a watt meter between the solar panels and the controller and another watt meter between the controller and the batteries. What figures should i be looking for on the watt meters. They record the volts,amps and watts plus record amp hours and watt hours. Should the batteries also be discharged for the test and should there be any load on the batteries during the test. Any help would be appreciated.

[Mike90250]

Decent MPPT controllers are >90% efficient. So if you have 300 watts input, you should have no less than 270 watts leaving the controller.

Input voltage should be close to the panel's Vmp, and output voltage should = battery voltage.

[tonys681]

Decent MPPT controllers are >90% efficient. So if you have 300 watts input, you should have no less than 270 watts leaving the controller.

Input voltage should be close to the panel's Vmp, and output voltage should = battery voltage.

Thank you for that information, i assume vmp means maximum volts. How will amps be represented by the figures to and from the controller ?

[Sunking]

First your test is the wrong way to go about it. Second the conditions have to be right before you can even perform such a test to obtain valid test results.

Fist you used the wrong meter, you should be using an Amp Meter, two of them so you can make simultaneous reading. One between panels and controller, and another between controller output and load (battery). But the battery alone is not enough. You also need a load turned on and operating at a significantly higher power level than the panels are producing. Battery alone is not going to work well if at all depending on its state of charge. If the battery is 80% or higher little to no current. To ensure you draw maximum power the load has to be there demanding more than the panels can supply.

In a nutshell the controller ouput current shall be higher then input current. How much depends on panel Vmp and battery voltage. For example lets say you have a 100 watt panel with a Vmp of 17 volts producing full power into a 12 volt battery. You should observe a panel current of roughly 5.8 amps and a battery current of 8.3 amps. Another example same test except a panel Vmp of 34 volts and you get 2.9 amps in and the same 8.3 amps to the battery. If you se that then you have a true MPPT controller.

On the other hand if you see that Input Current = Output Current or less, then you have a PWM controller. So lets go back to my first example using a 100 watt 17 Vmp panel. You would see roughly 5.8 amps going in and 5.8 going out for a whopping total of 69 watts.

[Mike90250]

Thank you for that information, i assume vmp means maximum volts. How will amps be represented by the figures to and from the controller ?

Vmp = Voltage maximum power Should be a sticker on the back of the panel.

Keep in mind, this is a very gross test. factories use test equipment that costs 100's of thousands of dollars. You can "rig up" something in your garage, but still need several hundred dollars of gear. if you really have a pair of DC watt meters, you are on your way.

[tonys681]

Many thanks for that reply. Yes i do have two watt meters that record amps and amp hours. The problem i have is that i do not know the capacity of my solar panels. They are attached to the roof of my motorhome and cannot be removed. I am guessing that they are about 350 to 400 watts. What sort of load would you suggest for this capacity. I have a 800 watt inverter attached to the batteries so i could use this to create a load on the batteries. What voltage do you suggest i should bring my battery down to prior to running the load?.

[Mike90250]

..i do not know the capacity of my solar panels. They are attached to the roof of my motorhome and cannot be removed. I am guessing that they are about 350 to 400 watts. ...

Nope, the largest panels they started making last year, were 250w I suspect they are no more than 200W each. Flat on the roof, they will not make full power for you, they need to be angled into the sun at a right angle. Hard to do with a motorhome.

[tonys681]

Nope, the largest panels they started making last year, were 250w I suspect they are no more than 200W each. Flat on the roof, they will not make full power for you, they need to be angled into the sun at a right angle. Hard to do with a motorhome.

Sorry i should have said i have four solar panels with total watts approx 350-400. Can i still check for MPPT even if i do not know the specifications for the panel.

[Pat_B_MN]

What is the brand and model number of your controller? SHould be a simple matter to look up the specs...

[tonys681]

What is the brand and model number of your controller? SHould be a simple matter to look up the specs...

The specs are at this link:http://rittalups.en.alibaba.com/prod...ontroller.html

Although i should mention there are no copper coils in the controller they sent me, even though i ordered it exactly as per the specification

[tonys681]

sorry this is the link

http://rittalups.en.alibaba.com/product/961043241-212463933/12V_24V_40A_with_built_in_copper_coils_MPPT_solar_charge_controller.html

[tonys681]

it does not seem to want to allow me to attach the link

http://rittalups.en.alibaba.com/product/961043241-212463933/12V_24V_40A_with_built_in_copper_coils_MPPT_solar_charge_controller.html

try again

[russ]

it does not seem to want to allow me to attach the link

http://rittalups.en.alibaba.com/product/961043241-212463933/12V_24V_40A_with_built_in_copper_coils_MPPT_solar_charge_controller.html

try again

If you want a boat anchor you can find one far cheaper than that. Buying through Alibaba for this type of equipment will get you burned for sure!

[SunEagle]

At that price it is more than likely a false MPPT type charge controller. Unfortunately there are a lot of places on line that sell them and seem not to get penalized for false advertisement.