I've just completed a pretty abusive testing of this DIY battery and thought I'd share. I've done a lot of research on these cells and they seem extremely safe. Very happy with the performance so far.
Pros:
Plenty of cranking power
Much lighter
Probably as safe as SLA with its battery acid and possibility of exploding if abused
Lasts all winter with no tender
A123 states 10 year life if properly maintained
Cons:
Expensive
DIY project(no manual)
These can heat up if punctured or shorted completely and possibly catch fire(I've shorted them and they just catch the wire on fire)
I bought a Dewalt 36v battery pack and disassembled to find 10 A123 lithium iron phosphate cells. After extracting them, I soldered them together to make a 4s2p pack(4 in serial, 2 in parallel so 8 total cells). Each battery is about 3.2v so 4 in series makes 12.8v. Pretty darn close to the 12v SLA we're all used to.
Pics are not mine. They come from http://ev.whitecape.org/insight/A123/
The pack
The cells
I used a string of 4 of these
An idea of how the leads are soldered to the ends
For my first pack I started with a 4s1p configuration. I soldered leads to the positive and negative terminals of that string of 4 I had. This was difficult because the cells contain a lot of iron which absorbs the heat quickly and draws it away from the solder. You cannot heat these cells to much as your soldering because the power will degrade significantly. The only thing I had that could deliver fast instant heat was a propane torch for soldering copper pipe so I used that which worked like a charm. After soldering the leads, I wrapped it in black electrical tape. You can see the result in my first video:
A123 battery in a motorcycle
At the time, I kept cranking and it worked beautifully. However, I had no idea that I just didn't have enough capacity. And without riding the bike all the time, it wasn't getting a proper charge. As I continued to work on the engine/carbs, I was cranking and cranking with no riding which eventually discharged the cells to the point where I needed a jump. At that point I realized the bike(cm400t) needed another 4 cells. I added the 4 cells and charged the pack fully before I stored it for the winter.
Come spring, I pulled the bike out and wham! She cranked just as hard as when I left her. I didn't pull the battery out, no tender, or nothing. I have been working on the bike a ton this spring and I have yet to jump it.
Here it is starting again with the 8 cell pack. I'll get a proper video or pic of the pack soon for you guys.
Cm400t project 2011
A proper note, I'm not using a BMS(battery management system). I'm not balancing the cells(they can eventually get uneven voltages). Basically this is because I don't care that much. It works and works well, so I'm happy. However, I understand that I probably wont get the full advertised 10 years out of the pack. If this pack does die, I'll probably spend the extra $ to get a balancer. The whole pack probably cost me $120 for the cells and shipping, but thats about it.
Pros:
Plenty of cranking power
Much lighter
Probably as safe as SLA with its battery acid and possibility of exploding if abused
Lasts all winter with no tender
A123 states 10 year life if properly maintained
Cons:
Expensive
DIY project(no manual)
These can heat up if punctured or shorted completely and possibly catch fire(I've shorted them and they just catch the wire on fire)
I bought a Dewalt 36v battery pack and disassembled to find 10 A123 lithium iron phosphate cells. After extracting them, I soldered them together to make a 4s2p pack(4 in serial, 2 in parallel so 8 total cells). Each battery is about 3.2v so 4 in series makes 12.8v. Pretty darn close to the 12v SLA we're all used to.
Pics are not mine. They come from http://ev.whitecape.org/insight/A123/
The pack
The cells
I used a string of 4 of these
An idea of how the leads are soldered to the ends
For my first pack I started with a 4s1p configuration. I soldered leads to the positive and negative terminals of that string of 4 I had. This was difficult because the cells contain a lot of iron which absorbs the heat quickly and draws it away from the solder. You cannot heat these cells to much as your soldering because the power will degrade significantly. The only thing I had that could deliver fast instant heat was a propane torch for soldering copper pipe so I used that which worked like a charm. After soldering the leads, I wrapped it in black electrical tape. You can see the result in my first video:
A123 battery in a motorcycle
At the time, I kept cranking and it worked beautifully. However, I had no idea that I just didn't have enough capacity. And without riding the bike all the time, it wasn't getting a proper charge. As I continued to work on the engine/carbs, I was cranking and cranking with no riding which eventually discharged the cells to the point where I needed a jump. At that point I realized the bike(cm400t) needed another 4 cells. I added the 4 cells and charged the pack fully before I stored it for the winter.
Come spring, I pulled the bike out and wham! She cranked just as hard as when I left her. I didn't pull the battery out, no tender, or nothing. I have been working on the bike a ton this spring and I have yet to jump it.
Here it is starting again with the 8 cell pack. I'll get a proper video or pic of the pack soon for you guys.
Cm400t project 2011
A proper note, I'm not using a BMS(battery management system). I'm not balancing the cells(they can eventually get uneven voltages). Basically this is because I don't care that much. It works and works well, so I'm happy. However, I understand that I probably wont get the full advertised 10 years out of the pack. If this pack does die, I'll probably spend the extra $ to get a balancer. The whole pack probably cost me $120 for the cells and shipping, but thats about it.
