battery analysis

[yaesumofo]

Hi guys.
I have been looking for an easy way to test my NP-1 batteries. In the process of looking I found something called a "west mountain radio CBA".
web page

Any of you battery freaks have any experience with this unit?
In my short time I have to say that it is able to tell me exactly where my NP-1'a are at in terms of charge and capacity.
This unit will discharge and analyze just about any battery.
it connects to the computer via usb and is VERY simple. and at about $89.00 I think it might be a great deal for somebody interested in discharge curves of just about any kind of battery.
Any thoughts?
Yaesumofo

 

[Tweek]

I've been looking at that unit a lot, and I can say that as soon as the funds are available (soon! /ubbthreads/images/graemlins/smile.gif ) I'll be ordering one. It will be much more capable than my Triton for discharge tests.

Chris

 

[rdshores]

I'd like to get one of those too. How about someone doing a group buy to see if we could get a better price deal.

 

[Tweek]

Well, I had the order page all filled out, and was about to submit it, then I noticed that they had CT sales tax added onto it... Long story short I drove on out to their office, bought myself one of these (and some other stuff that I didn't need! /ubbthreads/images/graemlins/grin.gif ), and I will be play-errr, testing this thing out soon... /ubbthreads/images/graemlins/smirk.gif

Chris

 

[SilverFox]

Hello Chris,

I have one on the way as well.

I am interested in what you think of it.

Tom

 

[rdshores]

I'll be watching for some results and opinions on this unit too.

 

[Tweek]

Right now I'm seeing how my various branded AA cells perform at 1C loads, my GE/sanyo 1600 cells delivered their rated capacity. However, the Maha 2200 is not faring so well in the same test... /ubbthreads/images/graemlins/smile.gif What I need to to is sit down and figure out a set rate to compare them all with each other and test them all the same. But first impressions are that this is a nifty gadget for sure!

Chris

 

[SilverFox]

Hello Chris,

I was thinking of measuring the actual current draw of a light, then testing battery types to see how they perform under actual conditions.

The 1C rate that you are doing is also a good test.

I am also toying with the idea of seeing how Alkaline batteries perform. Are Duracells better than Ray O Vac, or Wall Mart, or Kirkland, etc.

Another thing that I plan to do is match the capacity of my various cells. I have lights that use multiple re-chargeable cells, and I feel I can get better performance if the cells I put in them are matched for performance.

We had better be careful, this could turn into a full time job...

Keep us informed on what you find out.

Tom

 

[wptski]

[ QUOTE ]
Tweek said:
Right now I'm seeing how my various branded AA cells perform at 1C loads, my GE/sanyo 1600 cells delivered their rated capacity. However, the Maha 2200 is not faring so well in the same test... /ubbthreads/images/graemlins/smile.gif What I need to to is sit down and figure out a set rate to compare them all with each other and test them all the same. But first impressions are that this is a nifty gadget for sure!

Chris

[/ QUOTE ]
Chris:

What do you need connector wise, so one may just use clips to connect to a battery, etc.??

 

[Tweek]

What I did for battery contacts was rather crude, but it works very well, and I can use it for much higher currents than a AA will ever see. First, the unit comes with powerpole connectors on it, so you have to make an adapter to interface with these. I just happened to buy some wire, powerpoles, and the crimper (very recommended!) while I was picking up the CBA. I took a piece of copper sheet (roughly the same as a dime) and cut a couple strips about 2" long off one side. Took these and soldered them to some 10GA wire that I had crimped a pair of powerpole connectors onto. Combine with a couple of quick-grip bar clamps, and you have a very adjustable high-current capable battery holder! You could also substitute a couple pennies, but I prefer solid copper strips.

I'm gonna have to dig up one of my loose 3300 sub-c cells and see how much current I can pull out of it... /ubbthreads/images/graemlins/smile.gif I've seen people elsewhere get up to 20A or so before they start hitting the limits of the CBA and the wiring/connector resistances.

Anyway, for the imagination challenged, I took a couple shots, check em out:

Sorry they're a little blurry, but I', sure you get the idea... /ubbthreads/images/graemlins/smile.gif When I build the adapter, I sized it so that I could get the Magcharger pack in there no problem, I used the stocker from my SL20-X (same pack) for that. Worked great!

Chris

 

[wptski]

Chris:

Thanks! I love your clamp. /ubbthreads/images/graemlins/grin.gif

I posted in a RC Forum and found out, as you probably know that the Power Poles are non-gender. The crimper is a bit pricey for my limited use! I ordered the CBA, temp. probe and a extention cord. I can cut that cord in half an have two that I can make up to whatever I want. I'll put some 10A Radio Shack clips on one piece to start.

 

[Tweek]

[ QUOTE ]
wptski said:
I can cut that cord in half an have two that I can make up to whatever I want.

[/ QUOTE ]

There ya go, that's thinking! /ubbthreads/images/graemlins/smile.gif I went ahead and bought the crimper, I've already replaced a bunch of misc charging setup connections with these, and I love it! Soo much easier. I could see bending a few with pliers and soldering them, but for more than a couple, no thanks, these connectors have a small enough space to fit into in the bodies as it is. Not to mention it's a lot faster to crimp them versus soldering! /ubbthreads/images/graemlins/grin.gif

Chris

 

[wptski]

[ QUOTE ]
Tweek said:
[ QUOTE ]
wptski said:
I can cut that cord in half an have two that I can make up to whatever I want.

[/ QUOTE ]

There ya go, that's thinking! /ubbthreads/images/graemlins/smile.gif I went ahead and bought the crimper, I've already replaced a bunch of misc charging setup connections with these, and I love it! Soo much easier. I could see bending a few with pliers and soldering them, but for more than a couple, no thanks, these connectors have a small enough space to fit into in the bodies as it is. Not to mention it's a lot faster to crimp them versus soldering! /ubbthreads/images/graemlins/grin.gif

Chris

[/ QUOTE ]
Thanks! Once in a while the old brain still works! /ubbthreads/images/graemlins/grin.gif How did you connect for your tests on AA's?

 

[radellaf]

I wish the CBA also had charging features, too, and it seems to have enough electronics that it wouldn't take much redesign to add on to allow it to control power from a DC supply.

I look forward to getting something like it now that there will soon be a Windows laptop in the house. Everything else is Apple, and most of these hobbyist PIC things don't have Mac software.

 

[Tweek]

Wptski: All I did was use the same setup with a AA cell in the clamp instead of the 18650's in the pics. Also, I measured the lithium's voltage drop earlier, and at a 2A load, between the battery terminals and the CBA's measuring point, there's only a 2mV drop... /ubbthreads/images/graemlins/grin.gif

Radellaf: I'm right there with you. When I was there I had a good long talk with the head enigneer there. It seems they are also working on a couple other projects, including a Pro version (roughly 2X or so the discharge power), and a battery charger, although I think they're gearing the charger towards lithium primarily. Still, I'm keeping my eye on these guys! /ubbthreads/images/graemlins/smile.gif

Chris

 

[SilverFox]

I just got mine today. I have been playing with it. This is going to be a lot of fun...

I have some Saft 700 mAh AAA batteries and I decided to check them at different current levels. The first test is at 500 mA, second is at 700 mA, and the third is at 1000 mA. The testing was done on three different cells, so don't draw too many conclusions from it.

I wanted to test at 1/2 C, but the lowest current level is 500 mA. This is not much of a problem. I was just hoping to be able to test down to 250 mA. Oh well...

Here is the graph of the three tests on the Saft cells.

I am currently testing a 9000 mAh D cell. The CBA still is not getting warm and I am running the test at 9000 mA.

I did a quick check of a R-CR123. I ran it at 2000 mA and other than getting a warning that the rate was considered a bit high, everything went smoothly.

This is fun.

Tom

 

[Tweek]

Yeah, some of the warnings they have set in there are a bit annoying (to me, anyway). But I've been having a lot of fun with mine too. It doesn't really start heating up much until you start dissipating a lot more power with it. I ran a discharge on my portable 12V rig, to see what the capacity of the salvaged gel cell was. Not too shabby, as it turned out:

Sorry about the quality of the screencap, it didn't take too well to being downsized. Guess I'll have to work on that, as I plan on posting a lot more of these eventually... /ubbthreads/images/graemlins/smile.gif But hopefully you can get a look see, anyway. The test current I used was designed for an approximate C/5 rate for the battery, and was pretty close the the CBA's 100W power level. It did have some nice warm air coming out after a few minutes... /ubbthreads/images/graemlins/smile.gif

I noticed that 500mA minimum current too. I wonder if it's a hardware limitation or can be set lower in the software. I may have to call WMR up and see, as I would really like to be able to go down to 25mA or so, if the hardware is capable. I would also really prefer the bottom scale to be adjustable as to what units it sisplays, I would prefer a time scale for most tests. Ideally, this could even be implemented along the top of the graph, best of both worlds... /ubbthreads/images/graemlins/smile.gif

Chris

 

[evan9162]

Are you guys able to dump out a text file of measurements (so it could be imported into Excel)?

 

[SilverFox]

Hello Evan,

Yes.

I get a file that has time in seconds and the voltage of the cell at that time. A little math will get to capacity.

I spoke with the excellent folks at West Mountain Radio and the lower limit of 0.5 amps was reported as a hardware limitation. They have had several requests for a lower rate and are evaluating those requests.

Time to do more testing...

Tom

 

[evan9162]

Sounds good!

I bet the 500mA lower current limit has to do with the Rds(on) of the MOSFET they're using, along with (possibly) the resistance of the sense resistor, plus plug/wire resistance.

[edit]
one more question - can it do momentary current/voltage measurements? - so that you could sweep a range of currents and observe the voltage of the pack - that would allow you to get an idea of high current performance of your batteries, and see the internal resistance of the cells.