The problem is that mAh tells you absolutely nothing about battery capacity. An mAh rating is useful if you're comparing two single-cell batteries using the sam

The problem is that mAh tells you absolutely nothing about battery capacity. An mAh rating is useful if you're comparing two single-cell batteries using the same chemistry - but that's not what we are doing in practice. For example, a 100Wh battery could be built using a single li-ion cell, which means it would be 27,000mAh. Same battery using an LFP cell? 31.250mAh. But wait, it's a laptop - it's far more efficient to put multiple cells in series. Four li-ion cells in series would mean a capacity of 675mAh, or 540mAh if you use five cells. The five-cell one is probably more efficient, but if you blindly look at the mAh rating it looks like it has a significantly smaller capacity. Nobody is going to buy that, so the marketing team will convert it back to "single-cell equivalent" and put 27,000mAh on the box while still keeping an 18.5V rating, and people who passed a highschool physics class are going to think it's a 500Wh battery. It gets even worse with LFP, because now the marketing team is asking you to convert it to "single-sell li-ion equivalent" and the figure is now completely unrelated to what's actually happening! That 520mAh 6-cell LFP battery? Just put a 27,000mAh label on it: who cares, bigger is better.