Affordable battery storage (used electric car batteries)

[jjackstone]

Hi folks,
I don't get around as often as I used too, but had recently been thinking about repurposing EV batteries for PV storage systems. Now I knew I couldn't have been the first to think of this so I did a little research and found this write up.

Use of Nissan Leaf battery in Solar installation. - My Nissan Leaf Forum

Early disclaimer: All the things written below are just ideas. No plans to implement at this time.

I have been reading about various people buying used leaf battery packs in the $2000-2500 range. IIRC the leaf has 24Kwh pack. this puts the cost of storage at about $100/kwh not including controls. That's not too bad. Obviously you would have to derate the pack based on age and mileage and the inevitable losses related to charging the pack, but still not terrible.

In my own case,I use 10-15 Kwh/day. I figured with 5kw of panels and 50 Kwhrs of battery that I could likely go offgrid for $10-15,000. The 50kwh should give 3-5 days autonomy. I'd probably use a car to charge the battery pack if things got desperate but could just pick up an inexpensive generator.I'm in central CA so we average 6-6.5 hours of good sun/day. Of course I would do all the installation myself. Used to do a bit of electrical work and picked up a EE along the way so I'm ok working with power and did enough construction work to build about anything I need.

You may think this is really low priced. It probably is. But I regularly see surplus panels for sale in the area for 50-70 cents/watt. So 5Kw might put me in the $3500 range. As I said before I see the battery packs go for say $2500 average. I would need two of them so call it $5000. I'm guessing I could come up with the controllers,chargers ,wiring, mounting supplies,etc. for under $5000. So that's about $13,500 with a couple grand of slop money.

Anyway, I mainly posted this for the article I linked to. Enjoy.
JJ

[MEMPHIS91]

Though I can really offer no advice, I am thinking about doing just about the same thing you are. It had been suggested to me to use the new Tesla batteries but I haven't gotten around to looking into them yet.

I'll be following this closely. Thanks you posting!

[oil pan 4]

Why would you want to use super expensive lithium batteries?
Lead acid is cheaper and they can be recycled (unlike lithium).
Why not just go grid tie and save your self a few thousand dollars?

Originally Posted by MEMPHIS91

Though I can really offer no advice, I am thinking about doing just about the same thing you are. It had been suggested to me to use the new Tesla batteries but I haven't gotten around to looking into them yet.

I'll be following this closely. Thanks you posting!

Don't bother. Like all of teslas products they are over priced toys for the rich.
If money is no object, then go for it.

Originally Posted by jjackstone

I would actually use a gas powered car to charge the house batteries if it came down to it. CA cars already have the strictest emission standards in the US, so I would guess that I'd actually be polluting less than most of the power plants that provide energy to the state.

Nope not even close.
Per kilowatt hour of production your car is far worse all around than all but the worse coal burning plants found in china.
Once you average in the states cleaner sources such as nuclear, wind power, hydro electric and natural gas, its no contest.

[jjackstone]

Originally Posted by oil pan 4

Why would you want to use super expensive lithium batteries?
Lead acid is cheaper and they can be recycled (unlike lithium).
Why not just go grid tie and save your self a few thousand dollars?

Because even if the used lithium batteries were 25-30% depleted from new they would still have more cycle life than new lead acid batteries. Again, I would repurpose used cells at approximately $100/kwh. You can just barely buy new lead acid for that price and used lead acid will have no where near the life expectancy as most lithium batteries. Additionally the lithiums weigh half as much and take up less storage area.

Not sure where you get the idea that lithium batteries can't be recycled. the articles I read say they can. I will give you that there aren't a lot of lithium recycling plants yet since massive production is still in its infancy, but that will come around.

As for the grid tie, were I to start this project, I would no longer wish to be attached to any power company. That's a personal choice.

Originally Posted by oil pan 4

Nope not even close.
Per kilowatt hour of production your car is far worse all around than all but the worse coal burning plants found in china.
Once you average in the states cleaner sources such as nuclear, wind power, hydro electric and natural gas, its no contest.

Ah, I was making a guess. You appear to be stating fact. Could you provide sources to check those facts.?

Thanks,
JJ

[Robaroni]

JJ,
After doing this for over ten years now this is what I advise:

Going off grid options are best for individuals who just don't have grid access.

For those who have grid access and want to have the off grid option I would install an off grid/intertie system. Why run your house on batteries when you can sell power to the utility and use your batteries when you really need them? This way you save your batteries. Battery life is a product of two things, one cycles and two depth of discharge. The more cycles and the greater discharge to shorter life of your batteries.

I have two systems and intertie an an off grid/intertie. The intertie just feeds the grid, the off grid/ intertie feeds my house and send excess to the grid. In the event of grid failure, which happens here a few times a year, my batteries take over. I don't use them everyday so they will last longer, they are already in over ten years.

If you're really intent on maximizing your gain then charge your batteries and run your house at night during low rate times and run during the day on your batteries and PV, send the excess to the grid during high rate times.

Running off grid when you don't have to is too costly, again, I only recommend it when yo don't have a grid option.

LA batteries are still the cheapest overall, they don't really take that much extra work and in warmer climates you can keep them outside in a small hut or battery box. It's cheaper in the long run to put the money into modules. I'm buying new modules whole sale for under $1.00 a watt and it's a better option than used modules, dollar for dollar.

Buy good stuff! Don't cut corners to buy more PV, you can always add on over time. I've had modules go bad, it's not impossible. In fact I had a 25 year Bosch module go bad. Bosch is no longer making modules but the honored my warranty and sent me a brand new module. Try that with used modules.

Also, you're just getting into this and you have to live with it for awhile to learn the ins and out. Start smaller if your funds are low, adding on is not a problem and you may rethink your needs after a couple of years. If anything buy a larger capacity inverter to anticipate a larger system in the future.

Rob

[Mobile Master Tech]

One thing to remember about any form of grid-tie: your system has to conform to their specs and inspected to make sure it does, plus it may not save you anything depending on your utility's policy.

I have Jackson EMC. They charge an extra $10/mo for net metering, but only pay you "avoided energy cost" for what you generate, which is basically the cost of the fuel burned to produce it plus transmission losses. In the summer afternoons on a time of use rate, I would pay 35c/kwh to use electricity from them, but they would pay me only 3 or 4 cents per kwh to buy electricity from me. Unless I sell them more than 250kwh or so, it doesn't even offset the metering charge.

[pinballlooking]

Thanks for posting that project I really love reading about projects like this.

Check out this project it might interest you. he is using a Tesla battery pack.
Plan: Off grid solar with a Model S battery pack at the heart

I would love to do this someday but this winter we used 100KW one day now this was a Max usage day. We charged our car three plus times. But you have to plan for the worst day.
I think a EV car is great with solar but it makes it harder to go off grid.

[jjackstone]

Originally Posted by MEMPHIS91

Though I can really offer no advice, I am thinking about doing just about the same thing you are. It had been suggested to me to use the new Tesla batteries but I haven't gotten around to looking into them yet.

I'll be following this closely. Thanks you posting!

I am hugely under impressed with what Tesla is marketing for storage batteries. The $350/kwh is not terrible for new batteries but still is a bit high to be really cost effective. Also from what I read about the power output from the packs they seem kind of dismal. I have heard that they will be announcing a new pack in the near future. Again, mine is simply a good theoretical study. I don't plan on doing it any time soon, but thought it might give others a good idea of what is possible at current prices and with current technology.

Originally Posted by pinballlooking

Thanks for posting that project I really love reading about projects like this.

Check out this project it might interest you. he is using a Tesla battery pack.
Plan: Off grid solar with a Model S battery pack at the heart

I would love to do this someday but this winter we used 100KW one day now this was a Max usage day. We charged our car three plus times. But you have to plan for the worst day.
I think a EV car is great with solar but it makes it harder to go off grid.

Thanks for the link. Looks like it could take a few days to read.
I would actually use a gas powered car to charge the house batteries if it came down to it. CA cars already have the strictest emission standards in the US, so I would guess that I'd actually be polluting less than most of the power plants that provide energy to the state. Although as I understand it we are powered by a good number of natural gas powered plants.

Wow! A hundred Kwh in one day.I think the worst I've had in years is close to thirty on a roasting summer day. Still I guess electricity is still cheaper than gas to power your car.

[pinballlooking]

We make all the power we use with our 12.5KW array. We make more power in the summer than we use and bank that to use it in the winter to charge our car and heat our house.
I have a grid tied system.
http://ecorenovator.org/forum/solar-...lar-array.html

[stevehull]

EnPhase makes a very interesting battery. A client of mine in Australia is uses these to load shift.

https://enphase.com/en-us/products-a...age/our-system


Very easy to set up and a lot of ability to control where excess PV energy goes and at what cost. The Australia farm first fills up batteries and then sells excess power to utilities. They then can sell excess kWhrs at peak time back to the utility - or save it for on farm use.

All controlled by smart phone . . . .

Tesla is no where close on performance, cost or utility. But BIG on publicity.

Steve