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photo2000a avatar image
photo2000a asked

help w/Victron Energy SmartSolar MPPT 75V 15 amp

hi. i am new to solar and. hit a wrinkle that i hope is something simple/obvious i might have overlooked.

Using 2 solar panels 12v. i measured the output of ea. and was getting about 15v. I hooked them up in series and measured 30v. thought i was good.

plugged it into my Victron Energy SmartSolar MPPT 75V 15 amp controller, and measured across. the terminals and got about 12.5v. the bluetooth app showed same.

so i unplugged the solar panel measured across it again. 30v. so it seems once i plug it into the controller the pv terminals show 12.5. I measured the battery. and load terminals. got about 12v using it w/a 12v battery which for testing i did. disconnect and i had no load connected just a volt meter.

any ideas. why the controller isn't sending power to charge the battery w/30v from the solar. should be enough to activate the charge ckt, but. dunno why. i am not measuring 30v at the pv terminals when i plug it in

anyone have any ideas what i did wrong?

thanks

setup
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5 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

The manual says to always connect the battery first. So I would say you should try it again with the battery connected.

If you still get the same result you may have damaged the MPPT as you connected PV without the battery.

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Hi thanks for the responce, the battery was connected when i added the solar


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Check the fuse at the bottom of the MPPT.
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pwfarnell avatar image
pwfarnell answered ·

What Ah rating are the batteries, how charged are they, what power rating are the panels and how much light was reaching the panels when you connected them. Check on the phone what current was flowing. Also check all your connections for a poor joint, a poor joint may show 30V when the MPPT is disconnected but when the system tries to draw current, the high resistance of the poor connection creates a high voltage drop.

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hi, the single battery is. a 12v agm battery 18amp. was originally. 13.8 since dropped to 12.5. I am not sure how to quantify how much light is hitting the panels but as above. ea panel was measuring 15v at the time i was testing, it was a somewhat overcast day. the panels (2) are https://www.amazon.com/dp/B07C34GHGV?psc=1&ref=ppx_yo2_dt_b_product_details.

The cables are rock solid i just took them apart. look solid. good idea I did set the battery profile in the app to match my battery. I just can't figure what might cause the 30v to drop to 12.5 like that when attached to the controller. a single cell connected to the controller matches the panels output ie if a single panel is doing 15 and i connect it alone, measure across pv terminals. its about 14v

thanks.

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For the controller to operate, the panel voltage needs to be 5V higher than the battery. When you put one panel onto the controller at 15V it will not start to charge, so there is no current flowing so the voltage remains high at 14V and is not charging.

When you put two panels in series the 30V will start the controller charging so the voltage drops down below 30V but it should not drop as low as 12V. This indicates that the panels are broken or there is a poor connection with high resistance or the panels are not getting enough light (are you testing them indoors).

You can do another test if your multimeter can measure current. Do the open circuit current test by connecting the panels to the multimeter in current measurement mode rather than voltage (search for YouTube videos) and you should measure 2 to 3 amps flowing as long as you have enough light. You could measure each panel on its own and then both connected together. This will tell you if you have working panels and no high resistance connections.

Another test is measure the battery voltage without the solar power then connect the two panels and then measure the battery voltage. If it is charging then it should increase.

To do more trouble shooting you need to look at the LED lights on the controller and compare these to the manual which will tell you if it is charging or not. You also need to connect to the controller with your smartphone using the VictronConnect app and that will tell you the panel voltage, battery voltage and current flow from the panel to the controller and controller to the battery. That would make trouble shooting a lot easier.

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photo2000a avatar image
photo2000a answered ·

hi. thanks. i made a few more measurements today based on advice. and fact the sun is out.

Measured ea panel individually. volts 20v switching to the amps as in the video which said to measure directly across the terminals not sure that is safe but tried it. i got. .040 ea panel. i was expecting 2 or 3 amps. i got. the first panel little over a month ago. 2nd panel few days. ago. diff vendors. both panels seem to have same issue. not sure odds of that. but. they physically look excellent the controller. always says charger off. which i would expect w/it showing 12/to13v.

still puzzled why when i hook them up in series the controller shows 13v vs. 30~. guessing we have narrowed the problem to the panels. any other tests anyone might recommend. appreciate the tips.

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The panels have a poor contact in them somewhere. The voltage falls because the controller is trying to take more current than the 0.04 Amps the panels can supply so the voltage collapses. The only thing i can suggest you check is the connections in the black box if they open easily and see if you can test the amps on those terminals to confirm if there is a wiring problem or a problem in the panel itself. Or just try and get a refund.
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photo2000a avatar image
photo2000a answered ·

i did the ohm test. was zero one way. and 5 reversed. on both. can someone confirm if it seems like both panels are bad based on the results. of the suggested tests. do we have enough tests. to point me? at this point would it be safe to assume i do in fact have 2 bad panels? embarrassing and costly if i send them back and they are not broken. But seems between the amps measurement and. etc. seems. defective. welcome thoughts

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I have no idea what the resistance should be, as I wrote earlier all you need to test is the voltage and current with a multimeter, so it depends on if you had the correct type of meter and know how to use it especially to read the current, settings must be DC volts and DC amps.
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photo2000a avatar image
photo2000a answered ·

one last try. any further tests. or tips. or could someone share there option if sending it back maybe best at this point?

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Hi Photo2Ka ! I had such kind of issues due to a DOA diode. and another which was not correctly soldered. You can open the black boxes in the back of the panels, take a visual inspection if any diode is free, then check with the multimeter in Ohm position, it should give a value in one way, and nothing in the other (diodes schottky are used to avoid current coming back). If they are wrong mounted, or damaged, this can be the issue.


I will also recommend to check every link from the plug into the panel's box, as the connector itself could be damaged or wrong mounted. Take a look at the polarity if it is the correct one or not (I had some panels whose connectors were mounted inverted !!!)

Due the checks and report the results. thanks,

Michel

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