e-Bike batteries using Panasonic 18650 cells ... any good ?

[daniel.weck]

9Ah or 11Ah, 2.3kg ... any thoughts on using 18650 cylindrical cells ?

 

[daniel.weck]

 

[daniel.weck]

Panasonic NCR18650 or CGR18650E, 2900mAh Lithium-Ion 18650

Diameter : 18.25mm
Height : 65.0mm
Weight : 46g or 44g

Charge Method: Constant Current and Constant Voltage(4.2V)
Nominal Voltage : 3.7 V
Max. Charge Current : 1CmA(2900mA or 2600mA)
Max. Disharge Current : 2CmA(5800mA or 5200mA)
Discharge Temperature : -20°C ~ +60°C
Energy Density : 233Wh/kg or 219Wh/kg
Charging Time : 3hrs(Standard) or 2.5hrs(Rapid)
MADE IN JAPAN

 

[NRG]

This discharge rating is a negative for me but otherwise OK

 

[onmebike]

This discharge rating is a negative for me but otherwise OK

Doesn't the discharge rate multiply depending on how many cell's in parallel?

 

[NRG]

No, its still 2C, however, the current delivery will improve when more cells are paralleled up, in this case 2 in parallel will deliver 11.6 Amp, 3 = 17.4Amp etc at max discharge rate....however, its much better for the life of the cell if it can support higher discharge rates IE 20~30C = less stress on the cell and the Ri is lower so the voltage holds up better under high discharge.

 

[daniel.weck]

the Ri is lower so the voltage holds up better under high discharge.

Right, I'd like to see the voltage drop for a typical 36V 10Ah battery under a 10A current draw.

 

[NRG]

Can't help there Dan but it's well known, here's a link to an old page on batt uni, best I can do at this time of night plus I can't be bothered...have a search around the many threads on ES it's been discussed many times there...

Internal battery resistance

 

[onmebike]

No, its still 2C, however, the current delivery will improve when more cells are paralleled up, in this case 2 in parallel will deliver 11.6 Amp, 3 = 17.4Amp etc at max discharge rate....however, its much better for the life of the cell if it can support higher discharge rates IE 20~30C = less stress on the cell and the Ri is lower so the voltage holds up better under high discharge.

Lets see if I understand this correctly 1 x 3000mah cell rated at 2c = 6ah?
Four of the same cells in paralell would be 4 x 3000 = 12000mah so if still at 2c equate's to 24ah? The capacity multiply's but the c rating doesn't. Is that correct.

 

[daniel.weck]

Can't help there Dan but it's well known, here's a link to an old page on batt uni, best I can do at this time of night plus I can't be bothered...have a search around the many threads on ES it's been discussed many times there...

Internal battery resistance

Oh I know. Sorry I wasn't very clear, I actually meant that I'd like to see the voltage drop for this particular type (and brand) of cell

 

[daniel.weck]

Lets see if I understand this correctly 1 x 3000mah cell rated at 2c = 6ah?
Four of the same cells in paralell would be 4 x 3000 = 12000mah so if still at 2c equate's to 24ah? The capacity multiply's but the c rating doesn't. Is that correct.

This sounds about right

 

[onmebike]

This sounds about right

How many amps is a 36v 250w ebike going to draw at most?

 

[daniel.weck]

How many amps is a 36v 250w ebike going to draw at most?

It depends on your battery, controller, and motor. For example, my motor could theoretically draw more amps than 10A continuous, but in practice the controller has a current limiter, so the observed peak (using Cycle Analyst) is about 10A (actually the CA registers 15A because of the spike created by the condenser when connecting the battery).

 

[NRG]

This sounds about right

Actually that's not correct

A 2C 3Ah cell is still a 3Ah cell It means the cell can deliver 3amps for 1 hour or a maximum of 6amps for half an hour.

Four of the cells in parallel makes a 12Ah battery with a 2C rating. It does not make a 24 Ah battery.

 

[NRG]

How many amps is a 36v 250w ebike going to draw at most?

With hub motors in mind......

Something in the region of 20+ amps IE the Ezee Torq although the majority will be less.

My first kit for the Peugeot had a 30 amp controller (it was a 24v motor) which I modified to increase this to 33~35amp, if this current draw is required then the battery obviously needs the Ah to be high for range but it also must be able to do better than 2C for best life and performance.

There's probably no need for much above 3C in all honesty for a legal spec Euro e-bike but having better cells makes for a better performance and riding experience.

 

[onmebike]

Actually that's not correct

A 2C 3Ah cell is still a 3Ah cell It means the cell can deliver 3amps for 1 hour or a maximum of 6amps for half an hour.

Four of the cells in parallel makes a 12Ah battery with a 2C rating. It does not make a 24 Ah battery.

I know it doesn't make it a 24ah battery but the 2c rating means its max discharge rate is 24ah. Is that right?

 

[daniel.weck]

Four of the 3Ah cells in parallel makes a 12Ah battery with a 2C rating. It does not make a 24 Ah battery.

Isn't that exactly what he said ?

"
Lets see if I understand this correctly 1 x 3000mah cell rated at 2c = 6ah?
Four of the same cells in paralell would be 4 x 3000 = 12000mah so if still at 2c equate's to 24ah? The capacity multiply's but the c rating doesn't. Is that correct.
"

 

[NRG]

I know it doesn't make it a 24ah battery but the 2c rating means its max discharge rate is 24ah. Is that right?

Ah is the capacity not the discharge rate or current...so the discharge current is 24 amps

 

[daniel.weck]

Ah is the capacity not the discharge rate or current...so the discharge current is 24 amps

Oh sorry, I mis-read A vs Ah !