Any feedback on ETC cells?

[kite]

Does anyone have experience with ETC cells? Good? Bad? depends on who you get them from and what questions you ask?

This is the only thread mentioning them on the forum, though the buyer didn't mean to buy them in the end he was satisfied (and confirmed through a PM that they are working after ~100 cycles).

I got a quote from Xuba for 4 x 280Ah ETC cells that are almost $100 cheaper (for set of 4) than their 280Ah EVE cells.
ETC: "Grade A with QR code"
They send a screenshot of a portion of a datasheet. Things I noticed in that are:

• 277ah capacity - OK I can live with that instead of 280. Really anything close but reliable is fine with me
• < 0.4mOhm - EVE (and maybe others?) state < 0.25 or 0.3mOhm
• discharge cutoff of 2V - is this a red flag? i thought 2.5 was the absolute lowest LiFePo4 should go
• weight of 5.3 kg looks right for the capacity

looks like it has m4? threaded holes...

I found this data sheet online. It generally matches what they sent, except for discharge cutoff voltage. The photos look like at a minimum, a different wrap and cover on the cells...

Thanks for any insight you can give!

 

[Gazoo]

If they come with threaded 4mm terminals I would avoid them. Some of us have stripped the cells with 6mm holes using grub screws and a thread locker with only 6nm of torque or so. So it's been recommended to use no more than 4nm of torque. This is with EVE cells and the aluminum terminals are quite soft. Maybe ETC uses a stronger aluminum alloy? Perhaps you could ask @DIY-Dan the amount of torque he was able to apply.

I would ask the supplier if they can install laser welded studs at no additional charge. In fact I would not buy a cell with aluminum terminals that doesn't have laser welded studs as this has become the norm in most cases.

 

[kite]

Thanks for the input.

Xuba says they will weld 6mm studs on the cells before shipping . "There is a shop across the street that can do it very quickly"...
FWIW, Dans' setup has studs but I don't know if they came installed or if he did it himself.

Is it a red flag that they don't have a full datasheet? Just the screenshot I sent?

There is a data sheet here, though it's more limited than others I've seen. There's also a polished video that claims to show ETC production, but who knows where it actually is.

 

[UV-PWRD]

I purchased my own studs and used a basic 1/4" drive screw driver style hand tool to torque them, I did not use a torque wrench as I don't have one that goes that low - all of my tools are automotive based as motorsport is my other hobby.

That said, I have a reasonable amount of experience with stripping nuts/bolts etc so I have a "reasonable" torque gauge in my hand and I'd be fairly confident those studs have a little more than 4Nm in them, wouldn't be by much, but 4Nm is such a tiny amount that simply having then snug would run you over easily. I was very cautious during that process as you want enough torque to secure the washers onto the terminals for the balance leads and the busbars.

In an RV/Mobile setup bigger studs would be nicer, but it depends on how well they are cased and isolated/insulated from movement etc.

I did find these when I as looking last time.

 

[UV-PWRD]

Also, the 2v thing is irrelevant to you because you'll be setting your BMS at 3v or so. They are "dead" flat at 2.5v and nobody wanting any sort of useful life is going anywhere near that depth of discharge.

II should add I'm not saying buy them, only that I ended up with them and they work. I think 6mm studs would be better if they will do that for you, had I known in advance I would've asked. I was advised to ask for 2x the busbars which I did so I could double stack them.

 

[Derek S]

I've had my ETC cells for a while and used an electrician's torque screwdriver @ 2Nm. Generally good quality much the same as any other at that price range. Also, I got them from Selina at Xube when the price of EVE shot up.

 

[kite]

Thanks Derek. Did yours come with threaded holes or studs?
Did you capacity test your ETC cells from Xuba?

 

[Derek S]

Mine came with holes but I've ordered more with studs. M4 is just far too small and although I've never torn threads I'd much prefer studs.
I've only casually looked at the capacity of batteries that I have ordered and they all seem fine even under fairly heavy loads. Except for one Eve cell that flaked out fairly quickly in a 16s setup.

 

[kite]

Thanks Derek. I'm just about to pull the trigger on 12 etc cells from xuba. They offered capacity testing for $5/cell so I'll likely get 4 tested to satisfy my curiosity...
If I get those results I'll post them here

 

[kite]

Just got photos back from Xuba of studs welded onto the ETC cells...

 

[UV-PWRD]

Much better

 

[Derek S]

My new ones look the same. Selina shipped them out to me a few days ago and I'd say we're getting the same batch. Just make sure you have the correct torque and BMS is working 100% and you should be all good.

 

[Simi 60]

Just got photos back from Xuba of studs welded onto the ETC cells...

Inquired about them myself, same pics sent to me today

 

[kite]

Attached is an English version of the ETC277 datasheet that DIY-dan posted above.

According to Xuba:
"ETC280AH and ETC277AH are very similar, but the capacity of ETC280AH can reach above 280Ah or more."
"There is no ETC product specification for the time being, but I believe it will be available soon."

Anyways, I paid $20 for Xuba to capacity test 4 of my cells, which they said would only take a couple days. The testing was outsourced and that shop was backed up - to make up for the delay Xuba had all 12 of my cells tested.

Capacity ranged from 286-293Ah.
286Ah x 3
287Ah x 2
288Ah x 2
289Ah
291Ah
291Ah
293Ah x 2

The tests were run at 30A discharge (~0.1C) from 3.65V to 2.6V, then 5A until 2.5V cutoff. Attached is a voltage vs current plot from one cell, they all look similar at this resolution.

This was mostly out of curiosity since I really don't need every last Ah. I do like knowing they aren't abused/really old, and thought it might help others decide if they should buy the cells.

 

[kite]

Well, the resistance data is kind of interesting. I'm not sure what equipment they used or if this data is worth spending too much energy thinking about. Also, 12 cells were tested in 2 days so they much have had multiple sets of equipment, which could affect this measurement.
Maybe someone who knows more about this can help me interpret...

Attached are voltage/current and IR vs cell voltage plots for each cell.

The trend is consistent. Is it typical to see higher resistance outside the flat part of the voltage curve? seems like that's what's going on.

cells 1 - 4 & 7-11 look pretty similar.

Cell 5 has very erratic readings through much of the test. The voltage plot is also fuzzier.
Cell 6 is a less bad version of 5
I wonder if these could be bad connections at the terminals during the test? Or could it indicate an actual issue with the cells?

Cell 12 IR curve is shifted left (at least in the higher voltages). The initial voltage drop is bigger. Interestingly though, this is the highest capacity cell. Cell 9 is also shifted left some but not quite as much.

Interested in some expert interpretation. Thanks!

 

[kite]

Only able to attach 10 files. Here are the last two.

 

[kite]

So far so good on these ETC cells.

• All were ~ 3.2V with 3mV delta except for one that was 8mV lower (the highest capacity tested cell of the bunch pre-shipping).
• They were packaged well and looked good on arrival. Only small things noticed are two small sections of blue plastic wrapping that had been patched and one tiny tiny ding on a cell that looked like it touched another cell's stud before shipping (dented one tested highest capacity before shipping)
• I don't know how to interpret the QR codes but I'm guessing the cells are from three different batches based on different patterns in the serial numbers.
• welded studs have the same small contact area as the EVE cells I've seen photos of.

The first 4S pack I built capacity tested to 286Ah when discharged to 2.75V/cell BMS cutoff.
This pack was built with the cells that tested 286, 286, 286, and 287 Ah before shipping.

I didn't have to do much of a top balance balance because the cells were so well balanced on arrival. I charged in series with JBD BMS to 14.6V and the delta was < 8mV when the charge current dropped to 3A. I let the BMS balancing work on it for a bit and also plugged in a 5A active balancer briefly (I was curious and had already attached the balance leads), but only saw 100mA through a couple of the active balancer leads. After 5 hrs resting (without active or bms balancing) the voltage had settled to 3.53V/cell with < 0.4 mV delta.
- Side note here is that I have since re-calibrated the BMS cell voltages because I was reading larger deltas on the BMS than on my DMM, but we're talking a few mV so it probably didn't matter.
- It looks like the $5/cell capacity testing is worth it just to charge them back to very similar SOC. It also allowed me to batch the 12 into similar capacity groups

- capacity test was mostly at a discharge rate of 60A (~0.2C) with bursts higher as I tested the inverter.
- very minimal temp increase of cells and terminals
- voltages were very close through the flat part of the discharge. During discharge cell 4 was a little higher (< 10mV) but would converge with no load (this measurement is the only one that does not include a cell interconnect cable)
- after 2.75V bms cutoff the cell voltages were:

• cell1: 2.823
• cell 2: 2.828
• cell 3: 2.834
• cell 4: 2.882 this one started to diverge below ~ 3.1V

Cell 4 is the slightly higher capacity tested cell and a different "batch" according to my "interpretation" of serial numbers.

I'm putting these into service in my van now, if there are any issues I'll report back but so far I'm quite pleased.

 

[UV-PWRD]

I'm about 90 cycles in on my pack and all is mostly OK, I note I have 2 cells that want to hit HVD and LVD and I've checked terminals/washers etc so I do think there's a slight capacity difference. I leave the balancer on the BMS turned on (2a) and have contemplated getting a 5a to sit on top.

That said, I don't push them as hard as some others, 54.8 bulk charge, 54.4 float (3.4v per cell in float). They will settle to 53.6 on their own.

I have LVD set at 3V and was reaching that a few times in winter on higher loads at the bottom end of the capacity through voltage sag.

I note that as soon as the pack is like 60-70%, it's current limited in how much it'll take from the solar anyway (around 40-50a at these voltages), I'll only ever see 70-80a in if the pack is really flat and sun doesn't get going til 10-11 when the system can produce like 4-5kw.

Otherwise the pack just sucks in 40-50a and I've got overhead on the PV to use for loads as well (this is on an optimized 5kw system comprised of 2x 2.5kw arrays).

 

[bobh5597815]

Does anyone have experience with ETC cells? Good? Bad? depends on who you get them from and what questions you ask?

This is the only thread mentioning them on the forum, though the buyer didn't mean to buy them in the end he was satisfied (and confirmed through a PM that they are working after ~100 cycles).

I got a quote from Xuba for 4 x 280Ah ETC cells that are almost $100 cheaper (for set of 4) than their 280Ah EVE cells.
ETC: "Grade A with QR code"
They send a screenshot of a portion of a datasheet. Things I noticed in that are:

• 277ah capacity - OK I can live with that instead of 280. Really anything close but reliable is fine with me
• < 0.4mOhm - EVE (and maybe others?) state < 0.25 or 0.3mOhm
• discharge cutoff of 2V - is this a red flag? i thought 2.5 was the absolute lowest LiFePo4 should go
• weight of 5.3 kg looks right for the capacity

looks like it has m4? threaded holes...

I found this data sheet online. It generally matches what they sent, except for discharge cutoff voltage. The photos look like at a minimum, a different wrap and cover on the cells...

Thanks for any insight you can give!

The ETC 277ah in the picture you sent is reprocessed. The QR code position of the real GRADE A ETC 277ah is different. If the price you buy is cheap enough, it doesn't matter. It's still a good deal.We will soon have some real grade a etc 277ah arriving at the U.S. warehouse with an actual capacity of about 288ah（Including ETC test report）. When the battery arrives in the United States, we plan to do some promotion!

 

[kite]

well look at that! another QR code scratched off under the black cover.

@bobh5597815 what do you mean "reprocessed"? does this just mean "used" or is there actually some sort of reconditioning procedure that resellers/manufacturers do to bring old cells closer to original spec?
And are you speculating or do you know this is being done to ETC 277 cells?
Thanks for the insight.

@DIY-Dan I'm curious if your cells have 1 or 2 covered up/scratched out QR codes. In this supposed ETC Video there are is one shot of a cell with 2 QR codes, others with 1 QR code. I wonder if the 277s originally have 1 or 2.

Anyways, Xuba, who of course did not tell me any of this upfront, says:
"When we purchased from ETC brand factory, there were two QR codes on it for a long time.One of them was scratched because ETC DONNOT allow dealers to sell batteries with two complete QR codes. We guarantee that these products are Grade A, brand new and purchased directly from ECT."

And
"I explained to you, because the factory does not want these batteries to be used for civilian use, it is only the tracking code of the factory's internal system. Two-dimensional code cannot prove the battery (life, performance, use process)"