Voltage in wrong place

[aKO]

I have an old Style Victron 150-70 Blue Solar MPPT , the one with a small screen and 4 buttons on the front for Setting up , Monitoring and reading History etc . The unit has been performing perfectly until About 2 weeks ago when i removed my 16 assorted sizes Poly Solar panels as they were over 15 years old . I replace them with 4 new large Mono ones of around the same total Wattage , looking at history it was some hours after i had removed the old panels , the first night without any connected ready for the new ones to be fitted the following day that the issue started .

Yesterday i noticed through Victron VRM that the MPPT had voltage at the internal Panel input terminals . Looking back i can see that there has always been just under 2 volts through the nights but now i have 21 volts but no current , i know its the charge controller and not the panel cables that has the voltage in it as i tested it without any panels connected , voltage on the terminals but as i would expect nothing at all on the input cables . VRM shown the voltage is 23 volts if not connected to the panels at night and 21 volts when connected to them . I am really concerned that my new panels are going to be damaged so i disconnect the input cables every night and reconnect in the mornings . The 2 weeks before i had noticed they remained connected with 21 volts which i would imagine travelled through the cables to the panels . The MPPT is showing no sign of being effected in any other way , i have checked the voltages , temperatures , setting points for Bulk and Absorption , Temperature compensation , history , absolutely everything is spot on . Has anyone else experienced this and if so what was the results and what damage did it do .

 

[sunshine_eggo]

First, I assume you wired your panels in such a way as to not exceed either the 150Voc limit and PV input current limit of the MPPT?

Second, there's no way that 21V could possibly hurt your panels UNLESS it's sending actual current through your panels in excess of their rated current. Furthermore, that would be a likely be a very very very rapid drain on your battery, hot PV wires, etc.

Put a clamp DC ammeter on your PV wire and see if there's any current flowing.

 

[aKO]

The new Panels were wired for 100 volts coming in with but the issue came about the night before the new panels were installed and that night there were no panels at all connected to the MPPT . The screenshot is of last night which is typical battery voltage 24.7-24.9 , MPPT input termoals around 21 Volts , both showing 0 Current .

You mentioned " there's no way that 21V could possibly hurt your panels UNLESS it's sending actual current through your panels in excess of their rated current. " so i attached a screenshot of them also in the hope that its not .

 

[sunshine_eggo]

I understood. It's great that VRM says no amps are flowing, and mine says the same, but you should verify that with a clamp DC ammeter.

My 250/100 reports 0-ish V all night long.

 

[aKO]

I only have a Multimeter that reads up to 20 amps , i don't know if it helps or identifies anything but i set it to read Amps and the dial to " mA "and there was a tiny spark when i touched the probes to the terminal and the reading was 0.00 , when i changed the setting to " A "on the Multimeter it read 0.002 . When i removed the panel cables from the terminals it made no difference , still a tiny spark each time with same readings on each setting .

 

[MisterSandals]

I only have a Multimeter that reads up to 20 amps , i don't know if it helps or identifies anything but i set it to read Amps and the dial to " mA "

Can you post a pic of how your probes are plugged into your meter?
Are they in the right place to measure amps?
Having your meter dial on milliamps to measure (up to) 20 amps sounds wrong too.

 

[aKO]

The probes were plugged in exactly as in the photo , the dial also set to where it is in the Photo at " A " with a reading of 0.002 which i took to read 2/1000 amps and also to the setting above it above it " mA" with a reading of 0.00 . The small sparks each time i touch the probes to the Terminals were a bit of a concern that somethings happening .

 

[MisterSandals]

also to the setting above it above it " mA" with a reading of 0.00

Have you checked the internal fuse?

Or test it with something like a AA or AAA battery. I think these read about 2.5A. Its a good sanity check for the fuse.

 

[aKO]

Not sure what you mean . I did test the Amps output on some Solar panels that i had removed , by moving them around facing the sun while adjusting the angle they all eventually raised the output until they showed values reasonable close to the rated figures .

 

[MisterSandals]

Not sure what you mean .

Your meter indicates it has a 20A fuse inside. Its possible this fuse has blown. When this happens the amp reading will always be 0.

You can test the fuse easily by using the meter as you have setup on a regular AA or AAA battery. It should read about 2.5A if the fuse is good. If not, you need to replace the fuse inside.

Some meters have a spare fuse inside.

 

[sunshine_eggo]

You need a clamp DC ammeter.

 

[MisterSandals]

You need a clamp DC ammeter.

I was trying to see if that was AC and DC. How did you determine that it is just AC?

 

[aKO]

Its AC and DC symbols together next to the settings , it recognises which is which when the probes touch and confirms on the screen which it is . Tried about 20 different meters and found this one to be an excellent meter and very accurate with both Voltages . Others mostly good up to 1/10 volt but i wanted better , from the different pieces of equipment and friends Flukes i know it to be accurate to about 3/100 to 5/100 volt DC .

I tried with a new AAA battery as you suggested , went to 2.7A then figures moving around fast settling at 2.6a but the battery was getting noticeable warm .

 

[MisterSandals]

I tried with a new AAA battery as you suggested , went to 2.7A

Ok, the fuse in your meter is good. That was just a sanity check.

So reading from the top, your panels are producing 0A at night. Great.

Second, there's no way that 21V could possibly hurt your panels UNLESS it's sending actual current through your panels in excess of their rated current.

So all is good. Carry on. Those were good observations and good questions to ask.