Batteries and where to get them.

[Spasticteapot]

I've always been too timid to go more than 45MPH on any two-wheeled vehicle, and the insurance is prohibitively expensive for a someone my age anyway. However, I read an interesting webpage on a DIY electric bike design using R/C airplane parts, and figured I'd give it a go. (Before you ask - I already have a bicycle which I'll be using as my primary mode of transportation into the foreseeable future - this is just a toy.)

http://www.recumbents.com/WISIL/shumaker/e-cumbent2.htm

Getting a motor is not too difficult, and if I'm not using regenerative braking, getting a controller is pretty simple as well. However, I'm simply driven up the wall by trying to figure out what sort of battery I should use.

The list of options (as I see them) is:

1. Lithium-ion polymer.

Very cheap, very easily available, and capable of stupendously enormous discharge rates. However, they degrade after a few hundred cycles, and then you need to buy new ones. Oh, and they occasionally just sort of spontaneously combust in a steel-melting inferno.

2. A123
Awesome cells, don't explode, conveniently sold at Home Depot, cost enough to make all of the above moot.

3. Lithium iron phosphate
Run the gamut from a little bit more than a LiPo pack to a whole lot more than a LiPo pack. The cheap cells are often capable of only 2C continuous discharge and 3C bursts; better cells can manage up to 25C bursts. Last a lot longer than LiPos, don't explode. Very hard to get large-sized cells online - the best deal I've found are 10C BMI cells for $46.50 each, and that's just a little steep for the 48v pack I require. (It's actually enough that I could buy a crappy Chinese pack with four times the capacity - sure, I'd have 3C burst, but that's on a two kilowatt-hour battery!) AFAIK, Headway and other budget cells aren't sold here in less than 1,000 units.

I live in the USA. I'm not too familiar with battery management technology. I require a good 4.5kW burst and 3kW continuous. What do I do?

 

[julesa]

You don't say how far you need to go.

IMHO, for drag racing and other recreational activities where you can recharge fairly regularly and need high power, A123 and PSI are great solutions. They are also great solutions if you need to charge up quickly (or you just want to and can afford the higher prices).

For general transportation purposes where quick charging isn't necessary (or isn't worth paying the $$$ premium), you often need enough range that you might as well buy less expensive cells rated for 2-3C continuous and just buy enough of them to meet your power needs. 60Ah Thundersky cells are available from elitepowersolutions.com (A 48V 60Ah TS pack should handle your power requirements), or frodus will be announcing a Headway group buy pretty soon on this forum.

 

[dogman dan]

You will need to refine your motor choice a bit more before you plunge into batteries. It would get REALLY expensive to make a mistake there. I found it , and many others too, a lot cheaper to make my early mistakes with sla batteries. With my electronic ignorance at the time, it was a real good thing I did some of the more stupid stuff with cheap sla's for a power source. Once the bike is tested, you will then know just what you need in more expensive lithium.

 

[Spasticteapot]

You don't say how far you need to go.

IMHO, for drag racing and other recreational activities where you can recharge fairly regularly and need high power, A123 and PSI are great solutions. They are also great solutions if you need to charge up quickly (or you just want to and can afford the higher prices).
.

About ten miles at stupid speeds - so, about 30 miles with a more sane degree of acceleration.

For general transportation purposes where quick charging isn't necessary (or isn't worth paying the $$$ premium), you often need enough range that you might as well buy less expensive cells rated for 2-3C continuous and just buy enough of them to meet your power needs. 60Ah Thundersky cells are available from elitepowersolutions.com (A 48V 60Ah TS pack should handle your power requirements), or frodus will be announcing a Headway group buy pretty soon on this forum.

The 20Ah thundersky cells are rated for 200A burst - is the claim on the website bogus?

You will need to refine your motor choice a bit more before you plunge into batteries. It would get REALLY expensive to make a mistake there. I found it , and many others too, a lot cheaper to make my early mistakes with sla batteries. With my electronic ignorance at the time, it was a real good thing I did some of the more stupid stuff with cheap sla's for a power source. Once the bike is tested, you will then know just what you need in more expensive lithium.

I'm a bit confused as to why this is necessary. Isn't it just an issue of matching up the output drive gear ratio, and output torque of the motor? All you need to do then is find the correct motor controller and, of course, avoid overloading your batteries.

 

[frodus]

200A peak out of thundersky's will fry them... they do NOT tend to do very well over 5C at all. the most you should expect is 2-3C continuous and 5C peak. They're not very stout cells. Not that great density either.

medium format cylindricals are going to give you higher C rates and not be hard to put together.

There are some headway batteries that we're going to buy if you want some. They'll do 10C peak (tested to 15C) and have screw terminals. They're going to be under $18 a cell, plus shipping from Portland to you.

 

[julesa]

The 20Ah thundersky cells are rated for 200A burst - is the claim on the website bogus?

I haven't seen any test results, but personally I'm skeptical and think "burst" might be a very good word to describe TS at 10C. Take that with a grain of salt though, I really don't have any experience with them myself. If you're curious you could buy a cell and send it to DoctorBass for testing.

Anyway, 10 miles is an awfully short trip. I think it would be nice to have the option of going at least 20-30 miles before recharging, but that's just me -- I'm going to buy some Headway cells. Not as high power but you get more Ah for the $$. If you're happy with 10 miles range, you want a compact and lightweight pack, and you need "stupid speed" then it's worth paying for high power cells. PSI and A123 are looking good at that point.

 

[Spasticteapot]

The 20Ah thundersky cells are rated for 200A burst - is the claim on the website bogus?

I haven't seen any test results, but personally I'm skeptical and think "burst" might be a very good word to describe TS at 10C. Take that with a grain of salt though, I really don't have any experience with them myself. If you're curious you could buy a cell and send it to DoctorBass for testing.

I suspected as much.

10 miles is an awfully short trip. I think it would be nice to have the option of going at least 20-30 miles before recharging, but that's just me -- I'm going to buy some Headway cells. Not as high power but you get more Ah for the $$. If you're happy with 10 miles range, you want a compact and lightweight pack, and you need "stupid speed" then it's worth paying for high power cells. PSI and A123 are looking good at that point.

Actually, I'm figuring that a 30 mile range will end up being ten miles if you ride like an idiot. The fellow I linked to said he could get up to 30 miles on a 10Ah 48V pack - I figure I'll be able to do the same out of my LiFePO4 cells. Of course, he was using a belt drive that artificially limited his power output to about 4kW - any more and it shredded. I'm planning to use a mountain-bike triple chainring and mount a truly enormous sprocket on the rear wheel (possibly one from one of those "add a gas engine to your bike" kits.) Hopefully I won't kill it too quickly...

There are some headway batteries that we're going to buy if you want some. They'll do 10C peak (tested to 15C) and have screw terminals. They're going to be under $18 a cell, plus shipping from Portland to you.

I've been looking at those. Last time I considered building one one of these, LiFePO4 cells would have cost a whole lot more - it looks like a terrific price for a non-exploding battery. Any recommendations for a 15-cell BMS?

 

[frodus]

I'm working with Synkromotive on a BMS right now. the BMS here is a good choice for these as well. I can work with you directly if you need some help chosing.

How many would you want?

 

[dogman dan]

72v 10 ah psi or headway... looking at big bucks.

 

[dumbass]

I'm working with Synkromotive on a BMS right now. the BMS here is a good choice for these as well. I can work with you directly if you need some help chosing.

How many would you want?[/quote

OK, I'm interested in building a 24v 40ah pack. But I would likely do it as 2 or 4 separate packs of 8 or 16 cells each. That way when I am out riding alone I have all the power and distance I want. But if I go out with my wife I can split the packs and let her ride too. We are both running small 360w Cyclone motors so 20ah will take us a long way. I may upgrade mine to 500w but that shouldn't be an issue because they are running them on 10ah from the OEM.

My problem is also with the BMS and charger. I don't know beans about building or buying a BMS or charger. This is why I keep looking at the "kit" type of batteries that include the battery, BMS and charger. But without question I am not going to get the quality I would if I bought the 10c you are recommending. I think I would need 32 cells plus 2 spares. Do you agree? And how much would it cost for a BMS and charger? Remember I am talking about 24v and I can split them into packs of 4,8,16 or 32 for charging.

When and how do we pay for the order? And of course when will we see cells?

Thanks for all your efforts helping us newbies

 

[frodus]

I started a thread just about the group buy, there are more details there...

I'm putting together pricing right now.....then I'll get an estimated delivery date soon and plan the order for the 2nd week of may.

These are loose cell only for the headway order. There are a few BMS, including the 24 channel one on the forum. Chargers can be bought through Soneil and a couple other places. I just want to get the cells here first.... get the quantity high so we can get cells cheap.

 

[julesa]

frodus, I had no idea the Headway 38120S cells could do 15C burst !?! ...

72v 10 ah psi or headway... looking at big bucks.

Huh? Big bucks compared to what? A 48V 20Ah Ping pack will set you back $723 including shipping.

At $18 per Headway cell you can build a 48v 20Ah pack for $576.00, and that already includes shipping from China to Portland... so add $50 for UPS from Portland to you. I'm buying an 80A bms and 8A charger from www.ecitypower.com for like $105 *** including shipping ***:
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=9054&start=45

So you can get all you need to build a 48v 20Ah Headway pack, with an 8A charger, delivered to your door for $731, and if enough people order cells the price will go even lower than that. The next price break is at 1000 cells, and people have already committed to buying over 750 on the group buy thread:
http://www.endless-sphere.com/forums/viewtopic.php?f=9&t=9824
It's a good time to be building a bike!

Edited to add: I think maybe you meant "72v 10Ah PSI or A123" ?? Yeh, that would be big bucks.

 

[theyerb]

Wow, that guy has some fabrication skills I can only dream about. Those diy pedals at the end were phenomenal.

 

[frodus]

frodus, I had no idea the Headway 38120S cells could do 15C burst !?! ...

this is direct from Headway. It'l do it, just not GREAT for the cell, and there's no independant test results at 15C on temperature/etc.

 

[dogman dan]

Big bucks for any decent battery in 72v to run a 5303. To go slow is much cheaper, like a ping 24v 10 ah to run a bafang.

Fast is big bucks. But a ping 48v 20 ah and a 408, golden, aotema, etc, is pretty cheap transportation compared to a car. Compared to a just pedaling bike though, $1500 for everything is pretty expensive.

 

[dumbass]

I started a thread just about the group buy, there are more details there...

I'm putting together pricing right now.....then I'll get an estimated delivery date soon and plan the order for the 2nd week of may.

These are loose cell only for the headway order. There are a few BMS, including the 24 channel one on the forum. Chargers can be bought through Soneil and a couple other places. I just want to get the cells here first.... get the quantity high so we can get cells cheap.

If I recall your org. posting you are planning on ordering the Headway 38120P cells and they are rated at 8ah....correct? The pics from Headway are sometimes difficult to see clearly. But I am assuming the they have a threaded end on them for connections..........correct? Thanks

 

[julesa]

Big bucks for any decent battery in 72v to run a 5303. To go slow is much cheaper, like a ping 24v 10 ah to run a bafang.

Fast is big bucks. But a ping 48v 20 ah and a 408, golden, aotema, etc, is pretty cheap transportation compared to a car. Compared to a just pedaling bike though, $1500 for everything is pretty expensive.

I know a lot of people who don't blink at spending $2000 for a pedaling bike... though I think everyone would agree $5000 is pretty steep. :wink:
http://www.cervelo.com/bikes.aspx?bike=S32009

 

[frodus]

Incorrect.... I was only ever going to get 38120S cells.

The 38120S cells have a screw terminal at each end, not a threaded rod like PSI/Lifebatt. These are 10Ah batteries.

 

[julesa]

If I recall your org. posting you are planning on ordering the Headway 38120P cells and they are rated at 8ah....correct? The pics from Headway are sometimes difficult to see clearly. But I am assuming the they have a threaded end on them for connections..........correct? Thanks

The group purchase will be ordering the same cells that were tested in this thread:

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=7655

 

[Spasticteapot]

Note:
I'm not sure if other people here are using it, but R/C battery notation works as follows: number of cells in series + S + number of cells in parallel + P. A 3s2p pack would have six cells arranged into three series-wired sets of two parallel cells.

I'm working with Synkromotive on a BMS right now. the BMS here is a good choice for these as well. I can work with you directly if you need some help chosing.

How many would you want?

I'm still trying to figure that out.

Plan A is to run an R/C motor with a 15S1P pack. This is pretty much the limit of what most R/C motors and motor controllers are rated for - 50V at 80A. Any more than this, and buying R/C ceases to make sense.

Plan B is to run something else entirely (likely a 30s1p pack) with whatever motor I can find. I'm told 10kW Briggs & Stratton motors are great for this sort of thing.

At $18 per Headway cell you can build a 48v 20Ah pack for $576.00, and that already includes shipping from China to Portland... so add $50 for UPS from Portland to you. I'm buying an 80A bms and 8A charger from www.ecitypower.com for like $105 *** including shipping ***:
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=9054&start=45

Interesting indeed.

Which BMS are you using? Which charger?

Also, if I'm building a 15S2P pack, can I use the 16-cell BMS device they sell?

 

[julesa]

Interesting indeed.

Which BMS are you using? Which charger?

Also, if I'm building a 15S2P pack, can I use the 16-cell BMS device they sell?

Why not just build a 16S2P pack = 51.2V? I'd be surprised if 3.2V really made that much difference to the motor...

I'm using the EP-A 400W charger, and I'm kind of gambling on the inexpensive resistor-bleed BMS... but I would be more hesitant about going with that BMS if I expected to see 4.5Kw peaks often.

ecitypower.com said they are upping the high current cutoff of the resistor bleed BMS to 80A for me but I honestly doubt I'll ever hit it that hard. If I have problems with that BMS, I plan to build one of the kits that Gary and Richard and the gang designed (the "Endless-Sphere BMS?"). The board and parts add up to something like $120, and I was hoping to keep costs down which is the only reason I haven't ordered it already. I think most people would question the wisdom of protecting an expensive pack with an inexpensive BMS, but like I said I'm gambling a bit.

The ESBMS would be a better solution for your power requirements -- if you don't mind soldering. :wink:
http://www.tppacks.com/products.asp?cat=26
http://endless-sphere.com/forums/viewtopic.php?f=14&t=5416

Edited to add:
This guy set up the ESBMS for a 15S pack:
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=5416&p=139110&hilit=15s#p139110

 

[dnmun]

there are often bags of transistors and optos sold on ebay by the chinesesellers. maybe if enuff people could cooperate, then we could buy a big bag of the transistors and share them out and the optos too.

and the leds can be bot by the hundreds to share too. and maybe we could even find the power resistors too, i have seen some big wire wound ceramic power resistors on ebay too for absurdly cheap prices, like 5 for $1.36 when they are $2 each from digikey.

so maybe we could do that also after the cells arrive. i really wanna build the Endless-Sphere BMS, maybe 72V even.

 

[Spasticteapot]

Hmm. Looks like I'll need to budget more than I'd thought for the BMS.

Anyone have a recommendation for a motor controller?

 

[oofnik]

Spasticteapot,
I recommend you look at the non hub motor section here on Endless-Sphere. Matt is a fairly active member here under the name 'recumpence'. I stumbled upon Matt's e-cumbent one day about a year ago after I had already decided I was going to build an electric bike, and I wasn't going to use a hub motor. His elegant solution really motivated me to do something similar.

As for your batteries, I can vouch for the Headway cells. I built a 12-cell pack and it is performing wonderfully. The batteries are available in small quantities from Headway directly, several other Chinese vendors, or you can get in on to the group buy that's quickly coming together.

 

[jdbauman]

What is the website where you can order these cells directly from headway? I thought you had to order in quanities greater than 1000 cells. Thanks for you help!

Jerry