That’s actually an ingenious idea I hadn’t thought about. How much cheaper are these batteries once they’ve been retired? Would this be a viable option for someone running solar at home, and wanting to store the power for later use, or is a home battery still the better option?
this post was submitted on 20 Nov 2023
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Yea, with a car you can't really use them once the range gets low enough
With this, a bunch of batteries can work together for much longer. You also don't need to worry about weight since they're in one place
A Tesla Model 3, for example, has a battery capacity of 50 to 82 kWh. Let's assume the lowest capacity of 50 kWh. A car battery is basically unusable long before it has lost around half its capacity. So 25 kWh. American households on average consume 10.6 MWh annually or about 29 kWh per day.
So an old Tesla battery still provides enough electricity to power an American household for nearly an entire day.
There’s also something about their peak current being reduced with age, and in this use case, they don’t really need that peak current, so they really can stay useful for a long time in this use case
I thought I read that this was a plan Tesla had to repurpose the car batteries into power walls for home consumers. Not sure that ever ended up happening but great to see the retired car batteries given a second life
It’s the same cells inside both batteries. The difference is that the used EV car battery will store less power per volume since it’s worn out. It is a wonderful idea. A solar farm doesn’t care as much about volume and weight as a car does. For a home it would be fine as long as you’re trying to squeeze every inch cube of your property.
A 50 KWh or more battery pack will be overkill for most homes. But those will likely be available for cheap soon so it might still be a good option. Putting a pack that weighs several hundred kilos in your basement might be difficult, though.
I don’t know that a basement would be a good location regardless. If that thing sparks up, it’ll take out half the building before the fire department shows up.
I use mine as a box spring in my bedroom
Depends on the chemistry. I'd want NMC batteries outside and LFPs can be anywhere.
Im not 100% sure how the batteries are constructed from all of the cells (and I know it depends on the model), but the re-using process can work a lot better than just pulling out the battery and popping it down. EV batteries are in the range of hundreds of volts, but the cells themselves are about 4 volts. It's my understanding that the battery as a whole doesn't uniformly degrade, but you might have individual cells that degrade. If 1 cell in a chain of 10 goes bad, that chain can be made off limits to the battery, so you still technically have 9/10 cells that work fine.
The way a lot of people reuse/recycle/refurb (not sure what the right terminology is in this instance) EV batteries is to test each of the cells themselves, and get rid of the duds, and keep the decent cells. Tesla, for example, all used to use 18650 cells (and I think some models still do), which is the same exact cell that's in decent name-brand cordless power tools.
When you aren't required to keep weight, space, and extra circuitry to a minimum, you can really design a system that squeezes every last drop of usefulness out of those cells before they need to be melted down and remade.
I'm assuming that doing full charge/discharge cycles on them daily will put more wear on them than every day driving would?
But if your buying them at scrap value and the. Still selling them as scrap after a few more years I guess it works out.
The way lithium batteries work, they wear out less if you only discharge and charge them slightly. So a battery that is charged to 60%, discharged to 40%, and repeated like that will keep most of its capacity even after years of prolonged use. On the other hand, charging a battery quickly, until it is full, or discharging it until it is nearly empty will reduce its capacity over time.
A Tesla Model 3 has a battery capacity of at least 50 kWh. Even if it has lost half of its capacity, the 20% capacity difference between 60% and 40% charge, or more realistically, the 50% difference between 75% and 25%, still represents 12.5 kWh of capacity. Suppose you had an array of 1,000 such batteries. That would represent 12.5 MWh of storage capacity, enough to power ten thousand homes (at 1.2 kW each) for an hour. Certainly nothing to sneeze at.
This flies in the face of everything I thought I knew about charging my phone & laptop
Yea, back in the day, when first phones and laptops were coming out, the tech was different, and was better to fully discharge/charge the battery. Nowadays it's the opposite, but the mith still survives
An easy analogy for batteries nowadays is to see them as an elastic completely relaxed at 50%. At 0% or 100% the elastic would be fully stretched. You want to avoid that to maximize its life
If you have an android there should be a "protect battery" mode that literally caps the charge at 85%
Thanks, I knew it was better to not fully charge lithium ion batteries, but I didn't know Android had a setting for this. Just enabled it now.
I honestly thought once it got to 100% it stayed mains powered until unplugged to stop overcharging. Never realised 85% was optimal.
I think your right, its not going to keep cooking the battery. The problem is the battery doesn't need to go over 85%. Your supposed to not let it go under 20 or over 85. Kind of hard to do.
The voltage of a Lipo corresponds to it's charge level. So a Lipo at 4.2V (or in case of high voltage Lipos 4.35V) is full.
Up to ~80% of the charge, the lipo is charged by current limiting (basically, the voltage of the charging circuit raises so that it stays so much above the cell battery that it's charging at a set current). This is the fast charging part of the charging process.
After the charging voltage reaches the maximum allowed cell voltage (4.2V/4.35V), the charging circuit cannot go above that voltage because it would risk overcharging and blowing up the cell. So the carging circuit holds the voltage at maximum level until the cell voltage catches up. Since the voltage difference shrinks with every bit of charge on the cell, so does the charging speed.
That's why you only see "Charges the phone from 0-80% in X minutes" in the ads, and not 0-100%.
This means, that the charger in incapable of overcharging the phone.
But keeping the charger running even though it doesn't charge the phone anymore wastes energy, so what they do once you reach 100% is that it will disable the charger until the voltage is down to 95%, when it will resume charging. That's why it's quite likely if you unplug the phone after charging overnight, that the battery is not at 100%, but slightly below.
The old rules applied to nickel batteries or whatever the last gen was called.
NiCd was the one with the bad memory effect that required full charging cycles. They where also really toxic which is why they are illegal in many countries now.
NiMh hardly had any memory effect left, but would degrade comparatively quickly.
Li-Ion/Li-Po is what we currently have. They don't like to be full or empty for long times and like shallow charging cycles.
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Being packed away in a static location has much lower energy density requirements than driving around with the battery on-board. Getting the most out of them and then reprocessing the materials seems better than just reprocessing right away once they're no longer useful for EVs.
Exactly, it goes from being about the capacity:weight ratio to capacity:cost and as a bonus also postpones having to use powernto recycle them (and hopefully it'll be cheaper/more efficient to do so then).
In practice they're used more as a sort of capacitor to provide voltage regulation on the grid, basically what gas is doing for reliability. Not sure how often that wouldn't involve a full discharge, but I know most gas in this context is running way below its capability.
It sounds like this is being used for day/night storage here as opposed to spot demand, so it may be using more of the charge range.
I wonder if these batteries have reduced peak power output, can they fulfil the kind of balancing that you are suggesting? I guess if they had enough it would be fine.
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So like... do electric car owners just need to buy new batteries? That's the most expensive part!
Yeah, that's the bit that makes me think there will be a shitload of people cut off from vehicle ownership by the electric revolution.
It's time to end that stupid suburban sprawl, and make places walkable, cyclable, and have subsidised public transport. Because when the petrol age comes to an end, those people left out of the new one will revolt.
Sometimes, but not often. These are mostly 1st gen EV batteries, so they're pretty old. It's mentioned in the article that once capacity diminishes to the point of effecting range the old battery is replaced. Old units can be refurbished. These units could also be situations where the car surrounding the battery failed (accident, hail damage, etc) and they decided to scrap it and reclaim the battery.
At one time, they didn't last more than a few years, and needed expensive replacement. Newer batteries have better BMS controllers on them and last a lot longer. But any damage pretty much necessitates replacement. The batteries can probably be fixed but IDK if they can be put back into use in vehicles then. So there's plenty of used batteries that can be upgraded to use for stationary storage. You can buy them all day long on certain websites or auctions. It's a pretty popular thing for DIY solar.
Think of it like phone batteries, you dont, but overtime, the wear level of the battery is lower than new, and if that range is less than what you need to dailu drive, then people will get their battery swapped.
Its one of the reasons why car companies were hesitent to make lithium ion batteries for EVs
When they've reached end of life for the car, they are still useful.
EVs require high energy density so they get replaced when they don't store enough energy for their weight. However for grid storage, weight doesn't really matter (at least not as much) so a battery with 80% of its original capacity is a good (and cheap) solution.
When the market is mature, it will good for car owners who need to replace their batteries because the old one still has value.
This should make it less expensive if EV owners can sell their old batteries to be turned into a grid battery.
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What an atrociously dangerous planned design.
- Poor design: Thermal runaway is a serious problem that this setup has a very high chance of occurring. When it occurs, not if, it will spread fast from one container to the next and it will not be able to be put out that is the current fire fighting procedure for the state.
- It is very dangerous because these old batteries produce a very toxic and dangerous compounds when in thermal runaway. Again firefighting procedures cover hazmat requirements and it’s well documented the dangerous compounds that are present especially in these older batteries.
Net result. It will create another unstoppable fire that will dump poisons into ground water and the air recklessly endangering anyone down wind.
Solutions not problems:
- Isolate each container in an empty dam that is able to be filled with super chilled salt water the moment a runaway begins.
- Design fire suppression and shutdown to protect residents and the grid. Keep personal onsite to monitor with the authority to immediately react to fire incidents.
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This is a way to get off gas as it's used for reliability and voltage regulation. There's a few locations running pilots with different energy storage techs like this. One of the main problems with integrating renewables is they aren't dispatchable generation so you're basically throwing unknowns in to the system. This is mediated through programs like demand response and load following with gas, but the goal of decommissioning gas and fossils entirely while still providing reliability is hampered because of this gap in capability. Renewables paired with storage would accommodate more less flexible renewables and SMRs, and allow for more electrification of the economy with less climate impact. More electric arc furnaces!
Imagine that box there gets hit by lightning.
I mean, okay, but how much of anything can get hit by lightning and not be a smoldering crater without proper grounding and such?
One of my grandmothers great uncles.
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