48V 2P BATTERY- any good

[eddymunster]

I was looking at enerpower site and they are selling 48v 2p 10ah battery with 21700 cells -lg 50e, looks nice and light, anyone have any thoughts on whether this would run a bbs02 750w for a 9 mile commute.
I have a old school marin/whyte 46, so use a back pack. Its one of Jimmy's 17.5ah whale packs, cracking battery but bit heavy in a back pack, I normally get 4 days run time out of this as I hardly use the throttle, so was thinking of getting the weight down and charging in work for the run home.
My other option was to build a 14s 2p myself with the samsung 21700 40t cells, they are 35a rated discharge with 4ah capacity, the but is this will be my first battery build.

great fun this ebike lark though, nearly as much as mucking around with motorcycles

any advice would be appreciated.

 

[Nealh]

50E is Samsung, in 2p isn't going to cut it the cells are only 10a rated (9.8a) so they are going to be maxed out quite a bit and will die quite quickly. 50E is quite poor and only has a 60c upper rating before being compromised by heat.
At 5a discharge to 3.2v they will give 3750mah , 8a about 3180mah and the full 10a 2750mah. Discharge to 3.4v per cell is even worse.

40T at 10a to 3.2v is about 3000mah, 5a is 3280mah.

All the above info comes from two independent test results for different testers and both pretty much give the same results.

 

[vfr400]

If you ask Jimmy (www.ebikebatteries.co.uk), he can make you up a battery that will fit in a toolbag under the saddle. He made one for a friend of mine that used it with a BBSHD on a Marin. He provided the bag too IIRC.

I think that Enerpower battery would be OK. It should easily manage 9 miles. You won't get 10Ah out of it, but even if it only gives 7Ah, that's 350 watt-hours, which would be more than 70Wh per mile.

 

[eddymunster]

Thanks for the info, sorry cells are lg m50 but think thats splitting hairs, here's the link https://enerprof.de/fahrradakkus/softpacks/akkus-48v-13s/179/softpack-akku-48v-10ah-bms-20a-xlr-3-mit-m50

I have noticed a 52v 3p hardcase pack on ebay which looks like the one whoosh had on here a bit back but he is not supplying yet due to cost/value for money, but no idea on the weight.

Did speak to Jimmy and he isn't that impressed with the format at present, the seatpost is a bit of a non starter cause I am not as agile as I used to be and run a dropper post, tried the battery on the top of frame but that had a similar issue of height.

2 or 3p might provide with enough clearance to get back on the frame but I was thinking with the drop in amps its all going to get a bit saggy and hot with a 750watt motor, the current set up the battery is a bit warm to touch at the end of a run in the backpack and I do have that nagging thought this could go a bit pete tong, even though I put some vents in it, also it is a bit over the top weight wise at over 9kgs.

Open to suggestions really, I have a good rear rack but looking at the bolts that are on the linkage for the swing-arm - 6mm I am a bit concerned about sticking all that unsprung weight through them especially as the wheel already has an alfine 8 in it, always felt i would be pushing my luck on that one. As I say open to suggestions.

 

[Laser Man]

The LG M50 21700 cells look far better than the Samsungs that Nealh was talking about.
7.3A continuous per cell, so 2P confifuration would give 14A+
(7.3A is under 1.5C, so quite gentle on the cells)

 

[Nealh]

Life cycle for LG m50 is poor, capacity wise it isn't much better then the Samsung 50.
From what I read the value in using 21700 over 18650 doesn't compare, going 2p is none starter which proaby ties in with Jimmy's views.

 

[eddymunster]

Yes I believe life cycle isn't as good, I know luna have just released a 52v mini wolf pack in 1p using samsung 21700 40t cells but its only 4ah, watt hours too low for my use,they make some big claims about the cell choice but I think I might sit on the fence for now and see if anyone decides to use these cells in future rather than build my own 2 or 3p set up, Jimmy didn't seem too keen suggesting I went down the cell pouch route, bit unfamiliar with this though.

 

[Nealh]

We need a Guinea pig to try these .

NKON | K-Tech INR18650P 2500mAh - 12.5A - 18650 - Li-ion - Rechargeable batteries

<a href="https://www.nkon.nl/sk/k/INR18650P-1700-2500mAh-Product Specification.pdf" target="_blank">Datasheet</a>

eu.nkon.nl

 

[eddymunster]

not sure I want to let the genie out the box ha ha. How many cells do you reckon I need out of curiosity and do reckon we could get away with 3p.

 

[Nealh]

3p of Sony vtc5 are a bit cheaper then 2p of Sam 40T, both come in at about or just under £160 for the cells.
42 Sony's needed for 3p and 28 Sam's for 2p.
Weight wise the Sony's will be a tad lighter, both under 1.9kg.
Sony will be about 280wh actual capacity and Sam about 300wh actual capacity both should do your 9 mile return journey on one charge if you put in a bit of effort.

The other factor is cell life expectancy the 40T 1c rating is 4a , 2 in P will be 8a so possible at 25a you will be expecting them to cope with a 3.125c loading which is well within the 8- 10c max peak rating for them.

Sony are 8c at 20a max or 12c at 30a if under 80c temp, cells will see approx 2.7c loading at controller max amps.

 

[eddymunster]

looks like enerpower have gone down the 40t cell route on my behalf- 48v 12ah 30a bms- 320 quid so not a kings ransom over me building one. Probably next month so will report back

 

[anotherkiwi]

I'm interested in how you get on. For me a tiny light weight battery works for a motor you only need 250-350 Amps peak. I have been toying with the idea if an ultra light weight motor wheel - 1.7 kg - and an 11 Amp peak controller. Just something to get me out of the house, the rest of the ride being unpowered.

 

[eddymunster]

I'm interested in how you get on. For me a tiny light weight battery works for a motor you only need 250-350 Amps peak. I have been toying with the idea if an ultra light weight motor wheel - 1.7 kg - and an 11 Amp peak controller. Just something to get me out of the house, the rest of the ride being unpowered.

they are claiming 3kg all up- not the prettiest of things its a softpack- looks like i am going to to order in a couple weeks.