21700 cells with Higher Mah.

[Nealh]

I have noticed some news on two cells very recenlty.
BAK have a new cell at 5300mah, the 21700CD. A 1c charge rate and a 1.5c discharge rate which tbh is ok for a mediocre current rating.
Not much use for a 2p battery config.

The other cell is very much more interesting an LG M58T currently on Nkon. max discharge is 12.5a so though not stated is over 2c discharge and it appears has a 5700 mah capacity via independant testing.
Nkon state that the cells are from a cancelled car project, so expect they are a one off acquirement.

 

[Nealh]

I forgot one of the current best rated 21700 cells is the moli p42a/35a cell, it is soon to usurped by the new moli p45b/50a rated cell and an increase near 9% usable mah as long term tested by mooch on ecigs forum. One expects it not to be a cheap cell though.

 

[egroover]

What sort of capacity can we expect in a Hailong type 1 case with these new cells? I have 2 x Hailong 1 type downtube batteries at 36v/17.5ah (LG/Samsung 18500 cells) - Sorry don't understand the maths on calculating this yet
Thinking of the future, be nice to get up to about 24-25ah in the smaller Hailong 1 case

cheers

 

[Nealh]

Any capacity with 21700 is dependent on the case size to accept the larger cell format, but current case sizes one would expect 3 0r 4 cell in parallel max.
For capacity all one needs to do is X the cells in parallel by the cell mah rating.

So theoretically if one could get 4p of cells in a case one would be looking at about 22.8ah with the M58 or 21.2ah with the BAK. I don't really think we will see more then 6000mah in the 21700 format as current supply will suffer.

The BAK will be an ok cell for more capacity but only if one keep the bike legal and doesn't draw big current 15a would likely be good for life cycle, but until some independant graphs come out on performance no one will really know. I expect it will be similar to Sam 35e in life cycle as mediocre battery with the far greater capacity for range.

The current moli p42a was only introduced 4 years ago and now a newer better higher rated cell is about to appear.


To think now one can have a smaller lighterweight battery with only 2 parallel cells giving out 8 - 9 ah is pretty good. My current moli p42a 12s 2p is good for at least 22 miles towing a laden trailer of up to 200lbs with about 600m of ascent.
For my local usage my bike and trailer combo replaces the car and I still get exercise and fresh air.

 

[Nealh]

Sub 5000mah then we will be seeing some very good high discharge cells allowing for smaller/lighter batteries in the 21700 format, above 5000mah one expects most will be mediocre cells that will at least need 3 if not 4 or 5 cells still in parallel.

What folks have to be careful about is how long the larger capacity packs/batteries are going to take to charge, one can of course use the 1c max charge rate of most cells so about 4 - 5a charge rate but the down side is life cycle may suffer at the higher charge rate.

 

[egroover]

Thanks Nealh that's really helpful
I recently came back from a 9 day France/Belgium tour, took both of my Hailong 36v 17.5ah batteries. was doing about 80 miles per day, only really needed the 2nd battery for 10-15 miles at the end of the day as I was tiring a little (it was quite warm over there), so for a single battery in the smaller Hailong type 1 style, 23-24ah would be the sweet spot for me on those type of tours (plus losing the weight 3kg of the 2nd battery would help range)

Will see how those new 21700 cells you mention make their way into downtube type battery cases in the next 6 months with a view to buying one for next year

cheers

 

[Nealh]

One could nearly lose the 3kg weight entirely as 21700 cells are about 68/70g each compared to 48g or so of 18650 cells.
10s 5p/17.5ah of 18650 cells is approx. 2.4kg , 10s 4p/ 20ah of 21700 is approx. 2.72kg. So marginal weight gain per battery but yes the loss of a almost a complete weighty second battery.

 

[Nealh]

Generic 21700 celled batteries we will see are likely to be mediocre cells or ones the big EV boys have no use for.

19ah 21700 hailong's are already available from about £360 with Tesla Panny cells, but one expects these are either non graded cells not fit for Tesla or reclaimed cells.

Enerprof do a 25ah Sam 50e megiddo battery but will set one back likely £500 - £600.

These larger format batteries are not going to be cheap.

The nkon m58's are getting on for £8 a pop for a 5700mah cell so cell cost alone for 10s 4p is over £300 and more for 48 or 52v users.

One can get top notch cells for sub £4 but to do so one needs to diy a battery build with all the safety features required to make the build worth it.