Anderlan
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Gen2 multiple battery size guesses.

Fri Jan 17, 2014 11:57 am

This may be the wrong forum for this. Where can I put this with all the other guesses about the next generation?

I was playing around (with a spreadsheet I have here) and I think I found an ideal spread of 3 configurations close to the current. I think I heard rumors of battery size options a while back, that's what got me thinking about this.

S (or S battery level 1)
$28k, 28kwh, 100miles (125hp)..."100 miles*, same price as before, more power!"
*for real this time

SV (or S battery level 2)
$34k, 36kwh, 125miles (162hp)

SL (or S battery level 3)
$40k, 44kwh, 150miles (200hp)..."150 miles! 200 horsepower!"

I think this is a perfect spread. There's the marketing angle of 100 to 150miles and 125 to 200hp. There's the chassis angle: 28kwh is only 36% smaller than 44kwh, so wasted space in the battery bay isn't too bad. There's charging: Chademo goes up to 49kw, which is close to the max power a 44kwh battery can pull, typically based on the max charging rates (charging power over energy) of most packs used today.

Notice also that this would be a 150 mile car. Although it would be a high price point, it would be in (wishfully) 2015, at least a year before Model E, and the smallest range option would be at the current price point. While being slightly higher range. Slightly higher, but at the milestone 100 mile number*.

*for real this time

adric22
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Re: Gen2 multiple battery size guesses.

Fri Jan 17, 2014 12:13 pm

I would guess that in the case of a larger battery, Nissan would want to use the same modules in each size of battery pack. Otherwise producing a smaller module for one and larger module for the other would cost a lot more. So they'd probably want to find a suitable configuration where a whole series string of modules could be duplicated. If the entire battery pack were one series string, then they'd need to double the number of modules. If it were 2 strings then they could add 1/3 more capacity.

I seriously doubt they'd have 3 different capacities to choose from. The likelihood would be 2 choices. And I suspect the high capacity version won't be more than 33% more capacity than the low capacity version.
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Anderlan
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Re: Gen2 multiple battery size guesses.

Fri Jan 17, 2014 12:23 pm

The forum's wiki says 48 modules, so those are half a kwh each. Plenty of granularity. As far as the space efficiency considerations, 36% would be around the difference between the S's current options (and a LOT less than the original 40/60/85kwh spread). Given the price of batteries, and the ability to (effectively) charge a premium for the high end, I don't see why they wouldn't offer 3 pack sizes to go standard with each of the 3 trim levels.

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evnow
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Re: Gen2 multiple battery size guesses.

Fri Jan 17, 2014 12:31 pm

Anderlan wrote:SL (or S battery level 3)
$40k, 44kwh, 150miles (200hp)..."150 miles! 200 horsepower!"

Model E is supposed to be $35k to $40k and 200 miles. But that is in 2017, whereas Gen 2 Leaf is hopefully '15.
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dhanson865
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Re: Gen2 multiple battery size guesses.

Fri Jan 17, 2014 12:40 pm

Tesla software limited 60kw packs to create 40kw packs when they decided it wasn't worth making 3 packs.

How about Nissan does something in that line of thinking

S (or S battery level 1) no fast charging port, 6.6KW charger
24kwh usable out of a 32kw pack, greatly expanded turtle limit, slightly expanded max charge limit).

SV (or S battery level 2) 10KW charger + optional fast charging port of their choice
32kwh pack fully unleashed (normal turtle / max charge limits), allowing for more range than lowest trim level and faster charging

SL (or S battery level 3) 10KW charger + fast charging port(s) of their choice
42kwh pack fully unleashed (normal turtle / max charge limits) allowing more range than the middle level pack and faster charging

If they do offer larger battery packs I'm OK with having another 1% chopped off at top and bottom of the pack for slightly expanding turtle / max charge protection on the mid/high pack options.

I'm OK with substantial turtle expansion to create a virtual small battery pack (imagine a 32kwh pack with a >10% reserve at the bottom and ~10% reserve at the top to turn it into a 24kwh pack). This gives newbies to the EV world a bigger cushion to limp to a charger and reduces their ability to over charge/undercharge/leave sitting at wrong charge levels.

I'd like to see them buy into the supercharger network even if the Leaf can't make it from one supercharger to the next in rural areas just because the superchargers will be so common in urban areas. Of course they'd have to severely limit the supercharger rate to keep the battery temps in line so limit the supercharger rate to 45 or 60KW max and taper down. Force 80% SOC max charging limit on superchargers.

If they don't go supercharger then chademo but again limit the charge rate and max charge to keep the battery temps / degradation to a minimum.

I'd even be fine if the top model had chademo + Tesla supercharger connections or if there were a way for Nissan to sell a chademo to Tesla adapter (after paying the Tesla license fee of course).


oh and if they only want to do one pack then do it sofware limited like

S (or S battery level 1) no fast charging port, 6.6KW charger
24kwh usable out of a 36kw pack, greatly expanded turtle limit, greatly expanded max charge limit).

SV (or S battery level 2) 10KW charger + optional fast charging port of their choice
32kwh usable out of a 36kwh pack (expanded turtle / max charge limits), allowing for more range than lowest trim level and faster charging

SL (or S battery level 3) 10KW charger + fast charging port(s) of their choice
36kwh pack fully unleashed (normal turtle / max charge limits) allowing more range than the middle level pack and faster charging
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Anderlan
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Re: Gen2 multiple battery size guesses.

Fri Jan 17, 2014 1:00 pm

What Tesla did when leaving 60kwh packs in and dialing them back to 40 always fascinated me. Notice that they are no longer offering the option, so they are no longer shipping cars with un- (or under-) utilized cells. I don't know if that's a viable options. I'm sure they pushed the customers hard to unlock. It might make upgrading your pack easier by unlocking, but if these things really cost $250/kwh (or even $150) to manufacture, I still don't think it's a real option for an OEM. The cell costs still overshadow the shipping and labor costs for the fraction of customers that will opt for upgrading after factory.

I hadn't considered the heat problems of an unregulated pack at >25kw levels of charging. (I guess discharging levels go higher but they aren't sustained--the highest sustained discharge rate is cruising at 80mph which equals..around 25kw. Hey look at that. Sustained output power does equal sustained input power after all. So burst power may even be equal both ways, which may be how Tesla does some of there 120kw charging tricks. With proper knowledge of the battery state down to several cells, the charger can average a higher level over the 20 minute peak period by bursting.)

I really hope Nissan would build better heat management into a higher power pack. It's a crying shame not to charge a battery at close to its cells specs.

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evnow
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Re: Gen2 multiple battery size guesses.

Fri Jan 17, 2014 1:54 pm

dhanson865 wrote:Tesla software limited 60kw packs to create 40kw packs when they decided it wasn't worth making 3 packs.

How about Nissan does something in that line of thinking

No way Nissan will do that.

Even Tesla won't do it - if they had to start over. It was purely a tactical decision since cost savings were not worth it.
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planet4ever
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Re: Gen2 multiple battery size guesses.

Fri Jan 17, 2014 4:07 pm

Anderlan wrote:The forum's wiki says 48 modules, so those are half a kwh each. Plenty of granularity.
You are looking at the wrong constraint. Each module currently puts out about 8 volts, and all 48 modules are wired in series to yield the 350-400v the motor needs. If you try to do two strings in parallel you are down to half the voltage, and the first possible step up is to 96 modules. Each module has four cells wired series/parallel, so by changing the internal wiring to series only you could get about 16 volts out of each module. That would allow two strings (24kWh), three strings (36kWh), and four strings (48kWh), but nothing in between. And of course those modules would be incompatible with gen 1 modules.

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dhanson865
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Re: Gen2 multiple battery size guesses.

Fri Jan 17, 2014 4:23 pm

evnow wrote:
dhanson865 wrote:Tesla software limited 60kw packs to create 40kw packs when they decided it wasn't worth making 3 packs.

How about Nissan does something in that line of thinking

No way Nissan will do that.

Even Tesla won't do it - if they had to start over. It was purely a tactical decision since cost savings were not worth it.


Tesla wouldn't do it long term because they had a 33%/50% capacity difference (40kwh vs 60kwh). Nissan could do it with a significantly smaller percentage 24kwh vs 32kwh is a 25%/33% difference which is likely too much still, how about 28kwh vs 32kwh which is more like a 12.5%/14% difference.

Think about the opportunities that gives Nissan on warranty coverage. A degraded battery in a SV becomes much less degraded if you swap it into an S in that scenario. Build that difference into the expectation of the customers and you have the ability to give someone a 15% lower capacity battery as a refurb and it'll still look like a nearly new pack after software limiting.

And if the firmware of the software limited car allows the degradation to be hidden a low trim owner might not even lose their first bar until the true pack degradation reached 30%. I'm sure leafspy and such would still see the change in battery health but the software limited car would have a larger reserve to play with.

As long as you market the capacity difference and warranty coverage honestly and detailed enough people could accept the difference in capacity that creates.

You can also price the car appropriately so that it's more attractive to get the SV than the S so that you don't have a ton of the stripped down models running around with mid range battery packs. Or heaven forbid make the stripped down model a limited quantity run so that there aren't a ton of them on dealer lots in the first place.

Point is you could then have 3 EPA ranges out of 2 battery packs. Which goes back to the old marketing strategy of offering 3 levels instead of two so you sell more of the higher levels. Some people don't want to buy the cheapest, some don't want to buy the most expensive, either way if you have a middle option it plays to sales of that option in some cases.
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ydnas7
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Re: Gen2 multiple battery size guesses.

Fri Jan 17, 2014 6:17 pm

Tesla 40kWh packs demonstrate that Tesla chooses not to make make 40kWh packs.....

Tesla 60kWh/80kWh packs differ in voltage/cell count/cell capacity.
Mitsubishi 12kWh/16kWh packs differ in chemistry.....

My guess is that Nissan offers a 24kWh pack using similar cells as today and a 30kWh pack using HV equivalent cells. (as per NEC http://www.nec.com/en/press/201210/glob ... 09_02.html )

I would like Nissan to offer an additional 12 modules, but I doubt it will happen.

Nissan values simplicity of stocking choice (hence no automatic Altima etc) so its not easy for them to offer more pack sizes.

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