Bottle mount 48V 14.5AH w/ NCR18650B -last at 25A?

[karlInSanDiego]

http://www.emax-ebikes.com.au/store/p11/Dolphin_Frame_Mounted_Battery_Pack.html
Hey guys,
I've read as much as I can about these Panasonic NCR18650B cells (including in bikes, RC, skateboards), and that they must be charged slowly and that they are low C. I can't see this discharge spec(in C) on any Panasonic spec sheet, but rather people have quoted it many times as requiring discharge of .5C and even .3C . If I'm not mistaken, that would mean I would need to operate a 14.5AH pack at 7.25A continuous to stay in that safe discharge rate, right? Others have claimed they are 1C and 2C discharge rates. If that was the case I'd be at 14.5A or 29A respectively, is that correct? Perhaps if someone can briefly explain how you glance at a factory spec chart and determine the C rating, I can verify for myself that these cells won't work in this config.

Vendor is stating they will operate fine in a 14.5AH 48V pack at 25A.

I'm building a commuter for 21miles (w/some long hills) each way w/Bafang 750W BBS02 Midmount on a 26" rimmed 1.5" slick tired Maverick ML-7 full suspension mountain bike.

Would I be better off using 48v 11.6Ah (Samsumg 18650 29E Cells) which seem to be much better C rating, even though I'm losing all that capacity?

I'd prefer to overbuild the battery as I've got lots of hills on this commute, and I'm in lousy shape, so running out of juice and stamina will make this whole endeavor a failure. I also don't want to have to shower at work because I've built the wrong bike and this turns into way too much Karl-power, though that is an option while I get in better shape. The point is, I'm building this to improve my health, use electricity, not gas, and I ruled out Brammo Empulse and Zero S motorcycles as far too costly. I want to max out the Bafang on speed as much as possible. Commute will likely be 2 hours a day minimum (traffic lights and hills will always keep portions slow) so I'm planning on ~20-25mph speeds with pedaling when the road is clear, sustained.

Ewan at emax has been helpful answering my questions so far, and I don't mean in any way to disrespect his word, but this is the one point I'm not confident I'm getting right, so I'm asking for experiential opinions. If anyone has built / bought with these cells successfully, that would be a whole lot more valuable feedback than to refer me to other posts where folks considered or dismissed it. I've only seen two very anecdotal posts (not threads) where someone mentioned using them successfully, so I'd like to understand if that was anecdotal or responsible reporting of real world long term experience with them. Potentially the 14.5 AH will be oversized as I get in better shape (I plan to pedal assist but at first will be weak) and if it is over-sized, I will use a smart charger (Satiator) to extend the battery life by charging to 80% when if/when I no longer require all that juice. Also I'll be recharging halfway through commute (at work).

Thanks for any help you can give on clearing up this outstanding question.
-kARL

 

[eMax]

Hi Karl
Sorry to jump in - very valid idea to gather users opinions.

Here are a few details from the spec sheet for the battery. Unless you will be running your BBS02 at full current all the time battery will be ok. It will not be OK for higher powered hub motors pulling over 25a.

Item Standard Remark
Specification 13N10
Nominal voltage 48V
Capacity 10Ah
Size（L*W*H） 407*87*74 mm
Weight 3.1±0.15kg
Mass ratio of energy 140Wh/Kg
Standard discharge 15±1A
Maximum continuous discharge current 25A
Discharge cut-off voltage ≥38.0V
Charge voltage 54.6±0.2V
Standard charge 2±0.5 A
Resistance ≤180mΩ

 

[eMax]

Also mate as a sidnote running 48v @ 25a will be over the motors rating of 750w. Most vendors will not not ship with current limit of 25a.

 

[karlInSanDiego]

Fair point about the max current, Ewan. You can set it up around 1000W or so though, right? Seems a waste to not make available the reserve power it's capable of. I'm a noob, so correct me if that's bad logic. At 15A, I'd be running approx 720W which is a little under the 750W power it's spec'd as, though I understood that 750W rating was to conform to 750W road laws, not because it's the actual top safe operating mode. I'm fairly sure I will be able to make use of any extra speed I can get, but maybe that's also the uninitiated speaking. My other bike is a Triumph Daytona 675, so I'm not shy about strapping on the full gear if this bike can tear. I already ordered a Bell Super 2R full face bike helmet.

What is the cell configuration in that 14.5Ah pack? I was going to guess 13s4p. The specs you listed here show 10Ah. Are you sure that's the 14.5Ah Panasonic pack we were discussing.

 

[Nobuo]

Because the speed, and specs of these two cells, I would go clearly on the panasonic. It is very important to know what kind of BMS is installed in that bottle battery. I would use a 15A or 20A continuous BMS, panasonic NCR18650B are a beast and will work at a very efficient rate until 5A.

 

[wesnewell]

http://lygte-info.dk/review/batteries2012/Panasonic%20NCR18650B%20Protected%203400mAh%20%28Green%29%20UK.html
25A on a 5p pack is pushing it, but should be ok. Lot's of sag.

 

[agniusm]

Using these at 5P on 350W stand-up scooter. Forget 20-25amps on these. If you would get 2 of those battery packs, one on top of down tube one on the bottom for 10P you'd be OK. In the end, calculate these cells at .3C.

 

[Nobuo]

http://lygte-info.dk/review/batteries2012/Panasonic%20NCR18650B%20Protected%203400mAh%20%28Green%29%20UK.html
25A on a 5p pack is pushing it, but should be ok. Lot's of sag.

I think a 5p of these would work like a charm with a 15A or even a 20A continuous BMS

 

[karlInSanDiego]

Unfortunately, I don't believe 5P is possible in the two most popular bottle formats, when you need 48V. Since you require 13S to get to 48V, and the form factor fits 50 or 52 cells, you're left with 13s4p, so no hope for 5p until somone builds an unsightly big gulp bottle pack. I'm going to order the Samsung 48V 11.5Ah with 18650 29R's (happy at 2C discharge sustained). I understand they are not subject to the poor discharge limitations of the NCR18650B's . Here, Panasonic states the "B"s are intended for low current draw, long duration applications, like laptops and I know at some point I read that Panasonic uses a unique chemistry in them including nickel: http://industrial.panasonic.com/lecs/www-data/pdf2/ACA4000/ACA4000CE417.pdf

Thank you for all for your input. I'm sure those cells have their place, but not feeling good about them with this small form factor, and my plan for using the full potential of the BBS02 750W motor on a 42 mile, hilly commute that's replacing cars/motorcycles. I ordered some shields for my eyes tonight, anticipating the sustained velocity!
-kARL

 

[riba2233]

LOl there's no samsung 29R, it's samsung 29E!! If you want cells with higher capacity, but still 2C cont and 3C peak current, seek panasonic BE, lg mh1, lg mj1, samsung 32E.

 

[agniusm]

I just dont see "high capacity" and "hi discharge" is possible in one sentence. I dont know why you are limiting yourself to that particular type of battery case and those scarce options of cells on most important piece of hardware on e-bike.

 

[Nobuo]

I just dont see "high capacity" and "hi discharge" is possible in one sentence. I dont know why you are limiting yourself to that particular type of battery case and those scarce options of cells on most important piece of hardware on e-bike.

I think that "high capacity" is the best friend of "high discharge" if you assume you are paralleling cells of course battery cases are a limit, but there are still not very reliable solutions for DIY solderless battery packs, we must mesh with that cases for now

 

[karlInSanDiego]

You guys are making valid points, but this is IMO a relatively affordable, relatively safe route for a first time builder. If you look at it from a DIY perspective, it may not seem too logical, because the world is your oyster as far as spending hundreds on Aliexpress, soldering all the parts together, taking a risk that you bought fake cells, didn't test your cells properly before assembling the pack, hooked up a BMS incorrectly because the specs are in Chinese and you don't read Chinese, and the list goes on. I was young and single with big toy budgets before, but I'm trying to avoid being cavalier. I'm pretty sure with the benefit of some more experience with e-bikes and a lot more learning, I'll be in the chorus on here saying it's silly to not DIY your own battery pack.

I'm 45 years old, and married. Spending this money on a bike project is already a gamble because it's my reentry into cycling and it's not clear if I can make this whole plan work out, dedicating a lot more time each day to commuting on batteries. So I'm trying to minimize the risks involved with climbing the learning curve the hard way and possibly building a failed pack before I have a functioning bike. I can't pull the late-to-work-because-my-battery-caught-on-fire-again, card, and I'm guessing most of you wouldn't want to do that either. I prefer at first to not use a battery with no packaging hanging from a velcroed triangle sling with no rigid mounting, swinging the heaviest component of my entire bike into the sides of my knees, although I surely considered it. Rear rack isn't an option on my full suspension bike, unless I get creative with an actively hinged rack that pivots on bearings and articulates. Maybe a year from now, I'll have budgeted for a home built battery, built it and tested it, and fabricated an attachment solution for an additional 48V 10Ah, but right now I'm trying to build a clean, turn key package with minimal hacks and the subsequent heartburn that come with refining them.

I'm glad I posed the question here, and given that this is a product people are selling (that pack with very low C specs) it's useful to discuss the merits and downsides of such a design. Ewen was honest with me about the need to keep it real if I did purchase that combo (ie, operate it in a safe 15A range), but I decided I'd rather opt for cells that can be pushed. After I have the luxury of experience of riding my ebike, and have learned a lot more about the ins and outs of batteries, I'll be in a better place to judge how to improve any battery addition/upgrade.

 

[agniusm]

I think that "high capacity" is the best friend of "high discharge" if you assume you are paralleling cells of course battery cases are a limit, but there are still not very reliable solutions for DIY solderless battery packs, we must mesh with that cases for now

Your assumptions are wrong. Take 18650 of A123 cell at 30C and 1100mah, parallel two of them and you have 60A capable battery but @ 2.2AH. How many cells you would need like Panasonic 18650B to get that rate? Hm, lots.

Ant to the author. Have you seen chinese build quality? I have seen on this forum photos of cold soldering, wires falling off, bms'es shorting out. Not all but tjere are a lot o this in Chinese manufactured products.
In my previous post i meant that you could buy rigid battery pack with higher capacity, say 20Ah of those samsung cells. There are such batteries for the rear rack. Course if you are after sleak looks, you are limited to have EU legit 250w bike

 

[friendly1uk]

Same box, different vendor, different cells. 48v 12ah 40A
bmsb.
The bms used is 25amp, like you need. The cell spec of 40A is taken from panasonic, and you won't want to do it, like you won't want to take 25 from the pack posted. They are unlikely to be pack figures. Just single cells in free space and 20-25C ambient temperature.

 

[wesnewell]

I don't know how we got to A12318650 cells, but here is the specs on them.
http://www.batteryspace.com/prod-specs/6612.pdf
Note how much they sag at even 20A. I'd estimate they go below 2.5V at 30A. Also note that life cycle is based on a 1C discharge rate, That's 1.1A for those that don't know what C ratings are about. I'd need 240 of them at $9 a pop to replace my $275 10ah 24s rc lipo pack and still need to pull 3-4 times the life cycle testing rate of 1C, thus cutting life cycle in at least half, and probably more. That's over $2130. I've got over 10K miles and almost 3 years on my pack. I could buy 7 new packs for the cost of a single a123 pack and get 21 years and 70K miles with them. So when one of you get 20 years and 70K miles from one of these a123 packs, let my great grandson know. I'll be long gone.