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

Tue Mar 06, 2018 1:32 pm

From my experience, people usually just buy used or new direct from Chinese suppliers. The big companies (Sony, LG, Samsung, Panasonic...) don't like dealing with small quantity orders, so you always have to go through a 3rd party. Thanks to the vaping industry there are websites that sell individual cells, but they're at a premium. Not sure yet where to find that middle ground for quantities in the ~1-40kWH range.

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

Tue Mar 06, 2018 5:18 pm

jkenny23 wrote:From my experience, people usually just buy used or new direct from Chinese suppliers... Not sure yet where to find that middle ground for quantities in the ~1-40kWH range.

Do you think the Chinese suppliers are trustworthy? For an example, if I order a bunch of new, $1 per Wh LG 18650's from Alibaba.com, will I get new, real, LG cells or counterfits?

Also I've been following Jehú García on YouTube. Looks like he once did a group bulk buy. Maybe if several of us want cells we could get together and order some 100kWh of cells and then distribute them accordingly.
Last edited by IssacZachary on Tue Mar 06, 2018 5:32 pm, edited 1 time in total.
2013 SL 50,000 miles.
12 bars until 44,300 miles on June 2, 2017. :D
11 bars current. :)
The Nissan Leaf is the fourth best long distance car for highway driving. >>Best Long Distance Cars<<

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

Tue Mar 06, 2018 5:29 pm

The electric bike and scooter people can tell you which suppliers are good, but a lot of them just buy a small number of cells from an Ebay seller, then buy more if they are good.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

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

Tue Mar 06, 2018 5:37 pm

LeftieBiker wrote:The electric bike and scooter people can tell you which suppliers are good, but a lot of them just buy a small number of cells from an Ebay seller, then buy more if they are good.

It's hard finding a good eBay seller that can supply 10 to 60 kWh of Li ION cells that doesn't charge $300 or more per kWh. For smaller packs for bikes and scooters you can find sufficient quantities, but for a car is a whole other animal. There were a few, good, verified sales in bulk sizes by the dozens of kWh's a while back on eBay. But alas, they're all sold out at the time being.
2013 SL 50,000 miles.
12 bars until 44,300 miles on June 2, 2017. :D
11 bars current. :)
The Nissan Leaf is the fourth best long distance car for highway driving. >>Best Long Distance Cars<<

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

Tue Mar 06, 2018 6:08 pm

I suggest you sign up for a free membership at endlessphere.com and ask there. Lots and lots of people doing larger scale projects as well as smaller ones.
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2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
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arnis
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Sat Mar 10, 2018 5:34 pm

jkenny23 wrote:
Does regen improve any over stock "new" battery state? Regen seems to be limited by reduced Hx values, so I wonder if the converse is true?


Shouldn't be possible get better regen than with new vehicle.
Maximum regen Leaf supports (with brake pedal) is exactly 50kW.
Without brake pedal, around 30-35kW in B mode and high speed.

Regen is limited by software. Input for calculations are (at least): Hx value, battery temperature, SOC and maximum cell voltage.
When vehicle is started, regen limit is estimated by latest battery resistance value (Hx), temperature and SOC. Sometimes this limit is too pessimistic and during first regen event, regen can change a lot. Example, I charge vehicle to 90%, temperature around +10C, regen shows 2 bubbles. The first time I decelerate (or accelerate hard) regen adds 1-2 bubbles. It can be felt as well. It starts with 10kW regen and within 1-2 seconds it grows to 20-25kW. Clearly, voltage doesn't spike enough and more is allowed. Up to ~4.12V max cellpair.
The easiest way to fix regen is to find somebody who can access vehicle module software and remaps that regen capability.

Hx value is likely measured indirectly. It takes discharge/charge current (hall sensor), battery temperature (must be above +15C) and finds out, how voltage spikes/dips at those loads. If two batteries are in parallel, computer doesn't know that. As voltage dips/spikes are extremely small, regen capability map will adjust regen accordingly. But not more than 50kW with brake pedal and likely up to 30-35kW without (brake lights requirement).
My Hx on 4yo Leaf is jumping between 92% and 98%, depending on the season. Regen is almost always fully available (down to 4 Temp bars, aka +5C).

Easiest (cheapest) way to prolong range on a Leaf with worn battery is to find another worn 24kWh pack, connect them in parallel.
I bet safest connection point would be BEFORE contactors. So two batteries are ALWAYS in parallel. So there will never be arcing. Cable between two packs must be routed safely and reliably and also protected from possible damage. Secondary Leaf pack (in the trunk) must have DIY BMS that will balance out those 48 modules. Maybe original BMS inside secondary battery will work on it's own, but that must be manually verified. Balancing between two batteries will happen on its own.
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Short range EVs <30kWh -- Medium range: 30-60kWh -- Long range: >60kWh
Charging: Trickle <3kW -- Normal 3-22kW -- Fast 50-100kW -- Supercharging >100kW

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

Sun Mar 11, 2018 5:58 am

I have just finished my first trip on a tiny (8.7kWh nominal) trunk extender battery. For the first time this winter, even though I had a lot of headwind and rain on the way, I've broken 100km (60mi) with the Leaf, which is a decent feat in itself. But as a reply to the above: I've also gained back all of my regen. From about 4-5 bars down, I was able to brake at more than 20kW again, which was not possible on the worn stock battery.

So yes, you pretty much immediately gain back added regen with an extender battery. I guess the only thing the VCM cares about when mapping regen is internal resistance (Hx).

Edit: just published my video

https://www.youtube.com/watch?v=Z9knihRoyo4

Edit 2: thanks! [url] does indeed work better than the ostensibly obvious [youtube] tag...
Last edited by mux on Sun Mar 11, 2018 11:06 am, edited 1 time in total.

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

Sun Mar 11, 2018 10:13 am

mux wrote:I have just finished my first trip on a tiny (8.7kWh nominal) trunk extender battery.


Congrats! Now I really want to jump into this same solution, instead of giving away my Leaf for dirt cheap so that I can buy an ICE that will cost me much more than a 10kWh worth of cells just so I can make it 65 miles between charging stations. It looks like I've found a source for getting 10kWh's of name brand 18650's for as little as $1,500 or less.

mux wrote:So yes, you pretty much immediately gain back added regen with an extender battery. I guess the only thing the VCM cares about when mapping regen is internal resistance (Hx).


R = E/I

The question is where the current is being measured? It sounds like the Leaf judges battery resistance measuring current from the motor controller. In that case, the more you add to the main bus in batteries the less resistance the Leaf will sense and the more regen it will have. But if it measures current from inside the battery case and before the bus then it's only measuring the Leaf's own traction battery's resistance, and wouldn't include the auxiliary traction battery's resistance in the equation.

mux wrote:Edit: just published my video

[youtube]https://www.youtube.com/watch?v=Z9knihRoyo4[/youtube]

Try putting your YouTube videos in url brackets:

[ url ] YouTube Video [ /url ]
Last edited by IssacZachary on Sun Mar 11, 2018 10:36 am, edited 1 time in total.
2013 SL 50,000 miles.
12 bars until 44,300 miles on June 2, 2017. :D
11 bars current. :)
The Nissan Leaf is the fourth best long distance car for highway driving. >>Best Long Distance Cars<<

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

Sun Mar 11, 2018 10:29 am

IssacZachary wrote:
mux wrote:Edit: just published my video

[youtube]https://www.youtube.com/watch?v=Z9knihRoyo4[/youtube]

Try putting your YouTube videos in url brackets:

[ url ] YouTube Video [ /url ]

Or remove the s from https and you can leave it in the youtube brackets.

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

Sun Mar 11, 2018 11:24 am

First of all: IsaacZachary: Yeah man, you seem to be chomping at the bit to build an extender in your Leaf. I consider what I did to be 100% doable and, as long as you know what you're doing, safe and durable. Make sure to bolt down and fully immobilize the wiring, batteries and contactors, use locking nuts, loctite, whatever everywhere. Don't cheap out on the contactors. If you wish to work on it before I make a guide, we can collab on one.

I do recommend putting in more than I did for now. I have another 8.7kWh currently balancing, ready to install. That will increase the range to about 160km/100mi real-world in winter. I feel like your 10kWh figure is a bit on the low side. Take into account that the car only charges up to 4.05V/cell and down to like 3.5V, so a lot of capacity is left untouched. That 10kWh only translates into maybe 7-8kWh usable, which is 40km/25mi in hilly terrain or at high-ish highway speeds. Of course, once you have the wiring and contactors, you can essentially keep expanding every time you find a good deal on batteries.

Re: regen. If you look at the battery itself (plenty of youtube videos of people pulling them open): there is no current shunt anywhere internally. Well, in the pyrofuse (or whatever kind of active fuse that is), but not something that the BMS interfaces. So the motor HAS to be the primary point where current is being measured. This also explains why the car has to guess instead of properly measure auxiliary system power use. It literally has no way to sense it, it HAS to guess. So it also makes sense that engine power and regen power is regulated from the motor controller.

I will be *trying* to get a hold of a high-current CAN-connected current sensor. These things are ludicrously expensive (think: as expensive as 5kWh of batteries), so I have to find some second hand source, but wish me luck.

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