Batteries & Chargers Nicads, Nickel Metal Hydride, Lithium, LiPoly, Chargers, Cyclers, etc...

Big Scale with A123 power

Reply

Old 07-31-2008, 01:20 PM
  #1  
JohnMac
Thread Starter
 
JohnMac's Avatar
 
Join Date: Oct 2002
Location: Leeds, UNITED KINGDOM
Posts: 1,410
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Big Scale with A123 power

Hi Guys,
I have been reading your forum section with interest. I am planning to convert a scale model to electric power. Nothing unusual in that, I know. However my plan of using lipos has hit a snag as there is no easy way of of removing the batteries. Also, the batteries really do need to be as far forward as possible, and I was thinking about a ring configuration.
I have already started using A 123s for Rx batteries and I am very impressed so far. So why not use these cells for the scale model (a FW190, BTW). This way I don't need to remove the battery between flights, and I understand that I can charge at up to 3C.
The trouble is that I am acutely aware that I don't know what I don't know (if you get my drift).
So what are the wrinkles? What pitfalls are waiting for my size 9's? What about speed control cut of voltages? What about charging and balancing. If I decide to make up my own batteries, can I safely solder the cells, or is spot welding mandatory?
Apologies for asking what is probably a bunch of dumb questions.
Regards,

John
JohnMac is offline  
Reply With Quote
Old 08-01-2008, 12:01 PM
  #2  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Big Scale with A123 power

Take a look at my post a123 radial. Its on page 2. You might wnat to do something similar. It gets the weight up front and keeps the batteries cool.
BTW you can charge at 10 amps on A123's
dirtybird is offline  
Reply With Quote
Old 08-01-2008, 04:13 PM
  #3  
JohnMac
Thread Starter
 
JohnMac's Avatar
 
Join Date: Oct 2002
Location: Leeds, UNITED KINGDOM
Posts: 1,410
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Big Scale with A123 power

Hi Dirtybird,
That's an excellent idea. How did you connect the cells together? Did you solder or weld, or can you get tagged cells? I have only seen plain ones.
Regards,

John
JohnMac is offline  
Reply With Quote
Old 08-02-2008, 01:51 PM
  #4  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Big Scale with A123 power

The cells are not soldered or welded. They are held to the 3" PVC pipe base by the bar across the top of 2 cells in each bank that serves as the electrical connection between the two. The bar is clamped to the pipe with a screw that screws into a five fingered 1/4" plywood base mounted on the pipe. Electrical connection from bank to bank is provided by sheet brass glued to the pipe at the apropriate places.
The cells are also stuck to the five fingers with double stick carpet tape and the two cell bank is covered with 95mm heat shrink tubing.
There are two dummy cells. (1 in dowell) The motor is limited to 8 cells by the voltage limitation of the ESC
I have about 25 flights on the motor in a 62" Lazy Ace.
I usually fly about 3 min. but the recharge at 3A is only 30 min so I could fly at least 5 min.
dirtybird is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service