New LiFePo4 Battery supplier on Ebay

Unless someone hijacked his account, he has some feedback.

The bigger question is how hard will it be to keep the LiFePO4 cells balanced in a highly parallel battery pack?

There's actually a few new vendors on ebay suddenly that the ones in China cannot ship during the olympics.
I suspect they must be in Taiwan or Hong Kong instead.

Some of the prices seem too good to be true.

Then again there were alot of questions about pingping in the beginning too and his packs are doing fine.

I do not like the fact that you are using so many cells to make up a pack, one goes bad and it would be hard the find the problem. I wonder if they take up more room too?

Those prices are much higher then PingPing's are.

Deron.

Any of the duct tape packs are weak unless they are the 20 ah size. Generally each pouch in the cell can deliver about 5 amps. so to get 20 amp continuous discharge you need a 4 pouch per cell pack, 20 ah. But each of the pouches is 5 ah so it should be easier to avoid toasting one. With larger batteries paralelled in each cell, wouldn't the bms detect a low one sooner and be more likely to shut down the pack in time? I think those little cells are for radio controll small stuff.

Has anyone tried to remove the ducttape off of one of Ping's batteries to see what the inside looks like?

The only problem I have with Ping's and Sam's packs are that they don't have a high discharge rate (1.5-2C).
When climbing a hill this can be a big disadvantage.
Most "higher quality" LiFePo4 packs I've seen have 10-20C discharge rates. This is more like it.

I've got a pic, and there's loads of info on the Endless-Sphere site.

I got this 48V 20Ah one for cheap because of charging issues. Methinks it was a combination of a bad BMS and the fact this wire came off. Doesn't matter to me in any case, since I had planned on building my own sort of BMS from the beginning.

I treat it gently for now, but I'm loving it anyway. :D

he is only claiming 25 amp output on a 20AH pack, only a little more than 1C. Even Ping gets 40 amps output out of his 20AH pack. For about the same price FOXX battery has packs that are a true 3C and are readily available.

36v20ah LiFePO4 battery

http://www.atenenergy.biz/Foxx%20Specs.htm

I was warned to stay away from those types of packs with so many small cells. Internal resistance can be high, leading to large voltage drops when applying load

I was warned to stay away from those types of packs with so many small cells. Internal resistance can be high, leading to large voltage drops when applying load

These seem to work quite well. It's a 4p string, so there'd have to be quite a bit of resistance in the cells to have any significant impact.

This pack sags to about 47V under the full 40A load (as opposed to as low as 30 volts for the old SLAs I was using). :D

Oh, and FYI: My pack is did not actually come from Ping. It was originally bought from Anna, who I hear doesn't assemble packs as well as Ping. From what I've seen, I find that believable.

My complaint is the weak tabs coming out of the things. They're like a 1/64 - 1/32" thick. Making them 1/16" thick would be a huge improvement; any more and they'd potentially be hard to work with.

Has anyone here assembled a pack from DeWalt cells?

I believe so. A123s are, indeed, pretty much the best you can actually get for high discharge rates; they don't even blink at 60A from a single cell continuously.

But, they didn't come cheap to begin with, and packs are up to something obscene like $160 (10 2.3Ah cells in a pack) now.

This is my first post. :)

Crazy question...

but, if using so many cells is a bad idea, then why does Tesla Motors use thousands of cells in series and parallel for the roadster?

TESLA Roadster batteries:

Cell type: lithium ion, 18650 form-factor (18mm diameter by 65 mm length). Most laptop computer batteries already use this type of lithium-ion cell.
Cell count: 6,831 cells arranged into 11 modules connected in series; each module contains 9 "bricks" connected in series; each "brick" contains 69 cells connected in parallel (11S 9S 69P).

If they are using over 6,800 cells, I think using 200 or so for a 48v pack wouldn't be too hard to find a bad one of you needed to. Considering how reliable LiFePO4 cells are, one would think having to tear it apart to find a bad one wouldn't be an everyday ocurrance. Although, I could be horribly wrong.

There's nothing wrong with using a bunch of cells, but it's a pain to make them into a pack, and you get slightly less energy for the volume and weight because of the extra casing.

Can someone please check out this new ebayer. Seems like great feedback, but I'm not too informed on batteries:

http://cgi.ebay.com/36V-20AH-LiFePo4-Electric-Bicycle-Battery-Lithium-Ion_W0QQitemZ220257529870QQihZ012QQcategoryZ158998QQssPage...

here is the spec sheet:

http://img.auctiva.com/imgdata/7/1/9/4/9/0/webimg/152197875_o.jpg

He is claiming only 15 amp continuous output and 20 amp peak, which isn't even 1C. Other than that, it looks like a nice package. I think my e-bike wouldn't work with it because I pull 25 amps under full load. If you have a pedal first controller, it might work for you.

If you look at the ebay feedback for those new batteries sold by luckybbd, it looks like she has not sold any batteries yet because all of the feedback is for cheap jewelry. Now all of a sudden her ebay store is selling high-end e-bike kits. The batteries are attractively packaged, but her prices are higher than what you could get from some of the other sellers. I'll wait for some feedback on the new merchandise before I take a chance on buying from her.

Stick with Ping, just email him to see if he has enough stock to sell you one. Buy a 20 ah and you will have no problems with most setups other than hot rodded x5's.