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Old 01-01-2004, 06:46 PM   #1
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Default GFX Charting - "spike at 120"

I've spent the day plotting out the discharge curves of some of my battery packs so I can rank them as to what I'm going to race stock / mod / practice with.

Every data set has a voltage jump around 120 seconds. Can anyone explain to me what this is about?

Here's is a sample: of the data taken from 117 seconds to 130 seconds... voltage for four of the packs - you can see at 123 seconds each pack jumped up. Is the Turbo GFX doing something in its discharge cycle at this point?:

4.864 4.787 4.879 4.875
4.86 4.787 4.879 4.871
4.86 4.787 4.879 4.875
4.86 4.787 4.879 4.871
4.86 4.787 4.879 4.871
4.86 4.787 4.875 4.871
5.142 5.073 5.135 5.131
5.157 5.091 5.15 5.146
5.168 5.098 5.157 5.15
4.908 4.82 4.912 4.901
4.897 4.805 4.893 4.89
4.886 4.805 4.893 4.886
4.882 4.802 4.886 4.882
4.879 4.798 4.882 4.879

Here's the graph showing it happening for 11 packs in a row...

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Old 01-01-2004, 06:49 PM   #2
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I think this is where it is taking the AR reading. (actual resistance)

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Old 01-01-2004, 08:04 PM   #3
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Definately an abnormality in the data. Looks like the amp load dropped for a split second. I'd discard those numbers in your plots as outliers.
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Old 01-01-2004, 08:09 PM   #4
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Craig is right. The pause at 123sec is when the GFX is taking the AR reading. The reason it drops the "load" is it measures how long the cell's voltage goes back up and back down to where it was. This is how it measures the resistance.

Dont worry about it its completly normal.

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Old 01-01-2004, 08:09 PM   #5
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Yes, looks like the AMP load decreased.
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Old 01-01-2004, 08:13 PM   #6
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Looks like the unit stopped the discharge for a second for some reason. You may be able to find out whats goin on if you check out your manual. I have something similar happen on the CDC I use. If it gets to hot while discharging, it stops while it cools down. Then when it restarts the voltage is higher than when it cut out due to the battery having a rest. Looking at the numbers you have there is going to be a small amount of inaccuracy in you overall pack avg discharge voltage. you can still compare your packs tho which is really all thats important.
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Old 01-01-2004, 08:45 PM   #7
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In the manual..it will tell you to switch off Actual Resisitance (AR) if you do not want the spike at 120s....... Perfectly normal....
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Old 01-01-2004, 09:10 PM   #8
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Thanks gents...

of course I didn't RTFM
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Old 01-01-2004, 09:23 PM   #9
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Default GFX?

how do you change the number of cells? The instrustoins really bite.....
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Old 01-01-2004, 11:28 PM   #10
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go to 'set' mode, look where it says profile default:6CellNiMh and turn the dial one click at a time until you find the one you want, then hit start, and continue use as normal.
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Old 01-01-2004, 11:49 PM   #11
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???, that is only to name the different profiles, and select which one, you can change the type of cell, there, but you change the number of cells at the discharge mode
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Old 01-02-2004, 04:44 PM   #12
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Geek - How did you make that graph? I have the cable to connect the GFX to my computer, but am not sure how to convert the output into something useful.
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Old 01-02-2004, 04:46 PM   #13
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Frode S: Excel is what I have used.
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Old 01-02-2004, 05:26 PM   #14
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Tres - My experience with Excel is very limited. Any tips to lead me in the right direction?
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Old 01-02-2004, 05:28 PM   #15
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Let me check to see if I still have my template I used...
If not Geek may share his
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