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Old 02-25-2005, 02:47 PM   #1
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Default Voltage vs Runtime

Hi all

When buying batteries what is more inportant, higher voltage or higher runtime?

Also what would be better for 540 and stock?

Who is a better matcher out of these companies
SMC, Velocity Factory, team orion, Trinity, and Pro Match


thanks
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Old 02-25-2005, 02:48 PM   #2
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depends, for racing votage, for bashign runtime, i personally preffer longer runtime vene though I race as Im runnign low gearing which makes te motor run very high
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Old 02-25-2005, 02:49 PM   #3
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For stock classes, Voltage and a low IR are much more important. If you're running modified, runtime is the most important.
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Old 02-25-2005, 02:54 PM   #4
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thank you thecrow and John, looks like I'm buying the high voltage then

thanks again
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Old 02-25-2005, 03:21 PM   #5
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are SMC new 35 amp battiers good for running mod?
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Old 02-25-2005, 09:37 PM   #6
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Run time first more so in mod but important in stock. With extra run time you get further back on the discharge voltage curve therefore having higher voltage at the end of the race. Higher voltage means more speed.

Chris.
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Old 02-26-2005, 04:47 AM   #7
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You're forgetting about heat. With lower voltage you have to push more in the beginning to keep up. As a result batteries and motor heat up very quickly. This increases the internal resistance and as a result the voltage drops even further!

In my opinion it is allways best to go with higher voltage as long as the difference in runtime does not exceed say 20-30s at 30Amps. The higher voltage, even with the shorter discharge time (runtime is actually the wrong word!), will actually lead to longer runtimes (no need to push from the start!) and will give you a more constant (and higher) voltage throughout the run. The latter is only true if internal resistance is low to begin with, so low internal resistance is, in my opinion, also more important than discharge time.
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Old 02-26-2005, 06:58 AM   #8
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Default discharge graph

If you make a graph by putting your battery on a discharger and plot time vs voltage; you will see a long plateau where the voltage remains almost the same and then at some point it will suddenly start declining significantly at an increasing rate.

I would think if you were to plot a graph of the batterys voltage right after the finish of your race and you found it was still on that plateau, the battery has sufficient run time and the voltage level of that plateau would be what matters.
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Old 02-26-2005, 08:04 AM   #9
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Heat lowers the internal resistance of cells, not increases but that's not a big issue. How many drivers do you think can feel the difference between 7.05V and 7.1v? I know I can't and I have been racing for 13 years. If you buy run time batteries you can race stock or Mod without a problem. If you buy batteries for only voltage, you can really only race them for stock and you will still be out motored at the the end of the race by the guy's with better run time. When I come off the track I have about 55 seconds left when I run 12th stock, If I had voltage cells the run time on them woul dbe about 35 seconds less so I'd only have 20 seconds left. With that little left in my cells the voltage at the end of the race will be much lower.

Chris
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