# Working Backwards

Solar Expert Posts: 29
I jumped the gun and started accumulating parts for my small solar system before I had a clue as to what I actually needed. Below is a list of what I have. My question is, what can I do with what I have and what else do I need?

2 - Kyocera KD-135-GX-LPU 135W Panels
2 - Rolls S-530 6V/400AH Batteries
1 - Morningstar SS20L-12 Charge controller
1 - SS-MPPT-15L Charge controller (one will be a spare)
1 - Xantrex ProSine 1000 Inverter

I'd like to run a couple of 12V fluorescent lights and my ham radio station an hour or so a day. Realistic, or dreamin'?

Thanks for any info, ideas, comments.

• Solar Expert Posts: 1,341 ✭✭✭
Re: Working Backwards

So say 270w per hour x 4 hours a day of good sun = 1080 watt*hours per day of harvest.

Knock that down a ways since the panels won't put out full rated power when they are hot (and being dark and pointed at the sun they are usually hot), so 1080wh * .8 = 864wh per day harvest.

Knock that down again since neither the charge controller nor the battery is 100% efficient, so 832wh * .8 = 691.2wh/day that actually gets stored in the battery.

Then the inverter won't be 100% efficient either, so you'll lose some more when you draw the watts out of the battery.

That's an educated guess as to what your daily power budget will be. If your loads are 600w and you run them for an hour per day, then your solar system is in the ballpark.

EDIT: math corrected
Re: Working Backwards

First, check the Battery electrolyte levels, get them on a good quality charger, and get a good quality hydrometer...

You want to make sure they don't set around for days/weeks/etc. below 75% state of charge (typically recharge at least once per month in storage).

Next, define how you want to do your system. Frankly, for that size battery bank, you would want a minimum of (assuming a 5% minimum rate of charge and 0.77 system derating):
• 14.5 volts * 400 AH * 0.05 rate of charge * 1/0.77 derating = 377 Watt Array minimum
And those batteries could easily take 2x that amount of solar panels.

The parts you have are good quality--just not really well balanced.

Also, you may wish to think about a AC to DC battery charger (utility power, compatible with your generator) too.

Next, how much sun do you have in your area... A good starting estimate is around 4 hours per day of equivalent noon time sun (winter may be 1/2 that or less):
• 2x 135 watts * 4 hours of sun * 0.52 system efficiency = ~562 WH of 120 VAC inverter power per day
So--At this point, you have some decisions... Trade for some smaller batteries, or add solar panels (and bigger charger), and/or add an AC battery charger (basically turn your system into a UPS system).

Notice that you could run a 1,000 watt inverter about 1/2 hour per day with your current 2x solar panels...

If your loads are much smaller, you may wish to look at getting a 300 watt or smaller inverter as it will waste less power at low output wattage level (better efficiency).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 5,400 ✭✭✭✭
Re: Working Backwards

My quick, off grid rule of thumb:

Take the name plate rating of the PV, divide by 2 to account for all system loses, including panel efficiency, wiring loses, basic battery charging efficiency, controller loses, inverter loses etc, then take that number and multiply by 4 to account for the average number of hours of "good" sun one might reasonably expect, per day on an average, year round. This number can be adjusted up or down due to local conditions, but is seldom much mre than 4 on an on going, year round basis.

So in your case, 270/2=135*4=540 watt/hours/day.

In addition, I second all of what Bill says,,, as usual.

Tony
• Solar Expert Posts: 29
Re: Working Backwards

1) I am located in central Ohio. So the 4 hours per day might be a tad bit optimistic.
2) This will soon be our sole source of electricity, and the only thing we really need to do is to charge a few AA batteries, run a couple of low wattage 12V fluorescent lights, and run the ham transceiver in receive mode mostly (35W).

If I'm understanding correctly, if I run the system as-is, the panels will be incapable of keeping those monstrous batteries properly fed. Is that correct? If I run it as-is, are the batteries being harmed, or am I just going to have less available watt/hours/day available?

If I find some \$\$\$ to add a couple more panels, what should I look for. I don't think I'll find or afford more of the Kyoceras.

Actually, I don't even know what I was going to use the inverter for. I picked it up on eBay LNIB for \$200 and thought I could use it someday.

I've been carefully tending the batteries for the few months since I bought them new. Just performed a little testing, and today the voltage (no load) is at 11.8V where the charge controller's LVD kicked in.

Thanks again for all your expertise and wisdom (and patience with newbies).
• Solar Expert Posts: 5,180 ✭✭✭✭
Re: Working Backwards

typically you can run 2 charge controllers(CC) running to the same set of batteries without a problem, so I'd just look into picking up either 2 more panels like you have or another 200 - 300watts of panels and use the 2 CC you have. should give you a comfortable 1000 watt hours to play with, with a an eye on battery when you've had a couple days of poor weather.

We can't just say that'll be fine, since we don't know what you ham set, transciever, or reciever and transmitter run in actual wattage. labels here might not mean much, and % use of your transmitter might change your usage greatly.
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
• Solar Expert Posts: 5,180 ✭✭✭✭
Re: Working Backwards

Sounds like you need to get those batteries charged!

LNIB for \$200 for a prosine 1000 watt is a nice deal!

Is this for a radio club or something?

If it is you might get members to scower(?) the auto salvage yards looking for solar powered traffic signs that have been hit. There are places that sell non UL panels for under \$2 a watt. I have one Ebay seller with a good reputation that regularly has UL list blems for around \$2 a watt delievered. I'll see if he has anything posted and drop you a PM.
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
Re: Working Backwards

Storing the batteries below ~75% state of charge will kill them over the few months or year...

Their resting voltage (at ~77F) should be above ~12.40 volts (to around ~12.70 volts or so)...

Right now they may be around ~35% state of charge... Not a good level for them to be stored at. Depending on how long, etc., they may not be recoverable.

http://www.windsun.com/Batteries/Battery_FAQ.htm

Big batteries with a small array take a long time to recharge (more time in the <75% state of charge), and self discharge of a large flooded cell bank, particularly as they get old, gets worse and can become a significant part of the overall energy harvest of the panels. Leaving little energy left for your loads.

-Bill "I hope it is not as bad as I am guessing" B.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 29
Re: Working Backwards
Photowhit wrote: »
Sounds like you need to get those batteries charged!

LNIB for \$200 for a Prosine 1000 watt is a nice deal!

Is this for a radio club or something?

If it is you might get members to scour the auto salvage yards looking for solar powered traffic signs that have been hit. There are places that sell non UL panels for under \$2 a watt. I have one Ebay seller with a good reputation that regularly has UL list blems for around \$2 a watt delivered. I'll see if he has anything posted and drop you a PM.

Well, first off, I would love to add another 2 panels to the setup, but these Kyoceras are about \$900 per pair with shipping. OUCH! Are they worth the extra \$\$\$\$?

I did put the auto charger on the batteries to top them off again tonight.

And no, not a radio club, just one of a few local ham operators who can relay radio traffic in the event of a communications breakdown. I don't think we can count of the Internet and the cell system to be up 100% of the time, and I'd like an alternate mode of communications available.

Aside from that, we have no real electricity needs. We heat with coal. We have oil lamps if needed. Just have a few electrical toys (the ham rig, the laptop computer, and the LED TV) that we'd like to keep running if possible.

ALSO: Thank you to EVERYONE who has responded so far. There has been valuable information in every response. You guys are awesome!
Re: Working Backwards

Kyocera 135 watt panels are good quality panels backed by a vendor with a known history of supporting warranty returns on their panels. Also, 135 panels are around the maximum size you can ship using conventional means (possibly UPS, Grayhound Bus, etc.). And 135 watt panels are about as big as one would want for "portable" setups (remember to anchor so wind/etc. does not knock them over and shatter them).

You can get larger panels for not much more money (\$420 for a 185 Watt Kyocera panel + shipping)... but it really depends on your needs (and freight is not cheap--typically if you can find a place/make a group buy, you can get a pallet full shipped for not a whole lot more--as I understand).

You might find a local company (solar installer, etc.) that add panels to his order and get you a good price... Always check pricing as delivered (insured) to your front door.

Not too many years ago \$5 per Watt was a killer price. Now \$2.70 per watt for that 185 watt panel. A decade ago--\$10 per watt?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 5,180 ✭✭✭✭
Re: Working Backwards

If this is a residence you might well qualify for a 30% tax credit in the year you set them up. If you set them up last year both the batteries and panels should qualify, though they need to be installed to code. (or at least they use to) This is a tax credit and comes off the bottom line! if you have \$1700 worth of panels and batteries that @\$500.

I'll PM you some possible places for less expensive panels, though it's hard to beat the quality of the Kyocera and NAWS a winning combination!
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
• Solar Expert Posts: 1,341 ✭✭✭
Re: Working Backwards
Amishdude wrote: »
If I'm understanding correctly, if I run the system as-is, the panels will be incapable of keeping those monstrous batteries properly fed. Is that correct? If I run it as-is, are the batteries being harmed, or am I just going to have less available watt/hours/day available?

Your watt*hours per day is whatever gets harvested and actually stuffed into the battery. Say 500-600 per day.

Now say you run your radio at 35w for two hours. That draws out 70wh of the 500 you put in (plus a few extra for inefficiency - heat lost in the inverter and whatnot).

That would leave a 400wh/day surplus IN the battery.

As long as you put more into the battery than you take out (plus whatever gets lost by the battery self-discharge rate), the battery will eventually get charged.

The problem is, those deep case batteries need the electrolyte stirred up (bubbled) regularly, and that takes a bit more oomph from the charger. The 20a or so that your panels can supply should be enough to stir up the electrolyte - but it won't be very vigorous - probably barely vigorous enough.
• Solar Expert Posts: 29
Re: Working Backwards

PHOTOWHIT: As to the tax credit, that is why I got into such a hurry. Didn't learn about it until the end of 2010 and wanted in on that deal! I did claim and receive the credit.

BB: I think I'll just buy 2 more Kyoceras and connect them through my "spare" charge controller. I like the portability and quality of these panels.

DWH: I've come too far to have a weak link in my system due to my ignorance. I'll just add 2 more panels and chalk it up to "education".

If I had known that solar would have been such a pain in the.....
• Solar Expert Posts: 29
Re: Working Backwards

When I end up with a total of 4 Kyocera 135W 12V panels, what charge controller would you recommend? I don't ever plan on expanding the system beyond that amount.
• Solar Expert Posts: 5,180 ✭✭✭✭
Re: Working Backwards

I actually like the idea of using what you've got, I sent you a PM about what I would get, but forgot you had enough to cover the extra panels, I don't know what the SS-MPPT-15L will do if you run 24 volt nominal into it and it has a cloud effect day and can create more than 15 amps. likely either shut down or disapaite as heat, not sure might want to read up or ask the great knowledge base here!
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
• Solar Expert Posts: 5,400 ✭✭✭✭
Re: Working Backwards

http://www.batteryfaq.org/

Tony
• Solar Expert Posts: 5,180 ✭✭✭✭
Re: Working Backwards
Amishdude wrote:
Photowhit wrote:
I forgot you have Charge controllers to handle the extra panels, just posted reply in forum, Whit
Yeah, I just caught that. So you're saying that I should just duplicate my current 2-panel setup with the 2 new panels and my spare controller and just run that system in parallel with my existing panels into the battery bank?

Yeah, with a few caviots, the information from your morning star will only be partial, since much of the charge isn't going through it. Also if you run your loads back through it, it might give some odd feedback if you do the data logging with the optional meter. i think the low voltage shut down should still work fine.

It is a good question for the forum, also if this will handle the 2 panels and what will happen in near cloud events, a rare situation where the panel actually produces a bit more than rated due to the sun shining directly and clouds near the sun on the horizon reflecting more light.

This actually doesn't have the capacity to handle more than 15 Amp output, so I don't know what would happen if your panels were making enough current for then to reach their rated output. It can handle 15 amps in and out, so if you run the panels in series into the charge controller thats just 7.63 Amps(the panel rating), usually less than that at 24 volts nominal. SO if the panel is producing near this, the MPPT doesn't help as the output is limited to 15 amps as you'll be running a 12 volt battery bank, The Multi Power Point Tracking regulates the output of the charge controller to be just higher than the actual battery voltage then converts the voltage above that point to more current.

I don't know what will happen if the panels are producing near their marked value, if the CC will shut down and restart, until the input is reduced to something it can handle, or if it can short the panels in rapids cycles as to reduce the outgoing current?

I just don't know, Others on the forum will have delt with this matter, and it might well have been on the forum in the past.

Others?
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
• Solar Expert Posts: 262 ✭✭
Re: Working Backwards
I don't know what will happen if the panels are producing near their marked value, if the CC will shut down and restart, until the input is reduced to something it can handle, or if it can short the panels in rapids cycles as to reduce the outgoing current?

Photowit,

I have the MS MPPT-15 with two of the same 135 Kyocera watt panels. Assuming I understand your question, the controller doesn't shut down when given too much amperage, it just limits output to 15 amps. So, depending on the battery voltage, it's hard to get more than 200-220 watts through it with 12 volt batteries. As you say, the MPPT part isn't doing anything at that point.

FWIW, I've seen one of the Kyocera panels alone produce over 160 watts on a moderately cold (45 F) bright day, according to the charge controller.
• Solar Expert Posts: 5,180 ✭✭✭✭
Re: Working Backwards

Just curious, does the unit heat up or is it able to short out the difference some how? I'm just learning myself, I'm sure the "amishdude" will get use out of the info, good to know it doesn't shut down!

I have a Rogue MPPT, but haven't used it much as I still have a tiny battery bank.
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
• Solar Expert Posts: 5,400 ✭✭✭✭
Re: Working Backwards

An MPPT controller will only "through put" the rated amperage of the controller. It is not wasted as heat, it is, in essence, just not produced. An ideal situation is having a controller that most often runs near it's rated output, say ~ 25 amps for a 30 amp controller, but have enough panel capacity such that when the panels are really cold, or the batteries are especially low, the PV goes slightly over the controller capacity for a few minutes.

Most controllers have a recommendation as to what the maximum Pv input should be.

My 400 watts of PV have a theoretical maximum out put of say 35 amps. Almost never do they exceed 30 amps (the limit of the controller) but occasionally on a very cold morning, (like this morning,, -26) I can see nearly 30 amps. (If my battery were somewhat lower (12.5 starting in the morning,, ~ 85%) it might bump the limit of the Rogue,, 30 amps.

Tony