C rating Batteries

[renago]

I am working on my e-bike ,
got the motor Cry HT 3525 ,
got the controller 18 Fet Lyen .
bike is on the way .

which battery should I choose ???
which C rating and what kind of Ah should I allow ?
thinking to start with 10 AH
the use will be mainly off road ,
wheel 26 .

thanks for any support .

rgs Renago

 

[RC Extreme Power]

A lot of talk about batteries in the link below.

http://endless-sphere.com/forums/viewtopic.php?f=3&t=43449

Milton
milton@rcextremepower.com

 

[Ypedal]

needs more details.

your body weight.

how far do you plan to run

what voltage ( how fast do you want to go )

 

[dogman dan]

And more specific, what amps is your controller set to?

If it's more than 20 amps, then you don't want 2c lifepo4 for sure. 10 ah of A123's would get you into 50 amps with no problems expected. Discharging them at a mere 5c gets you 50 amps from a 10 ah pack. Ten ah of headways will work too, but they will be about maxed with 50 amps.

Once you get into lico, (RC lipo) then 20c stuff is quite adequate, but it should last longer, and will have better capacity if discharged more like 5c. If your wallet is fat, then go for huge c rates. If nothing else, they'll sag less allowing you to run them closer to 3.5v with less risk. Or just carry more than 10 ah, and never get close to 3.5v. Either way works fine with $$.

For off road, 10 ah will keep your ride short enough to lessen the risk of a melted motor. Especially if you limit yourself to about 3.7v minimum. 72v 10 ah is what I carry, 30c. I have some 20c, and you can tell the difference even though I discharge at only 4c.

 

[renago]

sorry guys , I missed some important info.
the voltage I think to run is 88 V
my weight is 88 kg
speed , well all depends from the terrain , but lets say 25 as average with peaks on 70 , very short .
and many parts between 10-20 km/ H
all off road , like enduro single track ,
I have 2 controllers one for 3000 W and another for 5000 W .
of course I understand that the bigger range , the bigger capacity I need .
but let's say I want range of 50km .
reading through the many interesting post it is rather difficult to understand the Wh/ km .
I got some indication around 11,25 Wh/km .
do you think this can be correct ?

Renago

 

[Ypedal]

generally speaking..

10 wh/km is going 30 kph pedaling lightly on level ground

20 wh/km you are going 50 to 60 kph on level ground, not pedaling. no wind

30 to 50 wh/km you are pushing most hub system to heating up and beyond that you need a temp probe and keep a carefull eye on your motor temps.

 

[arkmundi]

Ditto dogman on A123. You may want to consult my posts as I have a lot to say about them. FYI, I used this forum extensively for R&D before committing to a build, so you're on the right track. I suggest you continue asking these sorts of questions until you get a handle on what to do. There are lots of approaches, but I suggest that the A123 AMP20 cells are best. If there were another 'best' I would know, as I considered a full range of options.

For your situation, always start with motor->controller->voltage required for amps and watts required->cells in series required for the volts->cells in parallel needed for amp-hours for travel requirements (off-road, hills, weight, etc.). The motor will be rated & labeled. Start there. Good luck.

 

[renago]

as said most of things are already set .
I must take a decision on what kind of batteries to run.
the RC lipo are relative cheap , and offer the best ratio of power to Kg and volume.
the A123 , and Kokam are nice but , we have some big disadvantage :
power / volume per Kg of battery is lower then RC Lipo .
last but , not certain the cost .
I say not certain , because if we consider the long life of A123 , and Kokam , maybe in the final equation they might bee same or even cheaper then Lipo .
I mean W/$/Km .
in the immediate the RC are cheaper .
remember that the bike must stay as light as possible , and batteries must stay within the frame .
I do not want to carry 20kg of bulky batteries .

Renago

 

[Ypedal]

lipo is your only option !!! :wink:

smallest, lightest, and going off-road = crashing.. no sense in wrecking the most expensive cells available lol..

 

[arkmundi]

lipo is your only option !!! :wink: smallest, lightest, and going off-road = crashing.. no sense in wrecking the most expensive cells available lol..

A123 AMP20 are lipo and rock solid like a song. Am indifferent whether they are prismatic or 26650 format, just promoting the A123 route over other lipo. Nothing can beat nanophosphate LiFePO4 chemistry and A123 holds those patents. An assembled pack can allways be made crash proff for offroad use!

 

[Ypedal]

lifepo4, even in pouch form, are larger and heavier than RC lipo.. plain and simple.

 

[arkmundi]

lifepo4, even in pouch form, are larger and heavier than RC lipo.. plain and simple.

Yea, I'm not disputing that. My pack is way light, way cool. There are other things to consider besides weight. All considered, I'll never recommend anything but genuine A123.

 

[Ypedal]

genuine

.. hmpff.... might be genunie.. but back door, factory rejected QC cells ....

 

[renago]

let's say I want a 20 Ah pack .
keep it simple .
what kind of volume-size and money I need for A123 Vs RC Lipo ?

Renago

 

[renago]

forgot to say 88 V

 

[wesnewell]

Here's 24s2p (10ah 88.8V nominal) in my small triangle. pack with home made mounting system weighs 14 lbs. It;s roughly 5.5x5.5x7 inches. Could have been a shade smaller not using hardcase packs. Cost was ~$300 shipped.