Is MPPT suppose to charge at a higher amperage than the panels give?

[ElectroBlvd]

I have 12x 100w panels running in series 6 parallel 2 going to a Sigineer M3048NC 80a MPPT charge controller. My panels are rated for 18v which gives me 108v with how they are wired. I typically see them running around 103v during peak sun with around 10.8a which is 1,112w. But on the battery side I'm seeing 58.4v with 10.8a which is only 630w. Am I wrong in how I understood a MPPT controller works? Shouldn't I be getting more around 19a to the batteries? My understanding was a PWM controller would lower the voltage to match your batteries so you would lose a lot of the power produced but an MPPT controller would essentially lower voltage and raise amperage to get closer to the max wattage the panels are providing so you're losing less power produced. But I'm not seeing that.

Panel Specs:
18v, 5.56a, 22.5v Voc, 5.81a Isc

 

[Dzl]

What are the specifications of your solar charge controller (specifically max input voltage and current, and max output current rating).

Also what type of batteries and at what state of charge were they when this was measured?

 

[fafrd]

I have 12x 100w panels running in series 6 parallel 2 going to a Sigineer M3048NC 80a MPPT charge controller. My panels are rated for 18v which gives me 108v with how they are wired. I typically see them running around 103v during peak sun with around 10.8a which is 1,112w. But on the battery side I'm seeing 58.4v with 10.8a which is only 630w. Am I wrong in how I understood a MPPT controller works? Shouldn't I be getting more around 19a to the batteries? My understanding was a PWM controller would lower the voltage to match your batteries so you would lose a lot of the power produced but an MPPT controller would essentially lower voltage and raise amperage to get closer to the max wattage the panels are providing so you're losing less power produced. But I'm not seeing that.

Panel Specs:
18v, 5.56a, 22.5v Voc, 5.81a Isc

If your SCC is reporting 10.8A of solar input current at a voltage of 103V, that is 1112W of input power.

And if the same SCC is reporting a charge current of 10.8A at a voltage of 58.4V, that corresponds to output power of only 631W, meaning charge efficiency of only 57% (either impossible or a defective charge controller).

If that were the case, your SCC would be putting out 481W, meaning it would overheat very quickly.

It’s highly unlikely that SCC input current and output current are exactly the same 10.8A, so I suspect you’re confusing your measurements.

Please explain in more detail what you are measuring where (at SCC input/output versus at battery input) and how (equipment display, multimeter, battery monitor, etc…).

I suspect the reality is different than you are reporting…

 

[ElectroBlvd]

What are the specifications of your solar charge controller (specifically max input voltage and current, and max output current rating).

Also what type of batteries and at what state of charge were they when this was measured?

It's a 80a MPPT. 120a max, 40a utility plus 80a solar. Max open circuit voltage for the input is 145v. Max PV power input is 4500w.

 

[ElectroBlvd]

If your SCC is reporting 10.8A of solar input current at a voltage of 103V, that is 1112W of input power.

And if the same SCC is reporting a charge current of 10.8A at a voltage of 58.4V, that corresponds to output power of only 631W, meaning charge efficiency of only 57% (either impossible or a defective charge controller).

If that were the case, your SCC would be putting out 481W, meaning it would overheat very quickly.

It’s highly unlikely that SCC input current and output current are exactly the same 10.8A, so I suspect you’re confusing your measurements.

Please explain in more detail what you are measuring where (at SCC input/output versus at battery input) and how (equipment display, multimeter, battery monitor, etc…).

I suspect the reality is different than you are reporting…

I'm actually not new to electricity or it's testing equipment. I measured the amperage off of each group of panels using a AC/DC clamp meter at the PV combiner box input. Tested the combined amperage using the same meter at the output of the PV combiner box going to the controller. And used the same meter on the cables going to the batteries. All measurements were done on the negative cables. I compared that to the readings on the LCD display of the controller. I did not test voltage from the panels using a meter, I'm going off of what's displayed on the controller. I did test voltage at the output going to the batteries and see approx 58.4v.

 

[fafrd]

I'm actually not new to electricity or it's testing equipment. I measured the amperage off of each group of panels using a AC/DC clamp meter at the PV combiner box input. Tested the combined amperage using the same meter at the output of the PV combiner box going to the controller. And used the same meter on the cables going to the batteries. All measurements were done on the negative cables. I compared that to the readings on the LCD display of the controller. I did not test voltage from the panels using a meter, I'm going off of what's displayed on the controller. I did test voltage at the output going to the batteries and see approx 58.4v.

OK then, it sounds like you know what you are doing. If you’ve only made a single set of measurements, I’d guess that there is a high likelihood that you either clamped onto the wrong cable or got your notes confused (none of us are perfect).

Suggest you take a fresh set of measurements at three times during the day: mid morning, peak sun (midday) and late afternoon.

If you confirm with your clamp meter that input currents match output currents at all three times, you’ve got a defective SCC (though it’s extremely unlikely that that is the case due to excess heat buildup, as I’ve already stated).

You will lose some voltage through your cable drops, so if you fo confirm strange power mismatch once again, you might as well confirm incoming and outgoing voltages at the SCC as well as actual battery voltage at the terminals.

But I’m placing my bets on more careful measurements confirming a mixup in this first set you’ve reported…

 

[chrisski]

I can only confirm that if you’re seeing 1112 watts in from the panels before a MPPT SCC, you will get close to 1112 watts out. THat’s how my four Victron’s work. I’ve got my crate build on now running the crockpot and this is what I see:

Watts from PANELS: 39.52 Volts X 3.6 amps = 142.3 watts
Watts CHARGING: 26.39*5.3 amp = 139.9 Watts

Loss: 4 Watts.

 

[fafrd]

I can only confirm that if you’re seeing 1112 watts in from the panels before a MPPT SCC, you will get close to 1112 watts out. THat’s how my four Victron’s work. I’ve got my crate build on now running the crockpot and this is what I see:

Watts from PANELS: 39.52 Volts X 3.6 amps = 142.3 watts
Watts CHARGING: 26.39*5.3 amp = 139.9 Watts

Loss: 4 Watts.
View attachment 74689

Yes, that sort of mismatch between incoming amperage and outgoing amperage is typical. It is a near-impossibility for them to be identical…

 

[sunshine]

I did not test voltage from the panels using a meter

It is 'watts in watts out' ! The voltage at the panels at that instant would have been the same as the battery V, give or take a little%, if the amps on each side are the same.
Possible the mpp CC is just operating in a closed circuit state, because that is all it is being asked to do by the load. Just as a pwm would do!

 

[fafrd]

It is 'watts in watts out' ! The voltage at the panels at that instant would have been the same as the battery V, give or take a little%, if the amps on each side are the same.
Possible the mpp CC is just operating in a closed circuit state because that is all it is being asked to do by the load.

SCCs need input voltage to be at least ~2V higher than battery voltage to function.

I think we’re all wasting time speculating at this point and should just wait for the OP to report back with a larger set of more carefully-done measurements…

 

[chrisski]

I did not see it mentioned, so if there was a load running like an air conditioner or space heater, this would account for the discrepancy.

 

[ElectroBlvd]

I did not see it mentioned, so if there was a load running like an air conditioner or space heater, this would account for the discrepancy.

Usage (load) is 30w. I'm accounting for load. If I have the AC on I see the charge wattage decrease roughly by the amount I'm using to power the AC as expected.

I can only confirm that if you’re seeing 1112 watts in from the panels before a MPPT SCC, you will get close to 1112 watts out. THat’s how my four Victron’s work. I’ve got my crate build on now running the crockpot and this is what I see:

Watts from PANELS: 39.52 Volts X 3.6 amps = 142.3 watts
Watts CHARGING: 26.39*5.3 amp = 139.9 Watts

Loss: 4 Watts.
View attachment 74689

So that confirms my understanding of how MPPT controllers work to be correct and there is something going on with my MPPT controller where the output wattage is not as high as it should be. To me it seems like it's acting like a PWM controller instead of a MPPT controller.

 

[fafrd]

I did not see it mentioned, so if there was a load running like an air conditioner or space heater, this would account for the discrepancy.

Not if he was reading the negative wire out of his SCC (as he claimed)…

OP, does your ACC have a separate DC load output and is anything powered with it?

 

[Bud Martin]

I suspect measurement error.

 

[ElectroBlvd]

Not if he was reading the negative wire out of his SCC (as he claimed)…

OP, does your ACC have a separate DC load output and is anything powered with it?

There is no DC load output on the SCC. Only AC in, AC out, PV in and battery connections.

 

[MisterSandals]

watts in watts out

MPPT controller where the output wattage is not as high as it should be.

From what I know, if the output measured watts is lower than the input watts, the difference should be released as heat (as are most efficiency losses).

Is there any sign of your SCC getting warm or hot? ~500W should be pretty noticeable.

 

[fafrd]

I suspect measurement error.

Yup, you and me both. I’ve never seen output current equal input current and don’t even know if it’s possible.

My SCC is 97% efficient and requires PV voltage to be at least a 2 volts above battery voltage.

So I suppose that if my string voltage was exactly 103.1% of my battery voltage, input and output currents would match but only if 3.1% of battery voltage is at least 2 volts (meaning a 64.7V battery).

At 48V or 24V, impossibly for output current to match input current (at least with my Epever SCC)…

 

[fafrd]

From what I know, if the output measured watts is lower than the input watts, the difference show be released as heat (as are most efficiency losses).

Is there any sign of your SCC getting warm or hot? ~500W should be pretty noticeable.

Exactly the point I’ve been trying to make…

 

[fafrd]

There is no DC load output on the SCC. Only AC in, AC out, PV in and battery connections.

OK.

When can we expect a new set of measurements from you?

 

[ElectroBlvd]

OK.

When can we expect a new set of measurements from you?

It's 1800hr right now. The sun is down. I'll take pictures of the measurements tomorrow using my clamp meter and what it shows on my controllers LCD display.