Voltage drop, low charge power

[Vic]

OK Jose,

That almost looks like the STC string Voc.

But,   in any event,   strings of three is about the best that  you can do ...   think that SW 295s are 60-cell PVs.   Will look them up.

Thanks,   Vic

[Jose Miranda]

OK Jose,

That almost looks like the STC string Voc.

But,   in any event,   strings of three is about the best that  you can do ...   think that SW 295s are 60-cell PVs.   Will look them up.

Thanks,   Vic

Yes they are 60 cells.

[Vic]

Jose,

The STC Vmp of SW 295s is 32.3,   so strings of three have an STC string Vmp of essentially 97 volts.    As perfect as you can get on a 48 V system.

Thanks,   Vic

[Jose Miranda]

Jose,

The STC Vmp of SW 295s is 32.3,   so strings of three have an STC string Vmp of essentially 97 volts.    As perfect as you can get on a 48 V system.

Thanks,   Vic

I gave you wrong numbers.

My panels are the SW 295W, Vmp 31.5

[Vic]

Jose,

The differences between these exact PVs are quite small.

In looking at the SWA 295 Mono Black vs the 295 with natural frame color  is 0.1 Vmp.   Really matters not.  Still see SW 295 at 32.3,  vs 32.4 for the Black frame.

Your strings of three 60-Cell PVs on a 48 V system really is perfect with a Classic 150.   Strings of two = string Vmp too low,   strings of four Vmp  too high.   3=perfect.

FWIW,   good luck with the system.      Vic

[Vic]

Jose,

The STC Vmp of SW 295s is 32.3,   so strings of three have an STC string Vmp of essentially 97 volts.    As perfect as you can get on a 48 V system.

Thanks,   Vic

I gave you wrong numbers.

My panels are the SW 295W, Vmp 31.5

OH,  now I understand,   had thought you meant that you had given incorrect PV model numbers   ...   obviously (to me,  now),   that you were referring to incorrect total Vmp.

Thanks,   and have fun with the system.     Vic

[Jose Miranda]

Hello. I'm back. And still not having fun.

Everything is working fine with my system, except charging from the panels. I'm not sure what's going on. The system keeps jumping from Resting to Bulk. When it's in Bulk mode it only seems to be putting about 15W to the batteries. They are not charging. The charger mode is on. Battery charging parameters are to spec. Battery capacity is set correctly. I don't know what's going on. I can charge the batteries just fine using the inverter (it's currently set to charge during the night, in case there wasn't enough sun light to charge during the day).

[Vic]

Hello. I'm back. And still not having fun.

Everything is working fine with my system, except charging from the panels. I'm not sure what's going on. The system keeps jumping from Resting to Bulk. When it's in Bulk mode it only seems to be putting about 15W to the batteries. They are not charging. The charger mode is on. Battery charging parameters are to spec. Battery capacity is set correctly. I don't know what's going on. I can charge the batteries just fine using the inverter (it's currently set to charge during the night, in case there wasn't enough sun light to charge during the day).

Jose,

When the Classic is putting 15 W into the batteries,  what is the charge Stage?
What are the Classic Firmware Version numbers for the Classic,  MNGP and Network?
What is the charge Mode that you are using?
What are the Hydrometer readings for battery Specific Gravity (SG)?   Asking if the battery needs some charge at that time.   You need a good quality glass type Hydrometer   with what appear to be Trojan Flooded batteries ...

Later,  Thanks for any added info.    Vic

[boB]

Jose, when you see less than around 20 watts for around 90 seconds, the Classic will go to resting and wake up again so many seconds later like, maybe 10 to 20 seconds later...

The question is, why are you only seeing 15 watts ?   If the stage is BULK MPPT, then you will need to evaluate the PV input voltage that the controller is running at.
Please take note of the PV input voltage in Resting mode (the Voc) and the PV voltage when in BULK MPPT and let us know what that is.  This will give us an idea on the tracking of the PV array.  Sometimes this can indicate various issues as partial shading and even bad connections or defective Classic.

Also what is the Classic's output current and battery voltage ?

Thanks,
boB

[Jose Miranda]

Jose, when you see less than around 20 watts for around 90 seconds, the Classic will go to resting and wake up again so many seconds later like, maybe 10 to 20 seconds later...

The question is, why are you only seeing 15 watts ?   If the stage is BULK MPPT, then you will need to evaluate the PV input voltage that the controller is running at.
Please take note of the PV input voltage in Resting mode (the Voc) and the PV voltage when in BULK MPPT and let us know what that is.  This will give us an idea on the tracking of the PV array.  Sometimes this can indicate various issues as partial shading and even bad connections or defective Classic.

Also what is the Classic's output current and battery voltage ?

Thanks,
boB

Bob,

Voc=~110V
When in bulk stage the voltage gets down to around 54 to 56 V. Current is around 0.1 to 0.3 A.

Partial shading is impossible in my case, as there is nothing to cast shadows around the panels.

I think I mentioned it earlier, but this is a pre-assembled system. The Classic 150 and Schneider SW4048 comes pre-installed on a Midnite E Panel. So if there is anything installed wrong, it has to be the PV cables (it's impossible to put the batteries cables wrong, plus I know they are charging with the inverter). However, the MN E Panel is really easy to install. Everything is labeled. And the charger is seeing the panels Voc... I doubt I got a defective unit, since it is tested before shipping... I made a ticket with Midnite. I am planing on staying at home tomorrow, or coming earlier from work, in order to solve this with MN.

[Jose Miranda]

I am really hoping this is a settings issue...

[Vic]

Jose,

AND,   Please check the PV Combiner box  wiring,   and each connection in the Combiner  (the breaker connections,  and at the negative busbar).   These need to be tight.   These connections will loosen with the passage of time.

With strings of three of these PVs,   the voltages at the combiner are high enough to possibly be LETHAL,   so be very careful (or ask your electrician)  to check these.

Also,  please check the connections of the cables that attach to the input breaker in the MidNite Panel,   and the connection to the battery breaker.

You could switch off the breakers in the Combiner,   and make certain that each string of PVs is showing similar Voc readings.

Also check where the PV cables connect together for each string.   Make certain that  MC4 connectors on each PV are tight.

There was an early version of Classic Firmware that would Sweep the PV input voltage down to about 5.5 volts above battery voltage,   and hang there.   In those cases,   IIRC,   the PV production was very low   ...
SO,  please DO let us know the Firmware version numbers.

Speaking of Settings,   what IS the Setting for Absorb voltage in the Classic?

ANY shading of the PVs,   at all  will usually diminish PV production by large amounts.

Thanks,   Vic

[boB]

Bob,

Voc=~110V
When in bulk stage the voltage gets down to around 54 to 56 V. Current is around 0.1 to 0.3 A.

Partial shading is impossible in my case, as there is nothing to cast shadows around the panels.

I think I mentioned it earlier, but this is a pre-assembled system. The Classic 150 and Schneider SW4048 comes pre-installed on a Midnite E Panel. So if there is anything installed wrong, it has to be the PV cables (it's impossible to put the batteries cables wrong, plus I know they are charging with the inverter). However, the MN E Panel is really easy to install. Everything is labeled. And the charger is seeing the panels Voc... I doubt I got a defective unit, since it is tested before shipping... I made a ticket with Midnite. I am planing on staying at home tomorrow, or coming earlier from work, in order to solve this with MN.

OK, this sounds like a possible bad  PV connection, given the numbers you gave me....  Voc = 110 and Vmpp = 56V

Normally, the maximum power point voltage should be somewhere around 78% of Voc and that would be in the 80V range.

One thing I would try is to change the MPPT MODE in the Classic from SOLAR to Legacy P&O and see where the input voltage ends.

If you are getting similar results in full sun, then you most likely have a bad PV connection somewhere.

Even if the Classic was mis-tracking in SOLAR mode, you should be getting a LOT more power than 15 watts even at that PV input voltage so I am guessing loose connection or bad circuit breaker or something like that.


boB

[Jose Miranda]

Voltage went up to 74.2V.

[Jose Miranda]

By the way, it's 5 PM here... Almost no sun. But still goes from 56 to 72V.