My dad always thought you should just get huge concrete weights in your basement. Sun runs a motor that lifts them up on pulleys, then at night the motors run as generators as the weights slowly retract.
An ev battery probably isn't heavy enough for that.
In reply to Robbie (Forum Supporter) :
That technology is in use. But a much larger scale than a basement.
I'll be getting 4 LiFePO4 3.2 batteries from Aliexpress.
Now I think I will need to use the custom charge selection on the Magnum & setup the charging parameters because the default selections are Gel, Flooded, AGM1 & AGM2. Was reading that LiFePO4's re-charge much faster & they don't need a float charge. I'll call Magnum & see what they recommend for a charging program.
alfadriver said:Curtis73 (Forum Supporter) said:alfadriver said:In reply to mdshaw :
I see a lot of people trying it on University of Tubes videos. But I also think the cost of large storage using LiFePO4 batteries is getting so low, you may be better off getting a large set of those.
I have yet to see that kind of price lowering. I was just pricing out some LiFePO batteries and I was getting $7-10/Ah. For 100Ah, that's $1000 for something the size of a car battery.
I can see using LiFePO for weight savings and energy density, but not for cost savings.
I got a Renogy 100ahr battery for $500.
Right on. I was more thinking in the dollar-per-watt comparison. You can get a 100Ah lead-acid battery for $100. I'm not saying it's the best choice in all circumstances, but it's hard to compare $5/Ah to $1/Ah. It might be an inexpensive way to do it compared to some other exotics, but LiFePO isn't the "budget" option IMO.
In reply to Curtis73 (Forum Supporter) :
Is that lead-acid 100Ah really 100Ah? I don't know LiFePO, but it probably makes more sense to count actual useable capacity over a large number of cycles.
alfadriver said:In reply to Robbie (Forum Supporter) :
That technology is in use. But a much larger scale than a basement.
I think it's being done with water in CO. Pump it up into the upper reservoir when the sun is shining, spin the turbines at night.
In reply to ValeryHarrison :
And since "worn out" is 70% of the original capacity, that means you still have lots of capacity left.
It's been done on the DIY level and larger scale, usually with Leafs.
mdshaw said:We just got our 14.35kw solar system installed. No batteries due to cost & our power company has a decent net metering policy. I have been thinking of more cost effective ways of having battery storage & after reading about the Tesla battery packs, thought of using a repurposed EV battery pack. I know I would need a huge inverter also. Just curious if anyone has done this or any useful websites about it.
The shop that works on & stores my Samurai has off-grid power using solar panels, a small wind turbine, and Leaf battery modules...I don't have any more information about it, that just shows that it can be done. They still have to fire up a generator to run some of the big shop equipment though.
I have seriously threatened to park an old Leaf beside my shop and use it for storage :)
I'd like just enough battery to form a grid for the panels so I can use their production during a power outage. I'm okay with losing power at night, I'm more concerned with losing refrigeration for a long period. It seems this would be a good cost/benefit ratio.
With the price of server rack batteries coming down so far, I'd probably set up one of those for my home instead of trying to get an EV battery to work. Much of the work that would be done to adapt an EV set has been done, and they are pretty large batteries- you can get just over 300ah at 48V for about $5000, brand new with protections and displays. And it will fit into a server rack.
Nothing wrong with EV batteries- just a lot one needs to do so that you can use them- BMS, meters, housing, etc.
There are a bunch of used EV batteries coming, though. Eventually, there will be a plentiful supply that will be worth about what they're worth as raw materials to a recycler, like a worn but functional ICE. So it's worth looking into them.
300 aH at 48V is what, 14.4 kWh? A Leaf battery at 70% capacity - aka, "worn out" by EV standards - will have double that. And once Tesla batteries start aging out, there will be a bunch more coming on the market. They'll be the DIY option.
Here's an example of Leaf batteries being used at grid scale:
https://cleantechnica.com/2021/10/25/old-nissan-leaf-batteries-being-used-for-grid-scale-storage-in-california/
In reply to Keith Tanner :
Don't forget to add in the required BMS- which is specific to the battery chemistry (so the voltage set points)- and if you don't take the battery pack apart, a matching inverter. Having done (or at least tried) to do some DIY battery work, the rest of what it takes to make a working battery is consistently not included. If you can set it to 12, 24, or 48V, and the set point voltages- you can use the same inverter as the server rack- but you still need the BMS.
Compare that to the server rack battery, which just needs an all in one 48V inverter-charger.
And I also understand the cost- but while it looks easy to do a DIY battery, I will suggest to do it before saying it's easy and trivial.
It would be cool if you can use the vehicle level BMS, but that takes some hacking. And it would be cool if you can have an inverter that runs at the vehicle battery voltage. I'm sure there will be people that make those things eventually.
Seeing people who have been doing battery systems for their home for many years choose the server rack set up vs. the more available EV systems suggest that it's not such a simple choice. I would very much consider the rack system for easy and safety for my home. (oh, and some EV batteries are of chemistry that I would not consider inside home safe, especially if they are for DIY work)
OK, I'll try it at some point and then report back :) It's certainly being done, looking for "leaf powerwall" gets quite a few project writeups.
I'm suggesting that while the choice might be the cheapest rack mount server system from AliExpress today, the incoming supply of used EV batteries will change the economics. Especially since the majority of them will be from a single manufacturer for a while, given that the manufacturer in question was the largest seller of EVs for a good timeframe. So DIY will be more akin to following a cookbook guide and there will be BMS/inverter setups designed specifically for those battery packs - if they don't already exist.
So it's worth considering them, or at least being ready to consider them.
I've got a friend who works on the grid-level Tesla systems, I'm going to pick his brain and see how plausible my grid-forming small battery concept is.
In reply to Keith Tanner :
Go check out David Poz videos. In 2020 he had a bunch of leaf batteries for his home. And now he has server rack batteries to do the same thing. So he's paid twice to do the same thing.
I'm not saying that EV batteries shouldn't be done. Just that they are not as easy as it appears.
I generally don't do YouTube videos due to a poor time/information ratio and lack of transparency on if they are paid promotion. It would also be interesting to know if he actually PAID twice to do the same thing, I see that all of his server rack videos are full of discount codes for various suppliers. I'm all for a good fully packaged setup, but I like to know who's paying for the information.
Do you have any idea if he ever actually says why he moved away from the Leaf setup? I am truly curious.
In reply to Keith Tanner :
I never really looked. More of a high level look at his trends. But the other thing is that the very DIY site that I do look at (DIY Solar)- the guy who runs that has kind of abandond DIY batteries in favor of server rack batteries, too. There are people on his forum that certainly make their own batteries from individual cells, too.
So while it's very possible, seeing the trend away kind of makes my problems of a DIY battery more common than I thought.
Again, I'm in full support of anyone who wants to run their home with a DIY EV battery set up. But I just think it's a lot harder than it appears.
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