New alleged Panasonic battery failed to deliver in road test
- Thread starter OzTrekker
- Start date
e-beach
10 MW
The 58.9 on your charger is good. One problem with accurate readings on voltage meters is that most meters are not fully accurate. They may be close, or even very close, but the most accurate meters are expensive.
So you rode you bike and got 555.592 wh......Your pack was 59.9v.......555.592 / 59.9 = 9.275Ah.......
Something isn't adding up properly......at least from the numbers posted on this thread so far.
How many kilometers did you go on 555.592 wh?
What was your riding style?
Did weather impact this ride more then your usual ride?
With all things equal to your rides with the same AH lipo........you may need to open the pack and look at what you got.
What does the manufacture say about refund or replacement?
So you rode you bike and got 555.592 wh......Your pack was 59.9v.......555.592 / 59.9 = 9.275Ah.......
Something isn't adding up properly......at least from the numbers posted on this thread so far.
How many kilometers did you go on 555.592 wh?
What was your riding style?
Did weather impact this ride more then your usual ride?
With all things equal to your rides with the same AH lipo........you may need to open the pack and look at what you got.
What does the manufacture say about refund or replacement?
Just an update got the replacement battery and got shown a photograph. Appears to be red colored cells in the case.
Met the man with the distribution. Very charismatic gentlemen and i do empathise with his positive growth and goals for his business.
Its nice to see an individual with a true passion, the spark, for ebikes and is selling the product.
If the test goes to plan then i will be buying a number of engines from him.
Met the man with the distribution. Very charismatic gentlemen and i do empathise with his positive growth and goals for his business.
Its nice to see an individual with a true passion, the spark, for ebikes and is selling the product.
If the test goes to plan then i will be buying a number of engines from him.
e-beach
10 MW
OzTrekker said:
Sounds like Sanyo cells. Of course, Panasonic owns Sanyo now.
Apex
10 W
Google image says Panasonic G-A cells are red with a bright blue (not light blue) separator ring.
It's my understanding he drove over an hour each way to fix this problem.
eMax
100 W
OzTrekker said:
There are a number of issues with this type of pack which are seperate to your described issues. As a reseller of a similar battery I don't want to say any more than that publically. PM me if you would like to discuss further.
Yes he did spinning magnets,
I really respect the gentleman for doing this and genuinely would like to see him become a great success in the ebike industry.
Some people are in it for the money, this gentleman's involved in it because he is a true ebike enthusiast such as myself.
We had a great conversation about ebikes, then after he left i remembered a time this year when i was bilbao spain.
I met two ebike craftsmen near the Guggenheim in bilbao spain, they got the ebike shop - on the doorstep of one of the best cycle ways I have ridden on. Its more than a business to these builders - those basque ebike builders are good at what they do because they truely love what they do. Sometimes these small ebike businesses are inspiring for owner and the customer.
We need people like this gentlemen that can facilitate ebike craftsmen and women- otherwise we could end up with allot of mass produced cheap junk, which has engineered obsolesence factored into the design brief.
Its a good business deal when everyone walks away happy.
Ebikers are making the environment cities more liveable for everybody - and i believe it increases an individuals happiness index - its a win if we can build an ebike craft industry.
I really respect the gentleman for doing this and genuinely would like to see him become a great success in the ebike industry.
Some people are in it for the money, this gentleman's involved in it because he is a true ebike enthusiast such as myself.
We had a great conversation about ebikes, then after he left i remembered a time this year when i was bilbao spain.
I met two ebike craftsmen near the Guggenheim in bilbao spain, they got the ebike shop - on the doorstep of one of the best cycle ways I have ridden on. Its more than a business to these builders - those basque ebike builders are good at what they do because they truely love what they do. Sometimes these small ebike businesses are inspiring for owner and the customer.
We need people like this gentlemen that can facilitate ebike craftsmen and women- otherwise we could end up with allot of mass produced cheap junk, which has engineered obsolesence factored into the design brief.
Its a good business deal when everyone walks away happy.
Ebikers are making the environment cities more liveable for everybody - and i believe it increases an individuals happiness index - its a win if we can build an ebike craft industry.
Ebikes4Real
10 mW
- Joined
- Jun 26, 2016
- Messages
- 25
To the OP. What is the max current of the kit you are running with this battery?
Again, to the OP, I suggest you get an RC wattmeter (or better still a Cycle Analyst as this does a lot more and keeps the data when powered off), that provides both Ah and Whrs. Relying on just Whrs, is not enough, to get a clear picture of what is going on, you need more data.
There are some things that are not being considered here. Look at the graph you posted:
1. A typical BMS for this battery type will normally have an LVC of 2.75V/cell. In a perfectly balanced battery, that means the BMS will trip when it hits 38.5V, but in reality, it will normally trip at a higher voltage, due to any small imbalances, so 39-40V is what you might expect a 14S pack to trip at (if the pack is pretty well balanced). So, this means that the BMS will not allow the cells to be fully discharged to the 2.5V LVC, in order to deliver their rated capacity (~3.4Ah per cell in this case).
2. When a cell is discharged at higher current, it's nominal (average) voltage will be reduced (look at the voltage at a point on the curve where they each cross the 1700mAh, ~50% point, this is a close approximation to the nominal voltage for this cell). If the nominal voltage is reduced, the Whrs is reduced by the same proportion (Whrs = V(nom)*ah). If a cell is discharge at anywhere near it's limits, that nominal voltage will be reduced very significantly. Look at the graphs, it is all explained in there. At 2A/cell (8A for the 4P pack), the nominal voltage is ~3.6V (50.4V at 8A dicharge), at 4A/cell (16A discharge for the pack), the nominal voltage is ~3.5V/cell (49Vnom @ 16A discharge). At 6A/cell (24A for pack), the nominal voltage is slightly under 3.4V/cell (<47.6Vnom @ 24A discharge). At 8A/cell, the nominal is ~3.3V/cell (46.2Vnom @32A). At 10A/cell (40A for pack), nominal is ~3.2V/cell (44.8Vnom @40A). These are all best case scenario, new cells, no losses in terminations, cabling or voltage drop in the BMS.
3. When a cell is discharged at high current, it will still deliver close to the rated capacity (Ah figure, and that is important), but only if it is discharged to the lowest LVC (2.5V in the case of this cell). However, if you run the cell at close to it's rating and have an LVC higher than 2.5V (as previously mentioned, most BMS have an LVC of 2.75V) and it is typical to have a controller LVC equivalent to maybe 3v/cell (41-43V LVC might be suggested on a 14S pack). Then what happens is that the LVC kicks in before the pack is fully discharged. Again, look at the graph. Even with a low discharge rate and 2.5V LVC, expect ~3.4Ah, or a little less. Cut the discharge at 2.75V on that graph, and expect maybe 3.1-3.2Ah at even moderate discharge levels. At 3V LVC, expect 2.8-3.1Ah per cell (actually 2.6Ah at 10A, 3V LVC, and on a new cell).
So what does all this mean?
Well it means this (for the GA cell). At 6A/cell (24A for a 4P pack), expect a nominal voltage of ~3.4V/cell (47.6V) and a capacity of 2.9Ah/cell with 42V LVC (3V LVC, so 11.6Ah for 4P pack), or 3.15Ah with 2.75V/cell LVC (actual BMS LVC, can't do better than this, and 12.6Ah for 4P pack). 47.6V and 11.6Ah is 552Whrs (42V LVC, or 3V/cell LVC), 47.6V and 12.6Ah is 600Whrs (2.75V LVC, as per the pack BMS). At higher current levels, the situation will only get worse, with a lower nominal voltage and less capacity (Ah) delivered before the LVC, which will both work together to doubly reduce the Whrs available from the pack.
All these figures above are assuming pretty much best case scenarios. Perfectly balanced pack, no voltage losses in the cabling or BMS (there is some voltage drop on both, moreso the BMS and these will all reduce the nominal voltage). I have not even touched on, how the capacity will tend to decline much faster when a pack is discharged at high discharge rates. The above figures are all on a new, pack, again the graphs reveal how the capacity tends to decline when used at 6A (24A on a 4P pack).
Frankly, I do not think you have a bad battery, or fake cells, or anything of the sort. I also do not think the replacement will fair any better. What you are seeing is what you can expect to see, when a battery is discharged at the upper end of it's rating. If you want to use this cell type, for your application, you need a bigger battery with more parallel cells (personally, I'd recommend 6P for a safe/reasonable 30A max discharge rate, using these or similar type cells, more P if you need higher current), or if you want a small, but powerful battery, you need to use high power cells and sacrifice some capacity/energy density. The difference when you use those higher power cells, is that they will deliver their rating at a moderate discharge rate (maybe half their max rating), they will not tend to trip as early at 2.75/3.0V LVC, and not sag too much either (which makes it feel weak and reduces the Whrs delivered).
Unfortunately bigger/larger/higher is not always better/best
A big capacity, high voltage battery, in a small little case may look great on paper, tick all the boxes to the uninformed masses, and when it's being talked up, but it doesn't count for much, when it's probably good for a 500W kit, but being sold as the perfect battery for a 1000W (or even more powerful) kit. Enthusiasm and BS don't count for Jack when someone actually wants to use that battery at the power levels it is supposedly good for and they find it lacking...
Again, to the OP, I suggest you get an RC wattmeter (or better still a Cycle Analyst as this does a lot more and keeps the data when powered off), that provides both Ah and Whrs. Relying on just Whrs, is not enough, to get a clear picture of what is going on, you need more data.
There are some things that are not being considered here. Look at the graph you posted:
1. A typical BMS for this battery type will normally have an LVC of 2.75V/cell. In a perfectly balanced battery, that means the BMS will trip when it hits 38.5V, but in reality, it will normally trip at a higher voltage, due to any small imbalances, so 39-40V is what you might expect a 14S pack to trip at (if the pack is pretty well balanced). So, this means that the BMS will not allow the cells to be fully discharged to the 2.5V LVC, in order to deliver their rated capacity (~3.4Ah per cell in this case).
2. When a cell is discharged at higher current, it's nominal (average) voltage will be reduced (look at the voltage at a point on the curve where they each cross the 1700mAh, ~50% point, this is a close approximation to the nominal voltage for this cell). If the nominal voltage is reduced, the Whrs is reduced by the same proportion (Whrs = V(nom)*ah). If a cell is discharge at anywhere near it's limits, that nominal voltage will be reduced very significantly. Look at the graphs, it is all explained in there. At 2A/cell (8A for the 4P pack), the nominal voltage is ~3.6V (50.4V at 8A dicharge), at 4A/cell (16A discharge for the pack), the nominal voltage is ~3.5V/cell (49Vnom @ 16A discharge). At 6A/cell (24A for pack), the nominal voltage is slightly under 3.4V/cell (<47.6Vnom @ 24A discharge). At 8A/cell, the nominal is ~3.3V/cell (46.2Vnom @32A). At 10A/cell (40A for pack), nominal is ~3.2V/cell (44.8Vnom @40A). These are all best case scenario, new cells, no losses in terminations, cabling or voltage drop in the BMS.
3. When a cell is discharged at high current, it will still deliver close to the rated capacity (Ah figure, and that is important), but only if it is discharged to the lowest LVC (2.5V in the case of this cell). However, if you run the cell at close to it's rating and have an LVC higher than 2.5V (as previously mentioned, most BMS have an LVC of 2.75V) and it is typical to have a controller LVC equivalent to maybe 3v/cell (41-43V LVC might be suggested on a 14S pack). Then what happens is that the LVC kicks in before the pack is fully discharged. Again, look at the graph. Even with a low discharge rate and 2.5V LVC, expect ~3.4Ah, or a little less. Cut the discharge at 2.75V on that graph, and expect maybe 3.1-3.2Ah at even moderate discharge levels. At 3V LVC, expect 2.8-3.1Ah per cell (actually 2.6Ah at 10A, 3V LVC, and on a new cell).
So what does all this mean?
Well it means this (for the GA cell). At 6A/cell (24A for a 4P pack), expect a nominal voltage of ~3.4V/cell (47.6V) and a capacity of 2.9Ah/cell with 42V LVC (3V LVC, so 11.6Ah for 4P pack), or 3.15Ah with 2.75V/cell LVC (actual BMS LVC, can't do better than this, and 12.6Ah for 4P pack). 47.6V and 11.6Ah is 552Whrs (42V LVC, or 3V/cell LVC), 47.6V and 12.6Ah is 600Whrs (2.75V LVC, as per the pack BMS). At higher current levels, the situation will only get worse, with a lower nominal voltage and less capacity (Ah) delivered before the LVC, which will both work together to doubly reduce the Whrs available from the pack.
All these figures above are assuming pretty much best case scenarios. Perfectly balanced pack, no voltage losses in the cabling or BMS (there is some voltage drop on both, moreso the BMS and these will all reduce the nominal voltage). I have not even touched on, how the capacity will tend to decline much faster when a pack is discharged at high discharge rates. The above figures are all on a new, pack, again the graphs reveal how the capacity tends to decline when used at 6A (24A on a 4P pack).
Frankly, I do not think you have a bad battery, or fake cells, or anything of the sort. I also do not think the replacement will fair any better. What you are seeing is what you can expect to see, when a battery is discharged at the upper end of it's rating. If you want to use this cell type, for your application, you need a bigger battery with more parallel cells (personally, I'd recommend 6P for a safe/reasonable 30A max discharge rate, using these or similar type cells, more P if you need higher current), or if you want a small, but powerful battery, you need to use high power cells and sacrifice some capacity/energy density. The difference when you use those higher power cells, is that they will deliver their rating at a moderate discharge rate (maybe half their max rating), they will not tend to trip as early at 2.75/3.0V LVC, and not sag too much either (which makes it feel weak and reduces the Whrs delivered).
Unfortunately bigger/larger/higher is not always better/best
A big capacity, high voltage battery, in a small little case may look great on paper, tick all the boxes to the uninformed masses, and when it's being talked up, but it doesn't count for much, when it's probably good for a 500W kit, but being sold as the perfect battery for a 1000W (or even more powerful) kit. Enthusiasm and BS don't count for Jack when someone actually wants to use that battery at the power levels it is supposedly good for and they find it lacking...
Hillhater
100 TW
Good comment E4Real
Many folk ignor the detail of 18650 cell specs and simply compare capacity Ahr, and C rate.
But the voltage discharge profile is so different to RC pouch lipo, and when you take into account the sag of a 3C 18650, compared to a 20C RC pouch at any given load, the resulting performance difference is significant in many ways, particularly towards the last 30% of the pack capacity.
Many folk ignor the detail of 18650 cell specs and simply compare capacity Ahr, and C rate.
But the voltage discharge profile is so different to RC pouch lipo, and when you take into account the sag of a 3C 18650, compared to a 20C RC pouch at any given load, the resulting performance difference is significant in many ways, particularly towards the last 30% of the pack capacity.
eMax
100 W
I second all of the above ^^^^^^^ from Ebikes4Real
Regardless of how good a bloke the guy is and how into ebikes he is (good to hear btw) perhaps dropping the power of your controller would be the best bet. I have seen both the GA and LG MJ1 heat up quite a bit at 5a or above per cell so there is some concern especially for those cells in the middle of the pack.
Regardless of how good a bloke the guy is and how into ebikes he is (good to hear btw) perhaps dropping the power of your controller would be the best bet. I have seen both the GA and LG MJ1 heat up quite a bit at 5a or above per cell so there is some concern especially for those cells in the middle of the pack.
TheBeastie
1 MW
Good summary and good posts from everyone.. I think its good to have a short easily absorbable assessment of it...Ebikes4Real said:
1) there is no way the OP is going to be able to test the battery pack to its full potential with the BMS attached which is a short version of what a lot of people have been saying on this thread now. Only takes one cell to kick in LVC and ruin the test. We just can't stress this enough.
2) At least in my opinion 4P 18650 packs are baloney for high watt kits, having so much current go through 4 cells is really just a design that looks nice to sell.
3) At least for me I have had power meters on my ebikes that have always shown complete baloney min and max data because they record it when you first plug them in and you can't do anything about it, their just dodgy.
4)The OP posted the link that showed his cell being discharged to 2.5v but also charged at around 1amp listed as "0.99a" and just "0.1a" at cut off. Did your charger take 24 hours to charge your pack? Well according to other charts on this forum you can knock off about %10 capacity for merely charging your cells too fast..
https://endless-sphere.com/forums/download/file.php?id=201694&mode=view
Look at this thread here by member electricbike where he charged the 25R at two different charge rates but exact same discharge rate..
1 cell charged at 4.0Amps and the other at just 2.5Amps but the total capacity difference in discharge was close to %10.. for the larger GA cell its going to affect total capacity even more..
https://endless-sphere.com/forums/viewtopic.php?f=14&t=73883
https://endless-sphere.com/forums/download/file.php?id=187888
Frankly, I am sick of folks being overly paranoid about their battery pack. I say we ban this guy and permanently firewall his IP from the server so he can't even merely view it.
JK, hopefully with all the good information shared here maybe will see less of these.
Ebikes4Real
10 mW
- Joined
- Jun 26, 2016
- Messages
- 25
[/quote]TheBeastie said:
If you mean the OP, then I don't think he has really done anything particularly wrong here. The only thing that he has done is trust the information he was provided and assumed that the battery would deliver on it's promises. Details currently listed are:
•14ah massive for this size
• 702-watt hours means incredible range in small package (read article on watt hours)
•14s4p = 56 Genuine name brand grade a Panasonic 18650 cells (see breakdown on 18650 cells)
•30amp continuous BMS 60 amp bursts
It isn't really up to the buyer, to understand the detailed specs of what they buy and the components used to construct it. The buyer expects that the battery can reasonably deliver what was promised (52V, 14Ah and 702Whrs, 30A continuous, though not sure where the 702 comes from, as 52*14 is not 702). Sure, an 18650 cell pack may not stack up that well when compared to a 20/30C Lipo pack, but they aren't that bad when they are used reasonably either. Problems only occur when they used at excessive current levels. If the OP had a pack that was delivering 95%, or even 90% of what he expected (compared to his Lipo Pack), I don't think he would have a major problem, but when he's getting maybe 80% or less of what he was expecting, I think he has a valid reason to be upset and ask some questions.
Yeah, maybe the OP should make some more effort, to understand what he is getting into, BUT, he wouldn't have found himself in this situation, if the battery he bought, was really able to deliver on the promises made (or if more reasonable limits were provided, which is still the same thing). It also seems like he only came on here after direct contact didn't get him the response he was hoping for. It is nice that there has since been effort to appease him, after the OP had come on here and caused a fuss, but this is "Lunas Best selling pack" and nobody took the time (or had the knowledge) to look at their recommendations and provide reasonable data, specs and recommended usage? This is not a bad pack, it is typical of what to expect. I can only think that many of the buyers don't use their high powered kits too hard, or measure the Capacity their packs really deliver.
Let's face it, this is not a bad battery as such, and I don't doubt it is performing as the specs would suggest (for genuine GA cells). It would make a nice battery for a 500W kit, maybe even a little bit more, but it is being sold as both high capacity and high power (good for a 30A kit, at least). Frankly, it is only good for a high power kit, if you use that high power occasionally and for short bursts. If you really expect this battery to deliver 30A or even more, for any great length of time (as the stated specs seem to suggest) and to also provide anywhere near the Ah/Whrs promised, you will be disappointed.
That post by Greenmachine was astonishing, best laugh I've had all week. Many Thanks for enlightening us with the great depths of your battery knowledge :lol:
Apex
10 W
Pretty sure he was joking, thus the term "JK" after his statement.
I think you and most in this thread have conducted themselves in a mature, respectful manner.
Which is refreshing to me. I moderate a couple performance automobile sites, they tend to be populated by thin skinned, easily incited people with something to prove. Basically a toxic stew compared to this site.
I think you and most in this thread have conducted themselves in a mature, respectful manner.
Which is refreshing to me. I moderate a couple performance automobile sites, they tend to be populated by thin skinned, easily incited people with something to prove. Basically a toxic stew compared to this site.
Ebikes4Real
10 mW
- Joined
- Jun 26, 2016
- Messages
- 25
Please be aware, we are all part of a conspiracy against Luna. It must be true, it seems to be saying as much here:
https://electricbike-blog.com/2016/09/22/lunacycle-releases-their-50amp-bbshd-that-ive-been-testing-for-6-months-but-you-gotta-buy-the-whole-bike/comment-page-1/#comment-4466
An unhappy customer, then looking at some graphs, making reasonable observations, pointing out how a battery will perform (based on published data), and making some reasonable suggestions (such as more reasonable usage than is recommended by the supplier). No, this is not reasonable analysis to explain what was recorded by an unhappy customer? No, it's all part of the conspiracy....
A tad biased possibly? A tad paranoid?
Poor Luna, it breaks my heart, I hope it doesn't spoil their trip to Vegas.
Penthouse no less! BALLIN 8)
https://electricbike-blog.com/2016/09/22/lunacycle-releases-their-50amp-bbshd-that-ive-been-testing-for-6-months-but-you-gotta-buy-the-whole-bike/comment-page-1/#comment-4466
An unhappy customer, then looking at some graphs, making reasonable observations, pointing out how a battery will perform (based on published data), and making some reasonable suggestions (such as more reasonable usage than is recommended by the supplier). No, this is not reasonable analysis to explain what was recorded by an unhappy customer? No, it's all part of the conspiracy....
A tad biased possibly? A tad paranoid?
Poor Luna, it breaks my heart, I hope it doesn't spoil their trip to Vegas.
Penthouse no less! BALLIN 8)
Tom Tom
100 W
Ive always assumed watt hour ratings were a best case scenario/max available kind of thing.
Probably better to use a portion of it for longevity sake, and not to push your luck and be stranded.
Probably better to use a portion of it for longevity sake, and not to push your luck and be stranded.
TristanP
1 mW
Although you don't tell where in the Netherlands they told you that, it's nothing but correct and something you might expect over here. Watt-hours are generally considered to be the appropriate unit for measuring energy capacity of a battery. Ampere-hours are not a unit of energy at all.OzTrekker said:
The Dutch wouldn't had solved your initial issue, why you started this thread, though. If you don't take efficiency and the low voltage cut off into account energy (still) will be lost into thin air, leaving you disappointed. Also in the Netherlands, like in the entire EU, users are expected to inform themselves about a product, before closing a deal. Drawing the conclusion that you might expect to be able to use (close to) the entire energy capacity of a pack, with the maximum stated discharge current doesn't account for that. The basic science behind that is also taught to pretty much anyone in the first year of middle school here. Besides that your application falls outside the scope of a typical application for such a battery pack, as anything above 48V or 250W nominal is not road legal here and electric scooters are not really a thing yet.
I really wonder to which extent you may expect a retailer to inform you "better" in regards to specialised products like battery packs. Especially since complete solutions are available for the general public. Personally I would appreciate this situation a bit more and put less blame on the seller.
No, it's a unit of energy equivalent to 1 Watt of power expended over a period of 1 hour. The SI unit is Joule.Tom Tom said:
I am more of a field tester.
I go with what works, i am more function focused.
I did another small test today and I do understand whats going on - also thank-you to those who explained a few things.
However, you can understand why the consumer is paranoid please view attached photos of batteries sold on ebay!
I dont have time to go back and try to deal with the laws of thermodynamics, which snowed me under with confusion when I studied it, so I take a pragmatic approach.
I see great things in this battery, however is it a performance battery, yes and no.
Do I like the battery after this second test - yes
Do i like the costumer service i recieved - Absolutely.
As a consumer i see a different approach to marketing, of potentially a great product, supported by independent pragmatic ethical field testing.
There is a learning transition going from lipo to lion - too? and its a good one.
Positive
Negatives
New idea.
I am not into a he said she said debate, and yes I am well aware how difficult it is to get a 48v battery in holland.
I also realise the police in holland are cool and work in the interests of the community.
The only constant in life is change - i embrace change positively and increase the happiness index, within my idiot brain, Its the way for me.
The photo was too large a file to upload so I will try to work on the IT conversion if i get a low wind cool temperature day then i will hopefully post.
I am seriously looking forward to reporting this next test. I am super excited for it.
I go with what works, i am more function focused.
I did another small test today and I do understand whats going on - also thank-you to those who explained a few things.
However, you can understand why the consumer is paranoid please view attached photos of batteries sold on ebay!
I dont have time to go back and try to deal with the laws of thermodynamics, which snowed me under with confusion when I studied it, so I take a pragmatic approach.
I see great things in this battery, however is it a performance battery, yes and no.
Do I like the battery after this second test - yes
Do i like the costumer service i recieved - Absolutely.
As a consumer i see a different approach to marketing, of potentially a great product, supported by independent pragmatic ethical field testing.
There is a learning transition going from lipo to lion - too? and its a good one.
Positive
Negatives
New idea.
I am not into a he said she said debate, and yes I am well aware how difficult it is to get a 48v battery in holland.
I also realise the police in holland are cool and work in the interests of the community.
The only constant in life is change - i embrace change positively and increase the happiness index, within my idiot brain, Its the way for me.
The photo was too large a file to upload so I will try to work on the IT conversion if i get a low wind cool temperature day then i will hopefully post.
I am seriously looking forward to reporting this next test. I am super excited for it.
johnnyz
1 kW
I made a 24s 8p pack from the Panasonic NCR18650b cells, and I have to say I was suprised at a couple of things;
At first I used the normal 98 % nickle strip (see photos) and welded them all, Everything looked good untill I tested it.
View attachment 1
HUGE sag even at moderate amperage..at full throttle it would only pull 36 amps on a controller designed to pull 60. Voltage went from 96 to 76.
I took the blue shrink wrap off and got into the cells....well...
The attachment points where each parallel group joined the next got so hot that it melted the duck tape and turned color!!..On the cycle analyst, it showed resistance of .519 ohms...I then added extra metal strip to these areas and put it back together...Better...sag is less, now pulled 43 amps on full throttle and resistance was .430 ohms.
Decided to look into the pack again and although I didnt see any signs of the new tabs soldered over the originals getting hot I decided to add one more strip to each of the parallel groups and again an improvement...down to .335 ohms of resistance on the cycle analyst (compared to .198 on my headway cells) and now it will pull 55 amps, but still sags under full load but sagging under partial load like 10 amps is about 5 volts ...
Can anyone who has experience building packs kick in some advice?...maybe I should used the Sony VTC5, but I would have had to add lot more cells...
Also not getting near 23 watt hours out of the pack...more like 17.
Thanks
John
At first I used the normal 98 % nickle strip (see photos) and welded them all, Everything looked good untill I tested it.
View attachment 1
HUGE sag even at moderate amperage..at full throttle it would only pull 36 amps on a controller designed to pull 60. Voltage went from 96 to 76.
I took the blue shrink wrap off and got into the cells....well...
The attachment points where each parallel group joined the next got so hot that it melted the duck tape and turned color!!..On the cycle analyst, it showed resistance of .519 ohms...I then added extra metal strip to these areas and put it back together...Better...sag is less, now pulled 43 amps on full throttle and resistance was .430 ohms.
Decided to look into the pack again and although I didnt see any signs of the new tabs soldered over the originals getting hot I decided to add one more strip to each of the parallel groups and again an improvement...down to .335 ohms of resistance on the cycle analyst (compared to .198 on my headway cells) and now it will pull 55 amps, but still sags under full load but sagging under partial load like 10 amps is about 5 volts ...
Can anyone who has experience building packs kick in some advice?...maybe I should used the Sony VTC5, but I would have had to add lot more cells...
Also not getting near 23 watt hours out of the pack...more like 17.
Thanks
John
Marin
1 kW
johnnyz said:
only slightly off topic John, but I have a shark pack with the NCRB cells and it sags like mother ( 7 volts on the first hill) with the riding conditions that I have where I live, it seems fine if the riding is totally flat, not a performance cell at all judging by the one I have, pretty disappointing. All my other packs are 25r cells, only way to go for me with the steep and constant hills I deal with.
Stop using the battery pleasejohnnyz said:
Where did you buy the cells?are you 100% sure and test the strips are 99% nickel?The ncr18650b cells are 6A max so 8p pack 48A is the max
you need a 10A/15A cell.The welding on the nickel strips between the positieve terminals is also crazzy!
depends on how meny Ah the compleet battery is and how much Amps the controller takes from the battery.Marin said:
for a 36v e-bike 14A max is use always 10A cells(4p are 5p most of them) cells wil see only 1/2C and last longer...ir 12a stays under 100 Ohms :lol:
Use a magnet and test your "nickel" strip. It's probably just steel, maybe with nickel plating. People get shafted by vendors with that stuff sometimes.johnnyz said:
Where are you reading this value? Are you using the wh/mile? Because lower is better on that one. (and doesnt' have anythign to do with pack capacity)
If you are reading it at the total Wh, when using hte pack from full to empty, then even 23wh would be pretty incredibly crappy, at less than 1/30th of the pack's nomincal capacity (assuming 3.7v/cell average for 88v * 8p = 710wh).
You mgiht also want to check the calibration of the CA's shunt value to be sure it is correctly reporting the currents.
