I've made a dent!

Z

zerberfert

Member
Joined
Apr 14, 2020
Messages
58
Hello all,

It seems that all I do with my free time is open/precharge/charge/test batteries. I've gotten blisters from opening battery packs. I even dream about batteries. This is getting out of hand. At least I've made a dent. I am about half way 700/1400 needed to start building my battery packs.


image_tnclbv.jpg



image_uqfhyw.jpg


I can test 80 batteries a day. It seems I ramped up my testing more than I can open battery packs. Oh well, it keeps me busy.

Zerb
 
I can gladly help if you're in Romania :D
Anyway, keep going, but note that completing a number per day is not efficient.
It is more efficient to do a complete disassembly of all packs (1st step), sort (2nd step) and then start capacity-testing (3rd) and mark.
 
thats how i do it.
shuck all the packs,seperate into pairs,triples,quads,ect.
check ir of group and voltage.
weed out extremely low/0v,high ir,leakers.ect.
charge the groups that pass my tests.
wait a week and check for sd.
then test capacity of groups.
i usually test at 1a.
so a pair=2a,ect.
if i get a reasonable result for the cells rated capacity i mark the group.
if not i separate and test in case its one sick cell and not just worn out group.
this can considerably speed testing with an acceptable loss of accuracy.
 
Yea, I have it broken down into stations. However, I have to break them open to keep the assembly line going.

Thanks for the encouragement.
 
I just got a bunch of these - and have found that if I squeeze about 1/2 inch ofthe rounded 1/2 (right at the seam) in a vice, it will 'crack open' the end and let me pry the rest. Most pop easily but about 1/3 are a bit tougher... and you can turn it around and do the other end if you need to. Also, the vice tends to 'hold it' while I pry down the edge and I avoid jaming the screw driver into my hand.

I've found that in 99% of cases it will 'crack open' before denting the cell but it can be scary as it takes a fair amount of vice force. Here's a couple of pics to illustrate:

image_xjpobu.jpg



image_ryfhlk.jpg
 
Awesome, thanks for the info. I have been doing it a little different and have dented about 5 batteries. Not bad but won't use those in my powerwall. I will use them for less critical applications.

What percentage of Green vs Blue batteries are you getting? I am getting about 1/3 Green vs 2/3 Blue's.
 
zerberfert said:
Awesome, thanks for the info. I have been doing it a little different and have dented about 5 batteries. Not bad but won't use those in my powerwall. I will use them for less critical applications.

What percentage of Green vs Blue batteries are you getting? I am getting about 1/3 Green vs 2/3 Blue's.
Click to expand...
I've opened 192 units (384 cells) so far. 2 of them have been 0 volts - had to toss. 148 green (38.5%). So I'm seeing the same thing... I was hoping more 50/50.

I prefer to have each of my 14s88p (260ah)batteries be all the same cell type - so my plan is to build out a 14s88p blue and a 14s88p green as far as it will go with Ring NCR18650A(s), add the 100 NCR18650A(s) I had left over from a previousbuy and then get a few more from Power2Spare to make it come out right-https://www.power2spare.net/collections/all

Are you planning to mix?
 
What do you mean by "ring with NCR18650a"

Thanks
CG
 
@OffGridInTheCity - Thanks again for showing the way you crack the packs open. It is much faster than the way I was doing it (and less possible damage to the cells).

These 2 battery types are so close to each other do you think it would be bad to put them together in a pack? I was going to try a 50/50 split to make it even. Have you tested IR yet. Most of the Greens are about 25 mOhm and the Blues 36 mOhm for me. I hope that is close enough to not make much of a difference.
 
zerberfert said:
@OffGridInTheCity - Thanks again for showing the way you crack the packs open. It is much faster than the way I was doing it (and less possible damage to the cells).

These 2 battery types are so close to each other do you think it would be bad to put them together in a pack? I was going to try a 50/50 split to make it even. Have you tested IR yet. Most of the Greens are about 25 mOhm and the Blues 36 mOhm for me. I hope that is close enough to not make much of a difference.
Click to expand...
The cells are nicely matched at 3000-3200mah and the date codes I checked show 2018 - so these things look 'brand-new' to me :)

Its not wrong to mix 50/50. My 3rd battery is made of 14 packs where50% /130ah are NCR18650A (3000mah) and 50% / 130ah areLGABB41865 (2600mah) for 260ah/pack. It's running perfectly.

However... since all the IR discussions and some bad experience with mixing Sony G5/G7 in early days...I've shifted my 'best goal' to100% same type cell per battery.e.g. per 14s88-120p (260ahper pack) in my case. Its more about 'extra small step' for longer life/less-trouble? than a hard issue...

In this case, because I know I can get a few cells from Power2Spare I bought enough Ring to build 2 batteries of 14s88p for my plan. One will be 100% NCR18650A and 1 will be the blues :)


>Most of the Greens are about 25 mOhm and the Blues 36 mOhm for me. I hope that is close enough to not make much of a difference.
My battery bank is designed for max charge/discharge < 300ma - and I typically run 200ma/cell. The amount of power in/out per cell makes a difference. If you're more up at 1a/cell then I would say IR get's more serious.

My OPUSs are showing 80-120mOhm - most at 80'ish - on Ring batteries. This is perfectly fine in my experience. I've used the same 3 OPUSs for all my cells so far and have 84 packs @ 260ah each - and overall the cells range from 50-120mOhms - mostly around 80'ish. The 84 packs are healthy and I run 40mv (0.04v) max diff that varies between 0.03v and 0.05v thru the daily cycle from 3.54v low to 4.0v hi - with no problems. I have Batrium but balance is turned off - as I've only need to balance when I add a new battery. I've gone 9 months with no balance so far as my longest stretch between adding a new battery. I'm nearing 700 cycles the oldest battery.

Having said this - I don't bo-hoo @Wolf's work. It could very well be that tighter attention to IR, even at low ma, will have a longer-life affect. I'm just sharing what I've done - mostly out of ignorance :)

I did reject a batch of Green Sony G5/G7(s) that were showing 200-280mOhm on my OPUSs.. as this is too far out from my 50-120 base.
 
OffGridInTheCity said:
Its not wrong to mix 50/50. My 3rd battery is made of 14 packs where50% /130ah are NCR18650A (3000mah) and 50% / 130ah areLGABB41865 (2600mah) for 260ah/pack. It's running perfectly.

However... since all the IR discussions and some bad experience with mixing Sony G5/G7 in early days...I've shifted my 'best goal' to100% same type cell per battery.e.g. per 14s88-120p (260ahper pack) in my case. Its more about 'extra small step' for longer life/less-trouble? than a hard issue...

Having said this - I don't bo-hoo @Wolf's work. It could very well be that tighter attention to IR, even at low ma, will have a longer-life affect. I'm just sharing what I've done - mostly out of ignorance :)
Click to expand...

OffGrid,

Quick question. Your 3rd battery is 50/50 NCR18650A and LGABB41865.
Are the 2 types of cells intermingled in each pack or are the packs soley either NCR18650A or LGABB41865?

Yes the IR discussions...... the testing......... the discussions........
I remember your/my NCR18650A and Moli experimenthttps://secondlifestorage.com/showthread.php?tid=7873&pid=54447#pid54447

Bo-hoo or no bo-hoo in the final analysis we all have learned so much of how IR is a factor to consider in the successful building of a power wall.
OffGrid you have kinda vindicated my research along with many others. At least we are looking at IR whether it is with an OPUS that gives a result that may be wrong but it is a result that does change with the actual IR of the cell.We no longer have an excuse as to why our packs are not balancing properly.
Obviously same cell packs are going to be very successful if you are able to amass that many same brand and model cells.
The Medical Packs and Ring batteries are prime examples (if you can afford it) of how to build a powerwall with equal cells.
I personally am building my second pack with exclusively LGGBM261865/LGEBM261865 cells. Not like my first pack which wasthe Heinz 57 variety pack. :)

So believe me I am very happy that some have at least taken the research to heart and at least given IR a second look. I guarantee you will not be disappointedwith the outcome.

Wolf
 
Wolf said:
Quick question. Your 3rd battery is 50/50 NCR18650A and LGABB41865.
Are the 2 types of cells intermingled in each pack or are the packs soley either NCR18650A or LGABB41865?
Click to expand...
They are separate 'base' packs - joined as one, 260ah pack w/1 longmon. Each base pack is 1 type of cell = 130ah.Here's a pic to illustrate what I mean by 2 base packsjoinedby a copper bus bar.

image_efeywx.jpg


Wolf said:
Yes the IR discussions...... the testing......... the discussions........
I remember your/my NCR18650A and Moli experimenthttps://secondlifestorage.com/showthread.php?tid=7873&pid=54447#pid54447
Click to expand...
Yes - in fact I set the Moli's to the side because of your workas the discharge curves were quite different and it was only a few (150 out of 1500) cells... so no need to risk it. Thank you for that test.

Wolf said:
Bo-hoo or no bo-hoo in the final analysiswe allhave learned so much of how IR is a factor to consider in the successful building of a power wall.
OffGrid you have kinda vindicated my research along with many others. At least we are looking at IR whether it is with an OPUS that gives a result that may be wrong but it is a result that does change with the actual IR of the cell.
We no longer have an excuse as to why our packs are not balancing properly.
Click to expand...
Yes - exactly. My OPUSs tend to report 80mOhm (when its probably 40mOhm) and I've found success with 80mOhm +/- 30mOhm'ish. I think one lucky break for me is thatI've used the same OPUSs the entire time - so things are consistent. And, they helped me find/discard200-250mOhm Sony G5/G7(s)... which were a disaster.

Wolf said:
Obviously same cell packs are going to be very successful if you are able to amass that many same brand and model cells.
The Medical Packs and Ring batteries are prime examples (if you can afford it) of how to build a powerwall with equal cells.
I personally am building my second pack with exclusively LGGBM261865/LGEBM261865 cells. Not like my first pack which wasthe Heinz 57 variety pack.:)
Click to expand...
I actually have 2 x 14s100p batteries (out of 8) with mixed cells. In addition to the 3rd battery mentioned above,my very 1st one was 60% ICR18650 MF1 (Alarmhookup ebike 36v cells) and 40% ICR18650-22P (ebay ebike 36v cells). This one was 1-8s MF1s and 9s-14s 22Ps... and did have a couple of 22P packs that I had to 'add cells to boost' them to keep up. I think I just got lucky because both were new cells (low IR) and similar manufacture / 10a discharge profile - so maybe similar curves.


Now days - as I said - I plan to make them all the same cell or at least 1/2 and 1/2 per pack with compatible charge/discharge curves and IR that conforms to the overall battery standards.

@WolfThis conversation has help me get things a little clearer...-Fantastic work you have done!
 
@Wolf - Yea, thank you for all your IR work. I want to build the battery pack once, not over and over.

I think I got some good batteries to make a good powerwall. I have enough batteries to make a 300s14p. I will build them in 100s14p packs and hook them together. I think that would be best for troubleshooting issues, not to mention weight.

Thanks all for willing to help a noob out.

Zerb
 
zerberfert said:
@Wolf - Yea, thank you for all your IR work. I want to build the battery pack once, not over and over.

I think I got some good batteries to make a good powerwall. I have enough batteries to make a 300s14p. I will build them in 100s14p packs and hook them together. I think that would be best for troubleshooting issues, not to mention weight.

Thanks all for willing to help a noob out.

Zerb
Click to expand...
 
zerberfert said:
@Wolf - Yea, thank you for all your IR work. I want to build the battery pack once, not over and over.

I think I got some good batteries to make a good powerwall. I have enough batteries to make a 300s14p. I will build them in 100s14p packs and hook them together. I think that would be best for troubleshooting issues, not to mention weight.

Thanks all for willing to help a noob out.

Zerb
Click to expand...
Typo?

14s300p which is 14 in series and 300 parallel per series for a good sized powerwall.
 
OffGridInTheCity said:
[...] My OPUSs tend to report 80mOhm (when its probably 40mOhm) and I've found success with 80mOhm +/- 30mOhm'ish. I think one lucky break for me is that I've used the same OPUSs the entire time - so things are consistent. And, they helped me find/discard 200-250mOhm Sony G5/G7(s)... which were a disaster [...]
Click to expand...

Out of curiosity, what is theIR ofeach 3.7V mP parallelpieceof your nSmPpack? You can measure it on your Opus by wiring it to the Opus terminals, then subtracting out the the resistance ofthe wires, as computed ona known cell(i.e. subtract the IR of the cell itself from the IR of the cell with the wires). Choose a cell and slot that yield stable readings inasmuch as possible, and don't disturb the wiring to the Opus terminals between the measurement of the cell vs. mP pack(to keep constant their contact resistance).

Has anyone else posted such pack IR numbers for their packs with large numbers of paralleled cells?
 
I believe you can use the 1/((1/r1)+(1/r2)+...) parallel formula to calc what your resistance would be.

eg. 2 cells of equal resistance of 50m? would result in a resistance of 25m?

Typically if your using the correct gauge of connecting strips or wire, the resistance should be negotiable still at m? level.
 
gauss163 said:
Has anyone else posted such pack IR numbers for their packs with large numbers of paralleled cells?
Click to expand...

gauss163,
Funny you should ask as I have posted it before just not in this context.

image_xjzkni.jpg


You can also view the whole repacker sheet here.https://drive.google.com/file/d/1cWV59_ICnBIOe69mZhCduVmETRC1NgJT/view?usp=sharing

Wolf
 
Bubba said:
I believe you can use the 1/((1/r1)+(1/r2)+...) parallel formula to calc what your resistance would be.

eg. 2 cells of equal resistance of 50m? would result in a resistance of 25m?

Typically if your using the correct gauge of connecting strips or wire, the resistance should be negotiable still at m? level.
Click to expand...

That's true for the purely ohmic part of the IR - such as reported by an AC 1kHz impedance test (and wolf's measurements support this:all his80s pack IR areabout 1/80'th of the average cell AC IR). @wolf Those are indeed AC IR values, correct?

But iirc theOpus is doing alonger time DC IR test (vs. 1ms AC). So it is also measuring somenon-ohmic parts of the IR, i.e. additional components of the cell'sIR that don't behave linearly as in Ohm's Law and take time longer than 1mstoramp up to steady-state values(e.g. charge transfer and diffusion processes). This is why at the end of (dis)charge wesee both an instantaneous voltage change (from the ohmic part of the IR- whichbehaves like a resistor), followed bya much slower exponentially decaying voltage changethat asymptotically approaches the steady-state resting voltage (from the non-ohmic IR, which takes a long time (hours) to ramp down as various elecrochemical processes converge to equilibrium).

In many cases it is the non-ohmic part of the IR (vs. capacity degradation)that ends uplimiting the lifetime of the cell because it can degrade at 10 times the rate of the ohmic part, and this greatly drags down the voltage under load (esp. for high-current loads). Whether or nor this is a limiting factordepends on what type of loads you puton the battery. If your device only usesshort pulses (e.g. a jump starter or vape) then the non-ohmic IRplays little role since the discharges aren't long enough for it to kick in.OTOH if you are doing longer time discharges without big spikes then the non-ohmic IR plays a big role. Some loads are a mixture of both and require more complex analysis (e.g. to see if a constant load plus occasional spikedrags the voltage low enough for long enough time to trigger undervoltage protection).
 
You must log in or register to reply here.
Back
Top