New alleged Panasonic battery failed to deliver in road test

[Joachim]

you might also want to check this thing doesnt burn in flames :?

 

[johnnyz]

Well...my reading with respect to the wh per kms is as low as 23 wh/k and as high as 33 wh/k. When I get 33 wh/K its because im accelerating fast and going 50-55 kph, and keeping up with traffic..

You have to remember that I have a heavy ebike (Motorino XMR) looks like a real motorcycle. I have my Crystalyte Controller pulling 60 amps (thats what it pulled with my headways and Crystalyte h4080 motor on my trike)

The one pic shows the solder that I did adding the extra nickle strip..couldnt weld it because I wouldnt be able to get to it. The one reader seems to have confirmed my fears as he said he uses the same cell and gets crazy sag as well...

The cells are rated at 2c so i thought 8p would be able to handle 48 amps, but not true...but I guess that added resistance will skew the actual c rating of the cell...the more resistance, the greater the sag and performance.

I tested all the strips and they all stick to a magnet. Wouldnt 98% nickle also stick to a magnet?

Thanks

John

 

[amberwolf]

I tested all the strips and they all stick to a magnet. Wouldnt 98% nickle also stick to a magnet?

You are correct, and I forgot that.

But never fear, this page:
http://www.ebikeschool.com/how-to-differ-between-pure-nickel-strip-battery-tabs-vs-steel-core/
found with a google search for "are nickel strips magnetic?"
has some info on ways to tell the difference.

Method 1

The first option for testing the strips is with a Dremel or other rotary tool and a sanding or grinding attachment. Simply grind or sand at the nickel strip using a high speed setting. If you see sparks after a second or so, you know you’ve got a steel strip. Steel will spark when struck at sufficient speed with a sanding or grinding attachment. The wheel quickly goes through the thin nickel coating and reveals the steel below the surface. If you sand or grind away for more than a second or two and still see no sparks, you know you’ve got pure nickel.

Method 2

The next option is better if you don’t have a Dremel or other rotary tool. Simply scuff up the steel strip with sandpaper or any other rough object (a wire brush, a screwdriver, even a house key) and place it in a cup of saltwater. Make sure you’ve scratched up the surface to expose any steel below, if there is any. You’ll know there’s steel present in a day or so if you see rust forming. Steel rusts easily, but nickel is highly corrosion resistant. If there’s no rust after a day or so, you’ve got a pure nickel strip!

I don't know if your strips are the problem...but if your series connections heat up so much that they discolor like that, there is far far too high a resistance there.

In testing it on my 2WD SB Cruiser trike, I pulled currents in the range you're after (50A) from a Luna pack much smaller than yours, and while the cells themselves got pretty hot and voltage dropped becuase the cells couldn't handle it, the interconnects did not show any sign of heat issues (though they probably got warm too).
https://endless-sphere.com/forums/viewtopic.php?f=14&t=81108&hilit=luna#p1194271

 

[johnnyz]

Hi again. The 24S8P NCRB pack that you describe should have near 9 volts sag at 40A. At this rate it would be capable of 3200W average.
Anything extra is connection and wiring sag due to the extra resistance, creating heat. For your series tabs to get so hot as to discolor them they must also be heating up the cells closest to them, which will lead to premature failure. The cross-patterned nickel strips are not ideal and create additional resistance.

However if you simply replace your series tabs with copper wire you will alleviate the bulk of your resistance and sag issues.

At 40 amps it will sag from a fresh 96 volts to 80 volts.

Why would the cross pattern nickel strips cause added resistance?..

So your suggesting replacing the strips with copper wire?...thickness?...I will probably try that ..its alot of work but it's worth a try. At the beginning the resistance according to the cycle analyst was .510 ohms, and ive got it reduced to .333 ohms, but its still too high..

A curious note: when I got these cells, I tested them on my imax charger...charged them up to 4.2 volts and discharged at 1 amp. Got 2950 mah. Charger stopped discharging at 3 volts. Discharged at .6 amp and got 3050 mah. Others apparently have got 3200 mah or higher. I tested 6 different cells all with the same result. Either they need to be discharged to 2.6 volts to get the rated capacity or they are not genuine?...I bought them at NKON.

John

 

[Hillhater]

Those crossed strip connections are a major factor in your high pack resistance.
Notice the heat discoloration where the stripa are welded as they cross ?...
..that is because all the pack current is having to flow through those tack welds as there is no continuous strip to link all the cells to the next module.
You need to at least solder up those cross points ,..or better still rebuild the pack with "buss bar" straight strip links.
..Why did you cross them like that anyway ?

 

[johnnyz]

Wow...I thank everyone who chimed in on my posting...I realize and apologize if perhaps I am a bit off topic here, bt I really appreciate all the help.
I decided on the criss cross pattern after examining a pack made by a "reputable" pack builder whom I shall not name on the internet..after listening to the comments it makes sense that there would be an increase in resistance here...

I am going to be ordering some Sony cells that are rated for 10 amps each, and needless to say I am not going to be welding them up as I did before...It sucks to be the subject of how not to and what not to with regards to building a pack but as long as you dont repeat your mistakes.

So it would appear that nickle strips are insufficent when you want to draw as much current as I do?...or perhaps you can double up on the strips ? otherwise that would mean that you would have solder the copper wire to each of the parallel connections and series connections... not going to look pretty...

John

 

[Joachim]

i wil cal the battery shop local.

 

[Voltron]

I'm no expert... but it seems like you would need less cross connection on the parallel groups, and more connection between the series groups. It looks like the two strips that join the series groups is where the heat is being generated..

 

[nutnspecial]

Yeah me either, but the construction does seem bad.
This is a pic of just 2x 2s 8p of a large pack right? Is just the positive side and subsequent series connection on one 1s of each getting damage out of the whole pack? Those wires are just for balancing? Why the crisscross?

 

[Voltron]

I could see the crisscross adding some rigidity to the p groups... but def looks some more series connection would help.
And yay for insulating gaskets... that could have gotten ugly without them.

 

[johnnyz]

Yeah me either, but the construction does seem bad.
This is a pic of just 2x 2s 8p of a large pack right? Is just the positive side and subsequent series connection on one 1s of each getting damage out of the whole pack? Those wires are just for balancing? Why the crisscross?

Seems bad or improperly conceived? I dont think my construction is bad per say...Yes The one pic is one of the 8p groups before I connected them to the next p group..No almost all of the connections joining each parallel group got hot..

The wires are for balancing and charging ( I use battery medics instead of a bms and every once and awhile I need to bring a cell or 2 up thats why I use a thicker balance wire.

john

 

[johnnyz]

I could see the crisscross adding some rigidity to the p groups... but def looks some more series connection would help.
And yay for insulating gaskets... that could have gotten ugly without them.

I think your right...it's where the series connections occured that I soldered extra pieces in and then the resistance went down...





You can in the picture that this series connection didnt appear to get hot as there was 4 connections instead of 2...


If there were no insulating gaskets...well...It may have set off a series of unfortunate events..lol

John

 

[Hillhater]

No !
I will say this again..
In addition to the obvious weakness of the group links already identified,....If you follow the main current path on the +ve cell ends of the groups, you will see there is no direct "buss bar" type continuous connection strip to the next group
All the series pack current has to pass theough several spot welds. = big resistance issue !
That XX strip pattern has to go .
Please let us know where the original XX idea came from so we can avoid it .

 

[johnnyz]

No !
I will say this again..
In addition to the obvious weakness of the group links already identified,....If you follow the main current path on the +ve cell ends of the groups, you will see there is no direct "buss bar" type continuous connection strip to the next group
All the series pack current has to pass theough several spot welds. = big resistance issue !
That XX strip pattern has to go .
Please let us know where the original XX idea came from so we can avoid it .

If you must know...follow the picture....

Apparently this guy builds lots of these ....I read up on him and it all appeared good...

John

 

[Hillhater]

If you had followed his configuration more closely, you would see how he has avoided the problems you are seeing .!
It is very different in terms of current management to your pack.

 

[Hillhater]

discoloration indicates extreme overheating and very high resistance points with high current flowing.
But there can be many high resistance points carrying less current that wont show up as discolored.
... also, i hope this image is deceptive but,..
.. it does appear that there are some welds missing on the strip from the cell at the extreme lower RH bottom and its linked cell ( 2nd row from the left and 3rd cell up)...that strip doesnt appear to be welded to any of the other strips. ?

 

[johnnyz]

The strips were all welded. What is decieving in the picture is the fact that I used 2 different nickle strips as I ran out of the dull nickle strips and didnt want to wait another 3 weeks to get them. One was a flat colored and the other shiny...I noticed that when I welded the normal nickle strips the weld is very small and sometimes hard to see ..while the other strips the weld has seemingly better penetration.and appears bigger.and shows up quite well...

John

 

[johnnyz]

The pattern in that picture is not optimal for paralleling but is suitable for his arrangement as the XX is used to connect cells in series, so he has ~13x nickel strips for his series connections.

Hillhater previously pointed out the discoloring on some welds (this can happen during welding) but as he points out the current through those areas could be improved.

In your case the series are a problem and while it would benefit your pack to add more strips to help the outer 4 cells (certainly worth improving) if you connect copper in series to the middle cells of each group you'll be fine.

As I showed in the last picture I added extra nickle strip to each of the series groups and this improved the resistance from 500+ ohms to about 340 ohms. I will get into the pack sometime in the next couple of days and add some copper to the parallel groups and then retest on the bike...

Will post back when I do with results..this is my first attempt at building / welding a pack so for me its ok if I screwed up to get it right the next time.. :wink:

John

 

[neptronix]

none of the problems here are related to nickel strips.. an easy look at the discharge graphs from panasonic/samsung/lg for cells like these tells you what performance would be like over 1C.. and it's horrendous for pretty much every high density 18650.

I have 2 of those panasonic cells in a big vape.. i hit LVC of the vape early with 15% battery left.. so saggy :lol:

 

[johnnyz]

none of the problems here are related to nickel strips.. an easy look at the discharge graphs from panasonic/samsung/lg for cells like these tells you what performance would be like over 1C.. and it's horrendous for pretty much every high density 18650.

I have 2 of those panasonic cells in a big vape.. i hit LVC of the vape early with 15% battery left.. so saggy :lol:

Might be for these cells but I can assure you that cells like the Sony vtc5 can deliver...A friend of mine in Montreal has an ebike that will out accelerate a car and he pulls 100+ amps using these cells...I should have conferred with him before doing this but hey...im stubborn I guess...

John

 

[Hillhater]

If designed correctly, the parallel connections could be very small and act a cell fuses (as Tesla do)
BUT every good power circuit design should have the minimum amount of connections and wherever possible a continuous "buss bar" (strip) to carry the main current with the individual cells feeding onto that buss bar
This design doesnt have that, it has multiple short strips welded together. The overall resistance of that arrangement will be the sum of the resistances of each of those ( how many?) welds in addition to the resistance of the strip.
One or two poor/weak welds, and pack performance is reduced if not distroyed.

 

[neptronix]

Might be for these cells but I can assure you that cells like the Sony vtc5 can deliver...A friend of mine in Montreal has an ebike that will out accelerate a car and he pulls 100+ amps using these cells...I should have conferred with him before doing this but hey...im stubborn I guess...

John

No doubt, some 18650s can deliver the current.. but they're never high density cells.

 

[johnnyz]

Well....finally completed the battery..

Took off all of the welded tabs and replaced with 12 gauge solid copper wire...

But first a chronology of what I did...

First made battery as per previous photo's with welded nickle tabs.

Resistance according to CA was .530 ohms...As soon as I seen this figure and sag at only 10 amps dropping 6 volts and under full load going from 96 to 76..also, the maximum it could pull was 36 amps (Controller programmed for 65 amps).I knew I had a problem...

Took battery apart to find some of the tabs discolored due to extreme heat...I then soldered extra nickle tabs on all the series connections then put back into bike and re-test...

This time resistance went down to .400 ohms and sag was not as extreme and this time pulled 42 amps..


Took battery out and soldered extra strip of nickle onto all of the parallel connections ...put battery back and retest...

Resistance was better at .330 ohms and sag was not as pronounced and pulled 49 amps.

After peeling off all the tabs and debriding the tops of the cells, noticed that some of the paper that separates the + part of the cell from the negative was either burned or burned off!! creating a dangerous situation indeed...I filled these gaps with a resin before soldering up the copper..

Although it was ugly...It was so ugly I forgot to take a picture of it, never the less, back into service it went...

Well!!...as you can see, the resistance was down to .176 ohms according to the CA..and that is better than my headway cells...thats a HUGE improvement...sag at 10 amps is only 2 volts and full throttle sag goes from 96 volts to 86 and now it will pull 56 amps.

This tells me a couple of things...

The resistance now is probably mostly the result of the cells themselves and not any connections
Clearly there was huge losses in either the nickle strip itself or the methodology in designing the way the attachments went.

I have another 72 volt pack I made using the same techniques and this went into an ebike similar to mine that only drew a max of 25 amps...I am going to take it apart and see if there are any signs of overheating...I will either update this post or start a new post as I think this is significant.

John

 

[PH1]

Sadly scumbuckets le fastech sell counterfeit shrink wrap for 18650. They made them harder to find but they are still available.

Does FastTech sell counterfeit battery cells too, or is it only the battery shrink sleeve they sell which is counterfeit?
Does the battery shrink sleeve come with battery brand and model names on it?

 

[tomjasz]

Sadly scumbuckets le fastech sell counterfeit shrink wrap for 18650. They made them harder to find but they are still available.

Does FastTech sell counterfeit battery cells too, or is it only the battery shrink sleeve they sell which is counterfeit?
Does the battery shrink sleeve come with battery brand and model names on it?

I haven't purchased their batteries, but have been ripped off buying parts and the sleeves are available to counterfeit. I don't trust them. But can't confirm whether the batteries are good or not.