Nissan Leaf Cells Test Data

Batteries, Chargers, and Battery Management Systems.
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hillzofvalp   1 MW

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Re: Nissan Leaf Cells Test Data

Post by hillzofvalp » Nov 03 2014 12:49pm

how involved is it to drop the pack and swap cells out? I have an idea, but maybe you guys have first hand experience.

i was getting at buying a spare leaf pack on ebay and then assessing it's cells. if absolutely terrible and not worth putting in the car, I'd sell the cells off for nothing and then build my own pack inside, reusing the bms harness

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Re: Nissan Leaf Cells Test Data

Post by John in CR » Nov 08 2014 11:23am

I'm finally ready to turn 5 of my modules into a 20s1p pack, so 74V33ah nominal. After taking the cells out of a module and taking a hard look at the bars connecting the cells, I've come up with what I believe is the easiest way to accomplish this. If someone has a better idea, please let me know.
Nissn Leaf module change from 2p2s to 4s.JPG
Nissn Leaf module change from 2p2s to 4s.JPG (30.84 KiB) Viewed 2407 times
Basically I just cut the stock busbars in 4 places, leaving 1 series connection between cells number 2 and 3. Then add 2 relatively short wires, and one of those 4 connections uses the original center balance tap, leaving me just 3 wire ends to connect. If I can make my 4 busbar cuts at the bends, then I'll solder heavy gauge wire to them and drill a hole to form ring connectors. I'll drill a hole to match in the still connected pieces of busbar, and use my new ring connector terminated wires to clamp with a bolt. The result will be a tab sandwich with 2 pieces of busbar as the bread, one with the factory connection to the tab, and the other clamping from the other side of the tab.

One thing I like about this approach is that I don't have to solder on the tabs at all. I always worry about heat conducting into the cells by soldering on tabs. Plus the clamping reinforcement of the factory connection sure can't hurt.

The factory +/- terminals stay in place as original, so I should also be able to use the factory connectors to connect the five 1p4s modules for a 20s pack.

John

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Re: Nissan Leaf Cells Test Data

Post by Harold in CR » Nov 08 2014 11:32am

John, that is basically what I did, only, I added a 5th cell to each block for a 5S 4 block pack. I also soldered balance leads to make it easy to plug in a Cellmeter 7 and check for capacity of each block, + individual cell volts.

I used a pencil torch for heating those copper pads on the tabs. Pretty tough to get them hot enough, quick enough even with the 80W electric iron I have, with a somewhat hammer head tip. The tip eventually broke off, so, I went with the pencil torch. Just used a tin heat shield for not to heat up stuff and scorch insulation.
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Re: Nissan Leaf Cells Test Data

Post by mvly » Nov 08 2014 11:39am

John, in terms of number of cuts and wires required, I think it is the same. Your design have 4 cuts and 2 wires. Doing it the original way will also have 4 cuts and 2 wires. The only benefits I can see for your design is reuse of the screw tab terminal, which is a big plus compared to the soldering required if you do it any other way. But of course the complexity is less if you do it the original way. I.e. the top cell is the highest, the bottom cell is the lowest. With your design it is a bit unclear unless you look at you reference note. In the end, it comes down to what people want.

Good design never the less! Great to see more innovation here on used cells.

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Re: Nissan Leaf Cells Test Data

Post by John in CR » Nov 08 2014 7:28pm

Even before LFP told us crimpled connections are best, I disliked soldering on cells. The Konion packs I've made have lasted, but that was soldering tab-on-tab and never directly to a cell. If drilling the holes goes well, including a 4th hole on the the busbar I don't cut for it's balance tap, then I won't risk any heat damage to cells or poor solder connections. In the interest of longevity and durability those are big pluses for me. It should also save me significant time, as will retaining the factory terminals. Though I can't imagine ever doing it, with a different set of bolt on jumpers I could easily change them back to the original 2p2s config.

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Re: Nissan Leaf Cells Test Data

Post by Martin A » Nov 09 2014 7:14am

John in CR wrote:Even before LFP told us crimpled connections are best....
Have you got the link for that info John? I must have missed it. Thanks

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Re: Nissan Leaf Cells Test Data

Post by John in CR » Nov 09 2014 4:42pm

Martin A wrote:
John in CR wrote:Even before LFP told us crimpled connections are best....
Have you got the link for that info John? I must have missed it. Thanks
He has alluded to it on several occasions, but a quick search didn't turn up any good links for you. Tab welding with the battery tab connecting to a heavier busbar like Nissan does remains the industry best standard, since the busbar sinks the heat of the weld away, so it doesn't head toward the cells. The things that made his input really sink in for me was when he talked about the extreme care required in handling raw cells in one post I can't find, along with talk on several occasions regarding the detriments of solder in connections carrying high current (solder is relatively high in resistance and the risk of heat damage to the cell is high).

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Re: Nissan Leaf Cells Test Data

Post by oatnet » Nov 12 2014 11:03am

John in CR wrote:Even before LFP told us crimpled connections are best, I disliked soldering on cells.
I hadn't heard that LFP recommendation. I got a lot of critique when I used crimping to terminate a123 pouches in 2010, but it has worked out really well for me, so I am glad others are onboard with it now.

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Re: Nissan Leaf Cells Test Data

Post by inedible » Nov 14 2014 11:10am

Has anyone else experienced a ton of sag when these batteries are cold?

It's -15c outside and yesterday I went for a ride. My battery was 63v at rest, but as soon as I hit the throttle it sagged down to 53-55v or so.

I'm not really sure what my current draw is, but it's bound to be under 40A. I normally only get around 2.5v sag when the weather is warm out.

It looks like I'm going to need to invest in a warmer if I want to use this in cold temperatures. In the meantime, does anyone know if this causes any damage to the battery? Also is it ok to charge at these temps?

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Re: Nissan Leaf Cells Test Data

Post by drees » Nov 14 2014 12:13pm

If we use how Nissan manages the LEAF batteries as an example, we know the following:

1. The battery warmer turns on at -4F (-30C) and then turns off at 14F (-10C). It only does this to make sure the electrolyte doesn't freeze.
2. There is no issue with discharging the pack at cold temps at reasonable SOC (~3C). The voltage will sag, but as a benefit, this will warm up the pack. :)
3. It does appear to be sensitive to charging at low temperatures judging by how QC rates are slowed down in cold temperatures and how much regenerative braking is reduced in cold temperatures, especially as the battery pack ages. I'm not sure exactly what the limits are and at what temperatures, but to be safe, warm it the pack up to at least 14F / -10C before charging, and charge as slowly as possible.

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Re: Nissan Leaf Cells Test Data

Post by cassschr1 » Nov 16 2014 3:49pm

This is a PM I sent to John in CR. He asked me if I could post some pictures of my enclosure. So with the help of my wife here are the pictures along with the reply and my pm to John. 6 of my pictures were bigger than 512 KiB size so it would not let me upload them to this site. I do not know how to change the file size. Can someone tell me the steps to making file smaller. They came from the Galaxy S4 phone uploaded to my email.

John ,
I believe your drawing for the + post should be on the 2nd cell up from the bottom as the posts are in the middle of the pack originally. I built mine as 6s using all the plastic parts of the cells, encased in alumnium. I used flat braid as the connectors between cells, pencil torch for the job. Winding paper to protect plastic when soldering. And a wet rag on the cells for heat protection. I needed to cut some small plastic tits off a couple of them to get them to lay flat. my case looks like this , top view
[ ] with a sheet bent for each side that looks like a L. That protects the bottom. Those [ are bent exactly at the right dimension to keep things together. Then I drilled the holes for the corners. They overlap the large sides by a couple inches.They also provide compression as their bent past 90%. I used .100 IIRC. This method could be used for whatever size pack you wanted. Cass

Thanks Cass,

Maybe your cells are different, but when I cut the busbar between two + ends of the cells going to the module + terminal, I'm left with the terminal connected to the bottom cell. Yes the terminals are physically in the center, but Nissan bends them to get there.

If you get a chance please share some pics with everyone.

I'm still in the air for my actual construction. If it doesn't rain today I'll open 4 more cans today, but this time I'll just grind the lip off until the top pops off. I'm hoping it springs up a lot so I can use one or more as a flat plate spring at both end faces to achieve the compression I want to maintain. For the 1p20s pack I'm building, space is limited, so I may remove all but the top and bottom blue plastic spacers that spread the compression.

WRT to soldering, you guys have the skills but I don't trust mine, because I always spend too much time applying heat with high capacity connections, and never had any luck with flat braid, so I'm going with bolt together probably in the form of using 2 or 3 small bolts since I don't want to drill a big hole through the existing connection.

Thanks for the input,

John
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Re: Nissan Leaf Cells Test Data

Post by John in CR » Nov 18 2014 8:38pm

I opened another module today buy grinding off the overlap where the can and top meet. The can along proves 0 compression. Without compression provided by the threaded rods and end plates a stack of modules clearly has space between the rim of one can and the bottom of the next. The spacers help spread the load as the flat spring faces comprising the top and bottom of the cans put compression force on the cells as you screw down the end plates via the threaded rods.

Despite some care I ended up wrinkling the face of the top cell, so no more attempts to remove the 300mg cans for me. For the one 1p pack I will build, I will only cut off the amount of can needed to access the busbars to make the changes needed to go from 2p2s to 1p4s. The negative pole busbar from the cell to the connection is quite long, so I will try to bend that and use it to bolt to the next module's positive terminal and avoid.

I doubt I could come up with a better battery box that includes compression than I can with a rack of modules with only the terminal end cut open plus a bit of water proofing that is any lighter, so I'm sticking with the cans mostly as-is. That means no more high probability of damaging cells trying to remove them from the cans.

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Re: Nissan Leaf Cells Test Data

Post by teslanv » Nov 18 2014 8:47pm

Where are you guys sourcing these modules, now that Hybridautocenter is out of stock? Junkyards & ebay?
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Re: Nissan Leaf Cells Test Data

Post by John in CR » Nov 19 2014 3:08pm

teslanv wrote:Where are you guys sourcing these modules, now that Hybridautocenter is out of stock? Junkyards & ebay?
It's difficult to get them now that the word has spread about their value.

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Re: Nissan Leaf Cells Test Data

Post by Dougt » Nov 26 2014 12:43pm

If anybody is thinking on buying a salvage pack, I would be very interested in buying 3 or 4 modules (12 or 16 cells). (Each cell is 3.75V, 32 ah, of which maybe 28 ah is realistically usable). Max cell output is about 90 A.

Maybe we can do some sort of group buy? From what I been reading, salvage shops get about $2000-$2400 per pack. I think some have even listed occasionally on ebay. Each pack has 48 modules (192 cells). So there are at least enough cells for about 12 people. Assuming that whoever goes through the trouble of buying the pack, opening the pack, and mailing modules should get their cells for free, so others pay about 2200/11=$200 for 16 cells + shipping.

Any interest in organizing a group buy????

Maybe we can get people lined up and then have someone pull the trigger when a pack becomes available.

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Re: Nissan Leaf Cells Test Data

Post by teslanv » Nov 26 2014 1:09pm

Dougt wrote:If anybody is thinking on buying a salvage pack, I would be very interested in buying 3 or 4 modules (12 or 16 cells). (Each cell is 3.75V, 32 ah, of which maybe 28 ah is realistically usable). Max cell output is about 90 A.

Maybe we can do some sort of group buy? From what I been reading, salvage shops get about $2000-$2400 per pack. I think some have even listed occasionally on ebay. Each pack has 48 modules (192 cells). So there are at least enough cells for about 12 people. Assuming that whoever goes through the trouble of buying the pack, opening the pack, and mailing modules should get their cells for free, so others pay about 2200/11=$200 for 16 cells + shipping.

Any interest in organizing a group buy????

Maybe we can get people lined up and then have someone pull the trigger when a pack becomes available.
I would be interested in organizing another group buy on these.

Just need to find one with not too many cycles on it.

This type of group buy may pose more challenge since it's not something we could just order. We would have to be ready to pounce :pancake: when one become available.
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Re: Nissan Leaf Cells Test Data

Post by Dougt » Nov 26 2014 1:23pm

Awesome. Actually, I would be in for 5 or 6 modules (20 or 24 cells)...apparently its too early in the morning for me to do basic math.

I think the key thing to work out here is to protect to initial buyer from flakes dropping out or he/she being caught with a loss if the cells turn out to be faulty. People need to be committed to the buy even if the cells turn out to be poor. The buyer can do a basic due diligence of having the vendor check the voltage on the entire pack before buying it (I think under 300V would indicate a problem).

I don't know if there is a way to escrow such small amounts. But it seems there has been enough interest here in buying them that even if someone flakes, another buyer would likely be found easily.

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Re: Nissan Leaf Cells Test Data

Post by dnmun » Nov 26 2014 1:52pm

i suspect all of those batteries sold were from the hurricane Sandy flooded Leafs that went through the auctions i posted up about before. there were 2 of those flooded cars that just sold last week in somerville, NJ so that might be the last ones.

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Re: Nissan Leaf Cells Test Data

Post by Dougt » Nov 26 2014 2:55pm

I would assume that with over 60,000 leafs on the road in USA, a few go to a salvage yard every week as being "totalled". I would also guess that most have their battery packs intact. Somewhere these packs must be available. Just my guess, could be wrong.

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Re: Nissan Leaf Cells Test Data

Post by dnmun » Nov 26 2014 3:01pm

the ones in wrecks go through the insurance auctions. they do not go directly to a junkyard if they were insured. the junkyard would then buy it at auction but these cars are worth so much rebuilt that they are going to auto repair shops to be rebuilt unless they are massively destroyed which most do not appear to be in the insurance auction pictures.

the Sandy flooded vehicles actually looked pristine except for water intrusion. it was a shame the NY authorities label them as parts only, otherwise they could have been put back in service. if someone in mexico bot them they would be able to put them back on the road in no time.

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Re: Nissan Leaf Cells Test Data

Post by Dougt » Nov 26 2014 3:34pm

leafs currently up for salvage...from google search...don't know if this site info legit

http://www.carfrom.us/car/search/action ... ISSAN_LEAF

maybe salvage yard would only part with battery and then relist auction. maybe not.

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Re: Nissan Leaf Cells Test Data

Post by teslanv » Nov 26 2014 3:39pm

Dougt wrote:leafs currently up for salvage...from google search...don't know if this site info legit

http://www.carfrom.us/car/search/action ... ISSAN_LEAF

maybe salvage yard would only part with battery and then relist auction. maybe not.
OH OH. There's one in Seattle. Current Bid $1700. AND IT'S A 2013 WITH 4300 MILES!!! :shock: :)
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Re: Nissan Leaf Cells Test Data

Post by dnmun » Nov 26 2014 3:52pm

Dougt wrote:leafs currently up for salvage...from google search...don't know if this site info legit

http://www.carfrom.us/car/search/action ... ISSAN_LEAF

maybe salvage yard would only part with battery and then relist auction. maybe not.
those are all coparts auctions. the two in somerville are the last ones from Sandy. notice they are listed as 'parts only' which is what the state of NY did for those caught in the flood. i think there were about 120 of them over the last two years. otherwise perfectly useful.

if you wanna bid then go join coparts. i can help you set up a business title so you can bid and then you just put down a deposit or buy a premier membership which lets you bid higher than your deposit guarantees.

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Re: Nissan Leaf Cells Test Data

Post by Harold in CR » Nov 26 2014 5:12pm

I joined copart and have been following the Leaf and Volt auctions. NEVER saw either type sell for under $8000.00 or so. 1 Volt in particular, went on the block several times, before the insurance company finally let it go. Leaf batteries are 24 Kwh.

I thought about buying one, selling part of the battery to help offset my cost, and part out the rest of the car on flea bay. Need a way to transport, store and disassemble the car. LOTS of up front cost before realizing any cash flow, unless someone is flush with cash.

For the past 3 weeks, NO Nissan leaf batteries have come up on Car-part either. Now, nearly all the 16.5 Kwh Volt batteries are listing for $ 2400.00 and up, and, I can't find any salvage yards that will ship by freight carriers.

Flea bay has the 1eyedcruiser selling Volt modules, but, he has been banned from DIYelectriccar forum for unscrupulous dealings. He goes by several different user names and sells AC35 drive motors as much larger motors, also. WATCH OUT for this guy.
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Re: Nissan Leaf Cells Test Data

Post by dnmun » Nov 26 2014 8:40pm

you really have to be right there if you buy one of these at coparts auctions. otherwise it has to be transported if you cannot pick it up yourself and just towing across town is several hundred.

i have not followed the auctions but i am surprised the totalled wrecks are pulling $8k+ and i will watch the iMiEV on 12/19 to see what it brings because it is in very good condition imo.

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