I had an interesting conversation recently about power bank or power station ratings of mAh (milliamp hours) vs Ah (amp hours) vs Wh (watt hours). There is math behind how to calculate things, but let’s make this very simple to start.
When you see an item online that says, 90,000mAh, it sounds like a lot. But 90,000mAh is 90Ah, which can be quite a lot. However, if the ratings are not deceiving you will see either the number of volts (i.e. 13.6V) or number of Watt hours (i.e. 288Wh). Yes, there are a lot of deceptive ways to con people into buying large mAh power banks but it isn’t all equal.
Let’s say a power station manufacturer states that it is 90,000mAh (or 90Ah) and 288Wh. This is not a deceptive ad. But what is the voltage that derives these numbers? It is Wh/Ah=V (watt hour divided by amp hour = voltage) which will provide the number of volts. So, this power station is a 3.2V, 90Ah device. What does that mean when I am using the cigarette adapter to charge something with this power station? It cuts it in about 4. It would be a 22,500mAh (and loss of conversion from 3.2V to 12.8V so it would be less), power bank for 12V devices. As opposed to if you bought as 100Ah LiFePo4 battery, it will be about 13.6V so this is significantly more than a 90Ah – 3.2V power station.
I built a 40Ah power station at 13.6V loaded and it can run a Starlink Mini for about 15-22 hours. The 90,000mAh 288Wh Power Station can only run the Starlink Mini for about 6-10 hours. Good news is the latter Power Station will be lighter and potentially smaller so that length of time before recharging the Power Station to be sufficient. But if you need more time, a 13.6V LiFePo4 battery will be the better way to go.
Next time you buy a smaller portable power bank or power station, ask the right questions to find out how long something can run based on the specifications the manufacturer provides. If they only provide one of the 2 numbers you need to calculate the other, buyer beware.
Hope this helps in making the right decisions.
