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Old Jan 09, 2009, 05:26 PM
PLD
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John,

1kHz testing can be attained already, thankfully just in firmware changes (this is why i'm going to have to move to a slightly larger uC, need more flash space for the extra options ).

Of course, when it comes to selecting multiple tests and loads, we're then going to need to start putting a jog-wheel or selection buttons onto the board, starting to deviate away from the original simplicity of the unit... perhaps we can cram everything into the second prototype and suffer second-system failure syndrome (ref: The Mythical Man month).

Paul.
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Old Jan 09, 2009, 05:30 PM
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...or to keep it simple, perhaps perform both the DC test and the AC test and present both results ?
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Old Jan 09, 2009, 05:35 PM
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Quote:
Originally Posted by everydayflyer
FYI Hyp. 720i Net is a lot more accurate than the DUO was(is) which was off by approx. 250 to 300%.

Charles
Does the new 1.9 firmware improve the DUO's IR readings? I haven't upgraded yet...

Jack
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Old Jan 09, 2009, 05:38 PM
Southern Pride
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Me neither , to busy with 720i


charles
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Old Jan 09, 2009, 05:41 PM
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Quote:
Originally Posted by everydayflyer
Me neither , to busy with 720i


charles
I'll test tonight, I have a pack ready to charge and the firmware ready to go...

Jack
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Old Jan 09, 2009, 05:49 PM
PLD
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Quote:
Originally Posted by kgfly
...or to keep it simple, perhaps perform both the DC test and the AC test and present both results ?
Now where is the fun in -that- ?

I can cram on the board two momentary pushbutton switches (tiny 6x3.5mm) as a provision, since I've got the area spare - won't specifically use them but at least it'll have been planned.

Paul.
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Old Jan 09, 2009, 06:10 PM
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Quote:
Originally Posted by pldaniels
I appreciate that it'd be -nice- to sell these at $40 USD, unfortunately it's not going to happen. $60 would be about right for a first-release batch.
My price suggestion was not intend to offend anyone, but rather a reality check. CellPro 10S at the price of $190 provide fairly accurate cell resistance measurement. It probably wouldn't take hard for FMA direct to provide update firmware for their $79.99 CellPro Multi-4 to include such functionality.

This just some thing I would consider if I am working on a new product...

Brian
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Old Jan 09, 2009, 06:18 PM
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Quote:
Originally Posted by jfetter
I'll test tonight, I have a pack ready to charge and the firmware ready to go...

Jack
DUO II w/ 1.7 Firmware - TP 2100 3S, hooked up for 4 minutes, 42% charge, 70mΩ

UPGRADE FIRMWARE

DUO II w/ 1.9 Firmware - TP 2100 3S, hooked up for 4 minutes, 50% charge, 40mΩ

Jack
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Old Jan 09, 2009, 06:24 PM
PLD
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jfetter,

That's a big difference from the firmware change. I'm going to assume that that's a "whole pack" resistance (40mΩ), the sad question is, "which one is real?"

This is where doing your own testing with a pair of multimeters and a known load can be really useful.

Paul.
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Old Jan 09, 2009, 06:37 PM
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Quote:
Originally Posted by pldaniels
jfetter,

That's a big difference from the firmware change. I'm going to assume that that's a "whole pack" resistance (40mΩ), the sad question is, "which one is real?"

This is where doing your own testing with a pair of multimeters and a known load can be really useful.

Paul.
Paul,

Yes, whole pack resistance. Hyperion has admitted that they weren't discounting the resistance of the internal circuitry previously. Their new model is much more accurate in regards to IR and during Charles testing, when he noted that fact, it was implied this was a firmware fix versus a design change, this upgrade pretty much confirms it. Charles has taken readings againt the Duo and has shown it was 200% to 300% high, it was said it's for reference only. Hopefully this new firmware means we can use it not only for reference but for actual values as well...

Jack
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Old Jan 09, 2009, 07:06 PM
Southern Pride
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I really to not want to hi jack this thread but to show difference in IR at different temps.

http://www.rcgroups.com/forums/showp...&postcount=200

Subject A123 4S 2300 Zapped cells

Snip:

To my surprise it calculated and displayed IR after the discharge. This 4S has been a very recent test subject of mine and I knew IR was a nominal 16-18 m Ohms but this is temperature related. 720i indicated 23 m Ohms which I felt good about for a cool battery.



Next a CBA II discharge @ 20 amp. to 10V which yielded 2.092Ah and warmed the cells.

Next a 20 amp. charge .
As I expected the pack IR reading was much better with cells at 105F, 18 m Ohms which is perfectly in-line.



Charles
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Old Jan 09, 2009, 07:18 PM
PLD
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Well folks, I think I'm going to give this project the boot/bin.

Looking over a lot of data and the more I see the more I think that I just can't get the required accuracy without going silly.

At best I'd rate the unit as being good for +/-1mR but from what I've seen we really need 0.1mR resolution, especially for the larger cells and I just can't coax that out of the device, more so with the problems of contact resistance and the inability to factor out balance lead effects.

Chargers can offer decent internal resistance measurements without higher costs because they already have all the required internals as part of good lipo charging in the first place.

.. so, sorry about all the excitement but I think this is one that's just going to have to go into the "ends won't meet" bin.

Paul.
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Old Jan 09, 2009, 08:10 PM
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i would have really bought one of these items as i think its just a some thing to have in your toobox, me doing nation diplomer in electronics i know that its complex but insted of scrapping the idea i think you should stick with your first idea about 2 pins and its 1 cell testing and thats it, the rest about buttons and all that will only make the circuit more complex and bring the cost of the product

one thing which i hant seen so far is this product out and yes its some thing i would buy and recomend to every one

i think you should just make a small device that will test the cells IR and thats it dont make it any more complex

look at the cell spy and all them lipo monitors there all cheap and every ones got them
and i think that its a cool idea and i would 100% have your product in my toolbox
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Old Jan 09, 2009, 08:31 PM
PLD
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henal,

The problem comes down to "how accurate is enough?". Are people going to be content with +/-1mR etc.

At 1mR, it's more than ample for packs up to about 2000mAh-20/30C, but when moving to bigger cells at higher discharge rates, it becomes difficult to separate between the 'okay', 'weak' and 'great' when it's only a matter of 0.5~0.1mR difference

As a 1mR resolution, 2 (4) pin device, yes the IRM will work.
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Old Jan 09, 2009, 09:53 PM
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