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

[alozzy]

@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.

[EVDRIVER]

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.

[mux]

@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.

[jkenny23]

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:



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.

[mux]

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.

[jkenny23]

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):


These are all listed by GreenTec Auto here, and charge/discharge capability estimated from energy.gov reports: https://www.ebay.com/sch/Electric-Vehic ... specialist

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):

[mux]

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.

[jkenny23]

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.

[mux]

Ah, well... I have another conundrum for you then: pretty much all of the fast chargers I use don't show the charging current 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.

[jkenny23]

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:


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)