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With elementary math, consumers could easily calculate battery life by dividing watt-hours by power consumption.
I mean, for something like an LED, maybe, but a lot of computing devices can vary power consumption based on what they're doing.
I do agree that it's pretty ridiculous that anyone is selling a power bank without a watt-hour rating.
This shits driven me nuts for years. Rechargeable flashlights rated in milliamp-hours?? What the fuck is that? Like they said, it's marketing bullshit so you get tricked into buying something that sucks.
But GOD FORBID WE REGULATE ANYTHING RIGHT??
Lead-acid battery OEMs are also allowed to market Ah on batteries with a 50% DoD...
Lots of people don't realize lithium is actually cheaper because of this
I guess they could still lie about watt-hours, but buying anything based off of the reported mAh capacity is a crapshoot.
Ended up with a clearly fake 18650 in my collection. Weighs way less than an older 2200 mAh one but it's label says 9900 mAh. Again, it's an 18650.
The culprit:
Shit that makes you wonder why you're trying to earn an honest living when people get away with this bullshit
I've thought about selling out my morals, but realized I could never live with myself.
The one that tempts me is preying on SovCits. They're such suckers, you could milk so much money off them and fuck em, right?
But nooooo I have to have a legitimate career...
I may be re-thinking my morals for things like that here soon. My legitimate career relies heavily on federal grant money, and my skills aren't rare enough to hope France will adopt me. Maybe I'll start a meme coin or something lol.
Any 18650 with a rated capacity of more than 4Ah is a fake. They will usually be very low capacity. The low weight and the hollow sound when you tap on it is good indicator of that too.
There are a number of reputable sites for buying 18650 cells. Stay away from Amazon and Aliexpress, they are full of fakes.
I guess they could still lie about watt-hours
Your battery illustrates that; 9.9Ah * 3.7V is, indeed 36.63Wh. Buying anything without trust in the seller or verification by a third party is a crapshoot.
That's true, but this one came from a known (local) vendor. I took it back, and they were happy to refund it. Since they were gonna toss it, I asked if I could keep it (it works well enough to power an ESP32).
I'd be a little concerned about safety. A manufacturer or distributor that's willing to lie so blatantly about capacity might also be willing to sell cells that failed QC.
Yep. It's for an outdoor weather node on a metal pole, so damage would be fairly minimal if it had a bad day. It's also only charging at like 200 mAh (max) since it's got only a small 1W solar panel hooked to the charge controller. The only other concern would be summertime temperature, but I worry about that regardless of the cell.
As stated by another user, Wh is not a good metric for batteries because it will change depending on the load (voltage and current).
mAh is a strange unit, but it is the amount of stored charge (as in Coulombs) which does not depend on the load, so it makes sense to rate the capacity by this metric.
Why not just use the stored charge multiplied by the average cell discharge voltage at max load for Watt-hours? This may even encourage them not to go overboard on max load ratings.
Sure it could be a bit higher than what the user gets after voltage conversion, but if they are not maxing it they may get better?
I'm no electrical engineer, so this question isn't actually rhetorical - I'm wondering if this would work.
Powerbanks are where it's most problematic. They're usually reporting the capacity of the battery cells in mAh. Those cells will be at 2.8-4.2V during operation, but the powerbank outputs 5V, or in modern powerbanks some higher number. 5000 mAh at the 3.6V average of the cells during discharge is certainly not 5000 mAh at the 9V it's giving to my phone.
It's not going to give my phone 2000 mAh @ 9V or 18 Wh as the math would suggest either because it's well below 100% efficient. I'm not sure what's reasonable to demand in terms of advertising here since efficiency will vary with output voltage and output wattage.
Yeah, and my newer powerbanks all do PowerDelivery for 5, 9, 12, and 20 V.
I'm assuming watt-hours would be universal for them all (watts are watts, as the saying goes).
Well... sort of.
Batteries perform differently under load. A battery that delivers 10Wh under a 1W load will probably deliver less (and get warmer) under a 10W load. Power supplies also perform differently under load, and DC-DC switching power supplies perform differently based on the output voltage. Generally, a larger voltage conversion and/or a higher load is less efficient. There's also going to be some base power consumption in the circuit, so the most output power is probably achieved at some sort of medium load.
To make things more fun, batteries are usually tested under constant current, not constant power. The increasing current as the battery drains of a constant power load will result in less total power, and constant output power often means increasing input power as the battery drains.
In short, the real world is complicated. Giving best and worst case Watt-hours could be a reasonable approach.
Ideally they would provide a graph showing how many watt hours it will output from minimum to maximum load. If it supports multiple voltages, there should be a separate line in the graph for each voltage.
I don't understand why everything isn't just rated in Wh or mWh. It gives them a bigger number to advertise and it's voltage-independent. Sure there are load-dependent conversion efficiencies that complicate things a bit, but nobody is going to get up in arms about a 5% deviation from the advertised spec due to less than ideal conversion efficiency. Compared to trying to figure out how many recharge cycles I'll get on my 5000mAh laptop battery from my 20000mAh power bank (what voltage is that laptop battery running at again?) a 5% efficiency drop is a big nothing burger.
With elementary math, consumers could easily calculate battery life by dividing watt-hours by power consumption.
Power consumption oscillates a lot, I don't find power useful at all other than for light bulbs. Capacity of a power bank, on the other hand, is somewhat comparable to your device's capacity - even though there are some losses in this transfer.
