Am I on the right track?

[RiP-HS-]

"Nope. Bear in mind that you are not looking for permanency in your situation. Extension cords and power strips and whatnot are probably the order of the day."

LOL, that's not what I wanted to hear but expected it nonetheless.

Is there a way to test the efficiency of the panels short of just checking voltage? When I checked the other evening the sun had just started going down nowhere near direct sunlight and got 40vdc.

I shouldn't get below 50% of the battery bank correct? To tell if the panels can keep up, should I discharge to 50% and with no load see how long they take to charge back up?

*edit*

Is there a way to draw 12vdc from a 24v bank w/o damaging batteries. For example, we use 24v inverter to power lights/water pump while up and cooking, etc. Then at night use a small amount of 12v to operate a small 12vdc fan and charge phones, etc?

[AzRoute66]

Is there a way to test the efficiency of the panels short of just checking voltage? When I checked the other evening the sun had just started going down nowhere near direct sunlight and got 40vdc.

I wouldn't worry about it. If you have a 10A meter you could check short circuit current, but most people don't have that meter and I wouldn't spend any effort trying to find one [at this point]. Best way to find out is to attach it to a charge controller.

I shouldn't get below 50% of the battery bank correct? To tell if the panels can keep up, should I discharge to 50% and with no load see how long they take to charge back up?

50% is the common rule of thumb. There are other schools of thought. Nothing special happens at 40% or 30%, etc. Long term repeated cycles that deep build up to shorten battery life compared to one that gets babied. I can find others that say that a good deep discharge from time to time is good, just like a well saturated charging. We'll be able to tell a lot during your first week of use just by looking once in a while. There are lots of things we can do without one, but if you peruse the board on the subject you won't get far without running into advice to get a good $10 hydrometer - and use it. I am in that camp. You are light years ahead of most with an MT-50 and an energy meter though.

Speaking of the energy meter, with a DPDT switch, you can wire it to easily change between charge and discharge at the meter. Worst case with a small screwdriver you just reverse the two sensor wires on the meter terminals. A pain in the butt, but flip it to discharge around sundown, and back to charge when you get up in the morning and you'll get a wealth of usable numbers during your startup week. I'm too lazy so I bought two meters.

[AzRoute66]

Is there a way to draw 12vdc from a 24v bank w/o damaging batteries. For example, we use 24v inverter to power lights/water pump while up and cooking, etc. Then at night use a small amount of 12v to operate a small 12vdc fan and charge phones, etc?

Sure it is googled as a "24 to 12 volt" converter or regulator. This one is under $10 and was on the first page of the amazon results...

https://smile.amazon.com/SINOLLC-Con...volt+converter

Very efficient, note no heat sink required. Also, it is such a simple machine it can be home built in 100 different design approaches from basic components with a modest amount of skill.

Oh, and well done for not considering just 'tapping' the 12V off the battery bank.

[RiP-HS-]

Ok, thanks for that, I'll look to see if I can find plans, possibly I have some stuff laying around.

I'm about to start finalizing the wiring now.

Thank you again for taking the time to help me with this.

[AzRoute66]

Don't rule out an auto voltage regulator if a converter is hard to come by for you. If you find one in the neighbor's junk box, hook it up. If it smokes, look at him and say 'Oops', if it doesn't offer him a beer in exchange for it. Most of the time, you'll be giving out a beer.

[RiP-HS-]

A warm beer or cold beer? Two different animals around here right now..

For my panels say a 30' run, they are 92vdc in series and 8, call it 10 amps... Would #12 wire be fine or do I need to go up to #10? #10 seems a little extreme to me as the wires out of the panel are nowhere near #10.

[AzRoute66]

Cold if it works, pot luck if you said 'oops'. 12 AWG is good for 20 amps so that is fine. 30' run will be right at a 1% voltage loss so also fine.

Let's keep that in mind if you parallel the three panels at some point in the future. Your 12 AWG solution sucks for that.

You are just using me for a sanity check right? I mean, it is kinda important that you be looking this stuff up so that you are learning what you have and resources concerning it (besides some fool on a keyboard).

[RiP-HS-]

Lol, yes I am... Wire chart calls for #10 but it seemed like way overkill considering the wires on the back of the panel appear to be something like a #14.

I'm just bouncing my thoughts and trying to learn as much as I can from someone willing to share. I just don't want to screw anything up...

I have a decent working knowledge of AC electricity but the solar / CC / Inverter all of this is new to me. Just being cautious. I did a fair, albeit, fast down and dirty research to buy all of this stuff and I made a couple of mistakes. I want those to be the worst mistakes.

[RiP-HS-]

So I hooked panels today to the 24v and the 12v. The charge controller for the 12v is a little crappy. It doesn't have a manual with it and I didn't have a lot of luck with the setup. Apparently, you have to manually set up the panel and battery parameters, I'll have to look around and see if I can find any information on it. And it seems that for the CC to turn on, there has to be sunlight energizing the panels.
Unfortunately, it has been really cloudy here today so I didn't get to see a lot of action. The 24v was charging at 70vdc at .8 amps.
I also ran a 3 way cigarette lighter plug to the bedroom from the 12v. There should be enough juice to charge phones but I want to make sure it's charging properly before I plug a fan in.

Hope everyone's day has been good.

[AzRoute66]

So I hooked panels today to the 24v and the 12v. The charge controller for the 12v is a little crappy. It doesn't have a manual with it and I didn't have a lot of luck with the setup. Apparently, you have to manually set up the panel and battery parameters, I'll have to look around and see if I can find any information on it. And it seems that for the CC to turn on, there has to be sunlight energizing the panels.

That's a problem. If the battery has juice, there should be at least a blinken light. At least for the ones I have seen. Can the MT-50 be hooked to it, or does it have any interface port at all? I'll go back through your posts and try to find something on it.

For ALL charge controllers, make sure you hook up batteries before the panels.

Unfortunately, it has been really cloudy here today so I didn't get to see a lot of action. The 24v was charging at 70vdc at .8 amps.

This is also a problem. It shouldn't be charging much higher than 29-ish volts. Did you mean to say the panels were producing 56 watts? (70V x 0.8A)

[From earlier,] " yes I am... Wire chart calls for #10 but it seemed like way overkill ".

If you found a chart that calls for 10 AWG wire for 10 amps, it should be destroyed in favor of one that makes some fleeting reference to NEC on it.

Edit: I looked up the 20A charge controller, seems like a nice unit with built in display. As I said, make sure you hook it up to batteries before the panel. While I was at it, I looked up the 12V 3000W inverter that I encouraged you to peddle. It is 12-120VDC. That is a horse of a different color. A very nice unit that would be at home on a much bigger setup than you have, but wouldn't be a bad choice on a 24V battery bank. Although it seems spare (or the other inverter seems spare), make sure you get good value if you trade it.

Double Edit: Found a manual for the '20A' controller. Seems that it is a 10A controller. This may be the worst Chin-glish manual that can be found on the internet. I had to stop attempting to read it, but for what it is worth, here it is: http://www.lillyelectronics.com/down...MPT-7210A.docx

[RiP-HS-]

Lol, thank you! I found that same one. Today while the panels were getting light, it came to life. So it does get its power from the panels as of now its dark and the CC is off. It appeared to work properly today but there is some weirdness about it. I think when mail service gets a little better, I'll order a different one for the 12v.

The 24v setup was producing 76vdc and 2.8amp but again it was cloudy. I thought that under optimal conditions the panels should be producing 92vdc and a little over 8amps and that since they are in series if one gets some shade it affects the entire system, is that not correct? Being that it was cloudy, the volts and amps were going up and down throughout the day.

It does look like I jumped the gun a little on both inverters, as you said not near enough storage or panels for either. The 3000w inverter for the 12v is just a baby compared to the 2000w for the 24v (but it's an auto transfer and charger too). I was in a panic/rush and I couldn't find a diy type solar place at all. I had one company return my call but all they were interested in was huge installs. Oh well, I have some light and some decent equipment to work with, so we'll make it work.

Earlier I wired two (of our existing) overhead led track lights to the inverter on the 24v setup and both powered with the inverter draws 55watts, I'm afraid that'll drain me too fast. I may have to give up on the inverter, with just 210ah I'll have to be super frugal so, currently, I'm looking for some 24v lights that put out good light with a light draw to get away from using the inverter. Something like these....

https://www.amazon.com/gp/aw/d/B06XPGNJZX/ref=mp_s_a_1_1?ie=UTF8&qid=1509320110&sr=8-1-spons&pi=AC_SX236_SY340_FMwebp_QL65&keywords=24v%2Bled%2Blights&psc=1&th=1

https://www.amazon.com/gp/aw/d/B0728...UmL&ref=plSrch

What type of lights do you use, although, my situation is probably a little different. I considered some of the cheap RBG led strip lights. If I can just light one medium and one small room with a flood light, it may be the most efficient way. The 12v should run the pump just fine for short periods.

I was looking around for state of charge charts and came up with 24.2v and 12.10v for 50% depletion, does that sound right? I do have a hydrometer, how often should that be performed?

[AzRoute66]

[...] Today while the panels were getting light, it came to life. So it does get its power from the panels as of now its dark and the CC is off. It appeared to work properly today but there is some weirdness about it.

I was wondering about that. Before I chucked the manual, I thought I read that this charge controller wanted you to hook up the panels first. I put it down to my poor Chinese, but sounds like that might really be what they wanted. Don't chuck it just because it is different - it might do the job just fine after you get used to its quirks.

The 24v setup was producing 76vdc and 2.8amp but again it was cloudy. I thought that under optimal conditions the panels should be producing 92vdc and a little over 8amps and that since they are in series if one gets some shade it affects the entire system, is that not correct? Being that it was cloudy, the volts and amps were going up and down throughout the day.

Your panel Vmp is 37.3V x 2 = 74.6. Heat makes that go down, having less than full load makes it go up, lots of factors so you are right in the ballpark voltage-wise. If you have depleted batteries, or high load, I would expect the panel amps to go up to somewhere in the vicinity of Imp on a sunny day. Panels now have bypass diodes which alleviate some shading issues, but in general shade on any part of either panel will reduce array amperage.

What type of lights do you use, although, my situation is probably a little different.

Way different. I am slowly transitioning to LED as my existing incandescent and CFLs fail, but have no schedule. I have a very nice LED desk lamp to my right, but my 3-way incandescent on the left is the one that is on all of the time. It will probably be the last incandescent bulb in the house (county?) just because I use it so much and like the light.

I was looking around for state of charge charts and came up with 24.2v and 12.10v for 50% depletion, does that sound right? I do have a hydrometer, how often should that be performed?

You might hate this answer but - all the time. (Just when you are starting out.)

You start with lightly discharged batteries, have great sun, and batteries are in float by 1130. Your charge controller is saying they are fully charged, use the hydrometer to go check that. Multiple times. You know your batteries hold X watt-hours, when your energy meter says you have used 1/4th of that, you should be at a 75% state of charge, use the hydrometer to check that. You have two cloudy days in a row, check the specific gravity and see if it matches up to the energy meter and common sense. Get what I am saying? You want to find out what the correlation between what you are experiencing, and reading on the meter, and yes (sigh) voltage, have to what is really going on (hydrometer).

Using voltage to estimate state of charge will work, but only after you have a hydrometer generated baseline to compare it to. If you don't have that baseline, you use the charts [24.2V means ___%, etc] but guess what - those are open circuit voltages on a battery that has rested for hours. How often do you have that in a working off grid system - never. So, use the hydrometer as 'truth' and soon your eyeballs and energy meter will give you a good estimate of the truth, then use the voltmeter and perhaps at some point you will find some good correlations at specific points. Knowing those 'typical' voltages on your healthy system will likely be very valuable if you ever need to troubleshoot something gone wrong down the road.

Once you know your system, you probably won't use it much more than once per month to check for cell imbalances and/or perform equalization. Battery banks are attention hogs and costly to neglect.

[AzRoute66]

Also, I wanted to modify my charge 'controller' micro-rant. There are two aspects of charge that the controller really does control. That is they really do control discharge from the batteries through the panels at night and they also are great at preventing overcharge of the batteries. I may start calling them 'overcharge controllers'.

Let's check that Chinese 12V controller on that discharge prevention at night. It's not that I don't trust it, I just don't trust it yet.

[RiP-HS-]

Is it possible to just put a diode on the positive side to prevent any back flow of da juice?

To check the chinesium CC should I check voltage on the panel side after dark?

I still have a lot to learn about what I see when looking at the CC. The volts and Amps are ever changing and I have no idea if it's in bulk mode or float mode, maybe a better CC gives more info? As of right now the CC shows a for the Batts, so I take its word. Tomorrow, I'll check with the hydrometer and see what it says.

Thank You again for your help!

[Mike90250]

Is it possible to just put a diode on the positive side to prevent any back flow of da juice?

To check the chinesium CC should I check voltage on the panel side after dark?

I still have a lot to learn about what I see when looking at the CC. The volts and Amps are ever changing and I have no idea if it's in bulk mode or float mode, maybe a better CC gives more info? As of right now the CC shows a for the Batts, so I take its word. Tomorrow, I'll check with the hydrometer and see what it says.

Thank You again for your help!

you can simply use a proper size diode & heat sink ( we need the volt open circuit & amps of your panels, and how many in the array) instead of a charge controller.

a working charge controller can"leak" about half of battery voltage, into array at night, but there should not be any amps.