Solar System Assistance

[JohanNT]

Just a point I would like to make. When calculating the watt hour output of a pv system some people use the DC wh generated by the panels instead of the AC power used by the customer to see what want to off set.

There could be up to a 15% loss in the DC to AC conversion. So a DC system that generates 3600wh may only get you 3000 to 3400wh.

Hi SunEagle.

Yes, thanx for pointing that out. I do try and accommodate for that by just adding 200wh for "extra use". but, yes. please have a look at the drop box link and help me with the Questions.

[SunEagle]

Hi SunEagle.

Yes, thanx for pointing that out. I do try and accommodate for that by just adding 200wh for "extra use". but, yes. please have a look at the drop box link and help me with the Questions.

That is a long document but I can throw some answers to your questions.

I did not recognize the charge controller but based on your desire to have both the grid and a solar / battery pv system you will need equipment that is called a "hybrid" system which allows you to use the grid and also charge your battery system from the solar panels if the grid is down.

For your third question. It would be better to keep the equipment as one system instead of breaking down to smaller ones. Each "system" has losses and IMO you get more losses from multiple systems then one that is properly balanced.

For you 5th question. Battery usage is measured in Ah or watt hours not just amps. The watt hours is calculated by multiplying the battery voltage by the 20hr AH rating. For most FLA type batteries using 20 to 25% per day of the total calculated watt hours is about it. Using more will reduce the lifespan or "cycles". Based on your estimated 1200wh per day and your 48v 104Ah battery system, your daily usage comes to 1200wh / (48v x 104Ah) ~ 24%.

[JohanNT]

That is a long document but I can throw some answers to your questions.

I did not recognize the charge controller but based on your desire to have both the grid and a solar / battery pv system you will need equipment that is called a "hybrid" system which allows you to use the grid and also charge your battery system from the solar panels if the grid is down.

For your third question. It would be better to keep the equipment as one system instead of breaking down to smaller ones. Each "system" has losses and IMO you get more losses from multiple systems then one that is properly balanced.

For you 5th question. Battery usage is measured in Ah or watt hours not just amps. The watt hours is calculated by multiplying the battery voltage by the 20hr AH rating. For most FLA type batteries using 20 to 25% per day of the total calculated watt hours is about it. Using more will reduce the lifespan or "cycles". Based on your estimated 1200wh per day and your 48v 104Ah battery system, your daily usage comes to 1200wh / (48v x 104Ah) ~ 24%.

Thank you very much for this information.

From what I gathered based on Sun Kings response is that a 30 Amp Charge contoller should be sufficient in order to do the Job. However Im still a bit hesitant at the size of the inverter. Could you please check the links on the Charger controller and the Inverter and let me know if that should do the job?

Baes on your post, It looks like the Battery system should do the job. Ill probably Expand the Battery Bank to about 200 down the line.

Thanx.

[DanKegel]

when there is an outage it can range any thing from 2 - 4 hours. We at a few stage had an outage for 3 - 4 days.
...
I'm looking to run a Battery Bank of 4 X 104 AmpHour 12V Batteries in Series,
...
Ill probably Expand the Battery Bank to about 200 down the line.

Speaking strictly as a dumb consumer in a place with good grid power,
whose main knowledge of batteries is that they do fun things like cost
a lot of money, wear out quickly, and/or explode occasionally, here's my take.

If you had money to burn and hire a professional and do it right,
you wouldn't be asking these questions. Sounds like you're
trying to ramp up your skills quickly. I'd keep it simple for your first system.
You want to make mistakes on a cheap system, then maybe do it right next time.

If this is just a proof of concept, aiming for "makes your life better 9 weeks out of 10" would keep expenses low.
And if grid is working most of the time, by all means, use it.
Maybe you want a battery backup system that will handle a 4 hour outage
without solar at all, plus just barely enough solar to get your crying baby through
those 4 day outages, rather than a solar-does-it-all system?

So, don't worry about using multiple controllers, feeding extra power anywhere, or expansion,
at least for the first pass through the design. What's the simplest
you can make it, with just enough margin for that 4 hour use case?
And how does it compare to other DIY systems you've read about?

If your usage is 1200WH/day, you'd need 1200 * 4/24 = 200WH to ride through a single 4 hour outage.
(Or, looking at it another way, if your peak usage is 140W, you might need 4 * 140 = 560WH.)
Your proposed 100 AH x 48v bank holds, well, 4800 WH. At 50% DOD, that's 2400 usable WH; at 25%, that's 1200WH.
That seems about 2x to 10x more than you need for the basic 4 hour backup.
So you might be able to cut the battery bank in half and still feel like the system's making your life a lot better.

Good luck! Maybe the experts will look at my post, go 'yecch', and give you better advice

[JohanNT]

Speaking strictly as a dumb consumer in a place with good grid power,
whose main knowledge of batteries is that they do fun things like cost
a lot of money, wear out quickly, and/or explode occasionally, here's my take.

If you had money to burn and hire a professional and do it right,
you wouldn't be asking these questions. Sounds like you're
trying to ramp up your skills quickly. I'd keep it simple for your first system.
You want to make mistakes on a cheap system, then maybe do it right next time.

If this is just a proof of concept, aiming for "makes your life better 9 weeks out of 10" would keep expenses low.
And if grid is working most of the time, by all means, use it.
Maybe you want a battery backup system that will handle a 4 hour outage
without solar at all, plus just barely enough solar to get your crying baby through
those 4 day outages, rather than a solar-does-it-all system?

So, don't worry about using multiple controllers, feeding extra power anywhere, or expansion,
at least for the first pass through the design. What's the simplest
you can make it, with just enough margin for that 4 hour use case?
And how does it compare to other DIY systems you've read about?

If your usage is 1200WH/day, you'd need 1200 * 4/24 = 200WH to ride through a single 4 hour outage.
(Or, looking at it another way, if your peak usage is 140W, you might need 4 * 140 = 560WH.)
Your proposed 100 AH x 48v bank holds, well, 4800 WH. At 50% DOD, that's 2400 usable WH; at 25%, that's 1200WH.
That seems about 2x to 10x more than you need for the basic 4 hour backup.
So you might be able to cut the battery bank in half and still feel like the system's making your life a lot better.

Good luck! Maybe the experts will look at my post, go 'yecch', and give you better advice

Thanx for the reply.

I honestly dont understand the first half of your post LOL. But I think your trying to tell me that I must get by with just solving the basics and then work my way up right?

Though I dont mind that, the problem is I need to make this not just a 4 hour setup for in the odd event that the power grid gows down type of system. I want this to fulyl move my lighting system "off the grid". And given my current take on things the lighting is the "easiest" or least expensive system to move to completely solar. (This will be the first step in a big solar project to eventually go off grid completely, if its viable)

Thus Im looking for a system that will power my ligthing consumption based on the needs listed above. And dont fully know the right sizes of the inverter and its size required. I have calculated as best I can in order to accomodate for this, I just dont understand the Inverters specs. What size inverter would should forfull the need.

You are not wrong with me trying to learn a hell of a lot fast. However I dont mind taking my time with this. I just want to hear from the experts what is the equipment size required.

I will hire a professional to hook up everything, however I want to provide the equipment. Thanx for trying to save me money on the Batteries I dont mind spending a bit more of cash on getting bigger batteries, that might just allow me to plug in more items to be used off grid, like charging my phones, and other appliances. I must just be sure that the panels can charge them in a day or two and not a week LOL.

Hope you can help me with that.

Thanx

[inetdog]

Thanx for the reply.

I honestly dont understand the first half of your post LOL. But I think your trying to tell me that I must get by with just solving the basics and then work my way up right?

Though I dont mind that, the problem is I need to make this not just a 4 hour setup for in the odd event that the power grid gows down type of system. I want this to fulyl move my lighting system "off the grid". And given my current take on things the lighting is the "easiest" or least expensive system to move to completely solar. (This will be the first step in a big solar project to eventually go off grid completely, if its viable)

Johan,

It is admirable that you have thought through what you want to do and are looking at a phased implementation to get there.
I just am not sure that you are including all of the necessary calculations.
Based on the cost of panels, inverters, chargers, and most of all batteries, you can calculate the cost per kWh of "free" solar power. Based on US prices, that will generally come in at $.50 or much more per kWh.
Then look at the cost of utility (grid) power in your area. If it is $.50 or less per kWh, there is absolutely no economic reason for you to go to battery storage based PV. And any environmental benefits are hard to calculate, but probably minimal at best if your grid power source is anything but coal burning plants.

[JohanNT]

Johan,

It is admirable that you have thought through what you want to do and are looking at a phased implementation to get there.
I just am not sure that you are including all of the necessary calculations.
Based on the cost of panels, inverters, chargers, and most of all batteries, you can calculate the cost per kWh of "free" solar power. Based on US prices, that will generally come in at $.50 or much more per kWh.
Then look at the cost of utility (grid) power in your area. If it is $.50 or less per kWh, there is absolutely no economic reason for you to go to battery storage based PV. And any environmental benefits are hard to calculate, but probably minimal at best if your grid power source is anything but coal burning plants.

Hi Inetdog.

I'm fully with you on that one, however, I at this stage cannot put a price on the ability to say I am not a hostage to our Energy service provider anymore. It is really important for me to at least have my lights and be self sufficient in that regards.

Also, the current rate of tariff increases at this side of the equator is absurd. (speaking under correction but you'll get the gist). The Energy provider is a Monopoly in our country and are trying to boost the cost of electricity between 15 - 30 percent each year for the past 3 - 5 years. At this rate, I would have paid off the system long time ago. Capital Layout cost to get it going is really not a worry for me. The only problem is I don't want to hire a "so called expert" for something that someone can merely indicate for me here if you get what I'm saying.

Ill rather pay the expert to hook-up the relevant Cables and ensure that the system doesn't blow up LOL.

Thanx again for the reply inetdog.

I am however still uncertain as to what size inverter should be sufficient, as I know it wont need to power a tumble dryer and drill I'm sure that the power factor should not play to much of a roll in the calculations, I would honestly like to hear someone's answer on that for me.

Thank you.

[inetdog]

Is the dryer heated by electricity or by propane or natural gas?
Trying to run an electrically heated dryer from batteries is pretty much a lost cause.
The "solar dryer" consisting of a line between two poles is much more practical and requires less investment.
I know it does not work well when it is raining, but neither do the solar panels.

[JohanNT]

Is the dryer heated by electricity or by propane or natural gas?
Trying to run an electrically heated dryer from batteries is pretty much a lost cause.
The "solar dryer" consisting of a line between two poles is much more practical and requires less investment.
I know it does not work well when it is raining, but neither do the solar panels.

Hahaha Inet, no I was serious, I'm not gonna run "high" usage equipment on that system, its purely for the lights and a few Raspberry pi's etc. LOL.

Thanx for the humor.

[DanKegel]

I at this stage cannot put a price on the ability to say I am not a hostage to our Energy service provider anymore. It is really important for me to at least have my lights and be self sufficient in that regards.

OK,so the use case is not "I need to avoid problems caused by load-shedding", but rather "I don't trust the grid anymore and I want OFF".
That changes the calculation quite a bit.

How often are you budgeting to replace the batteries, btw? Warranties on 100 AH 12v lead-acid batteries on that site you linked seem to vary from 'none' to '1 year'.
(The site does offer some batteries with a 10 year warranty, but they don't use the kind of charge controller you were thinking of, and they cost ten times as much.)

[SunEagle]

OK,so the use case is not "I need to avoid problems caused by load-shedding", but rather "I don't trust the grid anymore and I want OFF".
That changes the calculation quite a bit.

How often are you budgeting to replace the batteries, btw? Warranties on 100 AH 12v lead-acid batteries on that site you linked seem to vary from 'none' to '1 year'.
(The site does offer some batteries with a 10 year warranty, but they don't use the kind of charge controller you were thinking of, and they cost ten times as much.)

There is no question that going off grid just about anywhere in the US would not be a financially good plan. But depending on where the OP lives (something about "this side of the equator") it is possible the electric tariffs are even higher then Hawaii or CA. That could justify an off grid system but like you (and others) have stated it will require labor and money to maintain and replace the batteries every few years.

[JohanNT]

OK,so the use case is not "I need to avoid problems caused by load-shedding", but rather "I don't trust the grid anymore and I want OFF".
That changes the calculation quite a bit.

How often are you budgeting to replace the batteries, btw? Warranties on 100 AH 12v lead-acid batteries on that site you linked seem to vary from 'none' to '1 year'.
(The site does offer some batteries with a 10 year warranty, but they don't use the kind of charge controller you were thinking of, and they cost ten times as much.)

Spot on, we usualy dont see warranties that exceed 1 - 2 years here for batteries. However, Im lead to believe that the batteries range anything from 5 - 10 years (Depending on usage, recharge cycles etc). Im contemplating on replacing batteries every 8 years. (I hope it lasts longer, but I believe given my usage paterns I would not deplete the batteries to a state where it would cause damage.)

If I may ask, what batteries are you referring to, and what charge controller should be able to power them? (The ten year thingy)

There is no question that going off grid just about anywhere in the US would not be a financially good plan. But depending on where the OP lives (something about "this side of the equator") it is possible the electric tariffs are even higher then Hawaii or CA. That could justify an off grid system but like you (and others) have stated it will require labor and money to maintain and replace the batteries every few years.

100%, problem is Im not from the US, and I believe I did mention that Im from South Africa in my first post or the link?

Im not shy of replacing batteries manually, given sufficient knowledge, I should be able to do so. The batteries Im looking at are sealed. Thus should not require mantainince, except for ensuring that they do not reach a 50% depletion level.

[SunEagle]

Spot on, we usualy dont see warranties that exceed 1 - 2 years here for batteries. However, Im lead to believe that the batteries range anything from 5 - 10 years (Depending on usage, recharge cycles etc). Im contemplating on replacing batteries every 8 years. (I hope it lasts longer, but I believe given my usage paterns I would not deplete the batteries to a state where it would cause damage.)

If I may ask, what batteries are you referring to, and what charge controller should be able to power them? (The ten year thingy)



100%, problem is Im not from the US, and I believe I did mention that Im from South Africa in my first post or the link?

Im not shy of replacing batteries manually, given sufficient knowledge, I should be able to do so. The batteries Im looking at are sealed. Thus should not require mantainince, except for ensuring that they do not reach a 50% depletion level.

Back to reality. FLA type batteries last longer by only discharging them a maximum of 25% / day. Also at this time there really aren't any FLA type batteries that will last more than 5 years even if you don't use them a lot. FLA batteries start to die the day they get filled with acid. Sealed FLA may require little to no maintenance because there is no fluid to keep an eye on but they also cost more then the FLA type and still need to be charged from something other than solar and may not last any longer then the FLA type.

Going to a different battery chemistry like Lithium / X will last longer but are also a lot more expensive and require a charging system that needs to be match to the battery.

[Sunking]

Johan you need to know Dan knows nothing about solar technology, he is a wannabe pretender. Careful who you listen to.

[Mike90250]

Spot on, we usualy dont see warranties that exceed 1 - 2 years here for batteries

Multi-purpose Marine batteries last 1-3 years. Golf Cart batteries last 3-5 years (properly cared for), and big solar batteries 5-10 years