Sanity Check Please

12VoltInstalls

Solar Addict
Joined
Jan 18, 2021
Messages
1,378
Location
Vermont
could potentially see 999 watts. I wonder if Epever overlooked that
The wording on their specs is odd to me; it reads like a hard limit on the watts. It’s not.

The hard limit is volts. You need to respect that religiously.

Overpaneling- despite the odd english in their specs- is fine. Over voltage is not.
If you are wired series to use high volts and maintain panel amps, the epever will provide output up to the amp rating if 40 or 60 at the set volts.
So it is conceivable you may charge at 100% of 40A but actually have unusable watts. (this doesn’t bother me; the goal is to have enough electricity and give yourself max battery life)
the lower voltage goal u mentioned weather related?
The sun affect on panels after cold temps was interesting. Doesnt apply to me

As the temperature goes down, the panels’ output voltage goes up. There are formulas and constants for this, but essentially (unless the 20% puts you close to or at the SCCs max volts) you are ‘generally’ safe if sum of VOC produced is 80% or less of charge controller max volts the factory smoke won’t be released. The temperature is important- not the weather.

So temperature does effect you.

Then there’s the battery type: as 32*F is approached, lifepo can be damaged by a high charge rate; below 32? Charging needs to shut down.

Lead Acid batteries can be charged well below freezing, albeit technically the rate shouldn’t be extremely high. Can’t recall the preferred c-rate. For small wattage systems this is sortof taken care of by the limited panel watts, but even 600W systems may actually need more attention to assuring distilled water is added as needed to keep the electrolyte over the plates.

So the temperature does effect you.
 

vdub

New Member
Joined
May 31, 2021
Messages
29
Thanks for the extra info. My panels are set up as S2P2. The Voc of each panel is 37.6, so that puts my max volts out to the mppt as 75.2 -- well within the rated max volt input of the mppt of 150V. GIven the shadows and the low winter sun we are now getting, I just can't possibly imagine ever going over the rated input on the mppt. I wish I did have that much sun light and fewer trees, but its just not going to happen.

I was all hooked up with everything yesterday and was ready to turn the system on, but it was raining and overcast, so thought I'd wait for a sunny day, which will be Monday (actually today is great, but I have other things to do according to my wife :). We have had several good rains and I'm less concerned with burning the forest down, so Monday will be a good time to flip the switches.

As for the batteries and cold temps... I have the Battle Born 12v bats with the built in heater. I gather that this is a new thing BB has come out with. At any rate, the heaters are connected and turned on and I will add insulation around the bats to help things out. In addition, the bats are inside a cabinet, which is inside a small building. I doubt the bats will see extreme low temps. With climate change, the low temps I saw on that mountain as a child, just don't happen anymore.

One last question.... In what order do I turn off or switch breakers to disconnect the system. I have seen several places where they talk about a specific order to disconnect things, but they were referring to a grid-tie system. I only have 3 switches; my inverter on/off switch, the battery charger breaker from the mppt, and the solar breaker going into the mppt. Does it really matter what order I turn these on and off? If there is an order, my gut feeling is that to turn the system off, I would first turn off the inverter, then the charge breaker, and then the solar breaker. Reverse it to turn the system back on. Does that sound about right? As always, thanks to everyone for helping on this project. Maybe this thread will help someone else, too. vw
 

acdoctor

Solar Enthusiast
Joined
Oct 5, 2020
Messages
126
Just the other day my bms opened. The sun was out. I lost some of the fuses in my 12 volt fuse panel. Some 12 volt items can’t handle the system voltage spike that can happen when the battery is discovered first. The last time it happened the smoke came out of the thermostat that controls the battery heating pad.
 

vdub

New Member
Joined
May 31, 2021
Messages
29
Something I've wanted from the very beginning of this project was a way to monitor how my system was doing from pretty much anywhere. I find it hard to imagine that none (at least, none that I've looked at) have a way to connect to the internet. Most have a local connection on an intranet for monitoring and setup, but nothing that traverses the internet. So, I bought a security camera and simply trained it on my mppt panel. I can tap into the security camera from anywhere I happen to be. Crude, but it works -- this, however, is just a video -- I'm not going to let everyone into my camera. click here I have 9 cameras on my property. Everything is solar. Pretty soon I'll be getting 3 or 4 feet of snow. I hope everything makes it through the winter. My panels are tilted to 20 degrees, so they should shed the snow pretty well and also catch enough winter sun to keep the bats charged.

WinterTilt.jpg
 

MichaelK

Photon Sorcerer
Joined
Mar 21, 2020
Messages
1,337
Thanks for the extra info. My panels are set up as S2P2. The Voc of each panel is 37.6, so that puts my max volts out to the mppt as 75.2 -- well within the rated max volt input of the mppt of 150V. GIven the shadows and the low winter sun we are now getting, I just can't possibly imagine ever going over the rated input on the mppt. I wish I did have that much sun light and fewer trees, but its just not going to happen.
It doesn't work that way. Panels can put at full voltage at only a tiny fraction of full sunlight. It's the amperage that goes up and down with solar intensity. So, like 12VI states, you need to respect that religiously. Even if your panels are shaded as much as you show in your pic, just a few milliamps at excessive voltage is enough to fry your controller.

The fact that you are 2S2p, running at 75V is fine though. Just don't ever get the idea that 4S1P is worth a try.
 

Hravn

New Member
Joined
Sep 1, 2021
Messages
3
Wow, I stumbled in here, but that’s almost exactly my sketch, but I’m starting with 2 parallel strings of three 360 watt panasonic panels a single eg4 24 volt 200 ah battery and will have a 24-12 volt transformer to run some interior lights, a fan, and etc. the panels will be at 90 angles, one ese, the other Wsw, to catch clear morning and afternoon sun from the cabin roof. My major ac load is a small hisense fridge, and the occasional power tool.
eventually the system will grow, but that awaits a couple of tree removals and shed construction, adding in a well pump to the load. Moving up from the po’s 4 golf cart batts and two old Kyocera panels, and an unfused, mess of household extension cords carrying 12 volts strung all over the place.
my primary concern is with cold weather shut off, when we’re not there. Easy to insulate the batteries, but I’d still be dependent on the bms shutting things down should they get below freezing and no one is there to warm the interior p for a month at a time.
 

vdub

New Member
Joined
May 31, 2021
Messages
29
Easy to insulate the batteries, but I’d still be dependent on the bms shutting things down should they get below freezing and no one is there to warm the interior p for a month at a time.
I insulated my batteries just yesterday and I'm now ready for winter. I'll be snowed out of the property in a few weeks and won't be able to get back in until March. So, we'll see how well it works. I have security cameras trained on the mppt status panel and a thermometer, so it should be interesting.
 

vdub

New Member
Joined
May 31, 2021
Messages
29
another option to both fuse and disconnect your solar panels....
The batteries don't charge well when the panels are disconnected.... :cool:

I want my batteries to be fully charged all winter because I'm running a verizon mifi router and 7 security cameras. We tend to get a lot of snowmobilers and hunters trespassing through our property. In the spring, the mushroom hunters like to trespass. No one anymore seems to have much respect for fences and no trespassing signs. The local sheriff frowns on exploding bobby traps or trip wires, so my options are limited.
 
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