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

Wed Apr 04, 2018 11:52 pm

I have exactly the same setup and have already messed with the EV-CAN bus, so nope, no issues at all. I do recommend using something like UTP/STP to run the wires to the back, because CAN is fairly susceptible to inductive coupling from other stuff in the car. You can see in my videos that I used very thin orange UTP. Oh, and when you run it to the back like I did, remove the back seat (not the backrests, just the seat cushion itself, it pops off without needing any tools). Makes routing it way easier than what I did.

Don't make my mistake and be gentle with the VCM connectors. There's a handle you have to rotate before you pull off the connector, and the handle is retained by a ziptie. Even though it's a bit of an uncomfortable position to work in, get some good lighting set up and patiently work on the VCM.

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

Thu Apr 05, 2018 4:30 pm

mux wrote:
IssacZachary wrote:I know this has been measured, estimated and posted on MNL but keep searching and searching, even at google.com with "site:mynissanleaf.com" and I'm still not finding this.

Does anyone know how many 18650's would fit in an emptied Leaf Battery case?


On a pure volume of the original cells-basis: The modules are 303x223x35mm, and there are 48 of these, so that's a total volume of 0.114m3 which would fit about 6000 18650s in a staggered pattern. Most likely you'd arrange them 60P, so it'd be 5760 cells for a maximum nominal capacity with modern cells of approx. 72kWh, but more likely around 55 if you include cell spacers, bus bars and all that jazz.


So it looks like your have to get some sort of 3500mah cells to do that. Looks like about €20,000 or $24,000. But I can get nearly that many 2600mah 18650's for around $8,500 with shipping and all. Of course that wouldn't be 72kWh but, it would be around 49kWh, double the original. But either way then one could sell the original Leaf cells. I see them going for $80-$125 on eBay. That's around $4,000 if you could sell them all. I'm not sure what all the rest would cost but say for $5,000 or so you could have a 50kWh traction battery all contained in the original case with optional battery thermal management.
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LeftieBiker
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Thu Apr 05, 2018 4:52 pm

Are you ready to deal with charging, testing and connecting 5000+ laptop cells? That's 10,000+ connections just for the cells, and soldering can damage them...
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jkenny23
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Thu Apr 05, 2018 5:24 pm

IssacZachary wrote:
mux wrote:
IssacZachary wrote:I know this has been measured, estimated and posted on MNL but keep searching and searching, even at google.com with "site:mynissanleaf.com" and I'm still not finding this.

Does anyone know how many 18650's would fit in an emptied Leaf Battery case?


On a pure volume of the original cells-basis: The modules are 303x223x35mm, and there are 48 of these, so that's a total volume of 0.114m3 which would fit about 6000 18650s in a staggered pattern. Most likely you'd arrange them 60P, so it'd be 5760 cells for a maximum nominal capacity with modern cells of approx. 72kWh, but more likely around 55 if you include cell spacers, bus bars and all that jazz.


So it looks like your have to get some sort of 3500mah cells to do that. Looks like about €20,000 or $24,000. But I can get nearly that many 2600mah 18650's for around $8,500 with shipping and all. Of course that wouldn't be 72kWh but, it would be around 49kWh, double the original. But either way then one could sell the original Leaf cells. I see them going for $80-$125 on eBay. That's around $4,000 if you could sell them all. I'm not sure what all the rest would cost but say for $5,000 or so you could have a 50kWh traction battery all contained in the original case with optional battery thermal management.


Assuming you are still talking about the alarmhookup cells for ~$170/kWH, I would say thermal battery management would be more necessary; the 2600mAH cells you would be getting are more likely LCO cells, which are more dangerous to let overheat than the chemistry Nissan uses (NMO I think). They are also not optimized for high power delivery, so 1-2C discharge is the maximum that would be normally used. For the 2 cells currently for sale, here's the specs:

https://www.ebay.com/itm/173233268660 - LGDBB31865 https://sep.yimg.com/ty/cdn/theshorelin ... 0-2600.pdf
Max charge current: 2500mA
Max discharge current: 3750mA
Multiplied out by 60P - 150A charge (no problem, 125A max for Leaf DCQC), 225A discharge (should be ok, but the Leaf can do ~280A max under hard acceleration)

https://www.ebay.com/itm/202272174364 - ICR18650-26F https://www.batteryspace.com/prod-specs ... 50-26F.pdf
Max charge current: 2600mA
Max discharge current: 5200mA
Multiplied out by 60P - 156A charge (no problem, 125A max for Leaf DCQC), 312A discharge (above 280A max, no problem)

Of course, you also need a very robust holder system that can live up to the stresses of automotive standards; think of driving over bumps/potholes; all wiring and cell holders, etc. need to be able to deal with that day in and day out.

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

Thu Apr 05, 2018 6:30 pm

LeftieBiker wrote:Are you ready to deal with charging, testing and connecting 5000+ laptop cells? That's 10,000+ connections just for the cells, and soldering can damage them...


Ya, it would be a lot of work. But a lot better idea than adding pedal powered generators in front of each seat.

jkenny23 wrote:https://www.ebay.com/itm/173233268660 - LGDBB31865 https://sep.yimg.com/ty/cdn/theshorelin ... 0-2600.pdf
Max charge current: 2500mA
Max discharge current: 3750mA
Multiplied out by 60P - 150A charge (no problem, 125A max for Leaf DCQC), 225A discharge (should be ok, but the Leaf can do ~280A max under hard acceleration)

https://www.ebay.com/itm/202272174364 - ICR18650-26F https://www.batteryspace.com/prod-specs ... 50-26F.pdf
Max charge current: 2600mA
Max discharge current: 5200mA
Multiplied out by 60P - 156A charge (no problem, 125A max for Leaf DCQC), 312A discharge (above 280A max, no problem)


Of course how often does one use full power? Would that be max continuous current or max momentary current?

jkenny23 wrote:Of course, you also need a very robust holder system that can live up to the stresses of automotive standards; think of driving over bumps/potholes; all wiring and cell holders, etc. need to be able to deal with that day in and day out.


One idea, but would be hard it impossible to repair in the future, would be to fill up the battery with epoxy.
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jkenny23
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Thu Apr 05, 2018 6:43 pm

IssacZachary wrote:
jkenny23 wrote:...


Of course how often does one use full power? Would that be max continuous current or max momentary current?

jkenny23 wrote:Of course, you also need a very robust holder system that can live up to the stresses of automotive standards; think of driving over bumps/potholes; all wiring and cell holders, etc. need to be able to deal with that day in and day out.


One idea, but would be hard it impossible to repair in the future, would be to fill up the battery with epoxy.


The spec is max continuous, but from personal experience, even at 1C discharge those cells will heat up to 65C in about an hour without good active cooling. Thankfully highway driving would be about 0.5C and it scales exponentially. Still something that needs careful testing.

To be fair Tesla does epoxy all their 18650s together, so it's not a bad idea. Does add a bit of weight though.

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

Thu Apr 05, 2018 11:49 pm

LeftieBiker wrote:Are you ready to deal with charging, testing and connecting 5000+ laptop cells? That's 10,000+ connections just for the cells, and soldering can damage them...


If you're connecting that many cells, you just use a decent battery welder and double-weld each tab connection. That will never go loose. That's not really a problem.

Soldering... will take you like, a month? That's just not practical at all, especially considering tab welders are a dime a dozen these days.

jkenny23
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Sun Apr 08, 2018 2:44 pm

Just thought I'd add an experiment I did to check how much capacity loss you would get using a 4.2V Li-Ion cell in the Leaf's 4.125V fully charged system; apparently you only lose ~6.2%. This was run at 0.8C discharge, which is on the high side (but realistic for Leaf's original pack at highway speed for full cycle). I'll try again with a more "typical" cell used for this type of application since this was a high drain cell.

Image

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

Sun Apr 08, 2018 11:00 pm

Note that this changes with chemistry and temperature (and quite a lot). For instance, an 8:1:1 NMC cell will only lose a few percent, while something slightly ridiculous like LMO-Ni (the original pack) can lose 10%.

Also, the Leaf doesn't consistently charge to the same voltage. It seems to vary between ~4.07V/cell and ~4.13V/cell, mostly dependent on temperature? More in summer, at least.

Lylou2
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Mon Apr 09, 2018 2:55 pm

Ok if I use f.eg. extra battery pack in baggage aprox 10kw/h, how does the charging/discharging gonna work? Or it deals in 2 batteries or its cannot be too 'heavy' for smaller battery?

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