Jan-Erik-86
100 W
- Joined
- Jan 23, 2019
- Messages
- 110
I've abandoned my first thought on simply adding some high power cells to my old pack, and have decided on making a new pack.
I have a DD hub motor with a shunt modded KT controller which pulls up to ~50A from the battery, but my load is normal in the range of 600-1000W. I mainly use the bike for commuting 16km each way, but do not have many hills on the way. My average power usage is around ~12Ah.
I ride it in the winter time as well, so cold temp performance is also important. I plan to stay in the 20-80% SoC range, but want a bit extra capacity for longer trips and expected capacity drop over time.
I have space for up to 9p14s and have been looking around a lot for which cells to use, and i think i've come down to 2 main options (or maybe 3).
The cells i'm mainly considering are either Sanyo GA or Sony VTC6. Now these are two completely different cells, but with the seemingly low price on the VTC6 I think it might actually be a very good option. I first thought the LG HG2 would be the best option, but that have dropped down to the "maybe option 3" on the list due to it's price vs capacity, power handling and cycle life.
From what i can see, this is how the two cells compare:
US18650VTC6: 9p14s / 126 cells + 5x vruzend kits = €649
Capacity: 27Ah, 60% Min. of Initial capacity at 500 cycles (from specs/graph with 4A charge, 15A discharge). (looks much better with the 7,5A discharge graph)
Max cont. current: 135A (270A)
Weight: 5,86Kg
Std. charge: ~22-27A (?)
Warm sag: 58,8V -> ~56,7V @ 45A ~25c
Cold sag: 58,8V -> ~45,5V @ 90A -10c
NCR18650GA: 8p14s / 112 cells + 4x vruzend kits = €614
Capacity: 27,2Ah, ~65% of Initial capacity at 500 cycles (from specs/graph with 1,65A charge, 6A discharge)
Max cont. current: 80A
Weight: 5,2Kg
Std. charge: 11,8A
Warm sag: 58,8V -> ~55,3V @ 40A ~25c
Cold sag: 58,8V -> ~46,9V @ 32A -10c
Now maybe i've overlooked something important here, but from what i can see the VTC6 will be slightly heavier and slightly more expensive, but other then that it will handle way higher both charge and discharge current, it sags less (significantly less in cold temp), and the capacity drop with cycle life does not appear to be an issue compared to the GA cell - at least not from the graph in specs.
On the other side I know the GA have been proven to be a very long lasting cells even when used at a high DoD and up to 3C discharge, and even though the specs don't claim it they appears to "settle down" after dropping to ~80% capacity. I don't know if any similar tests have been made on the VTC6?
However the GA do sag a bit under higher load, and i expect the sag to increase with the cycles even though the capacity drop settles, and i'm getting close-ish to the max current load.
Hopefully you guys can point me in the right direction here. I'm open for any feedback and recommendation, and just because i've been looking at these two cells does not mean you can't convince me to choose something else if it's a better option.
I have a DD hub motor with a shunt modded KT controller which pulls up to ~50A from the battery, but my load is normal in the range of 600-1000W. I mainly use the bike for commuting 16km each way, but do not have many hills on the way. My average power usage is around ~12Ah.
I ride it in the winter time as well, so cold temp performance is also important. I plan to stay in the 20-80% SoC range, but want a bit extra capacity for longer trips and expected capacity drop over time.
I have space for up to 9p14s and have been looking around a lot for which cells to use, and i think i've come down to 2 main options (or maybe 3).
The cells i'm mainly considering are either Sanyo GA or Sony VTC6. Now these are two completely different cells, but with the seemingly low price on the VTC6 I think it might actually be a very good option. I first thought the LG HG2 would be the best option, but that have dropped down to the "maybe option 3" on the list due to it's price vs capacity, power handling and cycle life.
From what i can see, this is how the two cells compare:
US18650VTC6: 9p14s / 126 cells + 5x vruzend kits = €649
Capacity: 27Ah, 60% Min. of Initial capacity at 500 cycles (from specs/graph with 4A charge, 15A discharge). (looks much better with the 7,5A discharge graph)
Max cont. current: 135A (270A)
Weight: 5,86Kg
Std. charge: ~22-27A (?)
Warm sag: 58,8V -> ~56,7V @ 45A ~25c
Cold sag: 58,8V -> ~45,5V @ 90A -10c
NCR18650GA: 8p14s / 112 cells + 4x vruzend kits = €614
Capacity: 27,2Ah, ~65% of Initial capacity at 500 cycles (from specs/graph with 1,65A charge, 6A discharge)
Max cont. current: 80A
Weight: 5,2Kg
Std. charge: 11,8A
Warm sag: 58,8V -> ~55,3V @ 40A ~25c
Cold sag: 58,8V -> ~46,9V @ 32A -10c
Now maybe i've overlooked something important here, but from what i can see the VTC6 will be slightly heavier and slightly more expensive, but other then that it will handle way higher both charge and discharge current, it sags less (significantly less in cold temp), and the capacity drop with cycle life does not appear to be an issue compared to the GA cell - at least not from the graph in specs.
On the other side I know the GA have been proven to be a very long lasting cells even when used at a high DoD and up to 3C discharge, and even though the specs don't claim it they appears to "settle down" after dropping to ~80% capacity. I don't know if any similar tests have been made on the VTC6?
However the GA do sag a bit under higher load, and i expect the sag to increase with the cycles even though the capacity drop settles, and i'm getting close-ish to the max current load.
Hopefully you guys can point me in the right direction here. I'm open for any feedback and recommendation, and just because i've been looking at these two cells does not mean you can't convince me to choose something else if it's a better option.