Battery for Blade/Zero style MotoX trail ebike ?

[lesdit]

Hi,
I've been searching posts and so far coming up confused on a power source for my project.

The project: An electric bike similar to the Blade or Zero, that is a light weight ( < 160 lbs) off road bike powered
by Mars/Etek motor. I have a Sevcon controller for the brushless version of the Mars, although I may still use the
brushed version. I am basing the rolling chassis on a Sikk Trail bike which I got a good deal on last week. The Sikk trail bike looks like a beefed up mountain bike with a 125cc I.C. powering it.

I've read with interest the threads on 'ping' LifePo4 packs. So far as I can grasp, the Ping guy as well as his competitors are buying pouch cells from an unnamed Chinese factory and assembling them into packs with BMS for sale to the western world.
Would it be feasible to parallel two of the 20AH LifePo4 packs to power the offroad bike? I can program the controller to limit the current to a safe level, I believe. I'm hoping the sevcon software lets me specify a peak current that is a limited duration peak value as well, to allow bursts of higher amperage for a couple of seconds.

The nature of off road riding is different than road riding, it is much more 'spiky' in power usage. I do single track trail riding. Not racing. Most of the time would be low power, say 8 to 15 amps. Crossing a creek bed or negotiating a tricky part of a trail requires big bursts of power for 1 second or so to 'get out of trouble'. Those of you that ride off road know what I'm trying to say.

Anyhow, any advice is welcomed.
-Les

 

[Link]

Hmm...tough call. Ping's stuff isn't very high quality, you know.

But, if you do decide to go with them, I'd say you'd want to use three, actually, since his stuff is only rated for 3C peak (120A for two packs; 180A for three). If you could afford it, four (240A) would be even better.

Plus, that many packs in parallel would give you lots and lots of runtime.

 

[lesdit]

Two , if they gave me 120 amps peak, would probably be fine. Like I said, I'm not racing

Every day we learn more about the china batteries. Perhaps someone will figure out where to order the cells from directly.
Does Ping or others offer replacement cells if one goes south ? I'd order now if that was the case.
Has anyone looked for markings on the individual cells to indicate who made it?
Anyways, I'm a bit uncomfortable buying packs that are held together with ghetto duct tape!

Here is another idea I've been contemplating: Use a Maxwell super capacitor to provide the current peaks I need.
Just an idea. I know Hybrid car designers are looking at this as well.

-Les

 

[olaf-lampe]

The brushless Sevcon has two programmable current values, but I do not recommend ping's or other low C-rated pouches for that kind of use. The battery tabs are to fragile too. Go for thundersky for the though housing they have or look for the cylindrical cells from LiFeBatt, Yesa, headway or peakbattery.

The idea of using supercaps in parallel isn't bad, but there has to be a current limiting circuit between the LiFePos and the caps.
BTW, Wima also has a series of supercaps. I didn't compare them yet.

Good luck
Olaf

 

[dogman dan]

I have to agree, the lower c rate cells like Ping uses would be better if you carry enough of em. But higer c rate cells are best for the kind of use you want, where keeping the weight low will be worth the money. Since you will need so much fewer of the high rate cells you may come out cheaper in the end. With the PSI cells , you could go 48v 10 ah for about the same price as two 20 ah pings and have a lot more power at your fingertips. just a bit more money to go to 60 v would be well worth it. And weigh a whole lot less. On a heavier bike, more like a 250 dirtbike frame, you could carry 50 ah of the Hi Power cells easily. But if the weight is the issue, you need less power like a geared hubmotor, or higher discharge cells.

 

[fechter]

I think the Ping type batteries will just puff out and fail if you discharge them at the kind of rate you're going to want for an off road bike. They might be OK if you can load enough of them on board to get the C rate down to their rated value.

The PSI cells would probably come closer to handling the current. A123's would handle the current no problem, but they're hard to find and very expensive.

One thought I had was to use a fairly small A123 pack in parallel with something like a Ping pack. The A123 would handle the peak currents, while the other pack would supply most of the capacity. They should both be around the same voltage. You could possibly parallel them on a cell by cell basis to share the BMS.

 

[voicecoils]

One thought I had was to use a fairly small A123 pack in parallel with something like a Ping pack. The A123 would handle the peak currents, while the other pack would supply most of the capacity. They should both be around the same voltage. You could possibly parallel them on a cell by cell basis to share the BMS.

What's needed to pull off such a set up?

Take a simple case, say you want to have a 36v nominal system with 12 high discharge capable cells (A123) and 12 lower spec ones (Ping packs). In that case, wired in parallel, would the Ping pack be essentially charging the A123 pack? Would anything be needed between the packs to protect the Ping pack from getting fried from high discharge of the A123 pack?

I would have thought that the lower spec pack would need to be at a higher voltage to charge the other one...

 

[lesdit]

I like the A1213 pack to supplement the lower C rated ping pack idea. If I ran them as separate packs in parallel
the assumed voltage sag of the ping pack would 'automatically' defer the high current to the A123 pack, right ?

Is the cheapest source of A123 cells the tool power packs ? How many amps can a A123 cell provide safely ?
I wish there were some more test results for the ping type packs. How does it's internal resistance compare, I wonder?

I did some Google searches for " china lifepo4 battery " and came up with a few manufacturers in china offering some pretty
interesting cells for small EV uses. You have to order 100 or so to get started. They tease us.

 

[Jozzer]

TBH, the only cells I know of that can really stand this type of use are A123 and LifeBatt. Anything else and you will regret it further down the line I bet!

Steve

 

[pwbset]

TBH, the only cells I know of that can really stand this type of use are A123 and LifeBatt.

You can follow YPedal's current pack build with the PSI cells (which LifeBatt rebrands) here:

http://endless-sphere.com/forums/viewtopic.php?f=14&t=6028&start=0&st=0&sk=t&sd=a

 

[fechter]

I like the A1213 pack to supplement the lower C rated ping pack idea. If I ran them as separate packs in parallel
the assumed voltage sag of the ping pack would 'automatically' defer the high current to the A123 pack, right ?

Right, that's what I was thinking. The weaker pack (Ping) would sag more and automatically shift most of the current to the stronger pack during high discharge rates. You could still run into a problem during an extended high current drain where you could deplete the A123 pack before depleting the

 

[drewjet]

I think the A123 or Lifebatts/PSI are the only way to go. A bit more expensive but worth it in the long run. I used Sony VT's in mine and regret it. They were about half the price but are not up to the task.

You may want to rethink the Mars brushless as well. While it is an excelent motor, well built and a good amount of power. It lacks in low end torque. At least mine does on 72 volts paired up with a Kelly. I am geared for a top speed of about 50 MPH, so maybe by gearing for a lower top speed would boost your low end torque.

Great project. I look forward to seeing your progress.

 

[Ypedal]

PSI cells can be had from Raymond King at PSI

raymondking " at " url.com.tw

I asked why not @psi and he replied from his psi email, too much spam on that account and some replies sometimes get missed ( i have about 4 emails myself, so i can understand that lol)

I have not personally tested this yet, but Jozzer and AndyH on this forum have on CBA and in real life applications, and a 10ah cell will provide 100 amps. ie: 10C . For a 200 amp controller a 20ah pack would not be that heavy ( 360 grams per cell, 16 cell per 48v 10ah, 32 cells for 48v 20ah, so 32 x 360 = 11.52 kg )

This is just bare cells, so you need to box and build them , this adds weight, but you all know the drill on that.. :wink:

Edit to add : For those who need to know, PSI ships with UPS on small orders, consider it about 50 cells in one box, to not make it " heavyweight " .. ships by air, i got mine like 5 days after sending the money via TT ( money wire, no paypal for now ) To get a big boat load of these we would need to get a min. something like 5000 cells and a full load would be 20,000 cells !!!! ( yeah... :lol: that could be soooo cool ) at about 25 $ per cell, and about 175 $ for shipping + duties and brokerage ( + 323 $ on my order here in canada !! ), i got mine with the copper straps, nuts and bolts, but i want to assemble my own as you may have noticed.. If you wanted pre-built packs, i'm sure it's possible but you would have to ask Raymond.
8)

 

[lesdit]

I didn't know that there was much difference between the brushed and brushless motors. Isn't it pretty much a constant ft-lbs/amp type of ratio ?
On your bike, what kind of pep does it have at 100 amps ? I'm trying to get an idea of expected performance.

Also, my brushless Mars, it seems to me that the motor could be lightened up some by turning off some of the motor housing on a lathe. It seems a bit
over built to me. On the brushless there is nothing but air behind the outer motor case, maybe the case can be thinned to 1/16 inch thick. It would help in
your sprung weight setup too. BTW, does the kelly make noise ? I heard that it doesn't make sin waves for the fields, and that may be why it lacks low end power?
-Les

I think the A123 or Lifebatts/PSI are the only way to go. A bit more expensive but worth it in the long run. I used Sony VT's in mine and regret it. They were about half the price but are not up to the task.

You may want to rethink the Mars brushless as well. While it is an excelent motor, well built and a good amount of power. It lacks in low end torque. At least mine does on 72 volts paired up with a Kelly. I am geared for a top speed of about 50 MPH, so maybe by gearing for a lower top speed would boost your low end torque.

Great project. I look forward to seeing your progress.

 

[drewjet]

Going off my memory, the max amps I pulled was about 160. If I set the controller higher it would cut-out on acceleration. I would not see the 160 amps till about 10 MPH or so. As I said it may be in the controller design, and the sevcon may do better. I do not notice any noise comming from the controller. I went with the kelly as it allowed higher voltages.

Yes the Mars is built heavy, remember it was designed to be a floor burnisher motor not a EV motor. I don't think you would save that much weight putting it on a lathe and machining down, maybe a pound or 2 at the most.

If weight is your primary concern then I would suggest going to RC motors and Lipoly batteries. I bet you could drop 15 to 20 pounds, maybe more.

What are your performance objectives? Top Speed, acceleration, range, weight, etc.?

 

[lesdit]

Objectives for this bike are single track riding optimized. Max speed 30 mph. Good climbing. Less than 160 lbs or so. Should be able to lift front wheel by pulling handlebars while stationary.
I'd like to add removable 'emergency' pedals too, for getting out of a trail under human power if something fails. Also helps legalize it on certain trails I'd like to visit. " if the dude is pedaling then it must be some new fangled DH bike, you know, the dudes that dress like they are storm troopers from star wars,all that MX gear/protection... DH nuts" Pass off as one of them.
-Les

What are your performance objectives? Top Speed, acceleration, range, weight, etc.?