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Voltmeter at tech station.

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Voltmeter at tech station.

Old 10-12-2023, 10:21 AM
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Default Voltmeter at tech station.

What voltmeters are everyone using at the tech station? Anyone using one that reads 3 past the decimal at 4 and 8 volts? So like 4.22x or 8.44x?
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Old 10-12-2023, 11:27 AM
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Most I know use a simple hand hold multimeter. If you get something like a Fluke you can let it calibrate every year. Calibration will take away any discussion by drivers who think the meter is wrong.
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Old 10-12-2023, 11:50 AM
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Just checked. My Fluke 87V read 12.54 consistently.

So yeah two decimals.

So 4.3 and 8.5 are DQ's. Not 4.28, for example.
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Old 10-12-2023, 02:30 PM
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Originally Posted by Roelof
Most I know use a simple hand hold multimeter. If you get something like a Fluke you can let it calibrate every year. Calibration will take away any discussion by drivers who think the meter is wrong.
There simply is no discussion. The only meter that counts is the one at tech. Period.
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Old 10-12-2023, 02:40 PM
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Originally Posted by DirkW
There simply is no discussion. The only meter that counts is the one at tech. Period.
Gotta be careful with that. I was at a club race and they were using someone's cheap meter. Everyone was complaining because no one was passing tech. I always have my Fluke 77 with me. They asked me to check and sure enough the other meter was reading half a volt higher than mine. They used my meter for the rest of the day.

Oh, and this is a pet peeve of mine, and you're all going to hate me for this, but the correct max voltage for a 2S battery is 8.40 volts, not 8.44. The 8.44 number is a misconception of the original rules that racers made and are not willing to let go of. And 4.20 for 1S
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Old 10-12-2023, 03:16 PM
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Well, half a volt difference is an extreme example. Thought we were talking just one or two drivers being slightly above and then arguing the meter, while all other drivers were within legal limits.

And yes, 8.40V is the limit here as well, and you'll not be entering the qualifier/race if you show as much as 8.41V (or more). But of course you could organize a race with a rule for 8.44V being legal - I just haven't seen any around me so far.
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Old 10-12-2023, 03:23 PM
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Originally Posted by DirkW
There simply is no discussion. The only meter that counts is the one at tech. Period.
Yes, that is possible as most have stated that in the rules but still it is wise to check it from time to time to be sure it is within an acceptable tolerance, it is not a first time some wise ass guy with a calibrated meter starts the discussion the tech one is wrong. You can find some precision voltage reference modules on Aliexpress with an exact 5.000 volt output (and sometimes with more voltages), then you can regularly check your meter and from others.

Like: https://nl.aliexpress.com/item/1005002255913671.html
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Old 10-13-2023, 07:37 AM
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Originally Posted by jiml
Oh, and this is a pet peeve of mine, and you're all going to hate me for this, but the correct max voltage for a 2S battery is 8.40 volts, not 8.44. The 8.44 number is a misconception of the original rules that racers made and are not willing to let go of. And 4.20 for 1S
The max voltage the track is looking for is irrelevant to my question. The track could be allowing 4.35 for all I care. I just was curious what model of voltmeters tracks were using and how far out in the decimal precision they were looking.
Example lets say you are looking for 8.40 are you looking for 8.400 or would 8.404 pass?
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Old 10-13-2023, 08:22 AM
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Most simple meters will show 8.40 so 8.41 is wrong. But yes, a good question if your meter can show 8.400000 and it shows 8.400001 then what will be the gain on the track? Even with 8.41 that is the question but still people will go for the max possible. So you need to set some tolerances.
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Old 10-13-2023, 08:41 AM
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What charger are you using that is accurate to the thousandths?
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Old 10-13-2023, 10:08 AM
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Originally Posted by gotheframe
What charger are you using that is accurate to the thousandths?
irrelevant to my question.
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Old 10-13-2023, 10:55 AM
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Originally Posted by mrreet2001
The max voltage the track is looking for is irrelevant to my question. The track could be allowing 4.35 for all I care. I just was curious what model of voltmeters tracks were using and how far out in the decimal precision they were looking.
Example lets say you are looking for 8.40 are you looking for 8.400 or would 8.404 pass?
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Just IMHO, if the rules specify two decimal places, then you would utilize standard rounding procedures for a meter that reads more than two decimal places. In your example above, if the rule is 8.40 volts and the meter reads 8.404, that is a pass. A reading of 8.405 would not pass, as in standard practice, that would round up to 8.41. I'm sure others will have differing opinions and there are valid arguments both directions:
Literally any reading over 8.400000000 is not a pass
or
8.409 is still a pass because the rule states the reading must be "8.40" and that meter is reading "8.40." and anything after the second decimal place is not accounted for in the rule.
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Old 10-13-2023, 11:42 AM
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Originally Posted by mrreet2001
irrelevant to my question.
Lucky for you I was the one asking a question.

Do share though how you intend to control charging to the thousandth.
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Old 10-13-2023, 12:56 PM
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What ever meter is being used, it is always nice if is has good probes that make it easy to get a measurement from the battery.
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Old 10-13-2023, 01:18 PM
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Originally Posted by mrreet2001
The max voltage the track is looking for is irrelevant to my question. The track could be allowing 4.35 for all I care. I just was curious what model of voltmeters tracks were using and how far out in the decimal precision they were looking.
Example lets say you are looking for 8.40 are you looking for 8.400 or would 8.404 pass?
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Well that was just a [REDACTED] statement that I wanted to make. Sorry can't use the P word

Now, if you want to speak to engineering absolutes, the rule is no more than 8.40 volts, so 8.404 is more than 8.400, and therefore fails. Now you really want to get mad at me? If using a 3 1/2 digit multimeter, if you're measuring 8.40 volts, the actual voltage is just a little bit above 8.40 because that's the only way the meter would display 8.40 In laboratory situations, they have voltmeters that go to 4, 5, or 6 digits, but they are very expensive and out of the range of your typical track.

But let's get back to reality. We're racing toy cars, and we just want to make sure no one is charging their lipo's to the point of explosion. It's about safety. Just like using lipo sacks. My Fluke 77 retails for over $300 and that might be a bit much, but I think it's worth it. But any decent Home Depot meter should be good enough, but it's a good idea to check.
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