Well, I was bored and wanted to show a little plot I made. My gens ace is 18 months old and has an IR of about 3, the turnigy is new and has an IR of 4. The gensace is also a lower C rating, but has more mah. Anyway, here is the graph. Also, discharge was 5amp and took over an hour. The numbers ar the bottom are seconds, lol. yes 3800 seconds. I dont feel like converting to minutes, etc



Uploaded with ImageShack.us

just goes to prove how good gens ace packs are.
is the 4200 you tested a shorty?

Check the plot lines WildCat,they're labeled wrong
Do you have any additional info like average voltage?

the avg voltage for any given time point is higher on the gensace also. I was very supprised. to top it off, the gensace gave out 5001 mah on discharge to 3.0v per cell and the turnigy put out 4150. Other name brand packs were short on mah by 300-500. the companies to me that was normal.

doh, your corrct, the gensace is the old pack. and the turnigy was the new one. otherwise the plots are correct.

I fixed the labels and added my 1 year old promatch to the graph also. Its a 65c pack with an IR of 5.

Good work,I'm thinking the Nano hasn't broke in yet so let's see. I'll contribute with a discharge to 7.4v on a puffed IP5600.
IP 5600 @ 5A dsc 'till 7.4v:
mAh 1039
AVG 7.630
IR 87
TIM

What time was the discharge completed at? I am asking because the discharge time in the graph is 1hour and you were at 5amps so I am surprised you didn't get down to sub 7 V within the hour for a 5.1 Ah pack, because it looks half full at the end of the hour.

Call me crazy but I am certain the capacity difference between the batteries is important at that low of a discharge rate. I would expect a larger capacity battery to have a slower voltage drop under an identical load to a smaller capacity battery. 5A is not nearly a large enough draw to push these batteries to depletion and cause significant voltage drop.

For a rough calculation, at 5A discharge:
5.1A battery at ~3800s is at the same voltage the 4.2A battery is at 3200s.

4.2/5.1*100= 83%

3200/3800*100=84%

So the 4.2Ah battery achieved the voltage of the 5.1Ah battery in ~16% less time, the same different in their capacities. This is measured at the half full voltage at the end of the chart where differences in voltage drop would be expected to be more sensitive to when the packs are full. This quick relationship holds throughout the curve at earlier points as well.

I was thinking something similiar. It would be more beneficial to see the same capacity over time. I think that the comparison to the promatch is a better comparison as the capacity only about ~5% different.

I agree, the pro match battery starts to drop off below 8V, after the first 30% or so which is consistent with its higher resistance.

how did you measure IR? because that number seems high.

yeah, my charger wont do it for me, but i have a 15amp discharger from my NIMH days. I also have a viper proguage to watch the voltage and cell balance. So I can manually gather the data and plot it. I found a few IR calculation online also, but the numbers are vastly different than my chargers. I always thought my charger used the 5amp load to check the IR, but I am thinking it used a resister that always checks the IR at the same load and it might be far below the 5amp discharge or the 15 amp charge. I want to pick up a watt meter and track what my actual max amp draw is. Once I know my max peak draw, then I can do an accurate test for my car. The watt meters only go up to 130amps, so i am sure its fine for 2wd buggy, unsure on sc 4x4 or 8th scale. I think I might be suprised how how low the max current in my 17.5 buggy is. I am guessing around 20-25amps. I already know my avg is around 15amps. I based that on how much capacity I drain over a 6minute race.

also, I think the IR equation is Discharge current / (start voltage - voltage under load) = IR . Can anyone verify?

R = V0-V/I