PWD's Yamaha XV250 Virago build

[pwd]

just to be sure, they would be laid out like the first way, not the second? (because they should ahve those large faces in compression)

View attachment 368125

That's right; I'm planning on laying them out the first way. Basically like this (not my photo, I don't have the cells yet) - the green line represent compression faces:

 

[pwd]

The cells have finally arrived but I'm a bit disappointed upon inspecting the first couple of cells. I may have been sold new old stock where the internal resistance is higher that I was excepting.

The first cell I looked at has a manufacturing date of March 2019 based on this info decoder site:

https://www.gobelpower.com/lifepo4_decoder.html

The datasheet says that between version D and E of the cell (revisions made in 2021) the internal resistance was specified as ACR(1KHz) ≤ 0.6 mΩ and then improved/changed to ACR(1KHz) : 0.35±0.1 mΩ;

I've measured ~ ACR(1KHz) 0.6 mΩ on the first cell @25C / 3.6V

Looks like I have some checking to do and a task I dislike - trying to prove to the seller I was screwed to some degree

 

[pwd]

I may have just discovered that the cells I received are not even the same brand or capacity I had ordered. Still doing some digging but my cells look an awful lot like Sunwoda 3.7V 75Ah and not Svolt 90ah.

 

[amberwolf]

I can see their response now: "bbbuuuttt...we sent you cells? why complain?" :/
FWIW, the tiny bit of the as-received cell I can see in your pic

doesn't look anything like the cell picture you'd posted (from their site?) previously, of the ones you were ordering

other than that it has a vent, posts welded to the contact blocks, and it's prismatic. All the details of all those things are significantly different.

 

[amberwolf]

Also, if interested, this is a useful video on how the QR code came about, and how to make one (which also means how to manually read one):

 

[pwd]

I can see their response now: "bbbuuuttt...we sent you cells? why complain?" :/
FWIW, the tiny bit of the as-received cell I can see in your pic

doesn't look anything like the cell picture you'd posted (from their site?) previously, of the ones you were ordering

other than that it has a vent, posts welded to the contact blocks, and it's prismatic. All the details of all those things are significantly different.

Yes exactly, they looks visibly different. The dimensions are nearly identical. I've sent the seller my findings and am waiting for a response.

This lithium cell code decoder actually shows the manufacturer; and the same production date:

Cell QR Decoder

Cell QR Decoder

www.xihopower.com

I found a fairly good explanation of how to manually decode the production date here:

QR decoder parsing differences

QR codes appear to be parsed differently in different QR decoders. In the Basen and Gobel online decoders, as well as the Android LiFePOQR decoder, the QR code eg 07HCBC1P22G06AC700002596 indicates a manufacturing date of 7 Jul 2022. However, on sites such as Docan Power, Energie Panda and...

diysolarforum.com

Here is the text from the key post in that thread:

"
Code decoding standard, informative but not super understandable:

GB/T 34014-2017 English Version, GB/T 34014-2017 Coding regulation for automotive traction battery (English Version) - Code of China​

GB/T 34014-2017 English Version - GB/T 34014-2017 Coding regulation for automotive traction battery (English Version): GB/T 34014-2017, GB 34014-2017, GBT 34014-2017, GB/T34014-2017, GB/T 34014, GB/T34014, GB34014-2017, GB 34014, GB34014, GBT34014-2017, GBT 34014, GBT34014
www.codeofchina.com

Code breakdown:
1-3 - unique manufacturer Id, 07H = Higee
4 - battery type, C = cell
5 - Chemistry, B = lithium iron phosphate
6-7 - manufacturer product code, not unique across manufacturers, C1 =that version of the Higee 120ah LFP cell
8-14, manufacturer custom info. Space left for manufacturers to put what they want, decoding only available properly for eve cells, p22go6a

15-17- Date of manufacturing. This is where at why things are confusing, they do not give in the English translation a format for the date just that 880 equals Aug 31st 2018. So people do not know if that is m/y/d or y/m/d. That is the difference you are seeing between the code readers above.
Days run from a-z (skipping a few) then 1-0
Month is 1-9 then a-c
Year is 8-9 then a-z
"

 

[pwd]

Update so far is that the seller admitted the wrong cells were sent but only wants to pay the price difference on the cells. I sent a reply to that and am awaiting a response.

 

[pwd]

I have come to an agreement with the seller and will be keeping these 75ah cells. I received a little compensation + $144 USD for the cell price difference and three replacement cells for ones that were dented. I am disappointed that I'll be using lesser cells but I really want to get this project rolling; I'd rather get it working than wait another 1-2 months + the cost.

In hindsight and for anyone new to ordering cells from China: do your research, ask the seller lots of questions and confirm the specs before ordering - at least then you'll have proof of what was supposed to be sent (I at least had that). Also, start the cell ordering months in advance if you have a planned date for build completion; then you have more time to deal with issues and can save money on shipping if you aren't in a hurry.

Here is the worst of the damaged ones:


Typical resistance of these cells @ ~20 degrees Celsius and ~ 50% State of Charge:


They won't be horrible, but I may lower my expected maximum current to 400A.

I started making the first tray for the battery pack - it will sit here but it still needs frame supports etc...



Here are the materials I'll be using to make each sub pack: aluminum end plates to keep the pack together/slight compression with coated stainless steel cable ties. I'll be using 2mm rubber between each cell and as padding in the tray:

 

[j bjork]

Is the rubber you plan to use between the cells the foam in the picture? I am not sure that is a good idea in that case, I think you should have something stiffer. In the cell modules with prismatics I have taken apart it has been ither a thin plastic sheet or grey paper (not sure what it is called, but you can probably see it early in the yz250f thread)

 

[amberwolf]

You don't want anything that can compress, allowing the cells to expand into the space it was taking up. If you have that, then you might as well not use cell compression stacks.

 

[pwd]

The rubber I'm using is the black rectangular cut sheet in the picture; it seems to not compress easily like foam. It's marketed as "Multy Home Black 4 ft. x 2.5 ft. 2mm Recycled Rubber BBQ Mat"

 

[amberwolf]

If it compresses, I wouldn't recommend using it.

 

[jkrienert]

Any listed shore hardness on the packaging?

 

[pwd]

I have thought about how much the rubber mat might compress; and it really doesn't compress any noticeable amount when I put pressure on it with handle of a screwdriver and at the very least; should make a good insulator and vibration damping.

My custom length (42mm spacing) bus bars have arrived. They are laminated copper sheets that are supposed to have some flexibility to them. The factory bus bar is shown underneath. The new bus bars have slightly less resistance (I measured around 0.02 mOhms less) as well.




I have pretty much all the materials I need to build the battery pack but I have to continue working on the battery tray/frame system before I begin pack assembly.

 

[bananu7]

This looks soooo much better than the prospect of welding 400 cylindrical cells already.

 

[pwd]

This looks soooo much better than the prospect of welding 400 cylindrical cells already.

Thank you. That is what I am aiming for; although the need to fixture and/or compress the cells does add an element that cylindrical cells doesn't require.

 

[pwd]

I've been working on the battery pack shelves. I work with steel only as a hobby so this is slow work and not perfectly square but should be good enough.







The plan is to have three shelves (one for each sub-pack). So far; it looks like I can fit 30S or 30 cells. Bottom will be 6S middle with be 16S and top will be 8S. The pack will be wide but seems to not interfere when sitting on the bike.