Charge Controller Does Not recognize correct PV

Douganator

Hey all,
So, I have 2 identical Victron 100/30 MPPT solar charge controllers that work fine on my other panel pair (Unisolar PVL-136)
I have 4 SanTan SST series 250.
I have wired 2 in series and I get around 52v with what sun is left today... but the controller only reads around 27v.
I have tried both controllers... same thing.
I have tried different pairs of the SanTans... same thing.
Anyone have any insights?

Thanks,
Doug

mike95490

What is your battery voltage ?

BB.

Is 52 volts the voltage on the Vpanel input connections for the solar charge controller? And 27 volts from the controller's LCD/Phone app?

What is the current from the panels and to the battery bank during the day while charging?

-Bill

Douganator

mike95490 said:

What is your battery voltage ?

Sorry about the lack of system context.
24v system
Batteries were at about 26.5v when this was tested

Douganator

BB. said:

Is 52 volts the voltage on the Vpanel input connections for the solar charge controller? And 27 volts from the controller's LCD/Phone app?

What is the current from the panels and to the battery bank during the day while charging?

-Bill

52v was what I was measuring straight from the panel wires before connecting to the charger.
Once connected the charger read around 27v on the Victron app
Measurements at the connection terminals was also around 27v

BB.

Do you know how much current was flowing from solar array and/or to battery bank?

Trying to figure out if you have a bad wiring connection somewhere (i.e., very little current flow/high resistance in wiring from array to controller). Check all connections are clean and tight.

Another long shot... Always make sure the battery is connected to charge controller first, then the solar array. And disconnect solar array first and then the battery bank.

If you have a solar array (under sun) connected to the controller and no battery bank... The controller can get "confused" and configure itself incorrectly, and in some cases, even damage itself.

The steps to properly reset controller electrical side:

1. disconnect solar array first
2. disconnect battery bank second
3. wait a minute or so
4. connect battery bank first
5. then connect solar array

Another possible thing to try... See if there is a "reset to factory defaults" in the controller software. On occasion, "computers" can have a corrupted configuration/database and a "clean factory" reset and reconfiguration can fix "odd operations".

-Bill

Douganator

BB. said:

Do you know how much current was flowing from solar array and/or to battery bank?

Trying to figure out if you have a bad wiring connection somewhere (i.e., very little current flow/high resistance in wiring from array to controller). Check all connections are clean and tight.

Another long shot... Always make sure the battery is connected to charge controller first, then the solar array. And disconnect solar array first and then the battery bank.

If you have a solar array (under sun) connected to the controller and no battery bank... The controller can get "confused" and configure itself incorrectly, and in some cases, even damage itself.

The steps to properly reset controller electrical side:

1. disconnect solar array first
2. disconnect battery bank second
3. wait a minute or so
4. connect battery bank first
5. then connect solar array

Another possible thing to try... See if there is a "reset to factory defaults" in the controller software. On occasion, "computers" can have a corrupted configuration/database and a "clean factory" reset and reconfiguration can fix "odd operations".

-Bill

Thanks for your input Bill.
I'm doing this live now...
The charge controllers show current at a measly 0.1A at 33v
When the panels are first engaged, it shows the proper voltage of 62v (now)
Then, the Victron controller does its calcs and we end up at 0.1A at 33v
Also, I have checked my connections as best I can... they seem ok but I suspect there may be some resistance like you mentioned.
Just so you know, when I connect my other, existing panels, all is well but they have different wiring... wiring with no issues for sure.
I may just remake my cabling from the new panels and see what I get...

BB.

Roughly solar panels are "current sources"... I.e., 100% sun, the panel will output Imp=3.15 amps or Isc (short circuit current) ~3.5 amps into a dead short...

More or less, around middle of the day on a reasonably sunny day, you will be seeing somewhere between 50% and 100% on your array... Or 50% of 8.0 amps Imp, or roughly 4.0 amps minimum (assuming controller is in bulk, batteries need charging, heavy load on DC battery bus).

When you see 0.1 amps and 27-32 volts (less than ~Vmp-array) on an MPPT controller under mid day sun on a clear day--Then you have bad panel(s) and/or bad wiring/connections somewhere...

You can set your meter to 10 amp full scale and check the short circuit current on each panel. If you have two or more panels, then checking each one (within minutes of each other) is a good test. Either they are close to each other and >~1.5 amps Isc, or you will find one with "higher" Isc and the other panel with lower Isc... More or less, the Isc of a solar panel indicated how much solar energy is hitting the panel.

If your panels are >10 amps Imp/Isc, then you should look at an AC+DC current clamp DMM. Very easy to "clip" on a cable to test the current, and much higher current limits for meter:

https://www.amazon.com/s?k=Uni-T+B4Q094+UT210E (inexpensive/good enough for our needs clamp meter)
https://www.amazon.com/gp/product/B019CY4FB4 (mid-priced clamp meter)

You can also short the array connections (disconnect from charge controller) and measure the total Isc too.

Note that MC4 and similar type "water proof solar panel connectors" do not last long if disconnected/connected under load. If you can, turn off beakers or throw a dark tarp over panels first.

-Bill