DIY Remote Solar Power System

[SunEagle]

Still cant post. So screenshotting my post again. Screenshot 2017-02-17 17.24.54.png

Based on you watt hour estimates it comes to 5.8kWh used daily. That amount would require a 12volt 2000Ah battery (5800wh / 12v x 4 = 1933Ah).

Good luck building that system out of paralleled 12volt batteries

[Hiro]

Am I correct with these figures?

Usage 2.643 kWh p/d
312 W Max peak load
System 24 V
Current 131 Ah
Panels 8 130W 12V
Controller 60 Amp
Inverter 600W 24V
Battery Bank 655 Ah 2 days 70% Depth

What benefit would 48V give with this system?

[Hiro]

The batteries won

[Mike90250]

Inverter 600W 24V

OK, so you aren't needing 2/O cables for that. As power levels go down, the need for higher voltage diminishes. Most you will pull will be 30 amps DC #6 wire is good for a few feet of that, But trying to get enough parallel batteries to get the amp hours needed at 24v is tough, With higher voltage, you need less amp hours for the same storage capacity.

[Sunking]

A 600 watt 24 volt Inverter only requires a 10 AWG cable assuming the 1-way distance is 5 feet or less. That would be 6 mm^2 wire.

I would like to help you, but I or we need to know how many watt hours you need in a day. You have already shot yourself in the foot assuming 2-day battery reserve. One item you must have being off grid is a generator and AC charger. If you do what you plan, the batteries will be dead in a month or two. So if you want to do this right, get ready for a major expense. Do it your way and you will loose your money and have a pile of useless junk.

Think of it this way. You want to come to the USA and all you have is a ski boat. Be sure to write your Will before you leave, because you not going to make it.

Example for 3 Kwh of usable energy per day you will need.

Panel Wattage = 1200 watts
MPPT Controller = 50 Amps
24 volt 600 AH Battery using 600 AH batteries, not parallel.
Inverter can be up to 1000 watts.
3 Kva Generator with a 75 amp 24 volt battery charger.

I have no idea if that will work for you or not because I am not convinced you have your daily Kwh usage nailed down. I can tell you what I just told you will produce 3 Kwh of usable power each day and if you learn how to take care of batteries, they should last at least 3 years. Maybe longer if you use high quality batteries. Thing is with batteries, you will destroy the first set until you learn how to care for them.

So please stop and think about this before you regret it later. OK?

[Hiro]

The batteries won

[Hiro]

Here we go again
Screenshot 2017-02-18 15.06.11.png


Screenshot 2017-02-18 14.53.21.png

[Sunking]

Current = Power / Voltage

So lets run a couple of math problems and see how it works.

• 1000 watts / 12.5 volts = 80 Amps
• 1000 watts / 25 volts = 40 Amps
• 1000 watts / 50 volts = 20 Amps

To find the Watt Hour Capacity of a battery = Battery Voltage x Amp Hours

So lets run some math problems to see how it works.

• 12 volts x 200 AH = 2400 Watt Hours
• 24 volts x 100 AH = 2400 Watt Hours
• 48 volts x 50 AH = 2400 Watt Hours.

What are your observations?

So lets say we go to Batteries R Us and we buy 4-12 volt 50 AH batteries.

• If we connect all 4 of them in Parallel we have 12 volts @ 200 AH = 2400 Watt Hours
• If we connect them two in series 2 batteries in series and and the other 2 in series, then parallel both of the strings we have 24 volts @ 100 AH = 2400 watt hours.
• If we connect them all in series we have 48 volts @ 50 AH = 2400 watt hours.

What are your observations?

Word of caution here the site you used to run your numbers is skipping over a few things and giving you bad advice. First they did not factor in system losses of a battery system. Now that I have your minimum Sun Hours and daily usage Panel Wattage = [2364 watt hours x 1.5] / 2.36 Sun Hours = 1502 Watts. So 1500 watts works and requires a 60 Amp MPPT Charge controller if using 24 volts.

Next huge error is they recommend using 130 watt battery panels. That would be very foolish because 12 volt Battery panels cost 2 to 6 times more per watt than a Grid Tied panel. You want to use higher voltage GT panels wired in 2 series strings. Use 6 250 watt panels. in a 2 x 3 series parallel combination. That is two parallel strings with 3 panels wired in series.That will save you a few thousand coins in both panels, hardware, and material cost. Even less than 1040 watts of battery panels they recommended.

Next is 131 AH @ 24 volts is nonsense. Current is Amps, not Amp Hours. I have no clue what that means other than jibber jabber nonsense.

Nest up they cannot do math with respect to battery AH's if you use 8 6-Volt 278 AH batteries configured for 24 volts, 4 in series, 2 string is 24 volts @ 556 AH, not 524 AH they said. Not only is the math wrong, recommending using parallel battery strings is just plain silly. Based on 2364 watt hours per day usage of 2642 Watt Hours at 24 volts = [2643 wh x 5] / 24 volts = 550 AH.

If it were me I would do this to save a few more coins:

Panel Wattage = 1500 watts using 250 watt GT Panels
30 Amp MPPT Controller. Note here if you go 25 volts requires a much more expensive 60 Amp Controller.
48 volt 225 AH Battery. The 8 Trojans they recommended will work just fine. You will work just fine. You would need 8 of them wired in series.
Inverter can be as large as 1500 watts. I would use a 1000 watt Inverter.

By using 48 volts with a 1000 watt Inverter no wire is required to be larger than 10 AWG or 6 mm^2. Real easy to work with and terminate. In the end I just saved you several thousand dollars over using what that site came up with.

One last thought to share. In Summer time you will have a huge surplus of power that will never be utilized. In Summer the panels can generate up to 6700 Watt Hours if it could be used. Your takeaway here is tell your dad if he has some power hungry application in Summer Months do so around mid day so he can utilize more power. Any power not used is lost forever because it has no place to go. When batteries are charged up, no power is pulled from the panels unless it has some place to go. That means he can make moonshine in summer around noon hours directly from the panels in summer months.

[Hiro]

This is excellent, insightful and digestible information Sunking

Battery configuration has always been difficult to understand for me.

The first math problem Amp=W /V
1000w @ 12.5V gives 80A so this will drain batteries quicker although providing more current albeit unnecessary
1000W @ 25V gives 40A
1000w @ 50V gives 20A These provide enough power to run the units and inverter for AC power conversion longer.

Second math problem confuses me; as I understood it, the more Ah in a battery bank the better. What I am observing is the life of the batteries will last longer on 48V as its producing less Ah for the same amount of Wh. Screenshot 2017-02-18 21.26.27.png

[Sunking]

This is excellent, insightful and digestible information Sunking

Battery configuration has always been difficult to understand for me.

The first math problem Amp=W /V
1000w @ 12.5V gives 80A so this will drain batteries quicker although providing more current albeit unnecessary
1000W @ 25V gives 40A
1000w @ 50V gives 20A These provide enough power to run the units and inverter for AC power conversion longer.

OK you are getting the idea, but not quite getting it. A 12 volt 200 AH Battery = 24 volt 100 AH Battery = 48 volt 50 AH Battery.

If you charge or discharge the above equivalent batteries at say 250 watts, the current rate is exactly the same at C/10. where C = the battery AH capacity, and the number 10 is the hour charge or discharge rate.

Amp Hours = Amp x Hours
Amps = Amp Hours / Hours
Hours = Amp Hours / Amps

So if I say we discharge or charge a battery at C/10 and the 12 volt battery is 200 AH I am saying we discharge at 200 AH / 10 H = 20 Amps. C/10 on the 24 100 AH battery is 10 amps, and the 48 volt 50 AH battery is 5 Amps. The rate is exactly the same C/10 hours.

Power = Voltage x Current

12.5 volts x 20 Amps = 250 watts
25 volts x 10 Amps = 250 Watts
50 volts x 5 Amps = 250 Watts

The rate is exactly the same. So your two statements above in RED are FALSE. Everything is exactly the same. I can construct all three batteries above with the exact same 12 volt 50 AH batteries. It takes 4 of them. If I put them all in Parallel I have 12 volts @ 200 AH, and if I put them all in series I have 48 volts @ 50 AH. If I apply a 250 watt load on them regardless of the voltage, each battery supplies 5 amps.

Kwh does equal Wh. I am not sure how you say they are different.

Watt Hours = Watts x Hours

In a battery the Watt Hour Capacity = Voltage x Amp Hours. So:

12 volts x 200 AH = 2400 wh or 2.4 Kwh
24 volts x 100 AH = 2400 wh or 2.4 Kwh
48 volts x 50 AH = 2400 wh or 2.4 Kwh

Remember I can construct all three batteries with 4 12 volt 50 AH batteries. On paper and theory they are exactly the same. However in practice things change. If I put all 4 batteries in parallel for 12 volts @ 200 AH and apply a 250 watt load via an Inverter, the Inverter will draw 20 amps total from all 4 batteries. However due to the battery internal resistance variances and cable/connection resistances the batteries DO NOT equally share the current. One battery will always be supplying more current than the other three. In real life I could expect to see 7 amps + 3 Amps + 4 Amps + 6 Amps for a total of 20 amps. The battery supplying 7 amps is doing most of the work and discharging faster than the other 3 batteries. That battery wil be the first one to die, and will die prematurely. To fix that problem we would want to use a single 12 volt 200 AH battery.

However if we went to 48 volts I can use a lot smaller less expensive wire. Not only do we spend less money, but we gain a lot of efficiency because we are not burning off as much power on the wiring running 1/4 the current. So yes we get more usable power with higher voltages. We get more usable power and save money on less materials and hardware.

Power = Current x Current x Resistance.

Example if we have a peice of wire with a resistance of say .01 Ohms and we run say 20 amps on it. How much power are we loosing. 20 x 20 x .01 = 4 watts. What happens at 5 amps? 5 x 5 x .01 = 0.25 watts. We gained 1600% efficiency by just raising the voltage by a factor of 4 (12 to 48 volts)

This is exactly why electric utilities run high voltages up to 1,000,000 volts. Think abou that. Your neighborhood needs 10,000,000 watts. At 1,000,000 volts requires 10 amps with 1 mm'2 wire. At 12 volts there is not enough ZEROS or copper you could use. At 12 volts is 1,000,000 amps. It would take a conductor the diameter of house. No tower could support it and you could not afford the electricity.

[SunEagle]

Here we go again
Screenshot 2017-02-18 15.06.11.png

Maybe my math is off but all I did was add up the list you provided.

1.5 +1.1 + 0.5 + 0.6 + 0.5 + 0.8 + 0.6 + 0.2 kWh = 5.8 kWh

[Hiro]

Screenshot 2017-02-19 12.12.02.png This is awesome...

[Sunking]

Screenshot 2017-02-19 12.12.02.png
This is awesome...

Dude you gotta quit using attachments for Text. I cannot quote you and have to retype your questions. I am not going to do it anymore. Its a PIA and I have better things to do.

No you do not fully understand. Voltage has nothing to do with making charging batteries easier or harder technically. In simple terms Low Voltage = Low Power.

A more detailed answer is the limitations on equipment, expense, and safety. The largest Charge Controller you can buy is 80 Amps. 80 Amp CC's have the following limitations on the maximum amount of input power they can handle based on battery voltage:

1000 Watts @ 12 Volts
2000 Watts @ 24 Volts
4000 Watts @ 48 Volts

So if you needed a 2000 watt Panel and went with 12 volt battery means you need two very expensive 80 Amp CC's. Pretty stupid don't you think? Hell even 24 volts would be foolish because you would max out a expensive 80 amp CC. At 48 volt battery you could use a much less expensive 40 amp MPPT controller. Not only a lot less expensive controller, but smaller less expensive wiring.

With 80 amps of charge current limits limits battery capacity to roughly 800 AH. Batteries need a C/10 charge current. Go over 800 AH and you would not likely meet the minimum charge requirement for FLA batteries. There are exceptions using other battery chemistries but I will not go into that. So if th eAmp Hour limitation is 800 AH means your rdaily watt hour consumption is limited by battery voltage. Roughly those limits are:

2 Kwh @ 12 volts
4 Kwh @ 24 volts
8 Kwh @ 48 volts.

OK next question you have is about circuit breakers and fuses. If you give it some thought you can figure this out yourself. How are Breakers and Fuses specified?

Please answer. Amps right? Over Current Protection Devices (OCPD aka breakers and fuses) are used to protect the wires from over heating and burning up. The amount of current (amps) a wire can handle is strictly based on the size of a wire. Larger the wire, the more Current the wire can safely pass without over heating. Voltage and power does come into play but not likely the way you think. Voltage is pressure like air or water pressure. A electrical device can only withstand so much pressure before it fails. Power is just the product of voltage and current.

Power = Voltage x Current.

So when you buy a OCPD it must be rated for the intended voltage, and whether or not the circuit is AC or DC. So if you buy OCPD's rated for DC and 50 volts you can use it on 12, 24, and 48 volts. Note here OCPD's cannot be ran at the maximum current continuously. Continuous loads like between Panels and Controller, or Controller and Battery, and even Battery to Inverter have to be derated. A good rule of thumb is 125%. So if you have a 20 amp OCPD the most continuous current is 16 amps. (20 / 1.25 = 16).

So how much power can a 20 amp breaker provide. Beats the fuk out of me because I do not know the voltage. What I do know is if the voltage is:

12 volts is 12 volts x 16 amps = 192 watts
24 volts is 24 volts x 16 amps = 284 watts
48 volts is 48 volts x 16 amps = 768 watts

Last words on OCPD's is the wire connected to the load side must meet minimum size requirements. Example a 20 amp breaker must have at least a #12 AWG copper wire or larger connected to it. The reason is a #12 AWG copper wire can only handle 25 amps maximum amps safely without over heating. There are some exceptions I will not go into other than in low voltage we over size the conductors to control voltage and power losses on the wiring.

You said:

ampre is power

is FALSE. Ampre is current not power. Power is the product of Voltage and Current. You cannot have power without voltage and current being greater than ZERO.

Your summary is wrong. Higher voltage is less expensive. Example solar panels come in two flavors, vanilla and chocolate. Vanilla panels are the low voltage 12 volt battery panels. Battery panels cost 2 to 6 times more per watt than chocolate high voltage panels used for Grid Tied applications. MPPT Controllers antiquated Vanilla low voltage 12 volt battery panels because MPPT Controllers allow you to use much higher voltages on their input. There are some Controllers you can charge a 12 volt battery with 600 volt panels. The MPPT controller you will likely use will have up to 150 to 200 volt limit called Voc or Voltage open circuit. So let's say you need 1500 watts. If you buy Vanilla 12 volt battery panels will cost you around $3000 to $9000. Use chocolate will cost you less than $2500. Additionally when you use chocolate high voltage panels means lower current on the input and that means smaller less expensive wire.

Battery cost is battery cost. Battery cost is $/wh. As I explained a long time ago in an example I can buy 4 12-Volt 50 AH batteries. Those batteries each have 600 wh capacity and with 4 of them a total of 2400 wh. With those 4 batteries I can configure them as:

12 volts @ 200 AH
24 volts @ 100 AH
48 volts @ 50 AH

Battery cost is what it cost based on how many watt hours you need not the voltage. However if I configure them as volts my material cost are lower because I can use smaller wire and not as many linear feet when I wire the 4 batteries in series.

LAST your wh hours numbers are all wrong and pure garbage. I am not going to do that work for you. YOU MUST DO IT. I will tell you if you are right or wrong. The very first step of any off-grid solar system and the most important step is determining the daily watt hour consumption. Get it wrong and you are in deep chit. So here i show you do it.

Watt Hours = Watts x Hours.

You have to find the total watt hours of each gizmo use din a day. Let's do an example.

100 watt Light Bulb for 6 hours is 100 watts x 6 hours = 600 watt hours
60 watt TV for 8 hours is 60 watts x 8 hours = 480 watt hours
Wifes favorite toy 25 watts x 10 hours a day is 25 watts x 10 hours = 250 watts, plus a divorce lawyer because you are not doing your job.

Daily total = 600 + 480 + 250 = 1330 watt hours per day usage or 1.33 Kwh.

In a off-grid battery system you size the battery for 5 days or more, so the minimum battery capacity is 5 times the daily usage. So 5 x 1330 watt hours = 6650 wh or 6.65 Kwh. So what size battery is that? Beats the fuk out of me because I do not know the battery voltage is as of yet. To find the battery AH needed requires you to know the battery voltage.

Amp Hours = Watt Hours / Battery Voltage so at 6650 wh:

6650 / 12 volts = 554 AH
6650 / 24 volts = 277 AH
6650 / 48 volts = 138 AH



OK your turn, run with it.

[Sunking]

FWIW one thing that is tripping you up is you do not understand the difference between Power and Energy. No problem we can fix that real easily.

Power in electrical units is WATTS, and Energy is WATT HOURS. Related but not the same thing.

Example a 100 watt light bulb uses or burns 100 watts. It does not tell you how much energy it will use. All WATTS tells you is the rate at which power is being used or burned. To know how much energy it will use you have to know the amount of time it uses 100 watts. The unit of time is HOURS

So if you have a 100 watt light bulb, turn it on for 10 hours, it uses 100 watts x 10 hours = 1000 watt hours or 1 Kwh. To run that light bulb in your area would require:

Battery = 5 x 1000 wh / 12 volts = 416 AH 12 volt battery
Panel Wattage = [1000 wh x 1.5] / 2.36 Sun Hours = 635 watts. You can get by with 600 watts. Or 3 200-watt panels wired in series.
MPPT Charge Controller Min Amps = 600 watts / 12 volts = 50 amps
Inverter min Req = 100 watts x 1.5 = 150 watts.

Easy peasy and is the reason you must know how many watt hours you need. Think of it like money. You make $10/hour and need 1 million dollars. You instantly know you need a better job. Example you make $100/day and it cost you $200 to live. Your bankrupt and will live on the streets.

[Hiro]

Maybe my math is off but all I did was add up the list you provided.

1.5 +1.1 + 0.5 + 0.6 + 0.5 + 0.8 + 0.6 + 0.2 kWh = 5.8 kWh

That would if he was using every item at the same time for one hour. He will use 3-4 items at the most... So peak load should be much less?