Small pack (2p14s) build

ro_balboa

10 µW
Joined
Apr 7, 2017
Messages
5
Hello, I've been reading this forum for months and got a lot of informations but just want to make sure if I am going to do something wrong (because there is no many small pack examples here)

I am building electric bike and want to build smallest pack possible (because I will use it on short distance from home to work)
I decided to go with 2p14s pack with samsung 30q cells.
This pack is reference: https://lunacycle.com/batteries/packs/52v/52v-mighty-mini-cube-samsung-ebike-battery-pack-30q-6ah-3-pounds/
But I am going to make longitudinal battery.


So, question is how to weld/solder cells so I can get max 25A ( bbs02 750W )

I got two versions so please look at, and give sugestions am I good to go!

Thank you!

v1.jpg
v2.jpg
 
2P on a 25A setup might irreversibly damage your cells... 12.5A/cell is no problem for short burst with these 15A cells, but if you're on the throttle continously, they'll probably heat up too much and loose capacity over time.
Oh and of course 3000 mAh is not at 12.5A/cell (it's 3000 mAh @ 0.6A). Put more in parallele and you'll gain some "usable" capacity because of less voltage drop (from internal resistance) and thus less heat loss in energy/capacity.
 
I am not sure what to think now.
I trusted lunacycle with this setup and their description( as they are reliable seller).
and this review said 1p can handle 15A continuosly with decent voltage drop and short pulse 20A (it gets warm >20A)
http://lygte-info.dk/review/batteries2012/Samsung%20INR18650-30Q%203000mAh%20%28Pink%29%20UK.html

And I intend to use it at double lower values - 15A for most the times and 25A for short period (for 2p configuration)

Well, I got all stuff needed to build the pack and have no room for 3p so I´ll give it a try. Any sugestions are welcome (regarding the weld/solder design), and I will post the progress for future readers. I am willing to take this as the test, even if it fails. Thank you!
 
I vote for version 2. The main reason is that the pack will be mechanically stronger. 12 gauge copper wire should be sufficient for the series current but the additional nickel strips will make the pack stiffer.
Report back and let us know how a 2P pack performs. Do you have a stronger pack for comparison?
 
With Samsung 30Q and 15A continuous and 25A max then 2P is probably pushing it a bit, but will be OK. Cell life may not be the greatest.

IIRC capacity at max continuous draw is more like 2.9Ah compared to 3.0Ah, so no that much less.

I agree, for mechanical strength V2 is better, but electrically not so (just additional unnecessary welds). Just make sure the copper series connections are sufficient (again, 12awg sounds good).
 
Thank you all,
I'll go with V2 (just in case)
I have larger pack for comparation (but with shity cells, so I guess this one will perform better).

It's hard to tell what means cell life - maybe it is worth to sacrafice few charging cycles for lighter pack, less material, easy of assembling, charging time, etc..

I am building it in next few weeks so I'll keep you posted with pics.
 
I think you will be fine, but much depends on gearing, speed, riding style and weight. If your riding includes extended periods at full throttle, the cells may get hot at the end of the ride. What is your estimated average current draw and ride time?
 
it depends on how you'll ride the BBS02. if you'll cruise at just 600w then your plan will work. the 30Q will still get warm but that's OK if you don't TRAP heat inside your pack's shell. here i bonded my cells to its aluminum outer shell w/ thermally-conductive silicone.

2vsrtzr.jpg


also look at higher power cells. maybe Sony VTC5A or something...
 
thanks for the response.
this build is especialy for my need.
I got 7km from home to job and that is the target range (15km with 3km slightly uphill)
from my calculation I can get this range only on throttle but I intend to use mainly assist mode so the range wont be a problem (with my 70kg).
and Ìll be very soft on bbs02 so I think this is the right choice for me.
and one more think: I really care how bike looks :) I want it to look like regular bike and with my design Its gonna look almost completely stealth (I`ll post pics when finished, its hard to explain). hm, and I`ll think about traped heat, i want to keep case smallest possible,I`ll try to make good airflow (I am gonna make custom 3d printed case wraped with breathable waterproof fabric).
 
Overclocker said:
yeah goretex won't work :)

or just sink the heat into your aluminum bike frame

uf, that changes everything :/
Can you explain what do you mean by "sink the heat into your aluminum bike frame" ?

And what if I make it so thight that there is no air traped inside? that means that the heat will transfer to outside ?
 
ro_balboa said:
Overclocker said:
yeah goretex won't work :)

or just sink the heat into your aluminum bike frame

uf, that changes everything :/
Can you explain what do you mean by "sink the heat into your aluminum bike frame" ?

And what if I make it so thight that there is no air traped inside? that means that the heat will transfer to outside ?


provide a thermal path from the cells to your metal bike frame
 
I have a mighty mini on a BBS HD. Comfortably get 18km on a charge using PAS 1, throttle now and again, and little up hill. The one thing I don't get is a hot battery. runs cool even after a lot of throttle only. It's a great pack.
 
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