3 ms·
Anyone know why using the wrong unit without enough info became common in the first place?
by jrochkind1 3y ago
Anyone know why using the wrong unit without enough info became common in the first place?
- jdietrich 3y agoMarketers like big numbers. A 3500mAh li-ion cell is more betterer than the same 12.6Wh cell, because 3500 is a bigger number than 12.6.
- falcolas 3y agoI'm not an expert, but as a (former) drone enthusiast, it's probably because of C values. C values tell you how quickly a battery can be safely discharged, and it's based on the amperage. Specifically, it's a direct multiplier for the amperage. And for batteries in the before times, the voltage was clearly printed on the battery, as was the mAh and C values.
- kec 3y agoC is a multiple of current but is linear with (nominal) energy, no reason that would force this.
- trashtester 3y agoWhat is the Wh of a "12V" 1000 AH car battery with internal resistance of 20 milli-ohm? Try that for starter engines that draw 50A, 100A or 200A One may think that at 100A, the starter engine will be able to consume 1200W However, if you pull 100A, the internal voltage used to overcome the internal resistance is 2V, so you really only generate 1000W, or 5/6 of the raw energy stored in the battery. At 50A, the voltage loss is only 1V, so the start engine gets 550W, or 11/12 of the energy tapped from the battery. Finally, at 200A, the voltage loss is 4V, meaning that the starter engine only gets 1600W, or 2/3 of the energy stored in the battery. And this is under relatively good conditions. If the battery is freezing cold, the internal resistance can become much higher. In all cases, the internal resistance leads to heat inside the battery. Hopefully, it should be clear that for low resistance / high wattage loads, the Wh metric is not very accurate.