Thought I had enough power

[Samsonite801]

Bought two 6500w MPP 6548 inverters. 12 TrinaSolar 330W panels, and three 48v BigBatteries each 103Ah.

Original plan was to power two campers off grid, One 50A the other 30A.

Was told this system would be enough.

Problem I have run into is lost power to the 30A camper, which is the only one connected now. (It is only using one of the inverters, as it is connected to L2).

Have monitored battery level, and after running the Class C A/C over night, and next morning Victron shunt showed 97% left.
Thought I had it made.
But about 6 hours later, with good Florida sun, power cut off. Batteries went down to cutoff setting of 44V. Had good sun angle, and not sure what's up.

Each string of three panels put out about 110vdc to the combiner box. But the inverter only registers 90vdc or so. Not sure why, as I have good quality wires.

Anybody else have a similar system, and have any problems?

Internet reviews only have praise for the system. I think I have something good, but not too sure now.

I'd also check for the correct calibration of your shunt (and watch voltage too while confirming the SoC % at least kind of lines up)...

I know just today on my setup (got up to 98° F here), I only had 1 of my 2 Dometic roof AC units running all day (it's all my 2800w inverter can do), and at around 4:30pm I started dipping into battery already (4s 405w pointing more East, 4s 405w pointing more West with separate charge controllers), and right now at 6:55pm (Sun is still up) with AC still running, my Victron BMV shunt is showing SoC already down to 88% (Time Remaining is showing 8 hours until it hits 20% as the low trigger) and I have 1680 AH of battery (22 KWh), so it doesn't seem right you were actually at 97% when you saw that indication (after running the AC all night). What's the amp draw on your AC unit?

Also, do you have a backup generator for charging? It should be for emergency only, I haven't had to start mine yet since I got the bigger solar going, but it's there with 120 amps of battery charging in case I get into a pickle (mine is only a 12v system but I'm off-grid so I consider a generator for redundancy an important feature for WAF).

Also on your question about solar voltage at 90v. Of course we'd have to know all the specs and wiring layout of your solar panels and array, but if the circuit is active (being controlled by the charge controller MPPT logic), the voltage will draw down and fluctuate, as MPPT logic can pull down voltage a great deal to increase amps while as it finds maximum power point in watts (it's a very dynamic circuit)..

 

[OleMan2765]

Check for un expected loads. If you have an electric element in your water heater and an absorption style fridge could really add to your loads. I’m not sure how your system is going to work to run ac in 2 rvs. I calculated that I would need that much to run a single ac in my 38’ 30 amp camper in sunny weather. Those rooftop ac units are hungry especially in the heat of the day.

Only thing on is the AC, and converter. Strange, because, first overnight run, all ran fine. Next morning at sunup only used 3% of my three batteries.
AC has soft start, and converter might pull 3A.

 

[OleMan2765]

I'd also check for the correct calibration of your shunt (and watch voltage too while confirming the SoC % at least kind of lines up)...

I know just today on my setup (got up to 98° F here), I only had 1 of my 2 Dometic roof AC units running all day (it's all my 2800w inverter can do), and at around 4:30pm I started dipping into battery already (4s 405w pointing more East, 4s 405w pointing more West with separate charge controllers), and right now at 6:55pm (Sun is still up) with AC still running, my Victron BMV shunt is showing SoC already down to 88% (Time Remaining is showing 8 hours until it hits 20% as the low trigger) and I have 1680 AH of battery (22 KWh), so it doesn't seem right you were actually at 97% when you saw that indication (after running the AC all night). What's the amp draw on your AC unit?

Also, do you have a backup generator for charging? It should be for emergency only, I haven't had to start mine yet since I got the bigger solar going, but it's there with 120 amps of battery charging in case I get into a pickle (mine is only a 12v system but I'm off-grid so I consider a generator for redundancy an important feature for WAF).

Also on your question about solar voltage at 90v. Of course we'd have to know all the specs and wiring layout of your solar panels and array, but if the circuit is active (being controlled by the charge controller MPPT logic), the voltage will draw down and fluctuate, as MPPT logic can pull down voltage a great deal to increase amps while as it finds maximum power point in watts (it's a very dynamic circuit)..

AC fan only is 2 to 3A. Compressor runs about 11A. Its only a 13,500btu.
Good thought on configs for shunt. I will need to look into that again.
Thanks

 

[Zwy]

Bought two 6500w MPP 6548 inverters. 12 TrinaSolar 330W panels, and three 48v BigBatteries each 103Ah.

Original plan was to power two campers off grid, One 50A the other 30A.

Was told this system would be enough.

Problem I have run into is lost power to the 30A camper, which is the only one connected now. (It is only using one of the inverters, as it is connected to L2).

Have monitored battery level, and after running the Class C A/C over night, and next morning Victron shunt showed 97% left.
Thought I had it made.
But about 6 hours later, with good Florida sun, power cut off. Batteries went down to cutoff setting of 44V. Had good sun angle, and not sure what's up.

Each string of three panels put out about 110vdc to the combiner box. But the inverter only registers 90vdc or so. Not sure why, as I have good quality wires.

Anybody else have a similar system, and have any problems?

Internet reviews only have praise for the system. I think I have something good, but not too sure now.

A few things, what are the bulk and float settings you are using? Second, you don't have enough PV. Third, you should run PV output voltage closer to the limits of the SCC. The LV6548 will not charge when PV voltage is under 90V, it says minimum 90V right in the specs. Reconfigure for closer to 250VOC. As these panels are around 40VOC, you should configure for 4 panels in series and not 3, 4S3P. Five panels would be more preferred but with 12 panels you work with what you have.

Get rid of the roof AC, my truck camper has a 11K btu roof air unit and it takes 1200W to run it. On my 24V system, right at 51A consumption. With your system of 3 48V 103AH batteries, you have 11,500W usable. With the small PV array and 11.5Kw usable, you will have a hard time recharging batteries running the roof AC for 8 hours.

 

[Zwy]

AC fan only is 2 to 3A. Compressor runs about 11A. Its only a 13,500btu.
Good thought on configs for shunt. I will need to look into that again.
Thanks

1320 watts is the draw, doesn't matter if 120V AC or 48V DC, it still is 1320 watts.

 

[OleMan2765]

A few things, what are the bulk and float settings you are using? Second, you don't have enough PV. Third, you should run PV output voltage closer to the limits of the SCC. The LV6548 will not charge when PV voltage is under 90V, it says minimum 90V right in the specs. Reconfigure for closer to 250VOC. As these panels are around 40VOC, you should configure for 4 panels in series and not 3, 4S3P. Five panels would be more preferred but with 12 panels you work with what you have.

Get rid of the roof AC, my truck camper has a 11K btu roof air unit and it takes 1200W to run it. On my 24V system, right at 51A consumption. With your system of 3 48V 103AH batteries, you have 11,500W usable. With the small PV array and 11.5Kw usable, you will have a hard time recharging batteries running the roof AC for 8 hours.

Bulk is 58.4V float is 58V. Outfit that sold me system wants three panels per string. I am getting around 110vdc from each of the four strings.
I have thought about a mini split AC, as they use much less power. Just don't have the 2500 now to do that.
My batteries, according to the victron shunt are 100% charged by 10AM EST.
Easiest expansion is to add another battery.
Thanks.

 

[Samsonite801]

AC fan only is 2 to 3A. Compressor runs about 11A. Its only a 13,500btu.
Good thought on configs for shunt. I will need to look into that again.
Thanks

Yeah, that's about what my Dometic roof units run at (also 13.5k btu), and they are power hogs... By morning today, my SoC on the 22 KWh battery bank was at 52%...

On the shunt thing, Victron official has a few You Tube videos you should watch about correctly configuring the shunts and BMVs (I had watched videos on the BMV-712 since that's the model I have), but there are a few settings that are important, so that it properly resets to 100% when it gets to Charged Voltage 13.9v (in my case), since the charge controllers absorption voltages are set to 14.2v .

Also have to set the battery capacity (overall AH of the entire pack, 1680 AH in my case), there are a couple other parameters like Tail Current (4% in my case) and Peukert Exponent (1.05 in my case) that need to be right for it to make proper sync on SoC value. There are also threads around here to explain the settings better. I just followed the videos, and my SoC % seems to line up with the six BMSs SoC numbers every day...

On the 90v thing, I agree with Zwy, I would put more put more panels in series (try 4s) to get the PV volts up higher, closer to 250v. Don't go too high unless you do the calculation for coldest temperature Voc compensation though.

Ref:

Solar panel maximum voltage calculator - How to work out the max voltage

To get the maximum solar panel voltage you should expect from your solar panel, use our solar panel maximum voltage calculator.

gold-coast-solar-power-solutions.com.au

 

[Samsonite801]

BTW, since I had run my roof A/C so much last night into the late evening, today my battery was at 52% this morning. Well today (even though it's hot as heck today too), I decided to just leave the A/C off to charge the battery up faster (it's been charging about 2300w for the most part), and it is now almost 2pm and the battery is still only back up to 96%.... That's with two 4s arrays of 405w ea (8 total) solar panels.

So I still have a hard time seeing the likelihood that your bank's SoC was actually at a real 97% by morning with a 13.5k btu A/C unit running all night (with your 15-16 KWh battery bank).

So yeah, just saying again to check that SoC calibration. My guess is the battery was on the low-end at that time it was reading 97%. Also check the wiring on your shunt, and make sure that all loads and chargers are on the one side (so they are metered), only the battery lead is on the other side of the shunt.

 

[Supervstech]

BTW, since I had run my roof A/C so much last night into the late evening, today my battery was at 52% this morning. Well today (even though it's hot as heck today too), I decided to just leave the A/C off to charge the battery up faster (it's been charging about 2300w for the most part), and it is now almost 2pm and the battery is still only back up to 96%.... That's with two 4s arrays of 405w ea (8 total) solar panels.

So I still have a hard time seeing the likelihood that your bank's SoC was actually at a real 97% by morning with a 13.5k btu A/C unit running all night (with your 15-16 KWh battery bank).

So yeah, just saying again to check that SoC calibration. My guess is the battery was on the low-end at that time it was reading 97%. Also check the wiring on your shunt, and make sure that all loads and chargers are on the one side (so they are metered), only the battery lead is on the other side of the shunt.

What is the kWh of your bank?

 

[Samsonite801]

What is the kWh of your bank?

Mine is six 12v 4s packs (280 AH cells), 24 cells total, 1680 AH total, and at 13.2v nominal, provides around 22 KWh or so.

Yours is three 48v 16s packs (103 AH cells), 48 cells total, 309 AH total, so at 51.2v nominal, it is roughly 15 KWh or so...

 

[Zwy]

Bulk is 58.4V float is 58V.

That is really pushing the limits. I prefer to run just in the knee area for bulk and have float about 0.5V lower than bulk.

Outfit that sold me system wants three panels per string. I am getting around 110vdc from each of the four strings.

Given the charge parameters they gave you and they want 3S4P , I'd stop listening to their advice. They also told you the system would provide all the power you needed for 2 campers, do you see the problem?

I have thought about a mini split AC, as they use much less power. Just don't have the 2500 now to do that.
My batteries, according to the victron shunt are 100% charged by 10AM EST.
Easiest expansion is to add another battery.
Thanks.

Adding another battery may not improve the situation as you don't have enough PV capacity. How do you intend to charge one more battery when you can't get full charge with what you have? While you claim the shunt shows 100% fully charged by 10AM, I don't believe that is correct especially if you had fully discharged the day before.

 

[Bobert]

You should revisit the idea of a mini split. It uses hundreds of watts less power than a roof top unit in the worst case scenario and if your roof unit is ducted you could potentially save nearly half of the power you now use. Home Depot sell the 12k pioneer 110v units for under $1000. Do the math for your situation but my guess is that it will more than double the effectiveness of your solar system. Not only that but mini splits are quiet that’s worth something in and of itself. If your rooftop unit is running steady and uses 1300 watts average and a mini split does the same at 800 watts you will save 12k of energy in a 24 hour period. To get a reasonably reliable system to produce this much power considering occasional cloudy days would require over 2500 watts of solar and probably 10k of battery. Obviously this is a stab in the dark estimate but if a casual calculating of your ac comes up with these figures a careful calculating using your exact situation has the possibility of similar results. If I offered you a 2500 watt solar system with 10k of battery that took up no additional roof space and took only 2 days to install for $1000 dollars would you want it? It’s certainly worth the time and trouble to discover if that’s effectively what you would get in your situation with a budget mini split.

 

[chess-equality]

Not really familiar with RV A/Cs, are these DC? Are inverter-type models (like the ones sold as household appliances) more economical?

 

[OleMan2765]

BTW, since I had run my roof A/C so much last night into the late evening, today my battery was at 52% this morning. Well today (even though it's hot as heck today too), I decided to just leave the A/C off to charge the battery up faster (it's been charging about 2300w for the most part), and it is now almost 2pm and the battery is still only back up to 96%.... That's with two 4s arrays of 405w ea (8 total) solar panels.

So I still have a hard time seeing the likelihood that your bank's SoC was actually at a real 97% by morning with a 13.5k btu A/C unit running all night (with your 15-16 KWh battery bank).

So yeah, just saying again to check that SoC calibration. My guess is the battery was on the low-end at that time it was reading 97%. Also check the wiring on your shunt, and make sure that all loads and chargers are on the one side (so they are metered), only the battery lead is on the other side of the shunt.

Forgot to mention, had an 04 Fault (low voltage shuts off at 44vdc). That shutdown the system, but still allows Solar charging. Still trying to find an Analog AC Clock. As I want to plug it into the RV to find out when 04 happens.

 

[OleMan2765]

That is really pushing the limits. I prefer to run just in the knee area for bulk and have float about 0.5V lower than bulk.



Given the charge parameters they gave you and they want 3S4P , I'd stop listening to their advice. They also told you the system would provide all the power you needed for 2 campers, do you see the problem?


Adding another battery may not improve the situation as you don't have enough PV capacity. How do you intend to charge one more battery when you can't get full charge with what you have? While you claim the shunt shows 100% fully charged by 10AM, I don't believe that is correct especially if you had fully discharged the day before.

As far as bulk, just going by what the battery manufacture has written on the label. Will look at your idea of half a volt though. I am at .8 lower now.
Not sure about their advice either. But I feel they need to have a chance to explain their system.
Didn't think that 44vdc was fully discharged. That is default in the MPP instructions. But they also say I can go as low as 42vdc also.

 

[OleMan2765]

Allot of good information here.
Thanks for all the responses.

Gives me allot to think about.

 

[OleMan2765]

Not really familiar with RV A/Cs, are these DC? Are inverter-type models (like the ones sold as household appliances) more economical?

Very much like a window AC, in a different case. Mine is 110vac, but recently they have come out with 12vdc systems.

 

[OleMan2765]

You should revisit the idea of a mini split. It uses hundreds of watts less power than a roof top unit in the worst case scenario and if your roof unit is ducted you could potentially save nearly half of the power you now use. Home Depot sell the 12k pioneer 110v units for under $1000. Do the math for your situation but my guess is that it will more than double the effectiveness of your solar system. Not only that but mini splits are quiet that’s worth something in and of itself. If your rooftop unit is running steady and uses 1300 watts average and a mini split does the same at 800 watts you will save 12k of energy in a 24 hour period. To get a reasonably reliable system to produce this much power considering occasional cloudy days would require over 2500 watts of solar and probably 10k of battery. Obviously this is a stab in the dark estimate but if a casual calculating of your ac comes up with these figures a careful calculating using your exact situation has the possibility of similar results. If I offered you a 2500 watt solar system with 10k of battery that took up no additional roof space and took only 2 days to install for $1000 dollars would you want it? It’s certainly worth the time and trouble to discover if that’s effectively what you would get in your situation with a budget mini split.

Yes, I have, but I wanted a dual zone system. When I saw the pricing, I stopped looking.

 

[OleMan2765]

What is the kWh of your bank?

Little over 15Kwh

 

[Samsonite801]

Forgot to mention, had an 04 Fault (low voltage shuts off at 44vdc). That shutdown the system, but still allows Solar charging. Still trying to find an Analog AC Clock. As I want to plug it into the RV to find out when 04 happens.

I wonder if you set up the MPP Solar Watchpower software, you could read the log message and see when the 04 happens (it should have a date / time stamp associated with the error message logged)...