Power up review PowMR (SRNE) POW-LVM3K-24V-H

[BuffaloTrace]

I certainly hear you and would be ready to do precisely that except for two issues;

1/ my current system is 24V and I’won’t be in a position to rebuild my 8S2P battery to 16S1P until next spring (or at best this winter).

So I won’t be in any position to test until then.

Losing 6-12 months of warranty coverage, to say nothing of wasting the 30-day return in case the unit is DOA seems stupid, so I figure I’ll just keep monitoring for any other early adopters in the meantime.

The one downside to this plan is that I could probably purchase the Y&H 10kW split-phase for under $1500 today (they are currently asking for ‘$1590 or best offer’) while prices may increase 9–12 months from now.

But especially when purchasing inexpensive power electronics coming from China, a 30-day no questions asked return policy is worth more than any price increase I could imagine (market is getting more and more competitive).

So if everything you’ve written in your above message remains valid 6-9 months from now is still valid, I’m there.

But in the meantime I’m afraid it’s ‘hurry up and wait’ (and monitor whatever any other early adopter’s report).

But it looks like a well-suited product to my needs at a very convertible price, so I’ll almost certainly be getting one unless red flags emerge…

Yea I definitely get that. You got a system that works and are just looking for more valuable upgrades. Also 24v - 48v is the next logical leap for a system but also a much different setup when it comes to the charging capabilities, and setup of the arrays. I like 24v systems.

 

[fafrd]

Yea I definitely get that. You got a system that works and are just looking for more valuable upgrades. Also 24v - 48v is the next logical leap for a system but also a much different setup when it comes to the charging capabilities, and setup of the arrays. I like 24v systems.

Me too, but the eventual arrival of an EV will mean more consumption and the need for more than ~1600W of offset powered by a small 1.1kW DC-coupled array.

I’ve learned a great deal over the past 3 years with my 24V system but I think I’m ready to move up to 48V.

That allows for higher-powered inverters with more headroom which has always been the case, but what has changed is the arrival of the Chargeverter (actually the 48V Emerson rectifier in my case).

That allows me to convert my DC-coupled 3P1S array to AC-coupled with Microinverters and absorb the energy I don’t want getting exported to grid rather than attempting to throttle Microinverter output.

Then I can add a new 1P6S array to keep the battery fully-charged and the new off-grid inverter happy 9 months out of the year with the Chargeverter / rectifier to get the battery through the night even on rainy winter days for the last 3 months.

I’ve been offsetting using two 24VDC GTIL inverters but want to move to a true offgrid system powering ~60% of daily consumption (fridges & freezers).

The Conext SW would have allowed me to stay at 24VDC but I would have had to add a separate HV SCC plus if offers no headroom for future expansion so it does not seem attractive.

 

[Mattb4]

One thing I should mention if a person decides to go the route of the higher PV voltage AIO. Keep in mind the input voltages for how you size your array. In my case I am using RV 100w panels that have a Voc of 22 and a Vmp of 18. This PowMr requires 150vDC to startup and has an operating range of 120 to 400vDC and a max Voc of 450vDC. I calculated that I needed a minimum of 8 panels in series to have proper operation. 8 x 22vDC = 176vDC for max array Voc, 18vDC X 8 = 144vDC for operating voltage at max power. The panels can develop watts down down to 120vDC before the AIO disconnects from PV.

7 panels in series would have place the operating voltage at 126vDC and would limit harvesting lower light conditions and the max 7 X 22vDC would only reach 154vDC and may not start up the MPPT except in the best of conditions.

 

[fafrd]

One thing I should mention if a person decides to go the route of the higher PV voltage AIO. Keep in mind the input voltages for how you size your array. In my case I am using RV 100w panels that have a Voc of 22 and a Vmp of 18. This PowMr requires 150vDC to startup and has an operating range of 120 to 400vDC and a max Voc of 450vDC. I calculated that I needed a minimum of 8 panels in series to have proper operation. 8 x 22vDC = 176vDC for max array Voc, 18vDC X 8 = 144vDC for operating voltage at max power.

The panels can develop watts down down to 120vDC before the AIO disconnects from PV.

7 panels in series would have place the operating voltage at 126vDC and would limit harvesting lower light conditions and the max 7 X 22vDC would only reach 154vDC and may not start up the MPPT except in the best of conditions.

You are absolutely correct that string design needs to be properly planned to work with a high-voltage MPPT (AIO or SCC) but I just want to clarify that as long as Voc_typical exceeds Vstart, the MPPT will start producing power.

So Voc_worst_case (at coldest temps) needs to be safely below maximum input voltage rating of the AIO/SCC and Voc_minimum (at hottest possible overnight temps) needs to be safely above Vstart.

Ideally, you’d like Vmppt_min to be below Vmp of your string at typical mid-day temps, but if it’s not quite there and the string is being operated at voltage slightly higher than Vmp on hot summer around midday when solar power is greatest, it’s not the end of the world. Your array will be putting out slightly less power than it could have at an optimal string voltage but since this will typically be in summer when your getting the most solar energy, not a showstopper.

 

[Mattb4]

So allowing for temperature correction on hot days what do you suggest that you have Vmp be above Vmppt-min? An earlier discussion about this with Hedges I had he seem to suggest about 10%. That would put a Vmp rating for my AIO at 120v+10% = 132vDC

 

[fafrd]

So allowing for temperature correction on hot days what do you suggest that you have Vmp be above Vmppt-min? An earlier discussion about this with Hedges I had he seem to suggest about 10%. That would put a Vmp rating for my AIO at 120v+10% = 132vDC

I think you asking what I recommend in terms of Vmp @ STC, meaning 25C / 77F.

So we’re going to assume you’ve properly designed your string to start up your MPPT every morning and we’re just looking at what point Vmp of the string translates to too much lost potential energy to be worthwhile.

First, I’d recommend focusing on average temps on the hottest months you care about and use PTC rather than STC. PTC is based on 20C ambient, so panel temperature will typically be higher than 25C but that is realistic.

By comparing PTC power rating to STC power rating you can calculate what temperature the panel is at operating in 20C ambient and from that calculate the realistic Vmp at 20C ambient.

If you care about worst-case losses at higher temperatures than 20C, adjust from there.

Now you have the ideal Vmppt_min under the highest ambient temperatures you care about.

If Vmppt_min is only 10% higher than that adjusted Vmp_min, power loss will be less than 10% -probably closer to 8%.

Current at higher voltage will be lower than Imp (adjusted) but by less than 10%. You can attempt to guesstimate from the radiance power curves (attempt to bracket how much lower power is at 110% Vmp) but it’s tough (my 380W panels deliver over 350W @ 110% Vmp, meaning less than 8% loss at 110% Vmp).

There is a wide ‘flatspot/hump and my advice would be to try to avoid going significantly out of it and losing more than 10% potential power.

The hump on my panels is close to +/-5V from Vmp of 40V, so let’s say +/-12%. You’re losing little-enough power in the flatspot that it’s certainly not worth abandoning your project or perturbing unnatural acts or spending lots of $$$s to get closer to Vmp.

So I’m basically agreeing with what hedges has recommended but suggesting to do so based on adjusted Vmp under estimated operating condition (adjusted PTC for the highest ambient temperatures you care about) rather than just using STC (or NOCT).

 

[Mattb4]

I think you asking what I recommend in terms of Vmp @ STC, meaning 25C / 77F.

So we’re going to assume you’ve properly designed your string to start up your MPPT every morning and we’re just looking at what point Vmp of the string translates to too much lost potential energy to be worthwhile.

First, I’d recommend focusing on average temps on the hottest months you care about and use PTC rather than STC. PTC is based on 20C ambient, so panel temperature will typically be higher than 25C but that is realistic.

By comparing PTC power rating to STC power rating you can calculate what temperature the panel is at operating in 20C ambient and from that calculate the realistic Vmp at 20C ambient.

If you care about worst-case losses at higher temperatures than 20C, adjust from there.

Now you have the ideal Vmppt_min under the highest ambient temperatures you care about.

If Vmppt_min is only 10% higher than that adjusted Vmp_min, power loss will be less than 10% -probably closer to 8%.

Current at higher voltage will be lower than Imp (adjusted) but by less than 10%. You can attempt to guesstimate from the radiance power curves (attempt to bracket how much lower power is at 110% Vmp) but it’s tough (my 380W panels deliver over 350W @ 110% Vmp, meaning less than 8% loss at 110% Vmp).

There is a wide ‘flatspot/hump and my advice would be to try to avoid going significantly out of it and losing more than 10% potential power.

The hump on my panels is close to +/-5V from Vmp of 40V, so let’s say +/-12%. You’re losing little-enough power in the flatspot that it’s certainly not worth abandoning your project or perturbing unnatural acts or spending lots of $$$s to get closer to Vmp.

So I’m basically agreeing with what hedges has recommended but suggesting to do so based on adjusted Vmp under estimated operating condition (adjusted PTC for the highest ambient temperatures you care about) rather than just using STC (or NOCT).

I am going to have to read your response several times ( ack!) before I understand it (perhaps early tomorrow before my afternoon dementia sets in).

 

[Mattb4]

OK I think I am understanding your post, Fafrd. One additional consideration for my setup (8S2P) that I had to make was for my panel setup and location. My panels are mounted 2 to a metal post 5 feet apart for the majority of them. Due to location the sun hits them from the left and exposes them one by one as it rises until they are all in full sun by Noon (this time of year). Ideally they work best in parallel but I needed as I mentioned a higher minimum voltage to run this new AIO. By using the 8S2P I get some production before Noon.

Someone with a better setup/location using 100w RV panels would likely be better served just going one string of 16 in series. That gives 352Voc and 288Vmp which would place both Vmppt_min and Vmppt_max in good ranges.

 

[fafrd]

OK I think I am understanding your post, Fafrd. One additional consideration for my setup (8S2P) that I had to make was for my panel setup and location. My panels are mounted 2 to a metal post 5 feet apart for the majority of them. Due to location the sun hits them from the left and exposes them one by one as it rises until they are all in full sun by Noon (this time of year). Ideally they work best in parallel but I needed as I mentioned a higher minimum voltage to run this new AIO. By using the 8S2P I get some production before Noon.

Someone with a better setup/location using 100w RV panels would likely be better served just going one string of 16 in series. That gives 352Voc and 288Vmp which would place both Vmppt_min and Vmppt_max in good ranges.

View attachment 157920

Funny, I’m in the exact same situation as you (but due to moving shade on one roof face in my case).

My current DC-coupled array is 1S3P oh half-cut panels for precisely this reason (get 100% output from any half-panel as soon as it is clear of any shading).

I’m adding 6 more 60-cell panels and cannot stay parallel and as I debate between 3S2P and 6S1P I’ve come to the conclusion that the second-best choice to full parallel is full serial.

I’ll need an inverter that can handle a Voc-max of 250VDC but the lower the Vmppt_min the earlier I can start getting output.

The SRNE 10kW split-phase hybrid I’m considering has a Vmppt_min of 125V, so this means I only need 3 fully unshaded panels to start getting full output from those 3 panels.

Vmp is 30.2V (@25C) so 4 unshaded panels will have Vmp of 120.8V - 6 x 0.7V (from 6 activated bypass diodes) = 116.6V, so I’ll be running at 2.8V below Vmp (-10%).

But that’s way better than waiting for all panels to be shade-free.

For 2 differently-oriented strings, you’ll get the most output by having 2 independent MPPTs.

If that’s not an option, a 16S2P might actually be preferable to 8S2P.

You’ll get full output from the early morning panels in the morning while bypassing the afternoon panels, full output from all panels at midday, and full power from the afternoon panels by bypassing the morning panels in the afternoon.

 

[Mattb4]

Just got done installing my PV shunt and meter. Not terribly happy with the box I bought for it as the plastic was easily scratched by my jig saw and it is rather malleable and not stiff as I would like. This means the meter that is a snap in fit does not hold the best. But it is working and showing that a fair amount of watts are being delivered even before the sun is on the panels.

 

[Hedges]

Shunt operates at PV voltage bias away from ground. Can it withstand voltage delta from logging equipment that connects to it?

I've used I2C or SPI isolators that have multiple kV test voltage, but intended for only a couple hundred volts. Something with transformer isolation might have higher isolation given dielectric bobbins, or as low as what enamel wire insulation is good for. Probably rated 600V. many plastics or enamel (likely actually polyester) are good for about 1000V/mil.

I've seen panel meters with LCD operating at a few thousand volts bias. That was in a research lab, and I wasn't confident it was good for human safety. I though a separate window over it would be better to prevent shock, rather than just LCD glass and bezel. Some 10's of kV equipment had extension plastic rods on potentiometers. In that case I would consider insulator, then metal piece with ground strap or sliding contact to ensure any surface leakage or conduction through contamination was drained to ground.

 

[Mattb4]

No logging equipment other than shunts own meter. Very basic in nature. It replaces having to use a clamp on and a DMM to figure wattage. I ran a similar PV shunt setup for a year on my previous AIO. This particular one is good for test voltage up to 300vDC (the PV array is 176Voc) and the shunt is 50 amp.

Handy since my AIO's measurement of incoming PV watts is not accurate.

ETA: Yesterday my 1600w PV array produced 5.03 kWh based on the PV shunt. Not bad considering most of the day was cloudy and with heavy haze. I expect better today with more sun though it is hot outdoors. (95F at noon)

Continuing review. This new PowMr SCC does a better job than my #2 EAsun unit in terms of percentage yield from panels. The PowMr is getting 72% from its 8S2P 1600w array while the EAsun is getting 65% from its 3S2P for the same time of day and sun condition.

 

[mib]

Handy since my AIO's measurement of incoming PV watts is not accurate.

i change the output to 220 volts in your case 120 volts

after all, there is an AIO efficiency and a DC line is noticeably less than an alternating one

 

[Scph9002]

have you tested how your powmr unit performs near max ac loads?

 

[Mattb4]

I try to limit max AC loading on the AIO to around 2500w, preferably less than 2000w. It seems to work fine with that as a limit.

 

[Johno1066]

Can these PowMr be run in parallel, been thinking of getting one of the 5000 watt units but may have to run 2 eventually.

 

[Scph9002]

I try to limit max AC loading on the AIO to around 2500w, preferably less than 2000w. It seems to work fine with that as a limit.

I meant ac out. Maybe you also meant that? Limit by simply not using to many appliances at once? You are unable to try and max pv power in I guess? Think I saw your pv setup in other thread. Looked quite small.

Reason why I ask is that powmr earlier units seem to have been total rubbish's, more specifically their 60 amp ssc but the newer aio's seem to be of same quality as growatt and epever

 

[Scph9002]

Can these PowMr be run in parallel, been thinking of getting one of the 5000 watt units but may have to run 2 eventually.

some definitely can up to 6 units, some cant I think.

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[Mattb4]

I meant ac out. Maybe you also meant that? Limit by simply not using to many appliances at once? You are unable to try and max pv power in I guess? Think I saw your pv setup in other thread. Looked quite small.

Reason why I ask is that powmr earlier units seem to have been total rubbish's, more specifically their 60 amp ssc but the newer aio's seem to be of same quality as growatt and epever

Yes I was referring to the 120vAC out loading. I could indeed max it if I wanted to since I have a 120vAC 2000w water heater and several space heaters I could use for a load test. But my use is not to test the unit for full out and beyond. I can not afford to test to destruction like a lab or someone like Will. Just a retired old nut living in the woods. Mostly on these Chinese thingies it is not a good idea to attempt to run full out anyway.

I have seen it to 2800w briefly while running a microwave, refrigerator and house water pump. I do practice load management.

My PV setup for this inverter is 1600w consisting of 16-100w panels in a 8S2P arrangement.

This is not PowMR manufacture. It is a SRNE rebadge. There is a ton of them with different names out there.

 

[Mattb4]

Can these PowMr be run in parallel, been thinking of getting one of the 5000 watt units but may have to run 2 eventually.

They have some listed for that. Mine is not parallel capable.