George S.
Well-Known Member
Ebike Batteries in Perspective
Five years ago, when I was going to buy my first ebike, the battery was a limiting factor. Basically, a 36 volt and 8 Amp Hour battery retailed for $700 or so. We now see mostly 48v batteries, even in the low end stuff, and 12 AH is pretty standard. In the replacement market or on Ebay, a 48v/12AH battery is maybe $300 to $500.The battery for a Rad Mini, with that configuration, runs $400 right now. Summing up, the batteries cost half as much and hold twice as much power.
Looking back 5 years, $400 is arguably a good deal for an ebike. How long should a pack last? True cost is more than upfront cost. Consider the life of a battery pack. A few vendors are using the Samsung 35e cells. There are maybe 50 cells in a pack, the standard 18650 cell. Vendors increasingly use Samsung, Panasonic, and LG, the big names. For $400, what might you expect from the pack?
This is a cycle life curve, but given in terms of the capacity of the battery. Every time you charge and discharge, the battery holds a bit less. An industry standard is the cycles to get to 80% of original capacity. The cell is rated for 3400 mAh for the first few cycles. It drops a bit to 3000 mAh within the first 150 cycles, and slowly droops to 2700 mAh, after 500 cycles. If there are 4 parallel sets in a 48v battery, you get 4x the 3400 mAh to start. That is 13.6 Amp hours, times the 48v, for 650 watt hours. But after 500 cycles the capacity is down to 518 watt hours. It’s good to start with more capacity than you need.
If you could get 500 cycles out of a 400 dollar battery, the cost ‘per ride’ would be something like 80 cents a ride. If you were commuting to work, 5 days a week, the cost over a year would be around $200. If you charged to 90% and kept the battery from going to 0%, you might double the cycle life. But after 500 cycles, you might just want to new battery or a new bike or whatever.
If they simply set the battery capacity to 90% of the total capacity, and set the charger to this rating, the cycle life would be very high, pushing 1000 cycles. But there would be less capacity over time, and 90% is less capacity to begin. You can see where making a bigger battery, but charging less, is a trade-off. Battery pack prices are low enough that most people won’t chase a few cents a day.
One of the surprises in ebike battery packs is how quickly the higher capacity cells peaked out. A few years ago, the Sanyo GA was a super cell, with a lot of capacity. Today the Samsung 35e has only marginally better capacity, and both the GA and SE seem to lose capacity fairly quickly. Old cells, like the Samsung 22P, continue to find favor.
If someone is on a budget, they should follow Micah Toll and Jehu Garcia. There are ways to get a basic ebike battery for $100, but it requires some research, maybe patience.
The net effect of cheap batteries is that people can also put a cheaper battery in a small motorcycle type vehicle. That may require 2 or 3 kWh of power, but it’s not going to cost much more than the small ebike battery of 5 years ago. That makes the motorcycle or scooter more of a focus. Toll bought a small CSC motorcycle for around $2800. It supposedly goes 45 mph, a true city commuter speed. Be interesting to see how it works out, since anything under $3,000 is an ebike kind of price.
Five years ago, when I was going to buy my first ebike, the battery was a limiting factor. Basically, a 36 volt and 8 Amp Hour battery retailed for $700 or so. We now see mostly 48v batteries, even in the low end stuff, and 12 AH is pretty standard. In the replacement market or on Ebay, a 48v/12AH battery is maybe $300 to $500.The battery for a Rad Mini, with that configuration, runs $400 right now. Summing up, the batteries cost half as much and hold twice as much power.
Looking back 5 years, $400 is arguably a good deal for an ebike. How long should a pack last? True cost is more than upfront cost. Consider the life of a battery pack. A few vendors are using the Samsung 35e cells. There are maybe 50 cells in a pack, the standard 18650 cell. Vendors increasingly use Samsung, Panasonic, and LG, the big names. For $400, what might you expect from the pack?
This is a cycle life curve, but given in terms of the capacity of the battery. Every time you charge and discharge, the battery holds a bit less. An industry standard is the cycles to get to 80% of original capacity. The cell is rated for 3400 mAh for the first few cycles. It drops a bit to 3000 mAh within the first 150 cycles, and slowly droops to 2700 mAh, after 500 cycles. If there are 4 parallel sets in a 48v battery, you get 4x the 3400 mAh to start. That is 13.6 Amp hours, times the 48v, for 650 watt hours. But after 500 cycles the capacity is down to 518 watt hours. It’s good to start with more capacity than you need.
If you could get 500 cycles out of a 400 dollar battery, the cost ‘per ride’ would be something like 80 cents a ride. If you were commuting to work, 5 days a week, the cost over a year would be around $200. If you charged to 90% and kept the battery from going to 0%, you might double the cycle life. But after 500 cycles, you might just want to new battery or a new bike or whatever.
If they simply set the battery capacity to 90% of the total capacity, and set the charger to this rating, the cycle life would be very high, pushing 1000 cycles. But there would be less capacity over time, and 90% is less capacity to begin. You can see where making a bigger battery, but charging less, is a trade-off. Battery pack prices are low enough that most people won’t chase a few cents a day.
One of the surprises in ebike battery packs is how quickly the higher capacity cells peaked out. A few years ago, the Sanyo GA was a super cell, with a lot of capacity. Today the Samsung 35e has only marginally better capacity, and both the GA and SE seem to lose capacity fairly quickly. Old cells, like the Samsung 22P, continue to find favor.
If someone is on a budget, they should follow Micah Toll and Jehu Garcia. There are ways to get a basic ebike battery for $100, but it requires some research, maybe patience.
The net effect of cheap batteries is that people can also put a cheaper battery in a small motorcycle type vehicle. That may require 2 or 3 kWh of power, but it’s not going to cost much more than the small ebike battery of 5 years ago. That makes the motorcycle or scooter more of a focus. Toll bought a small CSC motorcycle for around $2800. It supposedly goes 45 mph, a true city commuter speed. Be interesting to see how it works out, since anything under $3,000 is an ebike kind of price.
