Comments by "Chaos Corner" (@chaos.corner) on "Duracell PowerCheck: A genius idea which didn't last that long" video.

The interesting thing with chemical batteries is they have a voltage related to the chemical reaction which is a constant. So how does the voltage drop? The 'internal resistance' increases and you are effectively operating a voltage divider. This is why battery testers need to have a dummy load. Multimeters, especially old ones kind-of come with some load anyway but with semiconductor based multimeters, that's typically very high and may not be enough to give anything like a useful result.
1
@emmakai2243 I have some 9V replacement lithium batteries with LED capacity gauges.
1
@seraphina985 The problem with 'V=IR' is always true is that this is only the case if R can be considered dependent on many other factors such as temperature, possibly time and maybe even V or I themselves. Even in the case of electrocution, for instance, the resistance of the subject actually drops the longer the current is passing.
1
@rotaryenginepete The book you never opened, apparently.
1
@ChallengeTheNarrative It's simply the chemistry. Different chemical reactions provide electrons at different PDs. It's pretty much just a coincidence* that NiCADs and NiMH share ~1.2V and alkaline and lead acid are at 1.5V. Meanwhile LiPos are typically around 4.2V and will use fancy electronics to match other requirements where needed.
1
@Curt_Sampson The problem is, if you're considering it at a single point in time, the equation trivially reduces to that it is possible to divide V by I and you can't necessarily infer anything useful from that. By recognizing a class of components that we consider linear, it becomes much more useful.
1
@Curt_Sampson But I=V/R(V) isn't saying anything. And with the LED, you'll be using Ohms law for the resistor (which has a consant-enough resistance) but for the LED, you'll be looking at the V/I curve or be picking some 'default' value. That's not using Ohm's law.
1
@Curt_Sampson We seem to have started going around in circles which is something I try to avoid. Especially in YouTube comments which tends to be a less-than-ideal forum for discussion. Also there is lot of good info that explains it better than I ever could out on the web. All the best.
1
How we use batteries has changed a lot over my lifetime, even beyond the recent move to rechargeables. Remotes were rarer. Batteries had more of a use case where you were likely to be mobile and it be inconvenient to do replacement so knowing capacity would be useful. Along with just not being very good, I think they just caught the wrong end of a paradigm shift.
1