Power storage/capacity problem??

[ThaiTaffy]

Newbie and non expert at solar here but the fact you said overload in your original post would lead me to believe your startup current on the AC unit is too high for your system.
Anything with a compressor/motor that doesn't run off an inverter draws a massive load in comparison to working load.

I planned to power a fridge and chest freezer off my inverter the fridge was averaging 70w with a startup load of 170w due to its inverter, the chest freezer on the other hand averaged 100w with a startup load of +2kw as it had no inverter. First day I had constant overload warning so sadly the chest freezer got thrown from the party.

Personally (once Again no expert here) I would have think as your batteries start to drop to the lower end of soc the draw the AC unit demands at startup is so high it's putting the solar inverter to overload, not sure of pricing for your part of the world but here at least a better quality AC unit is cheaper than a decent battery.

Ps. When I say startup I don't actually mean when it's turned on, it occurs throughout the day as the compressor demands see graph below

 

[time2roll]

SOOO-the $6,000,000 question is-do I need even MORE batteries??
I use an online wh calculater and it added up to about 1300 hrs per day.
Any help appreciated!
Phil

Yes but not those batteries. Move to lithium. While at it move to 24 or 48 volts. The existing system is but a toy for very limited use.

 

[Mattb4]

It doesn't really die-the inverter shuts off when battery voltage drops below 11 volts. I use 0-4 automotive type battery cables if that is the "wire" you are asking about for all battery cables. If you mean the wire from controller to inverter-2 strands of 12 gauge stranded from the 2 + terminals and 2 strands of 12 gauge stranded for the - terminals as recommended by the controller manufacturer. And I just checked-the controller is rated at 160 volts max. input. And,not sure if it matters I'm using an automotive type inverter so essentially my house is connected to it via a wall socket.

It sounds like your present system is inadequate for more than very occasional usage. 12ga should be limited to 20-25a max and you are running a 60a SCC (that is maxed out for a couple of hours each day) even though you have 2 -12ga wires you really are exceeding safe levels. The 4 awg automotive battery cables to your inverter I would guess are only good to 100 amps. Thus at 12vDC system any loads of 1000w or more are exceeding its capacity. Your inverter being an automotive style is simply not designed for daily usage.

Your entire setup needs some rethought if you wish to use it for greater loading and more often.

 

[littleharbor2]

This controller only handles 80 vdc at a 12 volt system voltage.

 

[Brucey]

Newbie and non expert at solar here but the fact you said overload in your original post would lead me to believe your startup current on the AC unit is too high for your system.
Anything with a compressor/motor that doesn't run off an inverter draws a massive load in comparison to working load.

I planned to power a fridge and chest freezer off my inverter the fridge was averaging 70w with a startup load of 170w due to its inverter, the chest freezer on the other hand averaged 100w with a startup load of +2kw as it had no inverter. First day I had constant overload warning so sadly the chest freezer got thrown from the party.

Personally (once Again no expert here) I would have think as your batteries start to drop to the lower end of soc the draw the AC unit demands at startup is so high it's putting the solar inverter to overload, not sure of pricing for your part of the world but here at least a better quality AC unit is cheaper than a decent battery.

Ps. When I say startup I don't actually mean when it's turned on, it occurs throughout the day as the compressor demands see graph below
View attachment 220306

I have a French door fridge/bottom freezer, a 7 cuft chest freezer and a 21 cuft upright freezer all running on a Victron 48/1200 (bunch of other stuff as well). I'm sure the surges are significant but very momentary and the fan just ramps up for a moment and then settles down. Baseload around 150W.

 

[ThaiTaffy]

I have a French door fridge/bottom freezer, a 7 cuft chest freezer and a 21 cuft upright freezer all running on a Victron 48/1200 (bunch of other stuff as well). I'm sure the surges are significant but very momentary and the fan just ramps up for a moment and then settles down. Baseload around 150W.

guessing your probably very lucky and none have surged together especially the freezers that model inverter does have 2.2kw peak though. Im more curious now what OP`s inverter is i just re read the original post and he said its 6kw peak is that western standards peak or chineaseium standards?

 

[Brucey]

guessing your probably very lucky and none have surged together especially the freezers that model inverter does have 2.2kw peak though. Im more curious now what OP`s inverter is i just re read the original post and he said its 6kw peak is that western standards peak or chineaseium standards?

Yes the Victrons are known for strong surge, relatively expensive at $334 but can deliver day in day out far beyond what you'd expect. I'm guessing those are chinesium ratings for 6kW peak.

 

[ThaiTaffy]

Yes the Victrons are known for strong surge, relatively expensive at $334 but can deliver day in day out far beyond what you'd expect. I'm guessing those are chinesium ratings for 6kW peak.

I just had a look for similar stories on Reddit and couldn't find much just some guy doing the math on a Chinese 12v 8kw inverter needing 5/8 inch thick cables.

 

[DIYrich]

I think what happened is by the time I got to using the AC the batteries were already on the low side due to use and cloudy weather, the AC use was the tipping point.

Ok, so get another charge controller to fully take advantage of the panels you have.

 

[Philco Fan]

OK,I got 4 of those panels.

 

[Philco Fan]

60A on 12V system is going to be limited to about 860W. He's about 80% over-paneled.

So buy the one you picked out or the one I picked out? Specs say 12v system max input is 100 volts.

 

[sunshine_eggo]

So buy the one you picked out or the one I picked out? Specs say 12v system max input is 100 volts.

I missed that, and I forgot that the cheaper controllers often have that restriction rather than just an absolute (I have a cheap MPPT with that restriction, but I'm on 48V, and I didn't remember that bit). When I check both, I see 80V limit for 12V.

I don't think it matters which one since 2S panels generating near 100Voc is too high for a 100Voc controller. You will need to put the new panels in parallel on the controller and not series, but that should still perform just fine.

There's a lot of talk of surge issues, and I wanted to clarify that this does not appear to be surge related as it takes several days to manifest.

 

[Philco Fan]

Thanks for the clarity, I feel confident I'm on my way to a solid fix. I'll update when I can get back up there.
Thanks!

 

[sunshine_eggo]

Thanks for the clarity, I feel confident I'm on my way to a solid fix. I'll update when I can get back up there.
Thanks!

For clarity, please confirm that you didn't have any issues running the A/C until the battery was clearly at a lower voltage as you indicated here:

I think what happened is by the time I got to using the AC the batteries were already on the low side due to use and cloudy weather, the AC use was the tipping point.

Regardless, 1800Ah of battery with only 860W of usable PV (60A max) means you are charging your bank at too low of a current. Providing nearly 180A of potential charging should dramatically improve performance. You may discover that there are other system deficiencies, but you should be able to consume up to 10kWh/day without issue on days with good sun.

 

[Philco Fan]

Confirm, all was OK until I started to use the AC. My fridge [18cf full size] runs 60% of the time average, plus ceiling fans, LED lighting, TV, occasional microwave/toaster/Mr. Coffee, etc never bothered it. I even run my electric 5 ton logsplitter when needed-no issues. I wouldn't want to run micro,coffee pot,toaster and the fridge all at the same time though-that would probably have cause a problem.

 

[JBoffgrid2022]

I focused on this:



This tells me that the A/C unit operates without issue for at least the first 7 days, so you're continually eating away into your battery capacity due to excessive daily use.



I missed this. are you saying that you're only using 1300Wh or 1.3kWh/day? I don't think that's the case. I just purchased a 12,000BTU/h Midea Duo portable unit (mini split-like with inverter compressor and variable speed everything), and when running at full blast, it's a power hog at ~1500W.

When it's maintaining in moderate temps, it's still nibbling 100-200W continuously, and that would be 2.4-4.8kWh/day.

I had a similar situation at our off grid camp using AGM batteries. The system (kit) I purchased did not have the proper sizing, not even close! My setup was S2P3 200watt panels into a 60amp charger to a AGM battery bank of 6 x 12volt 200 amp batteries. This fed a 6k inverter that drew too much power and drained the battery bank. Over time the batteries stored less and less power because the panels couldn't provide enough PV power to fill the battery AND supply power to the camp. Long story short, I had to upgrade my system to a much larger 48v system with lithium ion battery back up. Also swapped the Aims Corp 6k inverter for an EG4 6k solar inverter charger. Regardless of whatever you think might be the problem is, there is a very logical reason why your system isn't working. Just try and understand one thing at a time because taking it all in at once is overwhelming! @sunshine_eggo knows his stuff along with most everyone else here! Hope you can fix your problem soon

 

[Philco Fan]

New item by Phil Hall

photos.app.goo.gl

Picture of my system.

 

[robbob2112]

New item by Phil Hall

photos.app.goo.gl

Picture of my system.

I love it, eyebrows and a mustache. Now if you moved the bottom end panels up a bit it would be smiling.

 

[Philco Fan]

I have 4 more panels now,I'll see what I can do! LOL

 

[sunshine_eggo]

I'm thinking ground mount to make it a goatee.

 

[Red_Fir]

I had a similar problem.
I have 1.8KW of panels and a massive battery bank of 16 L16's (two 48v strings paralleled) it runs a 1.5 hp deep well pump, a 1/2 hp distribution / pressure pump, three chest freezers anda welding rod heater plus incidentals a 3/4 hp air compressor rarely and lighting, grinders etc. I can comfortably pull 4KW for short periods throughout the day
My system will charge the batteries by ten am every day then just floats, and the we waste the rest of the days power, I had the batteries set to disconnect at 80% SOC and the inverter would shut down, ... mostly due to inrush, the system rarely got below 46.8 volts but it would get that low for longer than the timeout, it would shut down and then "recover" back to 51 volts within seconds.
I reset the lower limits of pulldown to 50% SOC and have yet to have it trip over the last quarter despite weeks of overcast, according to the log the lowest voltage actually reached is 46.2v. I have deep capacity (720 AH!) but the voltage drop under the combined load of both pumps, was just barely too much for too long.
I too was reluctant to add panels (holy spacetakers on my postage stamp of land, Batman!) my next effort would have been a soft start, or even better a bank of supercapacitors to absorb that initial surge required for motor start.
Your AC is likely giving a double whammy, a huge inrush and then sustained load, if the sustained load is within ah calculations then perhaps just tweaking timeout parameters will give your system time to re stabilize, if so then more storage might be enough to carry over the hump!