New Headway Group Purchase
Hi, I thought some of you might be interested -- Frodus is organizing a group purchase for Headway 38120S screw terminal 10Ah cells. It's loose cells only, so you'll have to buy your BMS and chargers separately, but the screw terminals will make for nice pack assembly and maintenance... GRIN. The price is currently $18 per cell, plus shipping from Portland, OR to your doorstep, but once the size of the order has been determined, the price will be discounted by some as-yet-unknown amount. We've got people committed to buying around 750 cells so far, and there's a price break at 1000 cells, so I'm trying to spread the word... more details here:
http://www.endless-sphere.com/forums/viewtopic.php?f=9&t=9824
If anyone wants to avoid the hastle and the potential problems with assembling the cells, here is a better way to go. Japanese SANYO 16V 4amp Li-ion battery pac with electronics builtin to protect against overcharging, etc. Price is as low as $20 in quantitys brand new. Contact cruisin@live.com for more info.
If anyone wants to avoid the hastle and the potential problems with assembling the cells, here is a better way to go. Japanese SANYO 16V 4amp Li-ion battery pac with electronics builtin to protect against overcharging, etc. Price is as low as $20 in quantitys brand new. Contact cruisin@live.com for more info.
Is there a date of manufacture printed on the case? Has anyone else built a bike pack from laptop batteries? Any idea what kind of current they can handle?
You would still have to assemble those packs into a larger pack, and I would think finding a way to charge those would be more of a hassle. Would you use a laptop charger? 4s3p = 14.8v nominal so it looks like you'd need nine of them for a 44v 12Ah pack... it's an interesting approach but I'm not sure it's any easier or safer...
I found someone else who is building a bike pack using these (or very similar) cells:
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=8612&p=135301&hilit=+laptop#p135301
Update: I found a whole thread devoted to these exact laptop packs:
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=5688
Apparently the cells are rated 2C -- just enough to power an average e-bike at a reasonable pack size. The only person who reported successfully using these on a bike took them all apart anyway and hooked them to a custom BMS made by Ping, because the protection circuit in the laptop pack is built to handle the current draw of a laptop, not an e-bike. Apparently these guys were getting them for more like $10/pack since they had been sitting on a shelf for a while -- according to them, AST went out of business in 2001... Anyway, be really careful using these flammable lithium cobalt cells.
Gee thanks for hijacking the thread which was to sell headway cells, not your cells..... thats pretty low.... whats wrong, can't start your own thread? Can't sell your Lithium packs? I'm sorry, go make your own thread.
The Headway cells are LiFePo4, not lithium Polymer or Lithium Cobalt (laptop batteries). This is a much safer chemistry. AST went out of business quite a while ago, so this is all NOS stuff.... NEW being at least 6-7 years old. The sanyo cells are good cells, what are they, UR18650's?.
Those sanyo don't have the safety of these cells, AND you have to weld to the tops of the batteries/solder a LOT of busbar. I've looked at those sanyo, they're the kind that like to catch fire if they overcharge. Especially if they've been sitting around. Plus, god knows how LONG those cells have sat on a shelf somewhere. Those protect from overcharging the pack, but they don't have balancing built in.... there's a HUGE difference Thats not even mentioning the fact that you have to rip 50 of these apart to get anything useful. 50 packs would be 600 batteries for 3200Wh. 100 Headway cells would do the same thing, require a fraction of the connections and be more efficient because of lower connection losses. 16V 4Ah is 64Wh.... and you have many connections. one headway cell is 32Wh.... and only require 2 connections. Headway are screw terminal and very easy to assemble so assembly is MUCH easier than those, and less time consuming. Plus they only do 2C..... these headways can do 15C Max.
If they were brand new and had screw terminals you might have an argument... but you don't. They're old packs that have sat around for who knows how long and they have welded connections. The Energy density and volumetric density isn't bad though.... but I'd rather not have an explosive package under my "package" when riding my motorcycle.
Not to mention that the laptop/sanyo cells will heat up when being operated so close to their max current rating, and I'd rather not risk overheating 1000+ wh of lithium cobalt...
Update -- the price has dropped, the order deadline is moving up to Thursday May 7, and BMS circuits are also available now.
Each cell is currently $16.50 each. These are 38120S cells with screw terminals. 10Ah, 3.2V cells, so that's $0.52/wh ($1.65/Ah), including shipping & import costs from China, for cells capable of 10-15C bursts. :-D
The 36v BMS with continuous discharging current of 60A and max. of 80A is $45 usd/piece
The 48v BMS with continuous discharging current of 60A and max. of 100A is $55 usd/piece
The 72v BMS with continuous discharging current of 60A to 100A, and max. of 400A is $80 USD/piece
Prices do not include UPS costs for shipping from Portland to you. You can avoid paying these if you're in Seattle and can meet Travis when the shipment comes in, or if you're near Portland and can meet him down there.
http://www.endless-sphere.com/forums/viewtopic.php?f=9&t=9824