15.93kW off-grid solar array batteries?

[mzs112000]

Okay, so within the next few years I would like to put up a 15.93kW solar array, off-grid of course. This is going to run an all-electric house, and charge an EV(Chevy Volt).

My question is, based on what I have heard about ChinaCrap LiFePO4 batteries, would I be better served with Lead-Acid deep-cycle batteries(like the Trojan RE or UPG one's) or a ChinaCrap?

I would like at least 10 years of useful life from this system...

[ButchDeal]

15.93kW solar array, off-grid of course. This is going to run an all-electric house, and charge an EV(Chevy Volt).

Are you going to charge the EV only during the daytime? or remotely?

[emartin00]

I hope you've got a lot of spare cash laying around... Enough batteries to run an all-electric house and charge a Volt is going to cost A LOT!

[J.P.M.]

Another person unaware of the practical limitations of alternate energy relative to grid power, the scope and cost of the project, the required maintenance and ongoing costs of PV, and the reality of what they think will be possible. And that's for starters.

[organic farmer]

Okay, so within the next few years I would like to put up a 15.93kW solar array, off-grid of course. This is going to run an all-electric house, and charge an EV(Chevy Volt).

My question is, based on what I have heard about ChinaCrap LiFePO4 batteries, would I be better served with Lead-Acid deep-cycle batteries(like the Trojan RE or UPG one's) or a ChinaCrap?

I would like at least 10 years of useful life from this system...

I think there is a lot of debate going on between the LiFePO4 proponents and the Lead-Acid proponents. I have neighbors who have been using Lead-acid for decades. One of our off-grid neighbors has been on solar-power since the 1980s.

They seem to all agree that your first battery-bank will die right around 10-years of use either way.

So I am not sure there is any advantage either way.

It is really all about the lifestyle changes that you must make. During sunlight you have surplus power. You can operate everything and you can easily afford to be wasteful. But once the sunlight goes away, then you have to shift to being frugal with power consumption.

We have a Prius Prime that we charge. We can drive into town and back home again before it's drive-battery runs out. So it works well for us.

[mzs112000]

Another person unaware of the practical limitations of alternate energy relative to grid power, the scope and cost of the project, the required maintenance and ongoing costs of PV, and the reality of what they think will be possible. And that's for starters.

I am aware of the practical limitations, in that you are limited with how much energy you can use and when you can use it, that it is much more expensive, daily work to operate a system like this is horrendous. And yes, I understand both the scope and cost of the project.

I was quoted a cost of $33,000 if I install myself, and buy and install my own batteries(and batteries are at an extra cost). And PVWatts says that this system will supply the full expected energy usage of the house and car, except during the winter, when the generator will need to run for a few hours per day...

My question was, based on people's past experiences with Chinese batteries, would it be better to go with the Chinese, or get a known high-quality Lead-Acid bank. The company that is supplying parts for my system does actually have a Lead-Acid bank available with 67kWh of capacity, two of those will easily bring me to where I never go below 50% SoC. They say the Lead-Acid batteries have a 7-year warranty.


P.S. My reasoning to go off-grid is to be fully self-sufficient in every way possible. My goal is not to save money, and yes, I do understand the magnitude of cost, time, and effort that goes into these systems.

P.P.S. I do have good knowledge of electricity, and I have done major electrical work on my own house before(which is already partially off-grid, all of the LED lighting is running off grid, uses its own independent sevice panel, connected to a 3kW inverter, and a 6kWh Deep-Cycle FLA pack, and a 960W solar array.)

P.S.S. Also, I understand the safety risks of doing work with electricity, and how to stay safer while working eoth electricity. I also know(and have seen) the risks of Lead-Acid batteries.

[mzs112000]

I think there is a lot of debate going on between the LiFePO4 proponents and the Lead-Acid proponents. I have neighbors who have been using Lead-acid for decades. One of our off-grid neighbors has been on solar-power since the 1980s.

They seem to all agree that your first battery-bank will die right around 10-years of use either way.

So I am not sure there is any advantage either way.

It is really all about the lifestyle changes that you must make. During sunlight you have surplus power. You can operate everything and you can easily afford to be wasteful. But once the sunlight goes away, then you have to shift to being frugal with power consumption.

We have a Prius Prime that we charge. We can drive into town and back home again before it's drive-battery runs out. So it works well for us.

Most of my energy usage right now is during the day(I monitor the grid averages and do everything when the amount of renewables on the grid is highest.). And I suspect I can lower the maximum energy consumption by a lot. For my daily driving, a Volt would need less than 7kWh. And there are several charging stations near me...

[J.P.M.]

I am aware of the practical limitations, in that you are limited with how much energy you can use and when you can use it, that it is much more expensive, daily work to operate a system like this is horrendous. And yes, I understand both the scope and cost of the project.

I was quoted a cost of $33,000 if I install myself, and buy and install my own batteries(and batteries are at an extra cost). And PVWatts says that this system will supply the full expected energy usage of the house and car, except during the winter, when the generator will need to run for a few hours per day...

My question was, based on people's past experiences with Chinese batteries, would it be better to go with the Chinese, or get a known high-quality Lead-Acid bank. The company that is supplying parts for my system does actually have a Lead-Acid bank available with 67kWh of capacity, two of those will easily bring me to where I never go below 50% SoC. They say the Lead-Acid batteries have a 7-year warranty.


P.S. My reasoning to go off-grid is to be fully self-sufficient in every way possible. My goal is not to save money, and yes, I do understand the magnitude of cost, time, and effort that goes into these systems.

P.P.S. I do have good knowledge of electricity, and I have done major electrical work on my own house before(which is already partially off-grid, all of the LED lighting is running off grid, uses its own independent sevice panel, connected to a 3kW inverter, and a 6kWh Deep-Cycle FLA pack, and a 960W solar array.)

P.S.S. Also, I understand the safety risks of doing work with electricity, and how to stay safer while working eoth electricity. I also know(and have seen) the risks of Lead-Acid batteries.

Your life/money/choices and NOMB. I've just seen a lot of very similar posts from and met folks who could or have written them, and to me anyway, they seemed ignorant of what those with skin in the game failed to tell them that wasn't all sweetness and light. You may be more aware than those folks.

Good luck.

[ButchDeal]

And PVWatts says that this system will supply the full expected energy usage of the house and car, except during the winter, when the generator will need to run for a few hours per day...

PVWatts doesn't really do off grid very well. It tells you on AVERAGE that you have good power to operate which works well if you have a net meter grid connection. Go off grid and you often have no place to store the power or no power stored and short days.

P.S. My reasoning to go off-grid is to be fully self-sufficient in every way possible. My goal is not to save money, and yes,

P.P.S.my own house before(which is already partially off-grid, all of the LED lighting is running off grid, uses its own independent sevice panel, connected to a 3kW inverter, and a 6kWh Deep-Cycle FLA pack, and a 960W solar array.)

You could be more self sufficient, and reliable with a bimodal grid tie system. Use the grid for a 100% efficient storage device and keep some batteries fully topped off in case of outage.
It will not only be a lot cheaper, but much more efficient and reliable. And you will be able to charge your car at night using solar power (net metered).

[mzs112000]

PVWatts doesn't really do off grid very well. It tells you on AVERAGE that you have good power to operate which works well if you have a net meter grid connection. Go off grid and you often have no place to store the power or no power stored and short days.



You could be more self sufficient, and reliable with a bimodal grid tie system. Use the grid for a 100% efficient storage device and keep some batteries fully topped off in case of outage.
It will not only be a lot cheaper, but much more efficient and reliable. And you will be able to charge your car at night using solar power (net metered).

I suspected that PVWatts wasn't the best tool for the job. Also, the goal(in my case) is to not have any connection to the grid. Also, I think I can reduce energy usage even further since I calculated my energy usage based on the assumption that the A/C unit would run during the winter, which is obviously not the case. Also, I assumed that the water pump would run 24 hours per day, which is not true(it only runs when water is being used). The last assumption was that the water heater, would use far more energy than it actually does. Also, since the solar is a ground-mounted array, there is plenty of roof space for a solar(with electric assist) water heater, which reduces energy usage even further.

[J.P.M.]

I suspected that PVWatts wasn't the best tool for the job. Also, the goal(in my case) is to not have any connection to the grid. Also, I think I can reduce energy usage even further since I calculated my energy usage based on the assumption that the A/C unit would run during the winter, which is obviously not the case. Also, I assumed that the water pump would run 24 hours per day, which is not true(it only runs when water is being used). The last assumption was that the water heater, would use far more energy than it actually does. Also, since the solar is a ground-mounted array, there is plenty of roof space for a solar(with electric assist) water heater, which reduces energy usage even further.

So, you're going to design and build what looks like a very large off grid system that needs to be sized for what looks like a very large off grid load by starting with what are probably less than appropriate design tools. That about right ?

Also, have you ever lived with a flat plate solar water heater ? Workable, and perhaps marginally more cost effective than a PV/heat pump water heater combo,but requires some maintenance you may not be aware of, particularly if you live in a climate that will ever see a freezing temp.

[mzs112000]

So, you're going to design and build what looks like a very large off grid system that needs to be sized for what looks like a very large off grid load by starting with what are probably less than appropriate design tools. That about right ?

Also, have you ever lived with a flat plate solar water heater ? Workable, and perhaps marginally more cost effective than a PV/heat pump water heater combo,but requires some maintenance you may not be aware of, particularly if you live in a climate that will ever see a freezing temp.

The company I am buying the solar panels from originally said that PVWatts was the best tool but I suspected that PVWatts wasn't going to work since there are aspects of off-grid systems that it doesn't take into account. An with off grid, you need kWh on a daily basis rather than just metering on a monthly basis...

[J.P.M.]

The company I am buying the solar panels from originally said that PVWatts was the best tool but I suspected that PVWatts wasn't going to work since there are aspects of off-grid systems that it doesn't take into account. An with off grid, you need kWh on a daily basis rather than just metering on a monthly basis...

That's probably because they don't know much about either irradiance modeling or PVWatts.

PVWatts has an hourly output but it's of very limited usefulness for off grid applications. PVWatts intended applicability is for modeling long term output (over say 10 years or so) of grid tied systems.Using the model's output for hourly predictions is absurd. Using it to predict one month's output is little better. If you read the PVWatts help/info screens you'll see it written that any month's actual output may be About +/- 30 % or so of what the model pukes out. Any year's output is probably +/- 10 % different than what the model might come up with.

In the end PVWatts is a tool for preliminary design of grid tied PV systems. It is not a short term performance predictor, or not really a performance predictor at all.

[SunEagle]

At this time I would not trust any battery to provide 10 years of useful life. Probably your best bet is to go with a super premium FLA type battery system and hopefully get 5+ years out of it. Maybe then Li chemistry type batteries will have come down in cost and proven to be long life.

[organic farmer]

At this time I would not trust any battery to provide 10 years of useful life. Probably your best bet is to go with a super premium FLA type battery system and hopefully get 5+ years out of it. Maybe then Li chemistry type batteries will have come down in cost and proven to be long life.

The same thing could have been said 10 years ago.