this post was submitted on 25 Feb 2026
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mAh/g (milliamp-hours per gram) is essentially still a measurement of capacity, but in terms of current instead of power.
We can do a little dimensional analysis here to translate between them. Power = Current x Voltage, so you'd multiply this (Current x Time)/(Weight) value by the nominal voltage of the cell to get to (Power x Time)/(Weight).
Phone batteries are often specified in units of Current*Time (e.g. milliamp-hours), but I'm not completely sure why. I think it has to do with voltages being standardized for certain types of cells, so the only real variable in the battery capacity is the current.
Edit: rearranged some ideas to make more sense
I think it's marketing
5000 mAh is much a bigger number than 19 Wh and marketing loves huge numbers
Kinda like BMW did with the i3.
In 2013 Tesla was selling a model with a 60 kWh battery so BMW had the genius idea to install a 20 kWh battery BUT refer to it as "60 Ah" battery.
Tesla introduced the 90 kWh battery? BMW responds with a 94 Ah battery (28 kWh)
Newest Tesla has 100 kWh battery now? BMW has 120 Ah battery (38 kWh)
"See? Higher number!", says the marketing
And in order to have a comparable range number they had to implement heavy weight reduction techniques like using carbon fiber for the body, negating any cost saving from the smaller battery AND giving the owner a total loss after small collisions as it shatters instead of bending
That's an incredibly longwinded way of saying "mahh Tezlur burns three times as much 'clean coal' per mile as a commie BMW, yee-haw".
This is the part that annoys me. The nominal voltage could vary between different batteries. 200Ah/g means different capacity for a 6v battery verses a 48v battery. I'm guessing battery scientists are using standardized nominal voltages for these tests or are seeing the same Ah/g capacity at different voltages (that I may have simply missed in the paper because I skimmed it and I don't claim any deeper knowledge on battery research)