Why that mAh rating is a lie, but still the truth

I’m not a socket plumber, and electricity isn’t my forte as you can see in some of my ratings years ago. Also potentially this article, but I do know a little about converting Watt hours to mAh when it comes to phones. This is just a short piece on recognizing when you’re not being sold what you think you’re being sold.

TL;DR – how a device advertising 140,000 mAh could deliver only 34,000 mAh to your phone and not technically lie.

You think a 5000 mAh portable charger will fill your phone’s 4000 mAh battery. You’re possibly wrong. As a note, this is aimed at consumers who aren’t particularly versed in the ins and outs of electrical minutia, so yeah be nice here. Feel free to correct me, I grew up around the American educational system and none of my education included a basic electronics class.

I was approached about doing a review of a 500 Watt Hour battery/charger recently. It listed the mAh it was capable as about 140K. This stuck out to me as off as your phone and most USB things charge at between 5 & 12 volts, and at 500 Watt hours that is a range of between 40,000-100,000 mAh. They were listing (on the top end,) roughly 40% more battery than they were going to deliver to a phone. I started investigating because the product seemed too good to be true, but also something I wanted for a school I’m associated with.

Yeah, the device is 500 Watt hours, the unit does other things and can run a car minifridge for about 4 hours. We’ll discuss that some other time.

The formula in case you’re wondering is (Watt hours)*1000/(Volts) =(mAh) – in the case of the unit above, they were using 3.6 volts as the volts. This was both correct, in that the batteries they are storing the power on internally in their device are 3.6 volts, but a consumer misrepresentation as the average consumer will be looking more in the 5-12 volt range (what your phone charges at,) which makes the mAh they listed about as useful to the average consumer as knowing your electrical socket in your wall could deliver all the power in the land to your TV… eventually.

So, only delivering 70% of what the consumers are expecting right off the bat. Then you’ve also got conversion loss. Of the remaining 40-100K in the battery you’re only going to get about 85% of that out to your phone. This is just the price we pay to move power from one spot to another and that’s not really something I expect them to factor in personally. On the 12 volt end that comes out to 34,000mAh, and the 5ish volt spectrum 85,000mAh.

And if you went Qi charging with that 34,000 you might be looking at 10,200mAh-27,200mAh to your phone. However, we’re going to look more at the 85,000mAh as being what you are getting.

I did some searching on Amazon on some off brand cell phone aimed chargers, and a couple of on-brand as well, but discovered the representation of mAh was generally more associated with the internal battery when the price looked too good to be true. Several companies also don’t bother to disclose what the Watt hours are, so reading reviews was the only way I was able to catch a few.

Your battery’s internal voltage also factors in to what you use from the charging side. But yeah.

So there you have it. Buyer beware. Ask questions. Use a Watts to mAh calculator. Buy from a company you can curse at on Twitter. Watt hours is your friend. mAh can deceive. Rage rage against the dying of the light. That’s a charger as the featured image as a note.

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Paul E King

Paul King started with GoodAndEVO in 2011, which merged with Pocketables, and as of 2018 he's evidently the owner. He lives in Nashville, works at a film production company, is married with two kids. Facebook | Twitter | Donate | More posts by Paul | Subscribe to Paul's posts