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

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@mux If your intention is to commercialize this, I'm guessing you would start in Norway first? Anyways, perhaps you should consider a crowdfund campaign in Norway, as I would think this will be a capital intensive business model.
 
To make a safe, reliable and commercially viable range product for a LEAF in the USA makes no sense based on present production numbers of the LEAF. The service issues, installation, economies of scale, battery density, complexity and most importantly the liability insurance cost does not support the limited and declining market for such a product. Most of the products like this supporting hybrids went out of business quickly and with the advent of longer range vehicles it makes it even less compelling. If there were many more LEAF cars with the same pack format the only sensible product would be a longer range pack swap but if there were money to made there or ever is Nissan will be doing it. There are always people that will buy such an item but it will have very limited sales. This is a topic that has been beaten to death here in the past and frankly interfacing to HV systems and packaging batteries in a cars passenger cabin safely and properly is just very costly and not a good business model. Safety is the biggest challenge here then cost and installation. If this were a great commercial business companies with the means would already be doing it and I would bet that anyone entering in this space in a proper manner would have to compete with Nissan because they are already way ahead for the obvious reasons. Bolt on packs are a cottage industry with big headaches and issues at multiple levels and the early adopters hungry for more range are just few and far between to pay the high cost for limited range extension.
 
alozzy said:
@mux If your intention is to commercialize this, I'm guessing you would start in Norway first? Anyways, perhaps you should consider a crowdfund campaign in Norway, as I would think this will be a capital intensive business model.

I'm starting in the Netherlands purely because I can easily adapt to the regulatory environment here. I'm not sure if I can manage to expand anywhere eles. That being said, I will ship hardware anywhere but waving all liability.
 
Some more data, may or may not be useful, but I'm still trying to figure out how an extender pack will behave with DC fast charging. Here are 2 "standard" 18650 LCO batteries (Samsung ICR18650-26H 2.6AH, technically 2C charge rate allowed, and Samsung ICR18650-22P 2.2AH, 1C charge rate allowed), charged at 2 and 3C rate vs. the Leaf's charge curve:

rGEBkhh.png


So far my takeaway from this is even at similar or higher charge rate, the 18650s still have a much slower voltage rise than the Leaf's LMO battery, so if they were to be charged in "CV" mode at the same voltage as the Leaf cell over time, the charge rate may be significantly higher than 2C. I'm trying to put together the equipment to do exactly this, which involves either putting a cell in parallel with a real Leaf cell and charge the combination at around 100A, or charging the 18650 alone with a high current programmable CV power supply.

Mux, I would be very interested to see some data on how much current your batteries are taking during a fast charge session (LeafSpy log for the Leaf battery + external current sensor/clamp meter for the extender pack), since this is still one of the biggest unknowns/challenges in my mind, unless you're using high C-rate capable hybrid batteries.
 
Leafspy logs are of no real use because they don't log the extender battery current. I'm not nearly done with logging tools for both batteries, but I have done some testing in various conditions with fast charging. Close to empty (couple dozen miles beyond VLBW) the extender takes about 30kW and the main battery about 10. The main battery then slowly tapers up to 13kW at 80%, and the extender down to a couple kW. That's at 8C outside temperature. I have a video somewhere of this, but I seem to have misplaced the clip. It's not on my channel anyway.

But of course these are super low internal resistance traction batteries designed for 10C charge/discharge sitting on the end of 00/000 cables. The main traction battery just doesn't count anymore at this point.

Note in your modeling that if you're going to use 18650s, the plurality of resistance will come from tabs and bus bars, not the batteries themselves, unless you use really crappy batteries like those ICR18650-26Hs. It's actually really hard to get the currentd istribution right at high currents.
 
Thanks, that's a good data point to know. Leaf Spy logs are actually pretty useful if you record the fast charger screen, which usually shows the power going into the vehicle from the charger side; basically you just subtract the Leaf Spy kW from the fast charger's kW to get the extender pack result. Of course that's a lot of tedious transcribing to get a nice graph, but I've used this method before for a couple experiments.

Just wanted to add some more battery options for used hybrid/EV cells on eBay (note I haven't done any work to see how/if this number of cells would reasonably fit in the trunk of the Leaf):
1CZ6dpM.png


These are all listed by GreenTec Auto here, and charge/discharge capability estimated from energy.gov reports: https://www.ebay.com/sch/Electric-Vehicle-Batteries/177703/m.html?_ssn=greentecautohybridspecialist

Another benefit, both of these types of cells are LMO chemistry, so they should play nicely with the Leaf system.

Edit: So the con is these are not volumetrically efficient in the slightest (118WH/L C-Max vs. 279WH/L for the Boston Power cells):
KlCoZdO.jpg
 
Nope, Leafspy doesn't record the charger amps, because it doesn't measure those at all. The only current sensor in the car as far as I can tell is in the battery itself, as well as on the 3 phases in the motor inverter. So the car really has no way of knowing how much current goes in during a DCQC. Only how much is going into the battery itself.

It does communicate current over CHAdeMO-CAN, but that's not available anywhere afaik. Not in Leafspy at least.
 
mux said:
Nope, Leafspy doesn't record the charger amps, because it doesn't measure those at all. The only current sensor in the car as far as I can tell is in the battery itself, as well as on the 3 phases in the motor inverter. So the car really has no way of knowing how much current goes in during a DCQC. Only how much is going into the battery itself.

It does communicate current over CHAdeMO-CAN, but that's not available anywhere afaik. Not in Leafspy at least.

I meant literally recording the screen of the DC fast charger (assuming it has one) e.g.: https://youtu.be/vQ977BU_XIY?t=41s

Then going back to the video and correlating the times of the video and power numbers displayed with the Leaf Spy .csv log.
 
Ah, well... I have another conundrum for you then: pretty much all of the fast chargers I use don't show the charging current :D The majority of fast charges I do are at Fastned.

That being said, the one time I did record it was at a Nissan dealer, who have a continuous display of the charging current. I'll try to remember to bring a camera the next time I do a DCQC and record that + a Leafspy log for you. Might take a while, we only need to quick charge on holidays and road trips and I don't have one of those planned for a decent while.
 
Well, I still don't have anything wired up yet, but a great deal on batteries from a Kia/Hyundai plug-in hybrid just popped up on eBay so I pulled the trigger on $900 worth of battery (9.8kWH, $91.84/kWH): https://www.ebay.com/itm/112897325279

Unfortunately they're not a "matched" set from one pack so we'll have to see how well that turns out. They're capable of 68kW discharge and 54kW charge, which should be no problem for DCQC, regen, or discharge (for the most part).

Here's approximately what it will look like in the trunk:
0Vz0ghB.png


Here's the full specs (as far as I've been able to find):
Battery type: LiPo
8s configuration per group
Nominal capacity: 27.2 Ah; Rated capacity 9.8kWH
Discharging power Max: 68 kW
Charge Power Max (-): 54 kW
Voltage: 240-412V (Cell Voltage 4.3V max)
 
Those specs... well, don't use them. No way those are lithium polymer, no way they're high voltage chemistry, no way that you can safely discharge to 2.5V and get rated cell life. That last point is moot anyway obv, as the Leaf will cut them off at 3.2V/cell anyway.

Well, I guess it's time to run the wiring now! Sounds like you're getting an extended Leaf in the near future.
 
Don't hold your breath, I'm moving to another state in a little over a month and have no garage (and no free time) now, so the actual installation won't be for at least that long. I do however plan to fully test all 12 modules (somewhat necessary since they weren't able to give me matched modules from a single pack), and will keep them in my trunk to see how living with the extra ~180 lbs and reduced trunk volume is. Currently I get between 4.1-4.7 mi/kWH depending on weather and percent of highway driving/driving with passenger.

I'm well aware I can't use the full voltage range of the cell, it was just an added bonus that they're technically rated for 4.3V, which means at only 4.03-4.11V charged these cells should last a very long time. I expect the real pack usable capacity will only be around 5-7 kWH. I'll run my same "4.11V vs. 4.3V" discharge test that I had done previously, this time on a 4.35V rated Sanyo 18650, to get a better idea of what I might expect.
 
mux said:
Those specs... well, don't use them. No way those are lithium polymer, no way they're high voltage chemistry, no way that you can safely discharge to 2.5V and get rated cell life. That last point is moot anyway obv, as the Leaf will cut them off at 3.2V/cell anyway.

Well, I guess it's time to run the wiring now! Sounds like you're getting an extended Leaf in the near future.

Leaf cutoff is around 2.6V. And it is absolutely safe to discharge down to 2.6V with no "excessive" degradation.
I do that constantly and I have one of the best surviving Leaf battery packs on this planet :lol:
 
arnis said:
mux said:
Those specs... well, don't use them. No way those are lithium polymer, no way they're high voltage chemistry, no way that you can safely discharge to 2.5V and get rated cell life. That last point is moot anyway obv, as the Leaf will cut them off at 3.2V/cell anyway.

Well, I guess it's time to run the wiring now! Sounds like you're getting an extended Leaf in the near future.

Leaf cutoff is around 2.6V. And it is absolutely safe to discharge down to 2.6V with no "excessive" degradation.
I do that constantly and I have one of the best surviving Leaf battery packs on this planet :lol:

It... is? Oh, you mean on the '13-'17 Leaf! The '11-12 Leaf has a 3.2V cutoff (with turtle coming on at 3.22V)
 
No, cutoff is hardcoded and completely dependent on battery chemistry. LMO/LCO batteries are always cut off well above 3V, because there is basically no charge under 3.5V. NCA on the other hand (the 'Lizard' and beyond battery chem) is usually cut off between 2.5 and 2.75V and still has quite a decent chunk of charge left under 3.5V.
 
Well my pallet of very well protected/packed batteries arrived today, only opened one up so far to check. Main battery terminals are on the smallest side of the battery, there's channels for airflow through it for active thermal management if needed, and there's a 10-pin balancing connector (no BMS on the battery module itself), with a little fuse block for the balancing connector on the side. Will start testing these modules next week:

Q9In1X4.jpg


I also got my Leaf module today (newer type, 500WH). I made up a couple cables to connect it to my 10A battery tester, and re-wired my other battery current/voltage monitor so I will be able to check the split of current between the Leaf module and the "extender pack" which is starting with the Boston Power Swing 5300 cells in 2s2p:

DNoRpQJ.jpg


Should be able to start that test cycle tomorrow and have it run through the weekend. At only 5A charge and 10A discharge it will take around 15h for charging and 7.5h for discharging.
 
Don't want to spoil an otherwise nice post, but you shouldn't have gotten the new Leaf module, unless your car has the same type. They only used LMOs in the '11-12, after then they quickly shifted to aluminum-based and those have very different discharge curves.
 
mux said:
Don't want to spoil an otherwise nice post, but you shouldn't have gotten the new Leaf module, unless your car has the same type. They only used LMOs in the '11-12, after then they quickly shifted to aluminum-based and those have very different discharge curves.

Is that true even for the 24kWH "lizard" pack? Info here suggests it kept the same LMO cathode but changed electrolyte: https://pushevs.com/2018/03/20/nissan-leaf-battery-degradation-data-24-vs-30-kwh-batteries/
 
Yup, the Lizards are not LMO. They're already relatively high-cobalt NCAs. Totally different chemistry.

Edit: meh, it's a lot more nuanced than that technically. The LMOs of first were heavily aluminumized LMOs to deal with the high discharge current. The lizards are probably manganese-cobalt-aluminum hybrids. You can't just change the electrolyte to deal with heat issues, the degradation is just as much due to electrode materials. That being said, all I have to go on is discharge curves, I haven't done any chemical analysis on them.

Regardless, you'll see more capacity down between 2.75-3.5V in a Lizard battery. It's not as pronounced as the difference with modern '16-'17 NMCs, but it's a decent enough difference that it's probably not a good analogue for the early LMOs.
 
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