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

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Just thought I'd update with the discharge test results of the Boston Power Swing 5300 batteries I bought (just 4 samples from a US supplier on eBay) since they're the leading candidate for a small range extender pack:

88elfvL.png


They fare average, keeping 90.9% of the 4.2V discharge capacity, with a discharge characteristic similar to LCO, though from what I read it's a Li-Manganese battery (NMC?). Will be interested to see the 2C charge tests once I get my 10A battery tester in a couple weeks. A 96s2p pack built with these cells should have a capacity of ~3.2kWH usable.
 
jkenny23 said:
Just thought I'd update with the discharge test results of the Boston Power Swing 5300 batteries I bought (just 4 samples from a US supplier on eBay) since they're the leading candidate for a small range extender pack:

88elfvL.png


They fare average, keeping 90.9% of the 4.2V discharge capacity, with a discharge characteristic similar to LCO, though from what I read it's a Li-Manganese battery (NMC?). Will be interested to see the 2C charge tests once I get my 10A battery tester in a couple weeks. A 96s2p pack built with these cells should have a capacity of ~3.2kWH usable.

Nice! Here's some more data from Endless-Sphere:

https://endless-sphere.com/forums/viewtopic.php?t=90938

final.png


What do we know about Queen Battery? Can they be trusted?

http://queenbattery.com.cn/our-prod...-discharge.html?search_query=boston&results=8
 
Note that if you want to make an extender with NMCs and mix them with the NCA-lite modern Leaf battery or LMO old Leaf battery, it needs to be a really large pack. As you can see, a significant amount of charge, even more than with NCA, is in the bottom end, so as the main battery discharges, the extender almost entirely takes over. NMCs are typically a bit lower rated (this one is rated for 0.7C charge/2.5C discharge) than NCA and LMO, so you either need to make sure never to use DCQC with an empty extender and to make the pack large enough that it can deliver your typical discharge current. If you make sure to drive the car gently, that means your minimum extender size is probably around 10kWh, so a 96S6P configuration.
 
mux said:
Note that if you want to make an extender with NMCs and mix them with the NCA-lite modern Leaf battery or LMO old Leaf battery, it needs to be a really large pack. As you can see, a significant amount of charge, even more than with NCA, is in the bottom end, so as the main battery discharges, the extender almost entirely takes over. NMCs are typically a bit lower rated (this one is rated for 0.7C charge/2.5C discharge) than NCA and LMO, so you either need to make sure never to use DCQC with an empty extender and to make the pack large enough that it can deliver your typical discharge current. If you make sure to drive the car gently, that means your minimum extender size is probably around 10kWh, so a 96S6P configuration.

Do you happen to know of any 18650s with a similar LMO chemistry/discharge curve? I'd like to bench test in my parallel cell setup to see the current sharing across the discharge/charge curve. I may just buy a real Leaf cell but at 64AH it's going to be a very long and very low C-rate test :)
 
There are basically no commercial LMO 18650s anymore. I know of none that are still sold.
 
Thanks, Leaf cell it is. I've got a 30A electronic load which I guess will be about 0.5C which isn't too bad, no way of charging at high rate though, my biggest power supply is ~20A.
 
Just got an updated price list of cells from the Chinese supplier (Queen Battery), here's the breakdown of best options for a Leaf extender pack, taking the most pessemistic assumption that the extender pack will need to provide 100% of the discharge current, and take 100% of the max charge current:

bVgbiMs.png


The Boston power cells still come out as the best option for minimum investment, which would be a ~39.5 kWH pack at $6,628 for full power.
 
That price makes the LEAF replacement pack deal offered by Nissan seem not so bad after all. Unless prices drop considerably, the DIY doesn't look to provide any savings, nor is there any warranty. Thanks for doing the leg work!
 
Yes, especially with their new replacement program (not yet rolled out in the US as far as I know), their pack prices are very cheap. This is only for those wanting to extend the range; which you can't do by buying a pack from Nissan as they take the old one back to refurbish/repurpose. Otherwise, if you can get a very large amount of cells, say from salvage laptop packs at free or low cost, an extender can definitely be done on the cheap, but you would need a very large capacity (around 96s40p or ~34kWH) to keep the per cell currents for quick charging/regen and discharge down, not to mention a much more capable BMS to handle larger balancing current.

I'm trying to get a Leaf module from Cor (also a member of these forums) to start doing some parallel charge/discharge tests between a Leaf cell and various common 18650 and the Boston power cells, to see what percentage of power is coming from the Leaf vs. extender pack at different points during the SoC curve.
 
alozzy said:
That price makes the LEAF replacement pack deal offered by Nissan seem not so bad after all. Unless prices drop considerably, the DIY doesn't look to provide any savings, nor is there any warranty. Thanks for doing the leg work!
But you do realize that for around the price of a new Leaf battery you are more than doubling the capacity! (39.5 + 24 = 63.5kWh!)

Plus, even if you're gutting your old Leaf battery and making a new one you not only could sell the used Leaf cells on eBay for up to some $4,000 (so you end up paying less than $3,000 for a 40kWh battery) you can also add whatever TMS system you so desire, in some cases improving both performance and longevity.
 
I'm thinking more of a commercially viable, after market extender solution for mere mortals. I'm hugely impressed by those who are actively pursuing this to extend their LEAFs range, but I have neither the skill nor the time to undertake such a project.

To be clear, I applaud your efforts and am envious that you'll end up with a long range LEAF for a lot less than a 2018/2019 LEAF.
 
I think if an aftermarket solution ever does exist, it will be via a newer chemistry/higher energy density battery (and somehow with active thermal management) in the original Leaf battery case, since the modification today requires splicing into either the VCM harness behind the glove box, or at the circular proprietary connector (my original plan) going into the battery, and splicing into the battery to inverter power cable (then running a long heavy gauge cable to the rear of the car).
 
There area aftermarket "solutions" that do exist. Enginer and a few companies selling on eBay have range extender batteries that can be installed in the trunk.

There are also battery refurbishing companies, but as far as I know they only restore the battery to original capacity. Maybe some day someone will do an aftermarket main traction battery with better range and hopefully better longevity.

Personally I would like to get a wrecked Leaf, take apart the battery and sell all the cells (by the sea shore) and the rest of the Leaf except the battery case (or get a good case from somewhere) and then put in whatever cells make the most sense and a thermal management system and then swap that with my Leaf's battery. I would take out my Leaf's BMS and add that as the final component to the DIY battery so there's no need to reconfigure.
 
I haven't had a chance to read it through in detail yet, but this is an interesting paper suggesting common high energy 18650 cells can take a lot more charging current than the datasheets suggest, especially if the current is tapered down as the cell charges (which the Leaf does of course), I'll have to compare this to the Leaf QC curve to see how it matches: https://reader.elsevier.com/reader/sd/5BC4D07FE684BD8834D13BB404BAF6A8BC5958FC149F08BACEC600FEB2B8D0A35AD0F8B2B3E794CA7E8C54A46296BCE2
 
IssacZachary said:
There area aftermarket "solutions" that do exist. Enginer and a few companies selling on eBay have range extender batteries that can be installed in the trunk.

But those are PHEV extenders that charge the car via a charger port, incurring significant losses along the way - not actual permanent extenders à la my car or a couple other forum members. And they don't fix the range shown on the dash, etc. etc.

An actual Leaf extender kit that works as if your car simply had a bigger battery doesn't exist yet, right? Like, I'm developing that right now, just making sure that I'm not reinventing the wheel here.
 
mmmike said:
mux said:
An actual Leaf extender kit that works as if your car simply had a bigger battery doesn't exist yet, right? Like, I'm developing that right now, just making sure that I'm not reinventing the wheel here.

I don't know what this person https://houston.craigslist.org/cto/d/2011-nissan-leaf-battery/6550198295.html is doing (or even if it's legit) but it appears the range shown on the GOM is taking into account the extra battery.

I've seen this guy before, and I'm pretty sure he's not actually adding up the capacity, he's just switching between BMSes. Also, very scant information for such a big project, and that amount of weight on the rear wheels may seem okay on the photo, but is going to require big coilovers to become manageable. I've driven around with that amount of weight and it's bump stop hell at that point.
 
mux said:
An actual Leaf extender kit that works as if your car simply had a bigger battery doesn't exist yet, right? Like, I'm developing that right now, just making sure that I'm not reinventing the wheel here.

Based on your knowledge and efforts, you potentially could develop a profitable business model for providing extender batteries for Gen 1
Leafs. Given the present low value of those Leafs, the availability of scrapped batteries, and "recovering" some of the Leaf's original range
could be profitable for a business venture on your part.
 
I sure hope so, because I'm betting on at least some success in this realm. I've decided over the last few weeks to pivot my business operations in this direction, replacing the consultancy work I've been doing in the past few years. So I'll need to make money doing it.
 
mux said:
I've seen this guy before, and I'm pretty sure he's not actually adding up the capacity, he's just switching between BMSes. Also, very scant information for such a big project, and that amount of weight on the rear wheels may seem okay on the photo, but is going to require big coilovers to become manageable. I've driven around with that amount of weight and it's bump stop hell at that point.

I talked with the Craigslist "seller". He states that he is a degreed electronics engineer from an African Country and works as a night watchman. He has two Leafs. He claims to have removed the battery from one, "chopped it up" to fit in the trunk (my words), routed the high voltage wiring directly through the Leafs vent (breather) to the relocated battery. My best guess from the conversation is that it is a bus to bus connection - two parallel battery packs working with each battery pack BMS (guess work here!). He did this because neither Leaf had the range to go to work and back. Now he does, but seems to have little ideas about what energy capacity he actually has. LeafSpy does not give him proper information, however he does use it to monitor the installed battery cell voltages - and that he uses it to "charge" the two packs. I've got to assume he does not really know the SOC, voltages, temperature of the trunk cells :oops: , but not sure. I may go see it to get more information, as he is quite close.

mux, please PM me to discuss several related issues
 
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