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

[fafrd]

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.

Cool. Hopefully we can help you to get things sorted out tomorrow (if any mysteries remain).

 

[ElectroBlvd]

So I went out to my trailer to send pictures of all the tests and now it wants to all show up correctly. String 1 was sitting at 3.4A, string 2 at 3.28A. Total, the panels were at 107V at 6.36A. From the controller to the battery I was getting 11A at 49.7V. So that shows my panels were providing 680.52W and I was charging at 546.7W. I have no idea why my several previous tests showed the input at 10A and output at 10A and now it's showing input at 6A and output at 11A. But I guess it's working properly now, or its always been working properly and I'm just an idiot.

 

[chrisski]

I only have my example to base this off, but my input and output from post #7 was 1% off. Your input is closer to 19% off. 135 watts is still a bunch of heat being lost. Enough to cook in my 4 quart crock pot on low.

 

[fafrd]

So I went out to my trailer to send pictures of all the tests and now it wants to all show up correctly. String 1 was sitting at 3.4A, string 2 at 3.28A. Total, the panels were at 107V at 6.36A. From the controller to the battery I was getting 11A at 49.7V. So that shows my panels were providing 680.52W and I was charging at 546.7W. I have no idea why my several previous tests showed the input at 10A and output at 10A and now it's showing input at 6A and output at 11A. But I guess it's working properly now, or its always been working properly and I'm just an idiot.

Sounds like your mystery is solved .

And none of us are idiots (hopefully) but none of us are perfect.

546.7W / 680.52W = 80.34% efficiency (which is still low).

First, if you check voltage at the input wire into the SCC (or what it reports), you will see it is lower than the voltage coming out of your combiner box (losses of ~3% are not unusual).

Second, when you state ‘from controller to battery’, is that measured at controller output or battery input? If you measured at battery input, there are more losses in those cables and as measurement directly at SCC output will give you a more accurate read on it’s actual efficiency.

Then depending on your SCC you can see what ‘max efficiency’ it specifies and discover how much worse the reality is than the specification.

Even if you measured voltages at combiner output and battery input and you have 3% losses in both sets of cables, that would still translate to 563.61W / 660.10W = 85.4% efficiency from your SCC.

That’s still pretty piss-poor and I’d still be concerned that 96.5W would hear it up over time…

As a reality-check, my 1000W GTILs are only 80% efficient and when they are taking in 1000W of battery energy to put out 800W of 120V AC, that 200W of internal heat causes the cooling fans to kick-in.

 

[fafrd]

I only have my example to base this off, but my input and output from post #7 was 1% off. Your input is closer to 19% off. 135 watts is still a bunch of heat being lost. Enough to cook in my 4 quart crock pot on low.

I agree.

Would be helpful to know what SCC model the OP has, what efficiency rating it specifies, and whether is has active cooling with fans or just passive cooling like most typically-efficient SCCs (my Epever 60A SCC has passive-cooling only but specifies efficiency of 97%…).

 

[ElectroBlvd]

I only have my example to base this off, but my input and output from post #7 was 1% off. Your input is closer to 19% off. 135 watts is still a bunch of heat being lost. Enough to cook in my 4 quart crock pot on low.

Honestly I wish I would have just got a Victron system now that I have a better understanding of how it all works. I also wish I would have gotten a 24V system instead of 48V. But at the time I was a bit intimidated and decided to just go with an all in one unit. I kept seeing Sigineer everywhere on Amazon and YouTube so I went with it. And I got these cheap panels off Amazon before I saw Will Prowse links to some better cheap panels....All in all I feel I wasted a lot of money but I'm just trying to make the best of it.

As far as the 135W lost goes, idk? It's not running hot. I don't know 100% if the fans are heat based or load based but they seem to be heat based and stay on low majority of the time. Once in a blue moon I'll hear them kick on high for a little while but then they go back low.

 

[fafrd]

Honestly I wish I would have just got a Victron system now that I have a better understanding of how it all works. I also wish I would have gotten a 24V system instead of 48V. But at the time I was a bit intimidated and decided to just go with an all in one unit. I kept seeing Sigineer everywhere on Amazon and YouTube so I went with it. And I got these cheap panels off Amazon before I saw Will Prowse links to some better cheap panels....All in all I feel I wasted a lot of money but I'm just trying to make the best of it.

As far as the 135W lost goes, idk? It's not running hot. I don't know 100% if the fans are heat based or load based but they seem to be heat based and stay on low majority of the time. Once in a blue moon I'll hear them kick on high for a little while but then they go back low.

As I just posted, you’re likely only generating closer to 95W of heat than 135W. And as long as you’ve got active heating and fans that are kicking-on, overheating should not be a concern.

Once you have accurately measured actual efficiency (meaning voltage measurements at the SCC input & output), if it is far below Sigineers’s specification for efficiency, you should contact them with that data. The fact that the unit includes active cooling suggests your performance is within the range they consider normal, but you never know. At best, you may have a defective unit that they might replace or repair. At worst, you can warn us all if Sigineer’s spec s should not be trusted.

To be fair, Sigineer is primarily known for their low-frequency inverters - SCC is a relatively new area for them…

 

[chrisski]

I have a passive cooling with heat fins on my Victron 100/75, 100/30, and 100/50. Maximum efficiency is 98%, typical is not listed, but I saw 4 when measured on Victron's software.

One thing I found out is that when there is enough sun to produce max power, but it gets hot, the max output is limited to around 80%. This has only happened when I left it in direct sunlight, and of course the manual says not to leave in direct sunlight.

 

[HRTKD]

I have to wonder if you guys are barking up the wrong tree with this heat issue. If my batteries are fully charged and the sun is out, my solar charge controller isn't putting much - if any - juice into the battery. The solar charge controller itself is not hot, hardly even warm. If it's working hard to converter the 80 volts down to 12 volts then it can get a bit warm.

 

[fafrd]

I have a passive cooling with heat fins on my Victron 100/75, 100/30, and 100/50. Maximum efficiency is 98%, typical is not listed, but I saw 4 when measured on Victron's software.

One thing I found out is that when there is enough sun to produce max power, but it gets hot, the max output is limited to around 80%. This has only happened when I left it in direct sunlight, and of course the manual says not to leave in direct sunlight.

You mean you left the SCC in direct sunlight and it got hot from the sun, right?

A good design will limit input power to avoid overheating, so sounds like that’s what your Victron is doing.

My Epever is in the basement where it’s 65F and I’ve never run it past 67% of max rating. The few times I’ve checked I’m getting efficiency pretty close to it’s 97% spec…

 

[ElectroBlvd]

Sounds like your mystery is solved .

And none of us are idiots (hopefully) but none of us are perfect.

546.7W / 680.52W = 80.34% efficiency (which is still low).

First, if you check voltage at the input wire into the SCC (or what it reports), you will see it is lower than the voltage coming out of your combiner box (losses of ~3% are not unusual).

Second, when you state ‘from controller to battery’, is that measured at controller output or battery input? If you measured at battery input, there are more losses in those cables and as measurement directly at SCC output will give you a more accurate read on it’s actual efficiency.

Then depending on your SCC you can see what ‘max efficiency’ it specifies and discover how much worse the reality is than the specification.

Even if you measured voltages at combiner output and battery input and you have 3% losses in both sets of cables, that would still translate to 563.61W / 660.10W = 85.4% efficiency from your SCC.

That’s still pretty piss-poor and I’d still be concerned that 96.5W would hear it up over time…

As a reality-check, my 1000W GTILs are only 80% efficient and when they are taking in 1000W of battery energy to put out 800W of 120V AC, that 200W of internal heat causes the cooling fans to kick-in.

I don't think there's a very noticeable loss from combiner to scc as it's a 6awg cable and only approx 0.5 meter in length. But I am definitely curious to test that and see what kind of loss I have there. From the scc to battery it is a 4awg cable approx 1 meter in length. I'm curious to know what kind of loss I have there as well but I don't imagine it would be a lot. Either way, I did measure the voltage at the battery as I did not have a screw driver to open the scc panel and my office manager was needing my attention on some paper work she found errors in. I have no doubt I was sitting higher than 49.7V at the scc output but not high enough to make up for the 135w difference. The combined losses from combiner to scc and scc to battery might make a dent on that 135w though.....I'll have to grab a screw driver and check that out. As far as the DC to AC goes, the manual states it's a transformerless inverter which I know produces a lot less heat since it uses electronic switching. But that raises more questions on the efficiency since transformerless inverters are suppose to be more efficient than transformer inverters. I'll do more testing and report back.

 

[fafrd]

I have to wonder if you guys are barking up the wrong tree with this heat issue. If my batteries are fully charged and the sun is out, my solar charge controller isn't putting much - if any - juice into the battery. The solar charge controller itself is not hot, hardly even warm. If it's working hard to converter the 80 volts down to 12 volts then it can get a bit warm.

The issue is not how much power the SCC is putting out but the delta between incoming PV power and outgoing charge power.

Once the battery gets out of boost and charger needs to start reducing charge power, it does that by raising string voltage to reduce solar current and solar power. Efficiency doesn’t change much.

 

[ElectroBlvd]

I agree.

Would be helpful to know what SCC model the OP has, what efficiency rating it specifies, and whether is has active cooling with fans or just passive cooling like most typically-efficient SCCs (my Epever 60A SCC has passive-cooling only but specifies efficiency of 97%…).

I actually posted the model number in my original post lol. Sigineer M3048NC 80a MPPT

 

[fafrd]

I don't think there's a very noticeable loss from combiner to scc as it's a 6awg cable and only approx 0.5 meter in length. But I am definitely curious to test that and see what kind of loss I have there. From the scc to battery it is a 4awg cable approx 1 meter in length. I'm curious to know what kind of loss I have there as well but I don't imagine it would be a lot. Either way, I did measure the voltage at the battery as I did not have a screw driver to open the scc panel and my office manager was needing my attention on some paper work she found errors in. I have no doubt I was sitting higher than 49.7V at the scc output but not high enough to make up for the 135w difference. The combined losses from combiner to scc and scc to battery might make a dent on that 135w though.....I'll have to grab a screw driver and check that out. As far as the DC to AC goes, the manual states it's a transformerless inverter which I know produces a lot less heat since it uses electronic switching. But that raises more questions on the efficiency since transformerless inverters are suppose to be more efficient than transformer inverters. I'll do more testing and report back.

We’re not talking about the inverters efficiency, we’re talking about the SCCs charge efficiency.

If you send a link to the specs I can tell you which spec is relevant.

When you are performing these measurements, I’m assuming the inverter itself is off. If not, standby power of the inverter needs to be subtracted from incoming power as it will be consuming a portion of those missing 95-135W…

 

[ElectroBlvd]

The issue is not how much power the SCC is putting out but the delta between incoming PV power and outgoing charge power.

Once the battery gets out of boost and charger needs to start reducing charge power, it does that by raising string voltage to reduce solar current and solar power. Efficiency doesn’t change much.

Ooooo could you help me understand this whole bulk, absorption, float charging thing? I'm only familiar with standard battery chargers that have a boost charge and a float charge. Boost has a constant current while float has a constant voltage. My 12v car battery charger has a 40A boost where I can see voltages going upwards of 15v and then it has a 13.6v float where amperage is usually around 1-2A. This makes sense to me. I don't understand all the extra charging language these scc's use. I have mine set at 58.4v charging voltage and 55.2v float charging voltage. I'm assuming the charging voltage setting (not float charging voltage) is for absorption charge? When does it hit bulk? And why can't I set that?

We’re not talking about the inverters efficiency, we’re talking about the SCCs charge efficiency.

If you send a link to the specs I can tell you which spec is relevant.

When you are performing these measurements, I’m assuming the inverter itself is off. If not, standby power of the inverter needs to be subtracted from incoming power as it will be consuming a portion of those missing 95-135W…

Completely forgot about the standby power! That's rated at 50W and yes its on.

 

[ElectroBlvd]

If you send a link to the specs I can tell you which spec is relevant.

3000W Off Grid Stackable PV Inverter 80A MPPT Solar Charger DC 48V to 110V 120V with 40A Utility Charger 50HZ 60HZ

3000W Off Grid High Frequency Stackable Inverter 80A MPPT Solar Charger DC 48V to 110V 120V with 40A Utility Charger 50HZ 60HZ. M3000H-48LV

www.sigineer.com

 

[fafrd]

I actually posted the model number in my original post lol. Sigineer M3048NC 80a MPPT

OK, so the specs say 50W of idle power, so even if you are not using any inverter power at all, 50W of your incoming PV power is going there.

Since there is no spec for SCC efficiency, I wouldn’t expect it to be anything worth bragging about.

Your wire lengths sound short enough that you are probably getting far less than 3% losses in each, but just using those losses to bracket, your charge efficiency sounds like it is so where between:

563.62W / (660.10W - 50W) = 92.4% and
581.1W / (640.3W - 50W) = 98.4%

I believe that 50W of idle power pretty much solves any remaining mystery and while your charge efficiency is probably a long way from best-in-class, doesn’t look like a disaster (or defective) either.

 

[ElectroBlvd]

OK, so the specs say 50W of idle power, so even if you are not using any inverter power at all, 50W of your incoming PV power is going there.

Since there is no spec for SCC efficiency, I wouldn’t expect it to be anything worth bragging about.

Your wire lengths sound short enough that you are probably getting far less than 3% losses in each, but just using those losses to bracket, your charge efficiency sounds like it is so where between:

563.62W / (660.10W - 50W) = 92.4% and
581.1W / (640.3W - 50W) = 98.4%

I believe that 50W of idle power pretty much solves any remaining mystery and while your charge efficiency is probably a long way from best-in-class, doesn’t look like a disaster (or defective) either.

Would bringing my panel voltage down to 72v by wiring them up I'm groups of 4 help efficiency at all?

 

[fafrd]

Ooooo could you help me understand this whole bulk, absorption, float charging thing? I'm only familiar with standard battery chargers that have a boost charge and a float charge. Boost has a constant current while float has a constant voltage. My 12v car battery charger has a 40A boost where I can see voltages going upwards of 15v and then it has a 13.6v float where amperage is usually around 1-2A. This makes sense to me. I don't understand all the extra charging language these scc's use. I have mine set at 58.4v charging voltage and 55.2v float charging voltage. I'm assuming the charging voltage setting (not float charging voltage) is for absorption charge? When does it hit bulk? And why can't I set that?

I can’t comment on how Sigineer’s SCC works, but here is how my Epever SCC works.

Bulk and bulk voltage is the target voltage you are charging in Constant Current Mode to. In CC, the charger is putting out it’s maximum current at a voltage dictated by the battery (below Bulk Voltage).

Once the battery reaches Bulk Voltage (or rather the SCC output reaches Bulk Voltage since there are cabling losses between SCC output and battery input), the charger typically switches to a Constant Voltage Mode at Bulk Voltage which is called ‘Absorb’. This means it is not allowing voltage if it’s charge output to increase above Bulk Voltage and is reducing charge current as needed to maintain that output voltage. My Epever controls this phase with a time, typically 10-60 minutes.

After the charger has completed the Absorb cycle (meaning reducing currents at Bulk Voltage), is switches to another CV mode but at Float Voltage rather than Bulk Voltage.

So Float Voltage should generally be set to whatever voltage you want a full battery maintained and the charger will basically provide any small amount of current needed to keep it there (offsetting internal leakage current if there is no drain and battery drain to feed loads if they are small enough to be supplied by the charger).

Completely forgot about the standby power! That's rated at 50W and yes its on.

Yeah, that’s what I suspected - mystery solved .

 

[fafrd]

Would bringing my panel voltage down to 72v by wiring them up I'm groups of 4 help efficiency at all?

As I just posted, I suspect your efficiency is probably not all that bad (accounting for your idle power).

In general, most SCCs have better efficiency when solar string voltage is closer to battery voltage.

So yes, if you are charging a 48V battery with 4S strings of 130V+, you might get better efficiency with 2S strings at 65-72V (though you will also be doubling your cabling losses between combiner and SCC).