What do I need for a new setup?

velraptor82 · January 8

Just picked up 6x Kyocera 36v 250 Watt Panels (KD250GX-LFB). Got a decent deal on them and they were brand new! So after reading and some research, I don't know what components I need to get? I know I need to get a MPPT charge controller, but what should I get? I want to run these 6 panels off grid on my detached garage for just basic lights and small power tools. Of course I need batteries, etc, but I just wanted to get an idea of what components I will need to make this work?

BB. · January 8

Would a 300 watt psw AC inverter work for your needs? Or do you need more power?

Bill

NANOcontrol · January 8

You don't have a really designed purpose and this is your first venture into solar. I suggest you buy a new battery for your car and use the old battery for the system. That should be sufficient for your needs till you figure out what you want in a system. Everyone seems to destroy their first battery.

MichaelK · January 8

You generally want to design your system based on your desired loads, and you build a battery bank and solar array to support those loads. You're going at the problem from the reverse direction, trying to figure what you can power with X amount of panel.

Assume in the real world your 1500 watts of panels will actually really produce about 1200 watts of power (look up NOCT rating). Assume that a 12V system charges at 14.4VDC, a 24V system at 29.3VDC, and a 48V system charges at 59.3VDC (Trojan specs). Assume that a battery bank likes to be charged at 1/10th of its amphour rating.

1200watts divided by 14.4VDC = 83amps which is too much amperage for a 12V battery (single string)
1200watts divided by 29.6VDC = 41amps, about right for 370-420AH Trojan L-16 batteries.
1200watts divided by 59.3VDC = 20amps, about right for a 225AH Trojan T-105 battery.

Your panels could adequately charge TWO 12V strings of L-16 batteries, or ONE 24V string of L-16 batteries, or ONE string of smaller T-105 batteries in a 48V string. Each battery configuration would have roughly eqivilent storage capacities.
420AH X 2 X 12V =10080 watthours of power
420AH X 24V = 10080 watthours.
225AH X 48V = 10800 watthours.

Lastly, assuming you never, ever want to drain your batteries more than 50%, and 10-15% daily consumption is about right, then you'll have between 1000 and 5000 watthours of capacity depending on how much you're willing to deplete. For L-16's, Trojan says that at 50% depletion their battery will last about 2000 cycles (that's ~5 years). At less than 20% depletion, those same L-16's might last for +5000 cycles (13 years). You decide for yourself whether you want more power, or longer lasting batteries, you don't get both.

Now that you know what amps you can produce, you can go about selecting a charge controller. For just 20 amps, you could select Midnight's Kid.

https://ressupply.com/charge-controllers/midnite-solar-mnkid-b-the-kid-charge-controller

In the 40 amp range though you'll need a more capable controller. Look at this Morning Star or Outback.

https://ressupply.com/charge-controllers/morningstar-ts-mppt-45-tristar-charge-controller

https://ressupply.com/charge-controllers/outback-flexmax-fm60-charge-controller

If you'll be producing up to 80 something amps, you'll need a high capacity controller like Midnight's 150 Classic. It can handle up to 96amps at 12V.

https://ressupply.com/charge-controllers/midnite-solar-classic-150-charge-controller.

The last thing you'll need to think about is an inverter. Most likely you'll want an pure sine wave inverter if you're using power tools. Your choice will depend on your system voltage. For anything above 1000Watts, you really want a 24V system, and anything past 2000 you'll want 48V. My 48V system can power my 1.5hp well pump.

velraptor82 · January 9

Thank you MichaelK for your information and that was very well laid out. I have found a lot of info, but what is confusing me is these panels are 36v, and I keep finding info for 12v or 24v setups. What my goal would be is to have my detached garage completely off grid and be able to use work lights, small power tools, etc. Would like to some how wire it up to a breaker box where I have outlets in the walls like normal. I know I will need a battery bank, and I am aware of some of the components needed. Mostly I needed some pointers on what equipment I should get to utilize these 6 panels I have. I don't plan on adding panels, but would be nice to have that option if available.

NANOcontrol · January 9

Don't loose sight that batteries suck. You pay more for having a battery than you will ever get back. Find something else to do with the solar panels like heat water or space. It is just not that easy for the average person to do something useful with solar.

Estragon · January 9

System voltages are typically 12, 24, or 48v. Nominal 36v panels would typically be put in series strings to an mppt controller. The size of the strings depends on the capabilities of the controller (maximum open circuit voltage produced by panels at record low temps at your location) and distance between panels and controller. 3 strings of 2 in series may work well assuming reasonable distance, which would give string voltage of ~70v - okay for 12/24v, but too low for 48v.

If the small power tools include a circular saw, for example, you'll want a good pure sine wave inverter ~1500w. You could do that with 12v, but 24v may be a better choice. You will want a unit designed to be hardwired, which you can wire up to a standard AC breaker panel.

MichaelK · January 10

velraptor82 said:

but what is confusing me is these panels are 36v, and I keep finding info for 12v or 24v setups. What my goal would be is to have my detached garage completely off grid and be able to use work lights, small power tools, etc. Would like to some how wire it up to a breaker box where I have outlets in the walls like normal.

Ok, your panels are NOT 36V. If you look at the actual technical specifications, it says they have an open circuit voltage of 37.8 and a maximum power point voltage of 30.5. What that means is if you took one of your panels, put it out in the sun, and touched a voltmeter to the +&- leads, you'd get a reading of ~37.8VDC. If you connected those leads to a load, such as a 24V battery, then the maximum voltage the panel could produce under load is ~30.5VDC.

With the MPPT controllers that I identified for you, the controller acts as a transformer to bring the voltage of the panel down to exactly what the battery wants. When the controller is connected to a 12V batteries, it will transform the voltage down to ~14V to charge the 12V battery. Connect the same controller to a 24V battery, and it will drop the voltage down to about 28V. As the voltage is transformed down, the amperage gets bumped up, so the wattage stays the same.

What that means in the real-world is that you can put panels in series to raise their output far above what the battery is. High voltage cuts down on the thickness of the copper wire that runs from the panels to the system. You can also put the panels further away from the rest of the system because voltage drop is less important. What you can do is wire three panels in series to get ~91VDC. You can make two 3-panel arrays, each producing about 8.2 amps at 91V (that's called a 3S2P configuration). Alternatively you could make 3 arrays of two panels in series (2S3P configuration), each array putting out 8.2 amps at ~60V.

One last thing. Some people get lured into the idea that they can make 12V work well for them because there are so many 12V RV appliances. You are really better off designing at least a 24V system from the start and forgetting about 12V completely. You've already got enough panels to support a 24V system with L-16 batteries, which are the standard for off-grid cabin people like me. The quality inverters out on the market are designed to be hard-wired into a standard electrical panel, and that's what I have done at my own cabin.

softdown · January 11

Don't buy a huge inverter with the plans to run it full time. Buying a huge inverter may be the most common mistake. Big inverters are like big car engines. They take a lot more power to idle.

Probably the most common mistake may be screwing up with batteries. There are at least a dozen ways to do that.

I can fully appreciate the desire to have back up power but battery's go bad just sitting there and the years fly by. Too bad we can't easily get dry batteries like we used to.

BB. · January 11

Interestingly, "Dry charged" Lead Acid batteries still only have a shelf life of 18 months (at least recommended for sale).

https://www.solar-electric.com/learning-center/batteries-and-charging/deep-cycle-battery-faq.html

Battery Lifespan

The lifespan of a deep cycle battery will vary considerably with how it is used, how it is maintained and charged, temperature, and other factors. It can vary to extremes - we have seen L-16's killed in less than a year by severe overcharging and water loss, and we have a large set of surplus telephone batteries that see only occasional (10-15 times per year) heavy service that was just replaced after 35+ years. We have seen gelled cells destroyed in one day when overcharged with a large automotive charger. We have seen golf cart batteries destroyed without ever being used in less than a year because they were left sitting in a hot garage or warehouse without being charged. Even the so-called "dry charged" (where you add acid when you need them) have a shelf life of 18 months at most. (They are not totally dry - they are actually filled with acid, the plates formed and charged, then the acid is dumped out).

These are some typical (minimum-maximum) expectations for batteries if used in deep cycle service. There are so many variables, such as depth of discharge, maintenance, temperature, how often and how deep cycled, etc. that it is almost impossible to give a fixed number.

Starting: 3-12 months
Marine: 1-6 years
Golf cart: 2-7 years
AGM deep cycle: 4-8 years
Gelled deep cycle: 2-5 years
Deep cycle (L-16 type etc): 4-8 years
Rolls-Surrette premium deep cycle: 7-15 years
Industrial deep cycle (Crown and Rolls 4KS series): 10-20+ years.
Telephone (float): 2-20 years. These are usually special purpose "float service", but often appear on the surplus market as "deep cycle". They can vary considerably, depending on age, usage, care, and type.
NiFe (alkaline): 5-35 years
NiCad: 1-20 years

-Bill

softdown · January 11

It was 1979, as memory serves, that I bought a dry motorcycle battery and dumped the dry acid with water into the battery. I think I have read stories of people storing dry batteries for "awhile"....

I suspect that one could store iron batteries for a very long time. But they are expensive and not made domestically for some reason. With the affordability of large solar arrays, iron batteries become a quite logical choice if they were priced where they should be.

A problem with lithium is the expense and need for cobalt that apparently is only mined in the Congo. Problems with supply could arise. I am also unsold on using hundreds of oversize AA laptop batteries like Tesla uses. Then again.....Tesla batteries are getting the job done.

BB. · January 11

Nickle Iron batteries are not bad. But charging efficiency is something like ~65% or so. With "cheap" solar panels these days, "over paneling" because of low system efficiency is not the worst solution in the world.

For Nickle Iron batteries, there is having to change the electrolyte every few years because the electrolyte slowly absorbs the CO2 out of the air and "goes bad". Having to store bags Potassium Hydroxide (sealed against CO2 and Moisture) mixed with distilled or de-ionized water. Supposed to be non-toxic for disposal.

-Bill

softdown · January 12

BB. said:

Nickle Iron batteries are not bad. But charging efficiency is something like ~65% or so. With "cheap" solar panels these days, "over paneling" because of low system efficiency is not the worst solution in the world.

For Nickle Iron batteries, there is having to change the electrolyte every few years because the electrolyte slowly absorbs the CO2 out of the air and "goes bad". Having to store bags Potassium Hydroxide (sealed against CO2 and Moisture) mixed with distilled or de-ionized water. Supposed to be non-toxic for disposal.

-Bill

Thanks for that info. Potassium hydroxide is very extremely alkaline. I do mean very extremely alkaline;

pH Value

"Potassium hydroxide has very high alkalinity as measured on the pH scale. This scale goes from 0 to 14 and defines the acidity or alkalinity of a substance, with 7 being neutral, and alkaline being higher than 7. Pure distilled water has a pH of 7. Potassium hydroxide has a pH of 12 to 14. Compare this to ammonia at 10 to 11, and borax at 9."

Even higher than sodium hydroxide aka: Drano.

One could really screw up very badly if accidentally mixing normal battery acid with a nickel iron battery base...potassium hydroxide. Going to have to get some of this stuff. For science. Incidentally.....this risk may be part of the reason that nickel iron batteries are generally not readily available. Putting battery acid in a functional nickel iron battery would likely be a somewhat spectacular event.

mike95490 · January 12

> Putting battery acid in a functional nickel iron battery would likely be a somewhat spectacular event.

Yeah, but you'd have to work at it. There is no battery acid laying around to "put" into the cells. Just 15 gal of distilled water.

Like lead acid batteries, who keeps acid around? Just distilled water. Batteries come with their own acid generally. If they do come with a pouch of acid, all that goes into the battery, you don't leave it around to use later.

But they are not efficient, I'm always adding water. But voltage is a great SoC indicator, I never worry about recharging to prevent sulfation, or if I have to EQ this month. The downside is replacing all the electrolyte every half dozen years, it's going to be real messy and a lot of work.

softdown · January 12

mike95490 said:

> Putting battery acid in a functional nickel iron battery would likely be a somewhat spectacular event.

Yeah, but you'd have to work at it. There is no battery acid laying around to "put" into the cells. Just 15 gal of distilled water.

Like lead acid batteries, who keeps acid around? Just distilled water. Batteries come with their own acid generally. If they do come with a pouch of acid, all that goes into the battery, you don't leave it around to use later.

But they are not efficient, I'm always adding water. But voltage is a great SoC indicator, I never worry about recharging to prevent sulfation, or if I have to EQ this month. The downside is replacing all the electrolyte every half dozen years, it's going to be real messy and a lot of work.

I have some regular 8Ds made in 2011 that are still chugging along nicely. Are you saying that I should replace the electrolyte? I can do that.

It seems as though regular batteries may work, more or less, if voltage stays above ~12.2. They can cycle alright but distinctly dislike deep cycles below ~12 volts.

BB. · January 12

Nickel koh electrolyte needs to be replaced every 6 years or so.

Generally, people do not replace lead acid electrolyte.

Assuming you are talking about lead acid batteries Softdown

Bill

What do I need for a new setup?

Comments

Battery Lifespan

pH Value