C discharge rate

[renago]

next week I will finally have almost all components for my first e-bike .
BUT......
I am very unsure on which batteries :|
the bike will be used for fun , 90% off road , single track , on hills.
motor Cry ht 3525 .
Lyen controller, 18 fet .
I was thinking to have aprox 15-20 Ah of capacity
which battery shall I use ????

the dilemma is between RC Lipo , which C rate ?
is 20-30 enough or shall I go higher ?
and A123 20amp HD-A , will they give me the right kick when I need it with just 3C ?

any suggestion is very much apprecieted

Renago

 

[migueralliart]

Range ?

 

[wesnewell]

To determine what C rate you need, find the max amp draw of your controller. Now divide it by the AH of the battery capacity you plan to get. Example:
40A controller with 5ah battery; 40/5=8C battery
40A controller with 10ah battery; 40/10=4C battery
40A controller with 20ah battery; 40/20=2C battery
AH times C rate gives max amp output.
So 20ah of 20C rated baatery can provide a 400A output.

 

[renago]

ok, this is clear , but which type of battery would you choose , Rc lipo , or A123 ?

renago

 

[dogman dan]

For that kind of ride, I've been very happy with 20-30c turnigy lipo. 20 c zippy hasn't been near as tough. Definitely more sag with zippy that low c rate.

If you have the coin, go for as much c rate as you can afford. I have found carrying more than 10 ah of 72v just leads to too long a ride that melts the motor.

So 10 ah carried. Come back, let it cool, then slap on more or wait for a recharge. Charge and cooldown about the same time if you have a decent charger. (300w or more)

 

[renago]

having a capacity of 15Ah , doest mean I must ride full throttle all the time .
in most cases the track is difficult so the average speed in motorcycle is only 25km/h .
in some point we speed up till 80km/h , but this is very short .
mainly I need the power to make some short acceleration, or climb steep and rough tracks .
heating up , I hope won't be a problem , otherwise I will install a water cooling system .
of course the higher capacity will stretch my range , hope to reach 70-80km , hope .

so you guys will suggest a 30 C discharge rate .

but no one answered about A123 or RC Lipo ???
no one is using A123 since the chinese have saved the company ?

Renago

 

[Hillhater]

having a capacity of 15Ah ,
....in some point we speed up till 80km/h , but this is very short .
.... I need the power to make some short acceleration, or climb steep and rough tracks .
...... my range , hope to reach 70-80km , hope .
.
Renago

I fear your combination of expectations is a little optimistic !
Steep climbs on rough tracks is not suited to a hub motor configured for 80km/hr road speed.
80km range will need more than 15Ahr !

 

[cal3thousand]

A123 is going to be difficult to get the C-rating that is available in RC LiPo

Interestingly enough, I am making a very similar setup:

Norco VPS
HT3525
18FET Lyen 4110

Battery: 24S2P RC LiPo - 8 x 20C 6S 5000mAh Turnigy. Which should allow me to do 20C * 10Ah = 200A at 100V. Which is 20kW... way more than my controller / motor will handle.

So based on the size packs that we are making with these RC LiPos, even 20C is plenty POWERFUL.

 

[The Mighty Volt]

ok, this is clear , but which type of battery would you choose , Rc lipo , or A123 ?

renago

A123, for me.

But its like asking how long is a piece of string.

Do you have a tab welder? Can you solder? Do you know about LiPo and associated risks and precautions?

 

[dogman dan]

If cellman was still in supply of round cells, an a123 pack would be a fantastic idea. There is a pretty good looking used pack for sale at the moment, in the USA.

But for trail riding, I wouldn't want to pack the weight of a 20 ah a123 pack over 36v.

Don't listen to me, I have no experience with dirt riding, or hubmotors. :wink: Go melt your motor, it's fun!

I live in a hot climate, it's true, but half the motors I melted have been done in winter. When I say hill dirt riding, It's a rocky mountans hill. So I can melt a motor in 40 min anyday I choose to. I just found that with a 10 ah 72v size limit, still a hefty 700wh, I tend to head for home just before I melt one down.

Much much much more importantly, the dirt bike doesn't handle for shit because I carry 20 pounds of battery.

 

[renago]

I think I'll go for the LIPO , at least on my first bike.

there is also a second in the pipe line , with a central motor.

the experience on the first one will a good learning curve .

Renago

 

[cal3thousand]

I think I'll go for the LIPO , at least on my first bike.

there is also a second in the pipe line , with a central motor.

the experience on the first one will a good learning curve .

Renago

Remember that LiPo is a Lifestyle. You probably won't go back, and it requires that you take your batteries seriously. Attention to detail is requisite