I have an electric bike with a 36V hub motor. I'm trying to make the lightest possible 36V battery pack with semi decent run time. (at least over 10 minutes continuous)
I already have a NiCD pack made of 30 5000mAh D cells, but its heavy. I charge it with the Robbe Infinity II which is an awesome charger and easily charges my 30 D cells from flat to full in around 2 hours.
The highest capacity NiCD C cell I can buy is a Sanyo 3000 mAH. NiCDs can be discharged at up to 10C and sometimes higher with hobby cells.
The highest capacity NiMH C cell I can buy is 5000 mAH.
But the prefered max discharge of NiMH is 2C - 3C.
The motor draws between 5 and 15 amps genrally. Somtimes it draws 15 amps for up to 60 seconds when going up steep hills. Occasionally it draws 20 amps when going up a monster hill, but not for long (about 10 seconds).
My question is can I use any normal 5000 mAH NiMH C cell for this application? Are some NiMHs better at high current draw than others? If so, which ones? In other words... will a constant 15A current draw severaly reduce capacity?
Its also strange that the best NiCD AA is 1000mAh and the best NiMH AA is 2300 mAh. However, the best NiCD C is 3000, but the best NiMH is only 5000mAH (not over 6000mAh)!!! The relationship is not linear! I suspect this is due to heat issues in the larger C cell but not sure. Can anyone throw some light on this too?
Thank you for any comments.
Sean
I already have a NiCD pack made of 30 5000mAh D cells, but its heavy. I charge it with the Robbe Infinity II which is an awesome charger and easily charges my 30 D cells from flat to full in around 2 hours.
The highest capacity NiCD C cell I can buy is a Sanyo 3000 mAH. NiCDs can be discharged at up to 10C and sometimes higher with hobby cells.
The highest capacity NiMH C cell I can buy is 5000 mAH.
But the prefered max discharge of NiMH is 2C - 3C.
The motor draws between 5 and 15 amps genrally. Somtimes it draws 15 amps for up to 60 seconds when going up steep hills. Occasionally it draws 20 amps when going up a monster hill, but not for long (about 10 seconds).
My question is can I use any normal 5000 mAH NiMH C cell for this application? Are some NiMHs better at high current draw than others? If so, which ones? In other words... will a constant 15A current draw severaly reduce capacity?
Its also strange that the best NiCD AA is 1000mAh and the best NiMH AA is 2300 mAh. However, the best NiCD C is 3000, but the best NiMH is only 5000mAH (not over 6000mAh)!!! The relationship is not linear! I suspect this is due to heat issues in the larger C cell but not sure. Can anyone throw some light on this too?
Thank you for any comments.
Sean
