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Replacing reduced capacity battery cells?

  • 20-09-2018 11:30am
    #1
    Registered Users Posts: 607 ✭✭✭


    Apologies if this has been discussed before - if there's a dedicated topic then I've missed it. I know I've read before that it's possible to "rejuvenate" an EV battery which has lost capacity, e.g. Nissan/Renault replacing faulty cells to bring a battery back to at least 70% of its original capacity while under warranty. I'm interested in some more specifics about this because I think it will become more relevant as the market for used EVs - which will by default have less of the battery warranty still to run - starts to grow. There must be a business opportunity for people with the skills & capability to restore or even upgrade a battery pack with newer, more energy-dense cells as they become available. Is reduced capacity usually caused by individual faulty cells which can be replaced as required, or do all cells lose capacity more or less equally, meaning that all cells would have to be replaced in order to restore the original range of the car?


Comments

  • Registered Users Posts: 64,548 ✭✭✭✭unkel


    It's mainly individual cells. There are already companies emerging in the UK, specialising in refurbishing EV batteries. In some cases it can even be done DIY as some people with Toyota / Lexus hybrids have proven

    I was recently told by someone on here that MKW motors in Dublin (Baldonnel) is into this now. I know them well, I'll find out in person next time I meet up there.


  • Registered Users Posts: 12,030 ✭✭✭✭KCross


    mr chips wrote: »
    Is reduced capacity usually caused by individual faulty cells which can be replaced as required, or do all cells lose capacity more or less equally, meaning that all cells would have to be replaced in order to restore the original range of the car?

    Both!

    Its possible that you can have one cell significantly weaker than the others and the whole pack is only as good as the weakest cell so that one cell could drag the pack down and cause turtle mode earlier than expected. Think of your phone when it says 10% left but then all of a sudden it goes dead!

    The fix in that case is to change the weak cell.


    However, it seems the packs are holding up better than the manufacturers expected and the cells are degrading more evenly so when it says its down to, say, 80%, it is really down to 80%. Changing the weakest cell in that case will have little effect on your overall range. You'd have to change multiple cells and the more you change the more expensive it is.


    Based on how the packs are holding up its more likely you wont be reconditioning your pack but replacing it with a new one and the old one goes onto its second life as a grid storage unit.


  • Registered Users Posts: 64,548 ✭✭✭✭unkel


    KCross wrote: »
    Based on how the packs are holding up its more likely you wont be reconditioning your pack but replacing it with a new one

    Based on how the packs seem to be holding, they will last the economic life of the car (albeit steadily degrading) and will not need to be replaced. Possible exception Nissan Leaf batteries.


  • Registered Users Posts: 36,161 ✭✭✭✭ED E


    This has been a thing since what, around 2004. Loads of UK places offering Honda IMA rebuilds (and Prius etc). Remember NIMH is muck compared to LiIon/LiPoly and those packs still work a decade on. Lifespan of BEVs with modern BMS units won't be short.
    Its possible that you can have one cell significantly weaker than the others and the whole pack is only as good as the weakest cell so that one cell could drag the pack down and cause turtle mode earlier than expected. Think of your phone when it says 10% left but then all of a sudden it goes dead!

    Thats the case with a laptop or a drone.

    Taking the leaf as an example: 48 modules in series. A dead module would bring down the overall pack voltage causing issues.

    BUT

    Each module is 2s 2p or 2 cells in series and 2 in parallel. This means you have 8.4v over the modules terminals but you can carve off half the pack and keep that voltage losing only 1/96th your pack capacity. Without doing a huge amount of reading the BMS should be able to facilitate such bypasses along with balancing of weak cells/modules.


  • Registered Users Posts: 607 ✭✭✭mr chips


    KCross wrote: »
    Both!


    However, it seems the packs are holding up better than the manufacturers expected and the cells are degrading more evenly so when it says its down to, say, 80%, it is really down to 80%. Changing the weakest cell in that case will have little effect on your overall range. You'd have to change multiple cells and the more you change the more expensive it is.


    So simplistically speaking, if e.g. 12 of the cells in one battery were degraded more than the rest, there'd be little/no point in replacing just 6 of them - all 12 of the degraded ones would need to be replaced to see any benefit. Similarly, five years from now there wouldn't be any point in replacing half the cells in e.g. an Ioniq with more energy dense ones available in 2023 to bring it back to or even above 28kWh. Is that correct?


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  • Registered Users Posts: 12,030 ✭✭✭✭KCross


    mr chips wrote: »
    So simplistically speaking, if e.g. 12 of the cells in one battery were degraded more than the rest, there'd be little/no point in replacing just 6 of them - all 12 of the degraded ones would need to be replaced to see any benefit.

    It would need further analysis on a case by case basis I'd say.
    Is one cell way worse than the others, for instance.

    Ultimately what you want to get is a well balanced pack so that as the voltage drops while you are driving they all hit the low voltage mark at much the same time. That ensures you have max range.

    mr chips wrote: »
    Similarly, five years from now there wouldn't be any point in replacing half the cells in e.g. an Ioniq with more energy dense ones available in 2023 to bring it back to or even above 28kWh. Is that correct?

    I suspect you couldn't just push a higher capacity battery into a car without re-programming the car and/or the BMS.

    I have watched a video of a guy putting extra capacity into his Leaf by adding modules in the booth but its not neat and he had to do a lot of hacking.

    Maybe that will change in time but for now it would need the support of the manufacturer and there is nothing in it for them to allow you to retrofit higher capacity batteries to your old EV... they are in the business of selling cars so thats what they want you to do is buy a new car.


  • Registered Users Posts: 607 ✭✭✭mr chips


    Cheers, that's all interesting stuff. Realistically, I would need to wait until the likes of a Niro/Model 3 was available at 4-6 years of age before I could think of switching over. I may still end up exploring the route of converting an existing car to EV once the price of batteries - even S/H ones - becomes more manageable. But that's probably even further away.


  • Registered Users Posts: 12,030 ✭✭✭✭KCross


    mr chips wrote: »
    Cheers, that's all interesting stuff. Realistically, I would need to wait until the likes of a Niro/Model 3 was available at 4-6 years of age before I could think of switching over.

    What would your rough budget be?
    Word of warning... Its quite likely that a 4yr Niro or Model 3 will still be commanding very strong money. Dont expect them to depreciate at the same rate as diesel. EV's are supply constrained with an increasing market which is holding values quite high.

    mr chips wrote: »
    I may still end up exploring the route of converting an existing car to EV once the price of batteries - even S/H ones - becomes more manageable. But that's probably even further away.

    I'd say much further away. Conversions aren't cheap unless you have the skills yourself.
    There are some brilliant examples of conversions (Porsche 911, VW Beetle etc) but they are big money!


  • Registered Users Posts: 607 ✭✭✭mr chips


    Yeah, I priced a conversion some months back - £15k sterling! That was using Tesla battery cells and for a range of maybe 180 miles.

    I've no budget in mind right now as nearly all spare cash is going into a business start-up, so it'll probably be at least 2 or even 3 years before I can plan on spending more serious money on any car at all. Until then it's bangernomics all the way, unless I happen to acquire a working used battery pack at a lot less than market value. A conversion isn't something I'd tackle on my own, but I know one or two individuals with the know-how who might be interested in taking on something like that as a one-off project - however that's more of a "never say never" scenario than any sort of commitment.


  • Registered Users Posts: 64,548 ✭✭✭✭unkel


    mr chips wrote: »
    Yeah, I priced a conversion some months back - £15k sterling!
    mr chips wrote: »
    unless I happen to acquire a working used battery pack at a lot less than market value.

    The battery pack is only a fraction of the total conversion cost. Most of the above quote is labour and profit (and presumably tax). And if you can do it yourself with your mates, then you're laughing. I'd say it wouldn't be too hard to pick up a Leaf battery pack for around the £2-£3k range

    What's stopping ya? :cool:


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  • Registered Users Posts: 607 ✭✭✭mr chips


    First, the aforementioned "all money into one pot" situation I'm in for the time being - second, I'd want the range of three Leaf battery packs! So for a conversion, I'd be better off waiting for something more energy-dense to become available. I posted elsewhere that I'd seen on another forum where someone in Poland has converted an ICE saloon car for a total cost of under €3500, but the car can only go up to about 70kmh, with range limited to 150km. It looked like there was definitely room under the bonnet for adding more cells, but not to double up the capacity, and the boot was effectively lost. That said, I don't think the space for the fuel tanks was used up so there could be the potential to increase range. No idea what was used for a motor.

    I've no other information about it but here's a couple of photos, if they'll upload...


  • Registered Users Posts: 64,548 ✭✭✭✭unkel


    That K-series in his R75 probably blew the head gasket so converting to EV or off to the scrapyard were his two choices :p


  • Registered Users Posts: 2,822 ✭✭✭air


    This means you have 8.4v over the modules terminals but you can carve off half the pack and keep that voltage losing only 1/96th your pack capacity. Without doing a huge amount of reading the BMS should be able to facilitate such bypasses along with balancing of weak cells/modules.

    Sorry, you're completely incorrect here.
    Any capacity loss in any individual module reduces the capacity of the entire pack. Nothing a (current) BMS can do about it unfortunately. This is why it makes sense to swap out a module with very low relative remaining capacity.
    The BMS in the leaf had tiny balance current too, around 30mA or something IIRC for 64Ah cells.


  • Registered Users Posts: 607 ✭✭✭mr chips


    unkel wrote: »
    That K-series in his R75 probably blew the head gasket so converting to EV or off to the scrapyard were his two choices :p


    Quite possible!:pac: Although AFAIK it turned out that a lot of the time, HGF used to get blamed on something simpler like a loosely-connected coolant hose etc - the same engine didn't have that reputation when fitted in a Lotus Elise/Land Rover etc.
    Wouldn't mind an EV-converted Lotus Elise, now! Wasn't the original Tesla Roadster based on that platform?


  • Registered Users Posts: 64,548 ✭✭✭✭unkel


    Yup, and just keeping an eye on the coolant temp and nothing bad happens. Had a cheapo R75 with the K-series myself for 5 years and it was very cheap luxury motoring.
    mr chips wrote: »
    Wouldn't mind an EV-converted Lotus Elise, now! Wasn't the original Tesla Roadster based on that platform?

    Aye. Those babies are classics already :D


  • Registered Users Posts: 1,589 ✭✭✭Stealthirl


    I came across www.indra.co.uk who do replacement 24kWh for £6500 about €7300 but more interestingly the have a waiting list for 24-40kWh upgrades for £8500/€9500


  • Registered Users Posts: 12,030 ✭✭✭✭KCross


    Stealthirl wrote: »
    I came across www.indra.co.uk who do replacement 24kWh for £6500 about €7300 but more interestingly the have a waiting list for 24-40kWh upgrades for £8500/€9500

    The owner is this guy...
    https://www.speakev.com/members/mike-schooling.446/

    He is a well known member on SpeakEV and regularly fields questions around batteries and modules and anything to do with the EV drivetrain. He buys scrapped cars and reconditions batteries and fixes inverters, working on V2G stuff also.... very knowledgable.


  • Registered Users Posts: 8,412 ✭✭✭Markcheese


    What's the expected life of the current leafs and zoe s,? (excluding the battery's).
    As the batteries degrade will it be worth replacing or upgrading them? If there's nothing else major to give up on the cars?
    I mean at the moment the 2 main concerns are battery life and new tech (range/charging speed)
    The depri iation on a well kept electric could be very low if you know theres a simple battery option..

    Slava ukraini 🇺🇦



  • Registered Users Posts: 12,030 ✭✭✭✭KCross


    Markcheese wrote: »
    What's the expected life of the current leafs and zoe s,? (excluding the battery's).

    Should be much the same as every other car.
    Markcheese wrote: »
    As the batteries degrade will it be worth replacing or upgrading them? If there's nothing else major to give up on the cars?

    Reconditioned batteries are available and the most likely option you will have when the car is 10+ years old.

    Buying a new battery will be too expensive to be worthwhile and the manufacturers will do everything they can to stop you buying/installing upgraded batteries as that means they lose a sale.


  • Registered Users Posts: 2,795 ✭✭✭samih


    The expected lifetime for a brushless electric motor is probably 1 million kilometers and the reduction gear should last a long time too. In case of a LEAF the suspension is very simple so should be easy to keep one going for a long time if suitable replacement third party battery packs are available.

    Rust is what most likely will kill it as they cannot be killed with lack of servicing.


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  • Registered Users Posts: 3,284 ✭✭✭cros13


    Markcheese wrote: »
    What's the expected life of the current leafs and zoe s,? (excluding the battery's).
    As the batteries degrade will it be worth replacing or upgrading them? If there's nothing else major to give up on the cars?

    Depends on the cost. There will be a lot of scenarios where just scrapping and buying a new vehicle will be the cheaper option.
    The battery is the big deal, since unlike combustion vehicles a motor replacement on an EV is unlikely up to ridiculous mileage and cheap to replace if it does go both in labor and parts (the motor is quite small in size... just unbolt disconnect and replace).

    The Leaf and other early EV are a special case in terms of battery degradation with Mk1. Nissan Leafs and Renault Fluences both suffering from a combination of design issues and chemistry issues. With more recent EVs with pack cooling/heating like the 34kWh pack in the 2016-2018 i3 you are looking at pack cycle lifespan to 70% capacity on the order of 500,000km for a typical driver.
    More likely is that a pack will end up being recycled with the rest of the car after the average 20 years of service.
    Markcheese wrote: »
    The depri iation on a well kept electric could be very low if you know theres a simple battery option..

    As more people realise the advantage EVs have in running costs, maintenance and lifespan over ICE used demand will be very strong. And there will always be a natural floor value for any EV because the re-use and material recovery value of the battery is high.
    Written-off EVs in the US see quite high selling prices at auction because a good few of the scrap guys have woken up to the opportunity presented by reselling the battery modules.


  • Registered Users Posts: 64,548 ✭✭✭✭unkel


    cros13 wrote: »
    As more people realise the advantage EVs have in running costs, maintenance and lifespan over ICE used demand will be very strong.

    This has already happened. People are trying to get on the EV bandwagon, but supply is short, so most second hand EVs have actually had negative depreciation over the last year or so, maybe a bit more


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