Large Scale Central

Smart Charger for Li-Ion Battery packs

Electronics Power and Sound
#21

Hi Dan, Individual lithium cells are not protected unless they were manufactured with a 3.7V PCB 18mm diameter PCB at the top of the cell. If you have a polypropolene rubber covering over top of the cell with two wire leads coming out of the battery, then you have purchased the singles cells with a PCB. Protected (with PCB’s) single lithium cells can not be wired in series. If that’s the case, I would ask them for a RMA form and send those cells back and get you money back. These cells from BatterySpace.com are extremely over priced ($12.95ea.): http://www.batteryspace.com/Li-ion-18650-Cylindrical-Rechargeable-Cell-3.7V-2800mAh-10.36Wh---LG-Bra.aspx These are the same LG 2800mah 18650 cells we use in all of our lithium battery-packs and I sell them for $6.95ea. Here’s the drawing for the PCB board. http://freightsheds.largescalecentral.com/users/izzy0855/_forumfiles/PCB Board.jpg A 14.8V lithium-ion battery is wired in series like this:

(http://freightsheds.largescalecentral.com/users/izzy0855/_forumfiles/Lithium-Diagram.jpg)

Any questions, give me a call… Rick Isard Cordless Renovations, LLC

#22

Just a personal opinion here, but I decided long ago that I didn’t want to mess around making my own battery packs. There is a bit of a safety concern, risk of damaging the cells, and I didn’t end up with a very nice looking battery pack. I decided the small savings I might reap, just isn’t worth it.

#23

Me too.
I wasn’t about to invest in a spot welder for the tabs, etc.
I let someone who knows what they are doing make the packs.

#24

Rick: the Cells I have do not have a rubber covering on the top of the cell nor does it have any wires coming out it them. They look like the one you had the link to except they are blue in color and as labeled S.S Battery 3000mAh 3.7V. Also the PCB’s that I purchased look just like the one you have pictured. The Data sheet I got for it shows that it is wires as follows.

Cell 1 + goes to B+
Cell 1 - goes to B1-
Cell 2 + goes to B1-
Cell 2 - goes to B2-
Cell 3 + goes to B2-
Cell 3 - goes to B3-
Cell 4 + goes to B3-
Cell 4 - goes to B-
wires to go to the motor are connected to P+ and P-

It all looks pretty straight forward and I don’t see any problems now that I know that the Cells I have are not protected.

Del and John: I thought that way for awhile, But I like to build things and know how things work because I never know what I am going to be asked to build for the Museum where I work. After doing the research and reading all of the warning notices and reading what other people had to say, I felt that it was within my capabilities to build a few for my own use with my G scale trains, plus I could build 4 packs for the same cost of one commercial Aristocraft pack that I use with my Train engineer. This looks pretty simple compaired to the RF train control system I just finished using 433Mhz RF modules, Picaxe Processor and TI SN75110ne Motor control chip and mp3 sound module.

Dan S.
Denver & Rio Grande Southern

#25

Dan,

Just be careful!

Rick Isard
Cordless Renovations, LLC

#26
Del Tapparo said:
Just a personal opinion here, but I decided long ago that I didn't want to mess around making my own battery packs. There is a bit of a safety concern, risk of damaging the cells, and I didn't end up with a very nice looking battery pack. I decided the small savings I might reap, just isn't worth it.
I certainly agree, Del. I'd much rather leave that to the "experts" in that technology.