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Battery Module Swap

Posted: Wed Sep 18, 2019 8:39 am
by athensevguy
Hi everyone, new member & Leaf owner here. I picked up a 2012 with 45K miles on it recently at a pretty good price. Of course, the range on it is dismal (45 mi / charge is what it guesses). I've been reading a lot of posts about battery upgrades, and that seems like a dead end for now. At least for me. $8500 at Nissan for a new 24 kWh battery is just insane. So, looking for options and I have a question / strategy for review:

I found a few suppliers selling "tested" gen 1 modules on eBay. They have decent ratings and seem to be a reputable US business. What about just buying 48 of those modules, cracking open the battery case, and swapping out the modules. From the "upgrade is possible" thread, it seemed like moving from 24 kWh to 30 or 40 kWh was problematic because of the BMS limiting how much of the battery was available, but if I'm looking to just swap out old 2012 modules for new tested 2012 modules with higher capacity, would it be pretty straightforward and avoid some of the headache? Getting back to an ~75-80 mile range would be a huge improvement, and hopefully it would last me long enough for Nissan to come to their senses and offer the Japanese refurb plan here (I know, don't hold my breath).

And, I've got another EV conversion project going on that I think the spent Leaf batteries could be repurposed for, so not a total loss. A 360 Volt 24 kWh battery can be pretty strong if reconfigured down to a 72 or 96 volt system, if I can find space for all the modules that is (converting a 79 Triumph Spitfire).

Re: Battery Module Swap

Posted: Wed Sep 18, 2019 12:19 pm
by LeftieBiker
The most important thing I can tell you is that you do NOT want 2012 modules! The chemistry used from 2011 through 3/2013 is terrible. Make sure the pack was manufactured after March of 2013. If you want to be extra safe, make it after April of 2013. 2015-2016 is the best "year" for 24kwh packs.

Re: Battery Module Swap

Posted: Wed Sep 18, 2019 1:42 pm
by Lothsahn
Agreed. Don't buy gen1 modules for cars. If you're putting them in a climate controlled basement for a solar storage project, they can be good.

You need gen2 modules. Now, you could buy 48 of those and do what you describe, and it would work properly. However, you'd want to test each one individually and verify that they have similar capacity. The BMS can balance the cells somewhat, but a significant cell imbalance it will not compensate for, and you will potentially get terrible range. Remember, your pack is only as good as its weakest cell, since they are in parallel. If you have 47 good cells and 1 bad one, you could end up with a car with 6 miles of range. Not exaggerating.

Also, companies selling packs individually typically are charging more than fully assembled packs, so this is an expensive way to go.

Personally, I'd look for a 24kWh pack that you can buy from a totaled Leaf from 2015/2016 (Note: Some 2016's have 30 kWh packs, you can't use those). If you get the whole pack, then you can still do a cell swap yourself, or you could potentially do a pack swap using a tool from evsenhanced. For this, you wouldn't even have to open up the pack. If you do this, get ALL the plastic battery cover panels from the wrecked leaf, as the panels differ between the gen1 and gen2 battery packs. Also, you will have to buy some mounting brackets from Nissan to adapt to the changed Gen2 case.

Also, multiple people have decoded the CAN messages and mounted a 40 kWh pack into a 2011/2012. There's a place in Canada offering this:
https://cleantechnica.com/2019/08/10/a- ... -of-range/

And someone else who has done it:
https://www.youtube.com/watch?v=9iEJBpOfoI4

So you might, maybe, just want to sit on it for a few more months, and end up with a range upgrade at the same time.

Re: Battery Module Swap

Posted: Wed Sep 18, 2019 1:55 pm
by Oilpan4
Order say 50 or 54 modules and use the best 48 out of those.
Then sell off the highest one and the lowest 3 or 5 or how many extra you buy over 48.

Your best bet might be to get a 30kwh battery and put the modules in your 24kwh case, use the 24kwh bms and have the dealer do a battery reset or pay the extra for a 30kwh battery to 24kwh car pairing mod.

If you put 30kwh modules in a 24kwh car and have it reset it just might show 103.74% soh for a few years.

Looks like the guys in Quebec are going to offer their 40kwh battery to 24kwh car mod as a kit for $1000. Now you just have to find a 40kwh battery.

Re: Battery Module Swap

Posted: Wed Sep 18, 2019 2:32 pm
by Lothsahn
Oilpan4 wrote:
Wed Sep 18, 2019 1:55 pm
Order say 50 or 54 modules and use the best 48 out of those.

Then sell off the highest one and the lowest 3 or 5 or how many extra you buy over 48.

It'll work, as long as you enjoy paying double the cost of buying a wrecked pack. You're much better off buying a wrecked pack.

Oilpan4 wrote:
Wed Sep 18, 2019 1:55 pm
Your best bet might be to get a 30kwh battery and put the modules in your 24kwh case, use the 24kwh bms and have the dealer do a battery reset or pay the extra for a 30kwh battery to 24kwh car pairing mod.

If you put 30kwh modules in a 24kwh car and have it reset it just might show 103.74% soh for a few years.

Looks like the guys in Quebec are going to offer their 40kwh battery to 24kwh car mod as a kit for $1000. Now you just have to find a 40kwh battery.
Putting 30 kWh Cells in a 24 kWh case: NO. DO NOT DO THIS. This is very bad advice.

The 30 kWh Modules have different voltage curves and the 24 kWh BMS will show VLBW for over half the range. In some cases, the car won't charge the cells fully.

Attempting to use the BMS from the 30 kWh pack will not work in a 2012 without a CAN MITM interpreter device.

Also, if you do a cell swap, you MUST use the BMS and all wiring from the ORIGINAL car. The wiring harnesses changed between gen1 and gen2 and using the wrong wiring harness WILL fry the BMS.

Re: Battery Module Swap

Posted: Wed Sep 18, 2019 3:24 pm
by Oilpan4
Sounds fun.
I guses buy the mod kit.

Re: Battery Module Swap

Posted: Wed Sep 18, 2019 3:47 pm
by SageBrush
Lothsahn wrote:
Wed Sep 18, 2019 2:32 pm
The 30 kWh Modules have different voltage curves and the 24 kWh BMS will show VLBW for over half the range. In some cases, the car won't charge the cells fully.
What voltage do the cells charge up to ?
Would they still be balanced by the BMS ?

I'm just musing about a cell swap for my late '13 LEAF from a 30 kWh pack in a couple of years. I don't really mind a goofy native display if I can drive by LeafSpy pack voltage.

Re: Battery Module Swap

Posted: Wed Sep 18, 2019 5:13 pm
by Lothsahn
SageBrush wrote:
Wed Sep 18, 2019 3:47 pm
Lothsahn wrote:
Wed Sep 18, 2019 2:32 pm
The 30 kWh Modules have different voltage curves and the 24 kWh BMS will show VLBW for over half the range. In some cases, the car won't charge the cells fully.
What voltage do the cells charge up to ?
Would they still be balanced by the BMS ?

I'm just musing about a cell swap for my late '13 LEAF from a 30 kWh pack in a couple of years. I don't really mind a goofy native display if I can drive by LeafSpy pack voltage.

The voltage curves of the 24kWh and 40 kWh packs can be seen here. The 30 kWh pack has a similar voltage curve to the 40 kWh pack:
https://pushevs.com/2018/01/29/2018-nis ... eal-specs/

So you can see the 24 kWh battery is near fully discharged around 3.6v, while the 40 kWh cells go down to 3.4v before the voltage really starts to sag.

I believe some have also reported potential issues (possibly caused by voltage sag under load). I believe Dala said something about random turtle modes occurring with the 2011 BMS paired with a later chemistry battery. However, it might have been bkvszomorito.