methods for viewing discharge curves

[mechanix]

I just bought a bunch of lifepo4 cells and want to do some testing on them. I have a dmm with usb output, but this method seems crude and I'm afraid that I'll over-discharge some of the cells if I'm forgetful and let them discharge too long. What is the best way to safely discharge cells at 20-40 amps? Are there "smart" chargers out there that are capable of this that won't break the bank? I'm looking for one that is pc-compatible so I can see those pretty discharge curves

Joel

 

[thomas]

cba 3 form west mountain radio is the best device you get for little money I guess.

 

[CamLight]

I agree, hard to find a better unit for the money if you want to do plotting/graphing:
http://www.westmountainradio.com/CBA.htm

 

[mechanix]

Thanks guys, that seems to be the ticket. Now I just need to inform my wife what I want for christmas!

Joel

 

[Doctorbass]

The cheapest way TO DISPLAY AND GRAPH ONLY is to buy the cellLog 8 !!

It already include the usb, dataloging and Logview software for 27usd! :wink:

It can do 8 serie cells at the time on the same graph!!.. not the CBA

The CBA is good but you MUST NEVER EXCED 35A :wink:

 

[CamLight]

Doc, the fuseholder in one of my CBA II's fell out at 29A.
But, hopefully the CBA III can better move some of that heat away from the fuse at high current levels.

 

[Doctorbass]

Doc, the fuseholder in one of my CBA II's fell out at 29A.
But, hopefully the CBA III can better move some of that heat away from the fuse at high current levels.

I know this problem, That's why I soldered copper sheet pieces on the fuse holder lead to help evacuate the heat produced by the resistance loss between the fuse lead and the fuse lead holders...

I also added a 5Vdc fan UNDER my CBA II to cool down the overqal circuit and traces.

It work very well now and i use the mosfet you sent me to upgrade it.

Doc

 

[thomas]

The cba3 got a 25A fuse and a 40A spare you can change your self.

 

[CamLight]

I know this problem, That's why I soldered copper sheet pieces on the fuse holder lead to help evacuate the heat produced by the resistance loss between the fuse lead and the fuse lead holders...

I also added a 5Vdc fan UNDER my CBA II to cool down the overqal circuit and traces.

It work very well now and i use the mosfet you sent me to upgrade it.

Doc

I remember the pictures for that mod...very nicely done.
I ended up getting a much more powerful fan for the top of my CBA II's, moving the stock fan to the bottom, and doing the MOSFET swap, to get the temperatures down to where I could actually do a 100W (or so) continuous discharge before hitting the 175C max temp rating of the MOSFET.

I'm aching to do the thermal analysis of the CBA III to see what power levels it can handle, but have four other projects needing my full-time attention for the next couple of weeks, at least.