Xuba Electronics: DEAL - 280AH LiFePo4 cells. Purchase & Review

[Ampster]

What does this mean? That the cells are packaged in such away that they cannot expand?

To me that means I will apply a moderate amount of compression and let any expansion apply the rest. My definition of moderate is on a stack of eight cells 1/4" thread rod is finger tight and two complete turns of the nut after that is tight enough. I do not want to distort the cells but I don't want them to expand either.

 

[Dzl]

I was reading the specifications on these batteries, and one thing stood out;
The battery cell is under the action of 300kgf force ,the battery cell is under the action of preset 300kgf force ...

What does this mean? That the cells are packaged in such away that they cannot expand?

A few (maybe a dozen?) pages back we discussed this in some detail with no clear answer (in my mind). Someone even reached out to EVE but apparently never received an answer.

What the datasheet shows is that there is an improvement in cycle life of 1000 cycles if the cells are under 'fixture' / a 300kgf force.

What the datasheet does not explain is how this is measured, when it applies, or how to achieve it.

In the absence of a clear explanation, what many people seem to be doing is securing the cells 'snugly' at low SOC, and hoping that the pressure at average or high soc will be in the right ballpark.

I do wish EVE would clarify what they mean. I'm also curious to know if manufacturers of any other large form factor aluminum cells recommend this as well

 

[FL Keys]

A few (maybe a dozen?) pages back we discussed this in some detail with no clear answer (in my mind). Someone even reached out to EVE but apparently never received an answer.

What the datasheet shows is that there is an improvement in cycle life of 1000 cycles if the cells are under 'fixture' / a 300kgf force.

What the datasheet does not explain is how this is measured, when it applies, or how to achieve it.

In the absence of a clear explanation, what many people seem to be doing is securing the cells 'snugly' at low SOC, and hoping that the pressure at average or high soc will be in the right ballpark.

I do wish EVE would clarify what they mean. I'm also curious to know if manufacturers of any other large form factor aluminum cells recommend this as well

Since EVE did not respond, has anyone tried asking Xuba? I would really like to know how to properly "squeeze" my cells also. Even better if someone could tell me how to translate "300kgf" to my torque wrench!

 

[Dzl]

Since EVE did not respond, has anyone tried asking Xuba? I would really like to know how to properly "squeeze" my cells also. Even better if someone could tell me how to translate "300kgf" to my torque wrench!

Not sure, and not sure that they would know. But if they truly have an official relationship and sales deal with EVE (as previously alluded to), they should be able and willing to find out on our behalf.

 

[FL Keys]

When I saw the 1.4 digit (100 microvolt) resolution of the meter in the Xuba test videos, I just had to find one (for a good price!). So I just bought the HP-770D DMM to test the voltage of my cells. It shows 1.4 digits (up to 4v) just like the one in the videos. There are good reviews of it here and here and It was only ~$40 with $2 off coupon. Just thought I'd pass this on.

(I'm guessing this is still on topic)

Even better, here is what looks to be the actual meter the Xuba guy uses, apparently from the manufacturer. It is the Yaorea YR1035+ and it is a dedicated battery tester (not a multimeter) that measures internal resistance down to 0.01 mΩ and voltage with 1.4 (maybe 2.4?) digit resolution (100 microvolts). The price is $45-$57 (depending on the leads) and free shipping. Amazon and ebay also have it for a slightly higher price and longer wait. So yeah, I went ahead and ordered one (combo #3, $57).

Note: Other vendors did have it cheaper, but I wanted to be sure I was getting the real deal.

(Sorry, wish I could edit my previous post)

 

[Steve_S]

I am actually in CHAT with Amy and I asked her specifically what they use:
Here is the link to the product on Tabao and this is what they are using at XUBA/LUYUAN.

Sorry, I don't know how to make it English properly, never used that site before.

淘宝网 - 淘！我喜欢

淘宝网(Taobao.com)作为专业的购物网站拥有全球时尚前沿的消费者购物集市,100%认证网上商城及超值二手商品区，同时购物安全，产品丰富，应有尽有,任你选购,让你尽享网上在线购物乐趣！

item.taobao.com

 

[Denis]

Even better, here is what looks to be the actual meter the Xuba guy uses, apparently from the manufacturer. It is the Yaorea YR1035+ and it is a dedicated battery tester (not a multimeter) that measures internal resistance down to 0.01 mΩ and voltage with 1.4 (maybe 2.4?) digit resolution (100 microvolts). The price is $45-$57 (depending on the leads) and free shipping. Amazon and ebay also have it for a slightly higher price and longer wait. So yeah, I went ahead and ordered one (combo #3, $57).

Note: Other vendors did have it cheaper, but I wanted to be sure I was getting the real deal.

(Sorry, wish I could edit my previous post)

This is exactly the one that I purchased,at the same time as my cells. I just wanted to confirm I like it, seems to be very accurate and it is very handy to monitor the cells.

I ordered mine on AliExpress,
Raceived it in three weeks.
C$ 17.31 25％ Off | New Original Four-line High Precison YR1035 Lithium Battery Internal Resistance Meter Tester YR 1035 Detector 18650 Dry Battery

 

[FL Keys]

I am actually in CHAT with Amy . . .

Maybe you might want to ask her what a "300kgf fixture" is while you're at it? Many of us are wondering about this. I'd ask myself, but you seem to be the liason here and we don't want too many people bugging her.

Yeah, they are the same meter. Here is a video review in English. I did notice that some of the cheaper vendors I saw lacked the yellow "Yaorea" in the bottom right corner. Not sure if those are a knock off or what. Apparently it is also printed on the circuit board inside. And it looked to me like Xuba uses the version with the "upgraded leads." They are only a few dollars more.

Also, in case anyone else orders one, make sure it supports English menus. Apparently some of them do not.

@Denis Good to know someone here actually has one in hand and likes it. Thanks!

And could you provide an acutal link to the one you bought? I didn't see any that cheap.

 

[Denis]

I paid 60$ cad, #2
C$ 17.31 25％ Off | New Original Four-line High Precison YR1035 Lithium Battery Internal Resistance Meter Tester YR 1035 Detector 18650 Dry Battery

C$ 17.31 25％ Off | New Original Four-line High Precison YR1035 Lithium Battery Internal Resistance Meter Tester YR 1035 Detector 18650 Dry Battery

star.aliexpress.com

 

[Sgt Raven]

Maybe you might want to ask her what a "300kgf fixture" is while you're at it? Many of us are wondering about this. I'd ask myself, but you seem to be the liason here and we don't want too many people bugging her.

Yeah, they are the same meter. Here is a video review in English. I did notice that some of the cheaper vendors I saw lacked the yellow "Yaorea" in the bottom right corner. Not sure if those are a knock off or what. Apparently it is also printed on the circuit board inside. And it looked to me like Xuba uses the version with the "upgraded leads." They are only a few dollars more.

Also, in case anyone else orders one, make sure it supports English menus. Apparently some of them do not.

@Denis Good to know someone here actually has one in hand and likes it. Thanks!

And could you provide an acutal link to the one you bought? I didn't see any that cheap.

KGF is a measurement of Force, commonly use in Russia/China for the output of Rocket engines and such.

 

[JoeHam]

KGF is a measurement of Force, commonly use in Russia/China for the output of Rocket engines and such.

Would I attach one or two rocket engines for the proper compression? ?

Yes, I’m just kidding around.

 

[FL Keys]

According to this web site, 300 kgf translates to 2970 ft lbs. My torque wrench doesn't go that high.

The point is, many of us would like to follow the specs for these cells, but we don't undersand exactly what they are asking for.

 

[BiduleOhm]

You can't convert kgf to lb.ft, the first one is a force and the second one is a torque. If you look carefully then you'll see the website is for kgf.m, not kgf.

 

[FL Keys]

You can't convert kgf to lb.ft, the first one is a force and the second one is a torque. If you look carefully then you'll see the website is for kgf.m, not kgf.

Oh, I gotcha. So then how to we apply that to making an actual box for our cells?

 

[Sgt Raven]

You can't convert kgf to lb.ft, the first one is a force and the second one is a torque. If you look carefully then you'll see the website is for kgf.m, not kgf.

Yeah, I looked and didn't find a way to convert it to something we could use. I only posted when the subject was brought up again.
For pressure I would think the metric equivalent of "PSI, Pounds per Square Inch" is what you would want.

 

[Steve_S]

Re the IR Tester you folks are talking about, this is not quite like what would be used for actually doing full-on Cell Matching & Validation. These can be used at different voltages to measure the IR at that set volt, then the next & so on, after which you charge up to the next voltage set (usual 1.0V) and do it all over again, this cycle repeats from 2.50 to 3.65 and back down again to evaluate the cells fully through their range. This is but e basic tool for simple & time consuming laborious evaluation.

Properly matching up cells, is done by an automated test rig, where the cells are mounted up and run through the test cycles producing individual cell reports allowing them to be matched up according to the values of the cells. On average this is a 3 day process and typically costs about $10 per cell to perform + wastage of any cells that do not fit within the groupings.

Re the compression, somewhere back in the other (possibly the other) was collectively figured out to be somewhere around 12PSI and mid charge. I built custom boxes out of 3/4" ply and the cells are bound and pushed in there "tight". The method many are using with the Threaded Rods and 3/4" Ply or other think solid material seem very accomodating. Alternately, the Shipping type strapping (think boxes strapped to shipping pallets) is commonly used in prebuilt packs to bind the cells very snugly together. Unfortunately they are not cheap to buy (over 200 USD) for a few quick uses. If you have a bussy in a warehouse, can't hurt to ask to use it for 15 minutes, worst they could say is no.

PS: Amy is sending me one of these testers (I had her get me the same one they use) and I should have it end of next week I hope. I'll post photo & info so people can locate it easier. There are different brands that look identical, even to model number. Hence why I asked her to get me a Known Good well used & abused & survived model. I hate buying anything twice.

 

[Luthj]

kgf is the same type of unit as lbf. Which for our purposes is the same as lb and kg.

300kgf is 660lbf. Cells are about 53.5 square inches on one side. So pressure is about 12psi. I can apply 12psi to 1 square inch with my thumb, so its not really a major load. In fact sufficient clamping force to prevent cell movement is probably at least 300lb unless some adhesive or rubber mat is involved.

I am kinda surprised about how many folks don't know how to calculate pressure or convert units...

 

[Sgt Raven]

Re the compression, somewhere back in the other (possibly the other) was collectively figured out to be somewhere around 12PSI and mid charge. I built custom boxes out of 3/4" ply and the cells are bound and pushed in there "tight". The method many are using with the Threaded Rods and 3/4" Ply or other think solid material seem very accomodating. Alternately, the Shipping type strapping (think boxes strapped to shipping pallets) is commonly used in prebuilt packs to bind the cells very snugly together. Unfortunately they are not cheap to buy (over 200 USD) for a few quick uses. If you have a bussy in a warehouse, can't hurt to ask to use it for 15 minutes, worst they could say is no.

I thought of that some time ago. If I still had access to Poly banding equipment with the plastic corner protection, I would use it in two places. Ideal would be the type that uses heat to fuse the strap together.

 

[Gazoo]

To me that means I will apply a moderate amount of compression and let any expansion apply the rest. My definition of moderate is on a stack of eight cells 1/4" thread rod is finger tight and two complete turns of the nut after that is tight enough. I do not want to distort the cells but I don't want them to expand either.

Regarding cell compression I believe you have the right idea and this is what I am planning on doing. The individual pouches that reside in the case don't know how much compression is applied to the case. However if the pouches expand beyond the case dimensions then they will know they are going out of bounds. IMO mounting the pack in a fixture to strong enough to keep the pouches from going out of bounds is all that's needed here.

Why do we need to do this in the first place? Slight swelling of the case is normal and I have read swelling can reduce cycles due to delamination of the pouches if allowed to expand to the point the case swells. The other reason is to eliminate the stress placed on the terminals if the case swells. It also might be a good for the cells to be less than 50% SOC before mounting in a fixture and applying high charge/discharge rates.

 

[Luthj]

The individual pouches that reside in the case don't know how much compression is applied to the case.

I would disagree. The clearance between the roll (or accordion stack) and the case is negligible. If you try to compress the center of a cell, it doesn't move appreciably, even with 20lbs of force. This tells me that the electrode/separator roll is tightly packed inside the casing. Also the fact that the spec lists 0.5mm of expansion during charging shows there is little or no free space inside. This makes sense of course, as movement between the two is likely to cause damage long term. The layers are as thin as possible to maximize energy and material density. The case itself is quite thin, and even the short sides would buckle if they were carrying significant load. Thus the majority of the clamping load is carried by the roll itself. Obviously the roll isn't crammed into the corners though. If memory serves, when they manufacture the cell, a tool expands the cell casing slightly, then the roll is inserted. A series of dies compress the casing and roll until its square ensuring a tight fit. Then the electrolyte is added, and the cell is capped.

The attached excerpt briefly discusses how pressure is needed in wound cell designs.

https://www.electrochem.org/dl/ma/203/pdfs/0106.pdf

X ray photo of an jelly roll from a lithium cobalt cell.