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geep avatar image
geep asked

Blue Solar MPPT 100/50 low output?

Recent purchase of this controller and two 170 Zamp panels. Hooked up first one, showed 65 watts, 20 volts, charging two lead-acid batteries in parallel. Added the second panel, and no change in wattage. I'd expected it to double. Panels wired in parallel for 12 volt system. Tried another battery that was completely discharged with similar results. I don't understand why the power level did not increase with the second panel, unless the controller is limiting not only the voltage to the appropriate level but also regulating current to a level appropriate for the battery load. The app was showing a bulk charge rate of about 4 amps. New to solar, trying to learn! Thanks

battery charging
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3 Answers
mattsmith avatar image
mattsmith answered ·

I had similar issues. AGM batteries wired in series and parallel. 24v and 320amps with four 230w panels. Highest charge rate I saw was 600w changed wiring etc, nothing helped. Finally replaced the batteries with LifePo4 and bingo, full charging rate achieved. It was the batteries ability to take the current causing the limit.

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geep avatar image geep commented ·

I hope I will see the same. I've been testing on marine batteries, and wondering if the charger was limiting the current output. You've confirmed that may be the case. Getting ready to finish the installation, and I will report back with how the system works with parallel wired panels and the LiFEPo4 Battle Born batteries. I've read the comments on series wiring the panels as well as done some more research, and have found that the MPPT equipment does function differently from PWM modules, making series wiring more attractive. I will continue to experiment. Thanks all who have answered.

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mattsmith avatar image mattsmith geep commented ·

I also run a Victron balancer, IMHO cheap insurance for expensive batteries. :)

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Correct polarity? Can you check the PV-voltage?

You can wire the Panels in series, the MPPT 100/50 can handle up to 100V PV-voltage.

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geep avatar image geep commented ·

Wiring is correct. I don't need higher voltage, they are in parallel to obtain higher current. I have a 200 amp hour LI 12 volt battery bank in a camper that I want to charge, need the higher current capacity to bring them back up. Thanks for commenting.

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geep avatar image geep geep commented ·

And I am seeing 20 + volts on the panel side in the app, about what I expected for late afternoon sun. They are rated at 23 volts max. Just not seeing the current output I would expect, and suspect that the charge controller is limiting current.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ geep commented ·

A higher PV-voltage don't change your charge current.

With the higher PV-voltage the MPPT will start earlier in the morning and charge longer in the evening.


Is the a fuse or switch between MPPT and battery?

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geep avatar image geep Matthias Lange - DE ♦ commented ·

Panel cables are fused vat 15 amps. No switch or fuse between the charger and battery. There will be a switch when I get done as the panels will not be permanently affixed to the camper.

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solardude avatar image solardude geep commented ·

Wiring in series has many benefits with zero downsides. Watts are the product of amps x volts. Watts are the true measure of power. If you you raise your voltage by wiring in series, you will get less voltage drop(more efficient), better morning and evening charging, and will net you more watts total during the day.

Just because you have more amps, doesn’t mean you are charging faster. Voltage has to be factored in as well.

Maybe try each panel separately and see if they both work as expected. If they do, wire in series. You will be much better off that way.

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geep avatar image
geep answered ·

As noted above, connecting the array to a lithium ion battery bank and putting in the correct settings cause the current level to do what I expected. I have the panels in parallel, and note that under heavy load, the voltage does drop way down. As several have suggested, serial connections could be a better, more efficient way to go, so I am going to experiment with that hookup and see what happens. However, I am able to charge the batteries as well as provide reasonable reserve to run DC circuits such as lighting, as well as AC loads with the Xantrex inverter and keep up with the solar charging no matter which wiring scheme I decide on. Thanks for the help.

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