What is my PV array doing?

[mesquito_creek]

48v mpp LV6048 inverter.... When I measure amps across + and - from my PV array I get 36 amps. When I measure volts I get 96... but my mpp solar display Shows 96 volts in and 56 watts of charging power. My batteries are low at only 47.5 v... I expect to see 3000+ watts of charging power? Any idea what is going on? Does the mpp charger trickle charge or something until the battery gets more charged up?

 

[MichaelK]

I'm not sure what kind of meter you are using, but I believe you are measuring the amperage incorrectly. My multimeter requires that the testing electrodes be connected in series for accurate measurement, and you can only measure between 10 to 20A, depending on the meter. You appear to be making your measurement in parallel. I've never see a meter that could read more than 20A, so your value of 36A is suspect.

Was the red test electrode wire plugged into the port marked 10A or 20A, or was it plugged into the port that is commonly labeled as VΩ? For any kind of measurement, the black wire is always plugged into the port marked as COM.

For serious amperage measurements, a clamp meter is a far better choice. Here's an example of a clamp that reads both ACamps and DC amps. The proper use of the clamp requires you to clamp over only one of the two wires leading through a circuit. So, you can't use a clamp on a power cord because the two opposing wires inside the cord cancel each other out.

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[mesquito_creek]

Ok... thanks for the help. I have an amp clamp, but when the clamp read less than 1 amp on my 4000 watt array I was suspect and used the probs. And of course now there is no sun so not much I can do now...

 

[MichaelK]

Ok... thanks for the help. I have an amp clamp, but when the clamp read less than 1 amp on my 4000 watt array I was suspect and used the probs. And of course now there is no sun so not much I can do now...

Ok, then something weird is going on? How many panels in how many strings do you have? Do you have strings of three panels that are supposed to be putting out 96V? There could be some kind of fault that "confused" the electronics. The very first thing I would suggest is doing a full shut-down, which would include disconnecting the battery connection.

Here's what I would do. Tomorrow morning, start by switching off the main AC-to-house breaker, then switch off the solar breakers (are there breakers?), then switch off the inverter, then disconnect the battery terminal to the inverter, so the unit is totally without power.

After a minute or two, reconnect ONLY the battery to the unit. You may need a resistor (lightbulb) in line for bringing your capacitors up. After the battery is connected, press the "ON" button and power up the unit. If it boots correctly and displays the battery voltage, flip the solar breakers back on one by one. Check as you close the breakers whether or not the amps coming into the system is going up. If you see the amperage going up, then the system just crashed in some way and needed a reboot.

If you do not see amperage increasing, you need to check each solar string for bad connections, and/or wire breaks. Does everything look clean, or are terminals corroded?

Once you think everything is OK, you an flip the main AC breaker back on to send power to the home. You might want to unplug as many things in the home as you can so the startup surge is not too high.
Good Luck!

 

[mesquito_creek]

I have a 10 panel array. Each panel is 400 watts. Wired 2S5P.

It’s morning, low sun but clear and cool. Panels have low sun angle, like 8 am sun

1). I wire the first two panels in series. Measure volts for polarity. 97 positive volts. I measure 0.8 amps.
2). I wire the second set of two panels in series. Measure volts for polarity. 97 positive volts. I measure 0.4 amps

This continues as I wire the rest of the panels with the amps seemly being split between the array. I expect the amps to increase as I add panels? Could my array just be to cold and not getting enough sun and is what I am seeing correct? Should the amps increase as I add panels even in very low early sun?

 

[mesquito_creek]

My panels are wired parallel at a combiner box into a positive buss bar and a negative bus bar. From there I have a single positive wire and negative wire running 50 feet to the inverter. I have a Klein cl800 amp clamp. When I measure the positive wire going to the inverter I only see .8 amps. Is my array just not producing power yet?

I have no load connected.

 

[mesquito_creek]

My battery bms does show 56v which is good I guess, which suggests it’s charging, but I just expect to see more from the array...does the mppsolar display maybe only show what is being consumed? With no load maybe all I can measure is what is being used. I expected to see and measure all the PV amps at the distribution box regardless of what the inverter is doing but maybe that is flawed thinking

 

[MichaelK]

If your panels are facing South, then their amperage output at 8am should be quite low, I'd say maybe about 5-10% of nameplate. The panels actually produce more voltage at cold temperatures, though that's not what's important now. The amperage will be low because the sun is at such an acute angle to the sun.

I think we will just have to wait till later in the day when the sun is at a more obtuse angle to the panels. But, these numbers appear low even for 8am. Assuming the panels are putting out ~7A at noon, I'd expect at least 0.7A from each string? For 5 strings, I'd expect maybe 3.5A. Can you take a pic of your combiner box, showing us the wiring?

One thing you could do later in the day is measure the amperage of each individual string before they get combined, then also measure the positive output wire from the combiner. It should be the sum of all the individuals. If it is not, that suggests a connection problem somewhere.

In the mean time, while waiting for the sun, I could suggest taking a screwdriver and CAREFULLY torc down each connection screw. Be very careful that you don't cause any arcs!

The fact that the battery is going up to 56V is a good sign. Perhaps the system is charging, but there is a bad connection somewhere? To really tell what the performance of your panels is, what you need to do is monitor the amperage/voltage before and after a large load is applied to the system. A toaster oven is a good load. Plug in the oven, and monitor output before and a few seconds after turning on the oven. Right after switching on the oven, you should see some voltage drop, and a big jump in amperage. If you do not, there's still a problem.

 

[mesquito_creek]

I checked the open circuit voltage at the busbar connection point with each two panels wired in series before connecting to the bus and got 97v each time which is what I expected. Not sure if that is a valid good connection reading... I have not waterproofed the combiner yet, just open door connecting for testing

 

[mesquito_creek]

I actually think things are sort of working... but my 48v bigbattery shipped dead 42.8v it now seems to not want to go above 47v. But today is the first day of 100% charging hooked to the pv array. Up until now I have been using a a little generator and off and on solar tests with 2 panels just using what I had available. I just have no idea what to expect to get a full charge with all the things like the battery bms and the mppt doing bulk off and on with its smartness etc..

 

[mesquito_creek]

I have one of these 15 amp fuses in line at each series pair and this is perko is what I have on the main pv line between the array and inverter for a dc cutoff

 

[MichaelK]

Glad that it is starting to come together now. What I would suggest is that you go into the BigBattery specifications and find the maximal charging values for bulk, absorb, and floating. I'd guess that once you get those parameters exactly set you'll get up to full charge.

I'm really glad you mentioned the fuses in-line with each string. As it is wired right now, your combiner would be considered unsafe if you did not have them.! Here is a pic of a Midnight combiner, which shows two different brands of breakers being used. Breakers are great for when troubleshooting needs performing. You have to be very careful about arcing when you disconnect solar leads under load.

With this Midnight combiner, you'd attach your negative solar leads exactly like you did on the left-side buss, but the positive wires should be screwed into the screw terminals at the bottom of each breaker. The top of the breaker buss (the big screw to either the left or right) then leads the combined amperage off to the controller.

 

[mesquito_creek]

I bought all the panels from Santan solar and they said these fuses and a buss bar would be ok! I like the breakers also... maybe after the first round of spend I can upgrade later.

 

[cgreen]

Hey, mesquito_creek... Did you ever figure out why you're getting such low amps? I'm having a similar issue. When I test each string individually, I get ~12A (supposed to get 18.46A but I have some slight shading issues right now). When combined, I'm reading 25A from my PV array. But the all-in-one inverter is only showing about 6A. I'm not losing any voltage, only amps. It doesn't matter what the battery's state of charge is, nor the load on the inverter... the amps stays the same. The highest I might get throughout the day is 12A when there's no shading, but I should be getting twice that! Any thoughts?

 

[mesquito_creek]

I had my mppt controller set too low so I was not allowing the PV array to flow into the batteries. Once I set it to 200 amps of charging it now pulls 90% of the PV in the right conditions

 

[cgreen]

I had my mppt controller set too low so I was not allowing the PV array to flow into the batteries. Once I set it to 200 amps of charging it now pulls 90% of the PV in the right conditions

Hmmm... My all-in-one inverter doesn't seem to have a setting in order to make that adjustment. Do you remember which setting you found that under on your MPPT?

 

[mesquito_creek]

#2 on a mppsolar LV6048 … but I have four 48v 5.3Kw batteries. Each takes 45 amps avg. of charging for 180 amps total.