Pack build

[Teeach]

can someone sanity check this please

building a pack for a scooter and think im going to to as follows,
18s3p

us18650vctc6 3000mah 30a cont discharge

[https://eu.nkon.nl/sony-us18650-vtc6.html](https://eu.nkon.nl/sony-us18650-vtc6.html?fbclid=IwAR3bktZ3lSDCuOZBoLui7IbIKlQ11aDhSq4EMaMvBh3AQ4vBsQK1zU6jbtk)

18 in series x 3.6v = 64.8 @ 3ah = 1 bank

3 banks in parrallel = 9ah = 54 batteries

ability to add another 3 banks in future would then
6 banks - 18ah - 108 batts

Or can I 6s3p X 3 in series?

Thanks

 

[goatman]

yes
6s3p in series, is that for hobby charger balance charging instead of using a bms?

 

[serious_sam]

us18650vctc6 3000mah 30a cont discharge

Sony VTC6 are not 30A continuous. You can do 30A for bursts with no problem, but keep an eye on temperatures.

Note the early cut-off due to temperature rise in this test data, for 20A and 30A discharge rates.
https://lygte-info.dk/review/batteries2012/Sony US18650VTC6 3000mAh (Green) UK.html

Internal resistance is measured by docware (thanks docware!), initially ~18mOhms per cell @ 50%SOC.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=103092&p=1547165#p1547164

In real life, I'm getting 25-30mOhm, based on voltage sag measured/logged by my motor controller. So this result includes all battery wiring, connectors, and BMS. The internal resistance does significantly depend on SOC, and somewhat on temperature.

 

[Teeach]

Thanks.

Not for the hobby king route. I can just visualize it better. Going to start a tech drawing later. Is there any advantage in having 3 the 3 packs Vs the one 18s3p?

I will purchase a BMS with Bluetooth so i can set cut off Temps and discharge etc... Any recommendations?

I need to look into BMS as I haven't done this before. From my initial thoughts each of the wires goes to a section of the pack?

 

[999zip999]

https://endless-sphere.com/forums/viewtopic.php?f=31&t=87300&p=1274969&hilit=Lithium+battery+book#p1274916

 

[serious_sam]

If you're going to use a BMS, you're much better off keeping the cells one single pack. That will avoid any connection errors, if you have to disconnect reconnect sections of the pack. But at the end of the day, packaging the cells on the bike will take priority. You gotta do what you gotta do.

Bluetooth BMS thread:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=88676

 

[Teeach]

Thanks all

Still have a lot of reading to do. Any quick quides on BMS?.not going to take a shortcuts but would.lile an overview before diving in.

The monitor cables go to (mini packs) in the pack I can't figure out how it would be able to minister this unless the cables have to be in order? As it know what's current/voltage is coming form each mini pack? Or does it monitor the the whole pack as one?

 

[999zip999]

All cells in parallel count as one cell first wire 1 cell or infinity. Second wire 1 cell to infinity as cell number two and so on. Lots of good reading here on E.S.

 

[Teeach]

Thanks think I got the jist of it just need to put the time in now. Just wanted to try and get the ordered placed then lookup the more tech details while awaiting the order.

In a summary this thread has told me the more parralel groups the better?

I have gone from 18s3p 54 battery pack, which would yield 64v @ 60a Max draw

To a 18s2p. This will reduce my initial cost for batteries and the ability to add to another 18s2p. Only problem I see correct me if I'm wrong please is, a BMS, it's slightly confusing? From reading here it monitors parallel groups? But then having conflicting searches saying make sure it has the correct S rating which would be 18 in my case? How does it work in series? would it look at S1 cell and see i.e 3.2 volt, then look at S2 cell and see 6.5v and deduct the 2 to arrive at 3.3v? And so on?

After reading this back before posting I think it has now clicked and would need a 18bms which then poses another quandary... I planned to just hitch the additional pack up at the + and - so it would be another pack in parallel to the original. This would need it's in own BMS and charger etc... Or I could add it onto the existing pack but would need to ensure the voltages are the same? I guess it wouldn't be too much work just to add it onto the existing bank of 2.

 

[Teeach]

Also sorry to be a pain. The voltage I'm looking at for a bms should be the nominal voltage? 18 X 3.6 =64.8v or the max voltage of 4.1 X 18 =73.8v

Thanks

 

[Teeach]

Also sorry to be a pain. The voltage I'm looking at for a bms should be the nominal voltage? 18 X 3.6 =64.8v or the max voltage of 4.1 X 18 =73.8v

Thanks