Search found 885 matches

by Matador
May 22 2019 11:35pm
Forum: Battery Technology
Topic: end cells always fail first, why?
Replies: 15
Views: 877

Re: end cells always fail first, why?

I'd say all of the above I think play a roll. Unequal current sharing if using too resistive conductors. Heat more promient at the deep core of battery (can't dissipate as easily), kind of depends on battery geometry too. Cheap BMS with unequal parasitic quiescent current drain Use of unmatched cell...
by Matador
May 22 2019 11:29pm
Forum: Battery Technology
Topic: 14s2p Minicube w/ 21700 batteries
Replies: 5
Views: 369

Re: 14s2p Minicube w/ 21700 batteries

Thanks - that was what I was thinking. Hopefully there will be a high discharge 21700 cell in the future, I love the small size of the minicube but would also like a little more capacity. This battery is close, but not suitable for a hill climber. Check out the Samsung 40T 21700 cells. Seems promiz...
by Matador
May 22 2019 11:23pm
Forum: Battery Technology
Topic: Actual Test of Pure Nickel Heat?
Replies: 24
Views: 829

Re: Actual Test of Pure Nickel Heat?

voltage drop is not the metric one should focus on, temperature is key. as long as the strip remains below 60ish degrees the standard aliexpress ABS cell holders and cell wrap wont lose strength or warp. you can bump this a bit if you use that green paper rings as extra insulation. personally i wou...
by Matador
May 22 2019 11:15pm
Forum: Battery Technology
Topic: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E
Replies: 65
Views: 2533

Re: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E

I agree with you as well Matador! :wink: The reason, why I bought a frog battery, based on the 21700 M50 from LG Chem, is because I use at 48V a motor (Tongsheng TSDZ2) with 250W. On 13S3P I have around 1,80A - 2,20A CDR on every cell...and I ride my bike in the city...and it is really flat (Hannov...
by Matador
May 22 2019 11:05pm
Forum: Battery Technology
Topic: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E
Replies: 65
Views: 2533

Re: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E

Just few remarks : 1) Zeroair finished measurement at 2,8 V. Discharging down to 2,5 V according specification is giving capacity nearly 5 000 mAh in the range 1 – 5 A. ( equipment : calibrated ZKETECH EBC A-10H, BF-2A fixture, 25 ±1 °C) Samsung 21700 - 50E f.jpg 2) Frankly, Zeroair measurement see...
by Matador
May 22 2019 11:43am
Forum: Battery Technology
Topic: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E
Replies: 65
Views: 2533

Re: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E

I think the INR21700-40T is very interesting in small dimensions of batteries like 10S2P, or 10S3P. I daubt it, if the 50E, or M50 will have more Wh at this configuration on 250W-350W motors?! I agree... Even if the 50E is supposed to be a 5000 mAh 21700 cell, that's probably only true at very low ...
by Matador
May 22 2019 12:39am
Forum: Battery Technology
Topic: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E
Replies: 65
Views: 2533

Re: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E

Still, the samsung 40T kicks ass. 60% residual capacity after 250 cycle when discharging it at 35A!!, without temperature cutoff.... Capture.JPG I mean, they sure as hell last reall long if you only pull 10A/cell on them from time to time... Wheras I really would'nt bet anything on the samsung 50E a...
by Matador
May 22 2019 12:23am
Forum: Battery Technology
Topic: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E
Replies: 65
Views: 2533

Re: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E

Agreed My VTC4 are rated for 30A, but I don't wan't to use them over 10A. So for the Samsung 40T, same thing, would'nt push past 10A. I don't think anybody ever got 300 cycle by pulling 30A continous out of VTC4 18650's in a large pack either. Plus the VTC4 were tested for cycle life with a 75 degre...
by Matador
May 22 2019 12:17am
Forum: Battery Technology
Topic: Actual Test of Pure Nickel Heat?
Replies: 24
Views: 829

Re: Actual Test of Pure Nickel Heat?

So voltage drop, heat production all depend on resistance, gauge used, conductive metal type and lenght, for a given maximal tolerable voltage drop... is what I understand from all this.... How do we define what is an acceptable voltage drop for our EV application... Is their a sort of consensus ? I...
by Matador
May 22 2019 12:06am
Forum: Battery Technology
Topic: Actual Test of Pure Nickel Heat?
Replies: 24
Views: 829

Re: Actual Test of Pure Nickel Heat?

Here are my original excel files
Metal Strips Ampacity & Resistances by Matador.xlsx
(87.62 KiB) Downloaded 13 times
by Matador
May 22 2019 12:01am
Forum: Battery Technology
Topic: Actual Test of Pure Nickel Heat?
Replies: 24
Views: 829

Re: Actual Test of Pure Nickel Heat?

That is soo cool. I'll add my table to this:Ampacity (Powestream extrapolation).jpg In my table that same 0.8 mm wide x 0.15 mm thick pure nickel strip is rated 4.9A, which is about 5 degree celcius above room temp judging from your graph... what is your derating factor? temperature? if so what the...
by Matador
May 21 2019 11:55pm
Forum: Battery Technology
Topic: Actual Test of Pure Nickel Heat?
Replies: 24
Views: 829

Re: Actual Test of Pure Nickel Heat?

Yes, I've done testing: https://i.imgur.com/mIOKzth.png That is soo cool. I'll add my table to this: Ampacity (Powestream extrapolation).jpg In my table that same 0.8 mm wide x 0.15 mm thick pure nickel strip is rated 4.9A, which is about 5 degree celcius above room temp judging from your graph... ...
by Matador
May 21 2019 11:47pm
Forum: Battery Technology
Topic: end cells always fail first, why?
Replies: 15
Views: 877

Re: end cells always fail first, why?

Could also be that some cheap BMS have unequal quiescent current drain, sometimes on the first cell in the series of cells... Sometimes it's the first three cells. Same thing with the CellLog from progressive RC, display and electronic are powered by battery it monitors, but the device does not drai...
by Matador
May 21 2019 11:43pm
Forum: Battery Technology
Topic: Is PCM good enough to replace BMS?
Replies: 13
Views: 1448

Re: Is PCM good enough to replace BMS?

Here is an example from the "BesTech Power" website... Example of Model HCX-D131A... You can buy the whole BMS (PCM+Balancing board): 201211422736929.jpg Link: http://www.bestechpower.com/518v14spcmbmspcbforli-ionli-polymerbatterypack/PCM-D131.html Or you can buy just the "Balancing board" part of t...
by Matador
May 21 2019 11:24pm
Forum: Battery Technology
Topic: Is PCM good enough to replace BMS?
Replies: 13
Views: 1448

Re: Is PCM good enough to replace BMS?

PCM is wired to cells in series. PCM applies LVC (low voltage cutoff): when one cell is getting too low, PCM shuts down the whole battery. No more discharge... neither the battery asa whole, nor any cells that constitute the battery will be allowed further discharge. Even is they are imbalanced. PCM...
by Matador
May 21 2019 11:02pm
Forum: Battery Technology
Topic: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E
Replies: 65
Views: 2533

Re: Panasonic/Sanyo NCR20700B vs Samsung INR21700-50E

flippy wrote:
May 16 2019 10:08am
you are not going to get any decent cycle life on any of the 2xx cell form factors, not yet anway. if you want hard cycle life you need to dial it back to 18650 and stay under 3000mAh.
What about Samsung 30T 21700 : 3000 mAh rated 35A
and the Samsung 40T 21700: 4000 mAh rated 30A...
by Matador
May 21 2019 10:58pm
Forum: Battery Technology
Topic: 14s2p Minicube w/ 21700 batteries
Replies: 5
Views: 369

Re: 14s2p Minicube w/ 21700 batteries

The Samsung 50E are rated at a max discharge rate of 9.8A. The ad is misleading to the novice. Yes the BMS supports a discharge rate of 30A, but the battery only supports a discharge rate of 19.6A (2P) configuration, but I would not run it at more than 10A to expect any usefull lifespan out of it in...
by Matador
May 21 2019 10:46pm
Forum: Battery Technology
Topic: Powerful inside-frame battery
Replies: 15
Views: 703

Re: Powerful inside-frame battery

The inside of your battery would most likely look like mine. Carefully review my thread on this Ancheer eBike. I posted tons of pictures for reference. Here is the link : https://endless-sphere.com/forums/viewtopic.php?f=2&t=93576 But I must say... I think a 1.5 kWh motor-controller setup on this is...
by Matador
May 13 2019 7:48pm
Forum: Battery Technology
Topic: Solderless weldless 36V and 74V batteries could do over 200A
Replies: 54
Views: 2792

Re: Solderless weldless 36V battery could do 200A

Must say that Agniusm's work look really solid !
Best solderless product i've see on the market.
I will eventually buy some when I can finally afford it (time will come)...

Agniusm are you an engineer ? I can't help but think you are looking how solid you know the specs of your designs...

Matador
by Matador
May 12 2019 6:04am
Forum: Battery Technology
Topic: Which high capacity 18650 cell for 250w ebike battery pack with heavy usage?
Replies: 35
Views: 1306

Re: Which high capacity 18650 cell for 250w ebike battery pack with heavy usage?

Wow great thread cool bikes, crazy stupid laws, so sorry for your troubles there! So worth checking out local laws, crazy for someone like me wants to van-dwell with ebikes around the country and overseas. Stealth mode, swappable drive trains, makes things lots more complicated Move out of NYC! No ...
by Matador
May 11 2019 6:40pm
Forum: Battery Technology
Topic: Which high capacity 18650 cell for 250w ebike battery pack with heavy usage?
Replies: 35
Views: 1306

Re: Which high capacity 18650 cell for 250w ebike battery pack with heavy usage?

Thank you so much for your insight, everyone :) I ride 100km on long days, but I live right in the city center, so I can swap battery packs at home once or twice a day. So I thought the best option was to get 2 packs around 600Wh-700Wh each and cycle them between 4.1V and 3.3V. I would like to go w...
by Matador
May 11 2019 6:09pm
Forum: Battery Technology
Topic: FIX for non trimmable Li-Ion charger that slightly overcharges eSkate
Replies: 19
Views: 1142

Re: FIX for non trimmable Li-Ion charger that slightly overcharges eSkate

More photos of the board and board guts. More specifications on the components (motor, PU sleeves, ESC mods, etc)... Info on overvolting / overclocking the board to make it go faster... Follow this link: https://www.electric-skateboard.builders/t/chinese-board-repair-and-upgrade-help-so-you-bought-a...
by Matador
May 10 2019 10:39pm
Forum: Battery Technology
Topic: Which high capacity 18650 cell for 250w ebike battery pack with heavy usage?
Replies: 35
Views: 1306

Re: Which high capacity 18650 cell for 250w ebike battery pack with heavy usage?

In the end, i would probably choose something cheap but good. samsung 30Q or Pananasonic GA. But if you want smaller than 4P, dont tkae the GA cells.
by Matador
May 10 2019 10:34pm
Forum: Battery Technology
Topic: Which high capacity 18650 cell for 250w ebike battery pack with heavy usage?
Replies: 35
Views: 1306

Re: Which high capacity 18650 cell for 250w ebike battery pack with heavy usage?

If you have to go 18650 and Li-Ion chem and if range is no issue with a 6P setup (I'd say 25 miles), Id go with Sony VTC4... Thes cell will run coll because they have low internar resistance (21 mOhm DC IR), thus very good cycle life. If really you don't care for range for a 6P setup (think 12-15 mi...
by Matador
Apr 06 2019 11:08pm
Forum: Battery Technology
Topic: FIX for non trimmable Li-Ion charger that slightly overcharges eSkate
Replies: 19
Views: 1142

Re: FIX for non trimmable Li-Ion charger that slightly overcharges eSkate

Thanks amberwolf, So kindoff going 1,2,3,1,2,3,1,2,3 gives the same result as 2,3,1,2,3,1,2,3,1 or 3,1,2,3,1,2,3,1,2 ? I read some post about this a minute ago ? This is really interesting stuff. I feel i'm really starting to better understand how ebikes work. I think it's a neutrally timed sensor p...