User avatar
IssacZachary
Forum Supporter
Posts: 838
Joined: Fri Jan 13, 2017 9:57 am
Delivery Date: 15 Nov 2016
Leaf Number: 420789
Location: Gunnison, CO, USA

Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Mon Mar 05, 2018 3:50 pm

davewill wrote:He's describing a second pack in parallel. I agree you don't need that kind of monitoring if you're inside the main pack's contactor and the cells are never disconnected from one another, but if that's not the case, then something has to verify that it's safe to close the secondary pack's contactor.


Yes. Really any battery in parallel outside of the main battery needs to have some sort of voltage comparing contactor closing device for safety.

mux wrote:As stated before, they somehow managed to get only 24kWh into a volume that can comfortably hold 45-50kWh...

I really, really would want to know, what would happen if you gutted out all the Leaf cells and replaced them all with something totally different. Would the Leaf recognize Ah capacities above that of the current cells? Would it freak out if voltage drop isn't as bad as it is in the current leaf battery?

Ideally, if a guy could take a wrecked Leaf battery, sell the cells and eBay and fill it with whatever cells make the most sense, hopefully doubling the capacity, and do that at no major cost to weight, that would be awesome! An actual thermal management system could be added too when doing this.
2013 SL SOLD :cry:
2013 Toyota Avalon Hybrid CURRENT

jkenny23
Posts: 84
Joined: Sat Aug 19, 2017 12:49 pm
Delivery Date: 19 Sep 2017
Leaf Number: 009318

Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Mon Mar 05, 2018 4:24 pm

IssacZachary wrote:Ideally, if a guy could take a wrecked Leaf battery, sell the cells and eBay and fill it with whatever cells make the most sense, hopefully doubling the capacity, and do that at no major cost to weight, that would be awesome! An actual thermal management system could be added too when doing this.


That would be the ultimate pack replacement. If you could work in a liquid cooling system that would be even better, there's conveniently located cooling lines just above the pack which run back to the charger; the radiator in the front of the Leaf is more than capable to handle cooling the pack as well (really frustrating that they left it out for "cost". It doesn't even have to be a "real" liquid cooling system like Tesla does, but maybe a liquid to air heat exchanger and a set of fans for air circulation inside the closed pack.

User avatar
IssacZachary
Forum Supporter
Posts: 838
Joined: Fri Jan 13, 2017 9:57 am
Delivery Date: 15 Nov 2016
Leaf Number: 420789
Location: Gunnison, CO, USA

Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Mon Mar 05, 2018 8:03 pm

mux wrote:... LFP ... but NCA ... but with 811 NMC coming up ...


Just a question. Where would you buy your cells? I mean, if it costs $40,000 to build a better battery, we might as well as just buy Teslas.
2013 SL SOLD :cry:
2013 Toyota Avalon Hybrid CURRENT

jkenny23
Posts: 84
Joined: Sat Aug 19, 2017 12:49 pm
Delivery Date: 19 Sep 2017
Leaf Number: 009318

Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Mon Mar 05, 2018 9:09 pm

Best current value for automotive scale batteries is ~$135/kWH for Volt modules (example from a quick eBay search, likely cheaper if buying a whole pack from a local salvage yard: https://www.ebay.com/itm/173190944540 ). Tesla modules (NCA) are pricier at $285/kWH (again on eBay, may have slightly better luck locally, but they're in high demand I think).

mux
Posts: 166
Joined: Sat Jan 13, 2018 3:52 am
Delivery Date: 13 Oct 2011
Leaf Number: 6177

Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Tue Mar 06, 2018 5:35 am

Ah, yeah, cost is a logical reason to go for something specific.

IssacZachary wrote:I really, really would want to know, what would happen if you gutted out all the Leaf cells and replaced them all with something totally different. Would the Leaf recognize Ah capacities above that of the current cells? Would it freak out if voltage drop isn't as bad as it is in the current leaf battery?

Ideally, if a guy could take a wrecked Leaf battery, sell the cells and eBay and fill it with whatever cells make the most sense, hopefully doubling the capacity, and do that at no major cost to weight, that would be awesome! An actual thermal management system could be added too when doing this.


Somebody has done this before, like a dozen times: replacing the old 24kWh cells with new ones. The BMS just adjusts to the new cells. It has nothing really to freak out over. Apparently the BMS is happy to both monotonically decrease and increase capacity.

I'm almost certainly going to do this kind of mod in the future, but not this year. Probably only by the time we regularly have to drive very long stretches without good fast chargers. So.... possibly never. Also: We don't have a Dutch version of copart and Leafs are a lot less common in Europe than in the US, so it's quite a bit more expensive to get a hold of a wrecked Leaf battery here. But once one pops up at a good price, I'm going to grab it obviously.

IssacZachary wrote:
mux wrote:... LFP ... but NCA ... but with 811 NMC coming up ...


Just a question. Where would you buy your cells? I mean, if it costs $40,000 to build a better battery, we might as well as just buy Teslas.


NKON.eu, probably the largest consumer-facing bare cell vendor in Europe, and it's like 70 miles from where I live. They have excellent prices on bulk, about 1.2-1.3x wholesale prices (typically $150-200/kWh). Although for my temporary extender pack I'm using second hand Yuasa LEV50s for about $100/kWh, but that's cheating. I don't think second hand cells are acceptable for permanent installation in a vehicle, unless you have a really solid BMS.

I'm not sure how you could ever conceivably fit $40k worth of batteries in a car :P. Batteries really aren't expensive at all anymore. If you're paying over $200/kWh, you are paying way too much. A couple grand worth of batteries and a few weeks of tinkering in your spare time should net car-sized battery capacity additions. Should be worth it for almost any BEV, as long as you enjoy the process.

User avatar
IssacZachary
Forum Supporter
Posts: 838
Joined: Fri Jan 13, 2017 9:57 am
Delivery Date: 15 Nov 2016
Leaf Number: 420789
Location: Gunnison, CO, USA

Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Tue Mar 06, 2018 10:30 am

mux wrote:Somebody has done this before, like a dozen times: replacing the old 24kWh cells with new ones. The BMS just adjusts to the new cells.


I've seen where they've put 24kWh cells in a 24kWh battery. But what if the cells (or combinations of cells in parallel) contain more than 24kWh? Has this been done? Let's say you do fit 50kWh of cells in the original battery box. Are we sure it will work?

mux wrote:Ah, yeah, cost is a logical reason to go for something specific... NKON.eu, probably the largest consumer-facing bare cell vendor in Europe, and it's like 70 miles from where I live. They have excellent prices on bulk, about 1.2-1.3x wholesale prices (typically $150-200/kWh). Although for my temporary extender pack I'm using second hand Yuasa LEV50s for about $100/kWh, but that's cheating. I don't think second hand cells are acceptable for permanent installation in a vehicle, unless you have a really solid BMS.


I'm glad you can find new cells at that price. Like jkenny23 mentioned
jkenny23 wrote:Best current value for automotive scale batteries is ~$135/kWH for [used] Volt modules...
Here in the USA it is hard to find new cells that aren't $15 for a pack of two 18650's, which is more than $1 per Wh, or $1,000 per kWh, (so a 24kWh extender or replacement comes to about $24,000 USD), although there are those Fire cells for cheap, but we all know that they aren't worth a thing.

So used cells may have to be the way to go here in the States. However, there are overstock cells that pop up every once in a while, like the ones sold by Alarmhookup on eBay: 100 LG 18650's $150 His cells come to about $215 per kWh if you include the shipping into the price. However, many times they are in limited supply. So if you can get his cells, you might be able to build a 24kWh battery for as little as $5,500. But you can't if he only has 5kWh of cells available, meaning that again, used second hand cells end up looking like the way to go.

One thing I've even contemplated starting a hobby of harvesting old laptop batteries. I'm quite scared of using generic brand cells, even more than using used second-hand name brand cells, and by harvesting laptops you know you are getting name brand cells. If it's truely Sony, LG, Samsung or Panasonic, new or used, I'd be willing to put those into my car. But still, there are a lot of counterfits out there too. I've never heard of Yuasa brand cells or batteries. Hopefully they are rebranded name brand cells. When I see deals for $0.50 per kWh for some Fire brand cell on Alibaba.com I'm sure it's too good to be true.
2013 SL SOLD :cry:
2013 Toyota Avalon Hybrid CURRENT

jkenny23
Posts: 84
Joined: Sat Aug 19, 2017 12:49 pm
Delivery Date: 19 Sep 2017
Leaf Number: 009318

Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Tue Mar 06, 2018 10:42 am

IssacZachary wrote:I've seen where they've put 24kWh cells in a 24kWh battery. But what if the cells (or combinations of cells in parallel) contain more than 24kWh? Has this been done? Let's say you do fit 50kWh of cells in the original battery box. Are we sure it will work?


I believe 30kWH cells have been fitted into a 24kWH Leaf pack, using the original BMS and swapping the original bus bars over. I don't think capacity will ever be reported correctly but the range will increase. I think there was also an issue of the old BMS only allowing a narrower range of voltage to be used compared to the newer 30kWH battery/chemistry. There is the option of WolfTronix's BMS microcontroller replacement, you would then presumably get full control of the start/stop voltages of the pack.

As for harvesting laptop cells, I think that's only acceptable for a purely hobby EV or stationary storage where if it goes offline then there's no harm and it's easy to debug. DIY powerwalls even using 80+ cells in parallel still have balance issues at 14s. Imagine a lower cell count in parallel with 96 in series, a lot easier to have problems. I think the alarmhookup new old stock type cells would be good enough, as long as you carefully test each cell. I've done some testing on Samsung ICR18650-22Ps I bought there in an 8s2p test pack, it kept balance for 30ish cycles I think but slowly drifted apart, even though I matched the cells as well as I could.

mux
Posts: 166
Joined: Sat Jan 13, 2018 3:52 am
Delivery Date: 13 Oct 2011
Leaf Number: 6177

Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Tue Mar 06, 2018 11:51 am

If there truly is no name brand bulk cell vendor in the States, this is a *massive* big gaping hole in the market. You have to be able to get batteries, right? How the hell is any small company supposed to survive otherwise? I would not be in business without NKON. Is this the same thing that's going on with solar panel and fruit prices in the US? I'm noticing a trend; anything green is hella expensive over there ;)

There really is no substitute for new cells. Modern cells have extremely well-matched initial capacity and degradation, especially when they are thermally matched in the pack. This makes even an un-BMS'ed pack stay perfectly in balance over >100 cycles. Hell, the vast majority of laptop batteries don't have a balancer, and they typically get 300+ cycles before something starts skewing, and even then it's usually not even due to cell imbalance, but excessive single cell drain by the BMS.

You throw all this away with recycled cells. Even if cells have a 1% mismatch and no drift, your BMS has to be able to continuously and reliably burn away tens of mA at typical EV charging/discharging rates per cell. An average automotive BMS frontend only has 5mA per-cell balancing, proportionally even less on something like the Leaf BMS. So you need some kind of custom, extra fortified BMS. There goes your entire financial advantage.

User avatar
IssacZachary
Forum Supporter
Posts: 838
Joined: Fri Jan 13, 2017 9:57 am
Delivery Date: 15 Nov 2016
Leaf Number: 420789
Location: Gunnison, CO, USA

Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Tue Mar 06, 2018 12:13 pm

mux wrote:If there truly is no name brand bulk cell vendor in the States, this is a *massive* big gaping hole in the market. You have to be able to get batteries, right? How the hell is any small company supposed to survive otherwise?


I've been told by some that on the east coast of the United States you can't even purchase your own contact cement to stick the sole of your own shoe back on, meaning you have to take it to a shoe repair shop so they can do it. If a guy makes his own company he has to be certified, which then gets him the licenses to buy what materials he needs. But if you're not certified you can't get what you need. And those that are certified can't just resell what they can get in bulk.

This is something I've mentioned before, that the EV seems to be just another step away from the DIY era. Sure, there are cheaper and better batteries out there. But the market is designed for these kinds of mods and materials to be left in the hands of aftermarket companies that will only do this if they see they'd make a profit from it. Once you add the certification and then liability all into the equation you end up with the final product being much more expensive, although with the idea it will be much safer than a DIY design.
2013 SL SOLD :cry:
2013 Toyota Avalon Hybrid CURRENT

mux
Posts: 166
Joined: Sat Jan 13, 2018 3:52 am
Delivery Date: 13 Oct 2011
Leaf Number: 6177

Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Tue Mar 06, 2018 1:29 pm

Obviously we're only looking at one side of the coin here, so this is not a good representation of the market or industry as a whole, but I'm really flabbergasted here. How is anybody supposed to do innovation in such a restraining business climate? I know the 'this is America!'-trope is not much more than that, but I was kind of under the impression that the US is more free in what you can and can't do than, say, the communist gulag that's called the Netherlands.

There are no red tape barriers here, we have free market prices for almost anything electronics related. I am a one-man company designing electronics, and except for some very specialist components from the US with export restrictions, I can do whatever, whenever, however I want. CE certification generally only costs me a couple hundred, maybe 1500 euros if I need to do EMC compatibility or stuff like that. The only red tape you get to is when you start selling stuff for profit and there is some kind of safety aspect to observe.

So sure, designing and building an extender battery pack for commercial purposes is probably not going to be a worthwhile venture. But designing and building it for my own purposes? No problemo! The rules and regulations on the design are public courtesy of the EU, so I can make it compliant without paying a dime for certification or whatever else. Again, this is how innovation is supposed to work, right?

Guess it's offtopic, just had to write this to show my surprise at your story, regardless of how accurate it may or may not be with respect to these projects. Not saying you're lying obviously, just that I'm sure there is more to it.

Return to “Engineering”