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paulz
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# Posted: 6 Mar 2022 11:41am
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Trying to understand the max specs for my CC. Per the manual, for my 40A controller, the rated charge power is 520W at the 12V setting. Makes sense, around 40A at 13V.
It also states "Actual operation of the PV array must not exceed three times the of rated charge power". That figure is listed as 1,560W, three times the aforementioned 520W. OK so far, I think.
My MT50 monitor does not show incomming Watts, just Volts and Amps. So does this mean if my incoming voltage is 100 (about what I have), as long as the amperage reading stays below 15 I'm not in danger?
I am overpaneled, it's the only way I can get enough charging with my northern exposure and tree canopy. Yesterday the sun hit all my newly repositioned panels for a brief period, showed 15A but that was on the output side to the battery bank. Unfortunately I didn't look at the incoming amperage. I'm hanging around today to see if it goes that high again.
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Nate R
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# Posted: 7 Mar 2022 08:17am
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15 amps on the output side is NOT the same as the input side with an MPPT controller. So just because you had 15 amps INTO the batteries, and 100 volts INTO the CC....no danger. It's about the combo of volts*amps... 15 Amps into batteries was probably 200 watts out? Probably only had 1/2 an amp on the panel side if you're pumping 100V into the CC.
Tell us more about your panel array..... What are the panel specs, how many, etc?
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paulz
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# Posted: 7 Mar 2022 09:51am
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Right, when I left yesterday I had about 70v coming in from the panels but only a couple amps, and several times that amperage going to the batteries.
What is confusing me is the Epever spec as shown in the pic of max array wattage of 1560, which if divided by 3 (the max PV wattage of rated charge power), equals the rated charge power of 520 (for my 40A 12V setup), which if divided by 12-13v equals the 40A rating.
I'm back at the city today but basically what I have are sets 3s panels at about 100v, in parallel, that I can plug or unplug based on need, with the ability to go way above the 1560 watt rating briefly on a sunny day. I have never seen the battery charge above 15A, and as you say on the panel side at 100V it's much lower. But if charge voltage is related to battery internal resistance then it's possible to have higher input wattage values that are not going to the battery and released as heat at the SCC? I believe that's part of the design. It has fins... 
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Nate R
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# Posted: 7 Mar 2022 10:08am
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MPPT doesn't work that way, it's not releasing all that energy as heat....That would require more than a heatsink!
Look at Morningstar's stuff: http://support.morningstarcorp.com/wp-content/uploads/2014/07/TechTip-EnclosureHeatDi ssipation.pdf
They're talking about like 30 watts of heat dissipation with their MPPT controllers.
Point being, just understand that the controller can adjust the INCOMING load to match what it needs on the outgoing side, but there are limits to that....
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paulz
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# Posted: 7 Mar 2022 10:55am
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Guess I'll be finding out what those limits are...
I have to be over that 1,560 wattage capability as most of my charging is shade charging. But in mid summer there is the possibility, if I leave all panels connected, to exceed it for a brief period during the day. And there is no mention of protection in the manual.
Wonder if I could put a breaker of some sort on the PV side?
Thanks Nate.
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gcrank1
Member
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# Posted: 7 Mar 2022 11:25am
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My scc specifies a max input voltage so I had to watch out on my panel series 'add ups', no watts calculations required. I have been under the impression that spec'ing is normal.
Ive read that some scc's can take a bit more than spec, and Some Cant before the Magic Smoke is released.
Ie, that spec not to be taken lightly.
Then there is the thing about cold weather is when the spikes happen, not in the heat.
The amps are regulated by the scc, it cant send more to the bat-bank that it is rated for, in your case 40A, even if the array is producing more.
Fwiw, my scc set on 24v input from my 2s/3p array never shows many amps on the display? But my use/recharge balanced out nicely most of the time even with overcast. I never checked the amps read with a clamp meter (oughta get one) from scc to bats.
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Brettny
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# Posted: 7 Mar 2022 01:17pm
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Your batteries will only take what they need. If they only need 15a to get to max charging voltage that's all they will take. Have you put a load on the batteries when the max you see is 15a? Arnt you in heavy pine trees too? You may never see direct high voltage and high amp output of the pannels.
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paulz
Member
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# Posted: 7 Mar 2022 02:27pm
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Haven't tried the heavy load yet, good idea. Yes I'm in the heavy trees, redwoods. I agree, getting direct sunlight on all my panels is impossible. They face different directions and as the sun moves behind the trees some uncover from shade, some cover up. It's a balancing act. I have hooked up more panels this year, and some up the hill behind the cabin where I took out a few trees, so the potential for highest yield will be coming in a couple months.
Again I wonder if there is a fuse or circuit breaker that will work with the varying voltage and amperage output by the panels before it reaches the CC. I can't be the only one who has overpaneled to compensate for poor sunlight...
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travellerw
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# Posted: 7 Mar 2022 04:28pm
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So a solar controller is no different than a battery charger (or the Meanwell). There are way more "potential" watts on the input, but the output is limited to its rated number. If it can only output 40A on the battery side, that is all it will do. Amps are pulled, not pushed, even from solar panels. So it will only pull the amps required on the input side to maintain the 40A on the output side (assuming the battery can accept it).
So if you over panel, it shouldn't be an issue (definitely not with amps). However, you NEED to watch the voltage, especially if you are in series. On a particularly sunny day with a passing cloud you could get a spike over the rated voltage of the controller. There is very little leeway on voltage and a small spike over that number will result in a dead controller.
I'm not really sure why the manufacturers list an actual max number. If you were to draw more than 520W on the input (say 6A @ 100V), then you would be over the ratings of the components on the output side and they would blow up! I think its a CMA number!
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paulz
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# Posted: 7 Mar 2022 05:28pm - Edited by: paulz
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Thanks trave, that is comforting. I'm aware of the voltage limits, I killed a Renogy with a 100V spec, my panels spiked just over it one day. Wife yelled from the cabin 'SMOKE!'. Blew the Mosfets. That's when I went to the Epever with 150V spec.
Speaking of panel voltage, I took your advice and rewired my shop array from 6s2p to 2s6p, it's made quite a difference in my shop FLA charging. Here's a good example of a typical sun exposure. 5 minutes later and it will have changed. There's 6g cables now running underground back to where I snapped the pic.
Kinda wish I had 2s (or maybe even 1s) instead of 3s at the cabin but it would take a bunch of M4 Ys, cables and work!
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Brettny
Member
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# Posted: 8 Mar 2022 06:47am
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You have a BN series 40a? The high input voltage is why I got mine.
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paulz
Member
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# Posted: 8 Mar 2022 09:00am - Edited by: paulz
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Yes two of them, one in the shop. I emailed Epever a couple weeks ago about firmware updates, had to provide my email addy. I've gotten a couple of spam emails from them, one yesterday inviting me to a 'Webinar' on the 10th, 'Wiring and protection in off grid solar systems'. Here's the link if you want to join in. I've never Webinared.
https://www.subscribepage.com/epeverwebinar1
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travellerw
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# Posted: 8 Mar 2022 09:57am
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Quoting: paulz Speaking of panel voltage, I took your advice and rewired my shop array from 6s2p to 2s6p, it's made quite a difference in my shop FLA charging.
That is great to hear that it made a difference..
I see what you mean about sun exposure. Pretty hard to get good coverage with all those lovely trees around. I commend you effort though.
Our site has pretty great solar exposure. The panels will go on racks directly behind where the truck is parked. The end wall of the cabin is facing directly south. The closest trees that direction are about 200 yards away. I'm getting excited to do my install as I have all the components now. Unfortunately we just had a 2ft snowfall, so it will be another couple of months before that happens.
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paulz
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# Posted: 8 Mar 2022 10:20am
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That's some nice open flat ground. Was it cleared? Plenty of forest behind.
It was a bear rewiring that panel! All the J boxes are connected with flex conduit, 10g wire and screw terminals. First I just left the boxes open and ran temporary wiring outside. When it tested well I ran the wiring though the conduit, but the nuts at the J boxes prevented the wires from going through. I was able to use some of the series wiring as tracers. Anyway it's done, buttoned up and working.
That is the array that got me interested it trying solar. I was buying a used inverter off CL, the guy offered me the array for $300 with a cheap PWM CC so i figured what the heck, I'll try some solar. A few days later, with it still on the trailer, I was telling a friend about it, he said he had a friend that was pulling all the solar off his house and I could have all the panels, free. So that's where I got the panels up at my cabin. This has been kicking around since then, glad to finally get some use out of it. My shop doesn't need a lot, just LED shop lights and a tool or two when I'm there. I noticed 3-4 amps coming in a couple days ago and the FLA in the high 12Vs.
As the months roll on the sun will clear more of the tree tops (they are 150'+) and a lot more sun hits the yard. Huge difference between summer and winter exposure. The cabin is 200' uphill, better up there but still hampered.
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travellerw
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# Posted: 8 Mar 2022 01:01pm
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Quoting: paulz That's some nice open flat ground. Was it cleared? Plenty of forest behind.
We have 160 acres in total, but about 20 are cleared. We were told that the old owner cleared those 20 acres with plans to plant hay, but died before he could finish. The land passed to his kids who just ignored it for 20 years before we bought it.
We built our cabin towards the back of the 20 acres with all the clearing between the cabin and the property line to the south. All the bush behind the cabin in the picture is our uncleared 140 acres. We spent last year starting a bunch of ATV trails in there. Its some super thick stuff.
Unfortunately the land was cleared with a CAT and the previous owner died before he could work the land any further. So its SUPER rough in the open areas. Our neighbour was nice enough to bring his big tractor and grade us a road. Its on my list to figure out how to flatten the rest this year.
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gcrank1
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# Posted: 8 Mar 2022 03:10pm - Edited by: gcrank1
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Big 'brush-hog' disc is what my dad used. He did land clearing with Cat dozers and an end loader with a rake ,instead of bucket, to pick up the stumps and brush to shake the dirt out, pile and burn. Too often that stuff is pushed out/aside with way too much dirt in it to burn down well. Once burned down next to a low spot in the field a hole was dug in the low, ash pushed in and covered. No more low spot. Any other dirt work to level out was done, then the brush hog was run over it all to smooth and final level.
I worked with him for a couple years. Would have been better if it hadnt been a father/son thing.....
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paulz
Member
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# Posted: 8 Mar 2022 07:50pm
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Wow that's a lot of land!
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travellerw
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# Posted: 9 Mar 2022 02:49pm - Edited by: travellerw
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It is a lot of land. I realized how much when I was making trails and at the end of the season I still hadn't crossed the half way point of my quarter.
We have tried a breaking disc but since the land has been overgrown for 20 years it just didn't cut it. Picture lumps about the size of 2 basket balls everywhere and the grass, rain and wind have had 20 years to make them hard.
It requires big equipment to cut them down and then backblade to bust them up. Either I need to buy or rent something BIG or just hire it out. We will see..
Anyway.. Back to our regularly scheduled program. I'm hoping Paulz sees some big gains with his changes this year.
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paulz
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# Posted: 9 Mar 2022 04:58pm - Edited by: paulz
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Advertise a Monster Truck or Tractor Pull event, no entry fee as long as they do the prep and clean up afterward.
Quoting: travellerw I'm hoping Paulz sees some big gains with his changes this year.
Just came up from the shop. The array above had it's moment in the sun earlier, 13A charge. But the real benefit of that rewire is the other 90% of the time when just a couple of panels are getting sun.
At the moment both SCCs have blinking green battery LEDs, meaning full charges. Quite a change from the struggles back in December. Might even watch a movie on the big screen tonight.
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Brettny
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# Posted: 9 Mar 2022 07:37pm
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If you leave the bank alone for a few days and put a load on it durring peak sun hours you can really see what the output of the CC is going to be. Any bit of shade or edge of a leaf on any pannel can really bring down the system in a big way.
I believe I have said this before but I get 3hrs of sun on my two 235w pannels. Noon to about 3pm, I'm sure theres some shade in there. Even only being there 3 days at a shot the key to my system keeping us comfortable is a 100ft extension cord and a sportsman 1kw inverter generator.
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paulz
Member
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# Posted: 15 Mar 2022 04:29pm
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Jumpin' catfish! Last two days I've been clearing trees blocking my array. Came into the cabin afterward, 39A charge going! On a 40A controller! And no real draw going, just the usual 4A or so. I ran back out and disconnected some panels to bring it back down.
So now I'm wondering, could I take the identical Epever 40A CC from my shop and use two on the same battery bank? Half my panels on one and half on the other?
The other odd thing is why, with my bank at 13.8V, is it charging so much?
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gcrank1
Member
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# Posted: 15 Mar 2022 06:27pm - Edited by: gcrank1
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Do you really have to discon?
The scc won't put out more than its rated for and the bat charge profile should limit what goes to the bats.
Should.
Yet I dont get why it shows that high at the bat ocon?
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paulz
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# Posted: 15 Mar 2022 07:03pm
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Quoting: gcrank1 Do you really have to discon?
Good question. I wasn't concerned about the batteries as long as the voltage stays in spec, just the SCC.
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FishHog
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# Posted: 15 Mar 2022 07:10pm
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You have a smiley face on your scc so what is the problem 
Honestly I don’t think you have an issue do you? Unless you don’t trust the scc to do it’s job
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paulz
Member
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# Posted: 15 Mar 2022 07:55pm
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I've gone over the manual again. For PV over current it says it will only charge up to the rated charge capacity, 40A. So no worries there. There is the warning mentioned in the picture above about not exceeding three times the rated PV wattage, which I am above, but travellerw thinks it's just their cover my ass disclaimer, which makes sense since it will only accept from the PVs what it needs to put out 40A.
So yeah, maybe I'm worried about nothing. Putting in my other controller would double the potential to 80A, not that I need it at this point.
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gcrank1
Member
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# Posted: 15 Mar 2022 09:29pm
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We all hate letting the Magic Smoke out of our equipment.....and I never liked running at redline for any length of time, but these units seem more voltage input sensitive than amperage.
Until they dont, I guess. I havent been at this long enough to fry anything yet so what do I know 
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paulz
Member
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# Posted: 16 Mar 2022 06:52am - Edited by: paulz
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Yes. I read a couple of threads on the DIY that say the same, keep the voltage under spec and don't worry about the watts, 'good' controllers simply ignore the excess.
Whether or not Epevers classify as good may be debatable.
When I had that 39A coming in yesterday the array was in it's hour or so of full sun, the rest of the time it's mostly shaded and cranking out 5-10A. Cutting down on panels means cutting down those 5-10A which is what really keeps the boat afloat.
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Brettny
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# Posted: 17 Mar 2022 05:00am
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I believe in the small print of your 40a Epever BN series it says for 12v you can hook 1500w of pannels to it. To me I would assume they only want 1500w of pannels in the sun at the same time, I know your heavily shaded.
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paulz
Member
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# Posted: 17 Mar 2022 05:55am - Edited by: paulz
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Yes that's what it says alright. I probably have double that.
If you look at the MT50 picture above, with a 38.5A charge on the output side it shows 92.7V and 5.7A on the input side, 530 watts, same wattage as on the output side. It will be interesting to see if it hits a full 40A charge and at that point will the input watts rise higher than the output watts. And if so, is that an accurate representation related to the 1500W limit.
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gcrank1
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# Posted: 17 Mar 2022 10:44am - Edited by: gcrank1
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On my 2s/3p (24v to mppt 50A scc) on a bright summer day Ive seen close to the max rated output Volts of the panels (with buffer room for the max input to the scc). As long as Im not crowding the scc for V Im not worried.
Basically, that was my test to see if the old panels were still good, and 'watts is watts', same watts if wired as 12v or 24v, just dif Amps. The panels cant output more watts than they are.
My understanding on the Amps is the only way panels meet their 'lab output rating' is ; pretty much in perfect 'lab conditions'.
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