Which Battery? 60V 10Ah, or 60V 15Ah, 72V 10 or 15Ah LiFePO4

[broloch]

In a hypothetical situation, let's say that you saved up about $1000 to put in your ebike. This money allows you to choose a LiFePO4 battery.

Whatever money you don't use from the $1000, you can put back into savings, pay bills, or buy other parts (e.g. disk brakes, etc.)

Let's say that for the sake of argument you are running a Crystalyte 408 motor, and can buy either:

1) 60V 10Ah LiFePO4 battery, $550, 13lbs., range around 18-20 miles, top speed 27 mph, $0.91/Watt
2) 60V 15Ah LiFePO4 battery, $750, 20lbs., range around 28-31 miles, top speed 27 mph, $0.83/Watt
3) 72V 10Ah LiFePO4 battery, $730, 16lbs., range around 22-25 miles, top speed 32 mph, $1.01/Watt
4) 72V 15Ah LiFePO4 battery, $900, 24lbs., range around 33-38 miles, top speed 32 mph, $0.83/Watt
5) Screw the battery, buying beer and lobster instead, see ya!

Which would you choose if given these options?

 

[vanilla ice]

I vote 2 or 5..

 

[broloch]

Cool. Thanks for posting. What are your reasons for choosing 2?

 

[vanilla ice]

Because $200 more for +50% compared with the 60v10ah. Also, it is lot of money to spend at once even for the 60v, $250 budget left for other parts is a decent chunk of change. To me 60 is already high V, and you could add a few cells to bump to 72 later if you feel the need.

Mebbe more important to your choice than $/Wh is what do you need your bike to do? What kind of batteries are we talking about here? What is your setup?

 

[biohazardman]

My personal experience with upping the voltage and having the extra speed available is that it will be used. Thus, overall distance will likely be the same or slightly less with higher voltage do to higher average speed traveled. Depending on the way, you mount the batts the extra bulk and 4lbs of the 72V might be more negative than you think a plus for 60V. Sixty volts might be more kind to your motor and bike but that depends allot on how you ride. If you want the extra speed then that’s a plus for the 72V. More AH on the other hand will get you farther down road so the 15AH is a sure bet no matter the voltage. Lots of variables not spoken of yet, terrain, heat range, type of bike, your physical health ect... I would go with 15AH no matter what but as far as the 60 or 72V, I would weigh the pros and cons mentioned and go from there.

 

[dogman dan]

Ever thought of dumping the 408? I don't know what your battery situation is, but tourqe will increase by switching to a 9c, and speed could be improved by using the faster wound version. Just seems like you want to throw a lot of current at an old school motor when similar results might be had at 48v with a different motor

Back to the batteries, I wouldn't opt for any 10 ah battery if it used 2c cells. 15 minimum so you have 30 amps avaliable without exceeding 2c discharge.

 

[broloch]

I haven't thought about dropping the 408. Tell me more about the 9c's.

Will I have to make new torque arms? Can they accommodate torque arms in the same way as the Crystalyte? Thanks.

How do they behave differently? Are they more like a 53xx motor? hence they use more Amps? Unaware.

 

[broloch]

With the added torque and higher speed, would the 9Continent have dramatically shorter range since it uses more power?

Or does it use more power, but not really that much because it is more efficient? How much more efficient is it compared to the X4's or X5's?

 

[dogman dan]

The 9c motors have a larger diameter which gives the motor more leverage mechanically, much like the x5 motors do. But the magnets are not as wide so the motor is not the power hungry monster that the x5 can be. So a faster wound version of the 9c motor would have similar tourqe and speed to your 408, without having to up the voltage quite so much. Range difference will depend on speed, since going 25 mph is a lot more costly than 20, and 30 and above gets really costly as wind resistance increases so much with every mph added. But ridden at the same speed you go now, the 9c will get at least as good range, but with better hill climbing and off the stop sign performance.

I don't know what you are lookin for with above 48v voltage, top speed or tourqe. But both could be improved by changing motors without increasing voltage. A standard 9c 9x7 motor would have similar speed, but better tourqe. For more speed, a faster version may be avaliable that would get you at least 5 mph more speed without being slow off the line.

Another approach would be an aotema motor, which goes about 29 mph on 48v. This is a sensorless motor so it would need a new controller too. The whole kit is $300 shipped right now.

The point I'm trying to make is, your 408 is wound for a certain specification, 36v goes 20 mph, to meet a legal requirement. It's not exactly the choice of motor for wanting to go 32 mph. Start with a motor that goes 25 mph on 36v, and then you don't need 72v to go a bit faster, 48v will be fine. This is for normal street riding, hills about 8% max, etc.

For serious hills, or dirt trails , halfpipes, skateboard parks, or hauling heavy loads, then more volts on a slower motor may be exactly the right approach. Don't get me wrong, you'll love how the 408 acts at 72v. But it might be a more expensive way to get to 30 mph than changing a motor for $250-300.

Edit, the same tourqe arms should work, that you have on the 408. If your motor is a rear hub, then the aotema is a front only, and more avaliablity is there on a front 9c than on rear.

 

[broloch]

I see what you're saying.

I was looking at the ebikes website and they don't have a lot in the rear wheels.

Should I opt for the 2805 and get it rebuilt, or the 2806?

I am really after a higher top speed.

I am currently running around 70V, around 31mph top speed. It's not that I use that, but would like to have it available in case I really need to go faster because I am late, etc. I don't mean that much faster either, but just a tad bit faster than cruising. e.g. going 28mph for a while, then drop to 23mph, then ramp it up to 26mph, etc...

I do intend to pedal upto speed, so torque isn't so much an issue, but I wouldn't mind having that.

I am currently running a small pack, NiMH, it's very weak...probably 2.8Ah, and it is being hammered. I am using an Infineon controller, that can probably take 85V nominal, but it's 25A.

Is the 25A controller gonna be a problem? Or is 35A needed for the controller?

So, what you're leaning towards me getting is a 48V20Ah LiFePO4, with a 9C motor, or something to that effect?

 

[dogman dan]

Well, if you want more than 30mph, you will need more than 48v. So get the motor that goes the speed you like at 60v.

Back to the battery, you could get the 60v 15 ah, and assuming it's at least 2c cells, you'd have plenty of amps for a 25 amp controller. But it would be a bit heavy, maybe 25 pounds? so carrying on a rear rack would handle like a 36v sla pack. If the cells are 3c or better, then you could get the 10 ah pack.

Personally, 30mph is plenty fast for me, I do that all the time on the downhill commute in the morning. So for that, a slightly faster motor and 48v is all it takes. Cops ignore me on my ebike, but they might take notice if I start going 35 mph all the time on flat ground. In my state the speed limit is 25 mph for mopeds or ebikes. Off road, I'd love a 45 mph bike

 

[broloch]

I'm sure that if I wanted 31mph, that I would also be happy if I had 30mph or 29mph as top speed.

Even if I went with a 9c 48V, I am sure that there would be no complaints.

The batteries would be 2C (Ping), but I have also been looking at Headways. So 15Ah would be best in this case over 10Ah.

48V 20Ah would be about 960 Watts, which is a bit bigger than even the 60V 15Ah pack.

It would be about $300 for the 9C 2805 rebuilt into a 26" wheel. Would it be worth it to pick up a 35A controller (+120) 48V max, or keep the 25A, maxing at 80-90V?
Then it would be an additional $600 for the batteries.

Could the Infineon 35A controller be modified to take on more voltage? e.g.. change out FETS, caps, and resistors?

 

[vanilla ice]

Didn't Y have a 40x on hi volts that he said performed really well? I remember seeing a vid of him and a neighbor flying up a hill with a hi-volt 40x racing a mid-volt 5xxx and they were neck and neck..

 

[broloch]

At around 70V my 408 isn't bad. It's just that the batteries are terrible that I have now, around 2.8Ah, and 70V...not really going to cut it.

The top speed keeps dropping as I ride. About 30 minutes of riding, the bike starts to drop from 50km/h top speed to about 20km/h

 

[GCinDC]

i had a 48V500 watt GM motor connected to the battery w/ household electrical cord, not sure the guage, probably 14awg. My top speed was ~33mph @ 80V (lipos).

when the gm rim broke, i got a 9C, and replaced the electrical cord with 10 guage wire and my top speed jumped to 40mph!

i'd thought that my max amps with my controller were 26, also and infineon. but with the new wires, max continuous amps were 35A...

another thing to think about. i've heard they should be as short as possible too.

 

[broloch]

nah...40mph...that's still too slow for me /jk

so it was that big a change with the 9C huh? which 9C do you have? 2805? 2806? 10x9 9x7 How does this nomenclature relate to another?

How fast would the estimated top speed be approximately for a 180lbs riding, flats, LiFePO4, 35A controller infineon, at 48V?

1) 2805 - 30mph
2) 2806 - 29mph
3) 2807 - 27mph
4) 2808 - 25mph?

Something like this? What do you think?

How about running one of them 48V 20Ah Pings with this set-up? Good? Would a 48V 15Ah Ping get 30mph for a 2805?

 

[Russell]

You can use the simulator at ebikes.ca to compare different combinations.

http://www.ebikes.ca/simulator/

However to estimate the top speed for each combination you need to know how much power is required to reach those speeds which is where a bike power calculator comes in handy.

Here is the simplest one;

http://bikecalculator.com/wattsUS.html

and two more good ones;

http://www.mne.psu.edu/lamancusa/ProdDiss/Bicycle/BIKEcalc1.HTM

http://www.noping.net/english/

-R

 

[John in CR]

I think you'll have more flexibility in the long run with multiples of 24v or 36v instead of 30v (like you would have at 60V). Talk Ping into selling you 2 36v15ah packs to be connected in series protected by diodes. That will also give you more mounting freedom than one big 72v pack. I ran 2 36v15ah Ping V1's in series for 6 months without issue before I decided I needed more power.

 

[dogman dan]

I have the 9x7 --- 2807 motor. It's speed is most likely very similar to your 408. Estimating actuall vehicle speed from the simulator is either a complicated, or inexact thing. The easy way would be take a motor you know, like your 408, and enter it's data. Then look at the peak speed, and your actual speed. That should give you a ballpark number to subtract from the peak speeds on the simulator for other setups, if they were put on your bike, with you on it.

I have no direct experience with other windings of 9c motors, but I'm reasonably sure that others get 30 mph out of the 2806 motor at 48v in a 26 inch wheel.
The 2805 might be a bit sluggish on starts and hills at 48v in a 26" wheel. But 35 amps of 72v would likely cure that.

It does begin to look though, like what you want isn't going to be gotten for $1000. More like $1500 for 72v 35 amps, and a new motor. It's a dilemma, last year I bought a 5304, wanting to put 48v 35 amps to it. But even affording that has been hard. I should have gotten a rear 9x7 9c, but mabye someday I'll have the money to build a small motorcycle with it.

But for a thou, you could get a decent 48v headway 10 ah pack and a 2806, giving you good tourqe and 30 mph now, and later a few more cells, a new bms, and a different charger gets you to 72v. mabye next year. You'd have around 8-10 miles of range at 30 mph I guesstimate.

Another approach would be to just go for the 72v battery you can afford now, and upgrading the motor later would be easy enough at $250. When I started this whole aspect of the discussion, I just wanted you to know that 30 mph is cheaper when you start with a slightly faster wound motor. 40 mph is exponentially more expensive. On the street, it could also be an exponentially more expensive ticket going 40. Depends on the cops, and how you ride whether you get ticketed.

Personally, I think a 48v 20 ah ping and a 2806 would be plenty fast, and the ping in that size would handle a 35 amp controller. With a 22 amp controller, the 48v 15 ah would be fine. I think you'd see 30 mph on the flats even with lower amps, just slower up hils. One thing about the battery upgrade, is you will gain a mph or so without the voltage sag of a smaller battery.

 

[broloch]

Yeah, I just assumed it would have been an easy calculation that someone knew the formula for.

For myself, weight, wheel size, etc... and the 408, I just used the simple formula speed(in km)=Volt x 0.72

e.g. 72V would give around 51km/h

And so far that has been verified by GPS.
So I was thinking of something similar with the 2806...e.g. 48V and 35A would be about Volts x 1.15 or something like that.

 

[broloch]

I would like to keep at 30mph, 40mph would be nice, but that is approaching motorcycle speeds.

I would like to upgrade the battery ASAP since the range that I am getting isn't good at all, and the voltage sag is really bad with my small battery pack.

I may have to hold off on the 9C for now. Put the funds into the battery, then upgrade to a 2806 later.

48V20Ah will get me only about 21mph on my 408
60V15Ah would be more acceptable for my 408
72V15Ah would be ideal, but expensive for the battery. 36V x 2 as suggested was a good idea.

 

[1of3]

#2,
helmet, steak & shrimp, beer, dollar bills (entertainment)

 

[The Mighty Volt]

From my own experience cycling, it requires less energy to get up a hill in a higher gear if you hit the hill at speed and maintain cadence than if you hit the hill at a low speed, gear down, and then knee-chin all the way up the hill spinning the pedals like a lunatic for every quarter turn of the wheel.

72v 10Ah may have more range than 60v 10Ah, if you look at it in those terms.

Accelerate, then maintain a more economical throttle until the hill is climbed, using the initial speed you hit the hill at to give you momentum.