I need help building a Lithium battery for my E-Bike

[Kingcodez]

So 15S9P will get me to 48v, 20.7AH?
I need 15*9, 135 a123 cells? Damn that's like 2 grand.
Every 2.3 AH @ 48v costs $135 (using $15 as a base figure)

Are the headway and umm ping battery packs using a123 cells, or some other cell?
How do the cheaper cells (Chinese?) compare to a123?
Other than build quality. I don't care too much about size, as I have a whole bay, and seat thing to work with. Nor weight, I just need it to go a little bit further than it does now. $2k is a lot considering the bike cost me $250 lol.

 

[Icewrench]

Headway Ping and 123 are all different cells.
Most common headway is a 10 ah cell. @ $ 17 each
Most common 123 is a 2.3 ah cell. @ $ 8 each
Ping sells assembled packs with bms and charger.
Make it easy on yourself and buy a ping 48 volt 20 amp hour pack and go ride.

 

[julesa]

He's got a scooter. I would want a lot more than 20AH in a scooter, because I'd want 60kph+ top speed, I'd want more than 60km range, and I live in a hilly area, so probably more than 40Ah. I wouldn't be looking for drag racing performance, so I would probably buy the inexpensive Thundersky cells and just pack as many amp-hours in there as I had room for in the battery compartment.

I just re-read his first post. He would like to go 40km with a 50km/h top speed, I think he's gonna need more than 20Ah. Might do it with 30Ah, depending on average speed, hilliness of terrain, etc.

Kingcodez,
Top quality cells like A123 are good if you want lots of power but don't need much range (think drag racing). Cheaper cells can't put out as much power as A123, so to get the same power, you need more amp-hours. But you need lots of amp-hours anyway. So you can go with cheaper cells, no problem.

If you consider yourself fairly technically capable, own a multimeter and a soldering iron, then a good option might building your own pack out of Headway or Thundersky cells (Thunderskys are cheaper, but should work well if you have 30 or 40 amp-hours). Headway cells are more expensive, but can put out more power. A123 are probably more than you need.

Another good option might be to measure all the dimensions of the battery box on your scooter, contact Li Ping at pingping227@hotmail.com (http://www.pingbattery.com) and ask him to make a custom sized 48V battery pack for you. Ask him how many amp-hours he can fit in that space, and how much he would charge to build it for you. The cell quality of his batteries seems to be in between Thundersky and Headway from what I've read.

 

[morph999]

Kingcodez, why don't you get 12 or 16 of these cells.

http://www.evcomponents.com/ProductDetails.asp?ProductCode=TS%2DLFP40AHA

give you either 36v40ah or 48v40ah.... 40ah will get you probably 50 - 60 miles.

for 36v40ah it will cost about $530.

Get some anderson connectors and a few lifepo4 chargers from batteryspace.com and you'll be set.

 

[Kingcodez]

yeahYeah I saw those. What the heck are they?
Are they simply a lifepo pack in q ruggedized shell? On there it says they are lifeypo4.
Do I still need a BMS for those ? On a diff site it said I did and then told me to buy a $700 Bms.
that is definately way in my price range.

 

[julesa]

Yes, those are prismatic LiFePO4 cells, inside a plastic case. If you're in Beijing, you certainly don't want to buy the batteries from an American company that already paid to ship them from China, and pay to ship them back across the water again. If you don't want to ask Headway or Ping to build a custom, integrated pack/BMS solution for you, I'd start looking for a source of Thundersky LiFePO4 cells near you. Maybe the manufacturer can recommend a dealer, if they won't sell them to you directly. I think this is their web site:
http://www.thunder-sky.com/contactus_en.asp

Yes, you'll need a BMS, but you can get one for a lot less than $750. There's a very high quality BMS available pre-built from here for less than $200 US:
http://www.rechargeablelithiumpower.com/
Or in kit form here for about $120 including parts purchased separately:
http://www.tppacks.com/products.asp?cat=26

I don't know of a higher quality BMS available for less money.

 

[morph999]

Here is what they are and what they look like when put in a series which is what you would be doing. (this is about 144v so your battery would not be near this big...this is for a car)

You could charge them individually and do without a BMS but it would take longer to charge. A BMS would be almost as much as it would for 2 or 3 chargers that you would need to do that.

 

[Kingcodez]

Wow that's huge, thanks for the pic, helps a lot.

I think I'll go with these, they seem to be more plug n play.
What voltage are these packs rated at?
I mean, I know they swing from 2.7-4v, but what figure do I use for building, are these 3.3v also?
When I build my pack, what baseline voltage should I go for, should I build exactly the number of cells to get to 48v?
Or 51.3, 54.6, ect.

If I use the baseline figure, for 48v, I need X cells, and when X cells are charged, their fully charged voltage will be in the 50's, maby 60's for voltage? (I'm trying to figure out that the meter on my bike will say) and I will be 'out of juice' when the batteries hit like 2.8v a cell * 15 packs? (so lets just say 42 volts, which is the same as my current SLAs Die at). I just wanna visualize what the E and the F numbers would look like on my 'fuel guage'.


Also another question, can I use capacitors/super caps, with my current SLA setup, to make stuff more responsive? So I can minimize the super slow acceleration when I'm loaded down?
I found out that: I weigh 90kg, my girlfriend weighs less than 45kg, and my bike is about 100kg lol. So 235kg. That's not including when we go out and buy tons of junk. And when my bike is down to half battery, and I have to make a hard start, it's tough, plus the cold here in beijing. Sucks.

And, with these prismatic cells, say after 200 -300 cycles (a year for me), I get hit in the face with a gold brick, and decide to buy 3-4 or so more cells, to make a 60 volt system, can I just wire them in, since the 'old' cells aren't that old? These things seem a lot more modular/versatile than loose cells. I plan to get a good BMS also, I'm not going to spend a ton of money on batteries, and then cheap out on a crappy charger.

 

[morph999]

I don't have any experience with BMS but the suggested charge on these thundersky or any lifepo4 cells for that matter is between 3.6v- 3.8v. That's the sweet spot. The technical cut off is at 4.25v but they save never to charge over 4.2v. Well, if you are going to use a BMS, I think the lvc is usually around 2.5v per cell so if you have 12cells (36v) then the lvc on the BMS would be 30v. I'm planning on using the same thing you are but without a BMS. I'm going to also use one of these which I highly suggest and it's very cheap...only $25

http://hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=10080

I plan on using the same kind of lifepo4 cells and probably will never allow the voltage to drop below 36v or 3.0v per cell (I'm getting a 36v pack). When you charge them, they will be at about 43v - 45v for 12 cells (3.6v x 12 = 43v or 3.8v x12 =45v) or about 57v - 60v for a 16 cell which what you are going to most likely. The less you use on the them, the longer the cycle. So if you only let the voltage drop to about 48v on a 16 cell (3.0v x 16) then you'll probably get more out of it.

 

[morph999]

yeah you can add cells later but you'd have to charge them individually unless you buy a bigger bms.

 

[julesa]

Wow that's huge, thanks for the pic, helps a lot.

I think I'll go with these, they seem to be more plug n play.
What voltage are these packs rated at?
I mean, I know they swing from 2.7-4v, but what figure do I use for building, are these 3.3v also?

LiFePO4 cells will rest at 3.2 or 3.3v unless they are freshly charged or almost empty. The exact voltages for max/min charge will change depending which BMS you buy, but Morph's estimates are good. You will want 16 serial connected cell groups because that's how many channels you'll find on every "48v" LiFePO4 BMS. 3.2 x 16 is a little higher than 48v but that's not important as long as your controller can survive the 58-60V it will see at full charge (...probably not a problem).

Your performance with 50V of lithium is going to be noticably better than you were getting with your 36V SLAs half empty. Lithium cells don't drop in voltage as much as SLAs do as they discharge. If starting performance was acceptable when fully loaded with freshly charged SLAs, you'll probably be happy with the lithiums even when the pack is half empty.

A supercap probably won't make any difference once you upgrade to lithium. If startup acceleration still isn't acceptable with the new pack, the next step is probably to modify or replace your controller to increase the amp limit.

 

[Kingcodez]

Yeah the picture made me realize, with my current box, I can only tetris like 9 cells, in, and still need to find a place to stick the other 7.

I could split them into three batteries I think, or make a small 2xSLA sized one, for 'tucking' into the recess, and then a 'tall' one so it can stand up through my little trunk thing.

Is it ok to have a battery made of 5 cells on one end, and then 10 on the other?

How would I connect them?
Right now my SLA's are wired to what looks to me a computer PSU cable, it's a 3 pronged cable, exactly like the computer ones.


Also, should I try to replace the wiring in the bike? Which ones matter the most? What about the various connectors? I think most of them are molex, or simply twisted together.

 

[MrKang]

Also, should I try to replace the wiring in the bike? Which ones matter the most? What about the various connectors? I think most of them are molex, or simply twisted together.

If the scooter is made in china....then yeah...you should check every connection..mine were clamped and easy to pull off there plug.
Very bad and loose connections can give bad performances. I re-fitted and rewired every connection by soldering with 10 AWG cable and connectors.

 

[julesa]

Yeah the picture made me realize, with my current box, I can only tetris like 9 cells, in, and still need to find a place to stick the other 7.

I could split them into three batteries I think, or make a small 2xSLA sized one, for 'tucking' into the recess, and then a 'tall' one so it can stand up through my little trunk thing.

I wonder if you can fit 48 (16x3) Headway cells in there. ==48V 30Ah
They're about 150mm long by 38mm in diameter each. The cans are 120mm long but the screw terminals on the ends stick out about 15mm on each side.

It's possible to split the pack but that can introduce new problems. Have you considered sending your battery compartment measurements to Ping and/or Headway and asking for quotes on built packs with BMSs that will fit?

I think Victoria does custom packs too. She's a Headway dealer in China.
Victoria <chcj55@gmail.com>

Edited to add: before purchasing, you might want to wait to see what prices look like on the new A123 prismatic 15Ah and 20Ah cells -- see Lynchy's recent post on this -- they're just now becoming available. VERY good quality cells, and surprisingly lightweight.
http://endless-sphere.com/forums/viewtopic.php?f=14&t=14719

 

[Kingcodez]

Well I drew it on paper, I can fit 9 batteries in the current box, and maby stack the rest in the seat area.
Some bikes around here have the tall SLA configs, where it's just SLA's stacked on top each other, and they go under the seat of a traditional bicycle type EBike. (Mcdonald's delivery bikes for ex) Yes they do deliver here.


Those 40ah cells are just too damn big, and the price is too much, I want a 20-30 max ah setup, 40 would be sick, but I can't justify spending 1200 US on a bike that cost me 300. Which is why I'm leaning more toward the premade crap pack on taobao. I wish they made 20ah cells. Just a little smaller.

I'm emailing Victoria to get a price for the pack and shipping to Beijing.

If you guys wanna buy my plane ticket, I think I can stuff 4 or maby 10 packs in my suitcase
From the sounds of it, a $1200 ticket is cheaper than shipping 4-5 packs alone lol..

 

[MrKang]

If you guys wanna buy my plane ticket, I think I can stuff 4 or maby 10 packs in my suitcase
From the sounds of it, a $1200 ticket is cheaper than shipping 4-5 packs alone lol..

hehehe , then you would carry a suspicious suitcase arround 275 kg! 8)

Better thing is to transport some lipo's !

 

[Kingcodez]

Yeah you should see my suitcases when I come and go from the US.
xboxes, laptops, iphones, ect.

 

[Kingcodez]

I got a price quote from Victoria about the headway packs, the difference from 48v 20ah and 60v 20ah is only $90.
To run 60v I'd simply need a controller upgrade correct? (To be safe, as I think my current one will run it fine)
But what about my motor, my 48v motor?

Does a 48v battery have the same capacity as a 60v battery, with both having the same AH?
IE Will I be able to drive distance with 48v and 60v, if no other changes were made to my bike?

So 48/20 or 60/20 are within my price range.

How much power difference does a 48v 800w motor make compared to a 60v 1500w motor? Isn't this calculated by the amp draw?

 

[wookey]

HI KingCodez. I'm working through all the same thoughts as you. Except I'm in the UK, and my existing machine is 48V with a 1500W motor.

No-one sells liFEPO4 cells in the UK (except lifebatt, and they are _super_expensive_), so I can pay for shipping from the US or from china, both of which sting a bit (especaily after local duty/taxes).

Yes, 48V 20Ah and 60V 20Ah packs have the same Ah (current over time) capacity, but the 60V pack has more watt-hours (Energy) in it. To a first approximation you can go the same distance with both, but you can there faster with the 60V pack (in practice it's a bit more complicated than that, but volts essentialy affects top speed and amps affects acceleration). Because there is more energy in the 60V pack, if you take it easy you should actually be able to go further with it in practice.

The motor doesn't care much about the voltage (within reason). A '48V' motor will happily take 60V, and probably 72V. The only problem is overheating - the more power you put in the hotter it gets. Let it get too hot and the magnets die or wires melt.

Controllers are more sensitive and need componets rated higher than the input voltage. Take it to bits and check the voltage on the big capacitors and the power FETs. Mine are rated for 100V despite it being a '48V' bike, but that's unusual. If it has high enough numbers then you can just use it. If not you either need to get a higher-voltage one or upgrade the parts in your existing one.

Yes the power the motor generates is simply the volts times the amps. The controller (and throttle) sets the amps. My controller maxes out at 50A. (or 12A in '1st gear' mode). Thats 50A x48V max input power = 2500W. Keeping the same controller and upgrading to 60V would make the max input power 3000W. So the motor power rating again is fairly nominal, but a 1500W motor will take more current for longer than an 800W motor before overheating.

Hope that helps.

The ping packs are possibly a bit underpowered as their 48V 20Ah packs have a built-in cutoff at 50A. That's zero headroom on my bike (it can go up to 52A current draw). It might be OK for you. Next cheapest are Foxx cells from aten energy (which allow pulse discharge to 60A). I have only found a US source for these. WSEGO cells looks very similar (and may in fact be the same) - they are available in China, as both cells and packs. Headway are next best value and have much higher discharge rates (max 150A), but they are cylindrical cells and 10Ah each so you need twice as many and putting toether a pack is rather fiddlier.

There are also Yesa, tenergy, A123 and PSI cells but they all cost a lot more. Thundersky no longer make a cell as small as 20Ah, so, as you have discovered you have to go to 40Ah and that's just too bit to fit.

I can fit either 24 Foxx or 48 headways where my existing SLAs went. Possibly 60 headways if I really packed them in. A nice feature of using the headways is that I can configure tham either as 48V30Ah for max range or 72V20Ah for max speed. I would appreciate advice from the experts on whether it is better to set up a 72V 20Ah pack as two separate 72V 10Ah packs, each with a BMS, or as 24S2P single pack? I assume the separete packs is better because then each cell is individually monitored, but I'd be spending quite a lot more ($225) on the second BMS, for relatively little gain?

 

[Kingcodez]

Great post, I think I will go with the Headway packs, Victoria said they could custom shape them, and a 60v 20ah pack is just $90 more than a 48v pack.

Which is more 'fuel efficient'? Using my 60vbattery, 48v motor, at 20km/h, or using a 60v battery, 60v motor, at 20km/h?
I'd assume that the bigger motor is more efficient at slower speeds, since it will have to go at less 'RPMs" correct?

What kind of Headway prices do you guys in the US get?
48v20Ah 440usd/pack FOB Shanghai, including the case and the BMS; 16S2P of our single cells 38120S;
48v30Ah 616usd/pack FOB Shanghai, including the case and the BMS; 16S3P of our single cells 38120S;
60v20Ah 535usd/pack FOB Shanghai, including the case and the BMS; 20S2P of our single cells 38120S;
60v30Ah 760usd/pack FOB Shanghai, including the case and the BMS; 20S3P of our single cells 38120S;

Shipping for me to Beijing is $60 hehe.
The 60v20ah looks like the best bet. 30ah of 60v is too expensive, but 48v30ah dosen't look too bad.

Can someone tell me how big a 60v pack is?
Will it fit, in two pack halves, into a 300*180*180 compartment? Or do I have to make a big tall battery?

 

[MrKang]

Great post, I think I will go with the Headway packs, Victoria said they could custom shape them, and a 60v 20ah pack is just $90 more than a 48v pack.

Can someone tell me how big a 60v pack is?
Will it fit, in two pack halves, into a 300*180*180 compartment? Or do I have to make a big tall battery?

Best you can ask victoria with your dimensions..

 

[Kingcodez]

I asked her she said she didn't have a spare pack at hand so yeah.

 

[Lock]

I'd assume that the bigger motor is more efficient at slower speeds, since it will have to go at less 'RPMs" correct?

Thought you were tapping about hub motors... Same RPMs at a given speed and wheel diameter regardless of power (although some hubs have internal gearing.) If you are in a lot of stop-go traffic, there is a point below a certain # of RPMs where efficiency gets pretty horrible for most motors... Here is a graph for one motor for example:

tks
Lock