Electronics aren’t my strong suit so can someone explain for a dumbo like me how this would work.
Some handheld flashlights (torches) have a powerbank feature. If such a flashlight had a fully charged 3000 mAh 18650 battery in it and it was connected to a phone with a flat battery of 3000 mAh capacity what would happen?
1 Nothing because flashlight powerbanks are a sales gimmick con trick and don’t actually work
2 Would the flashlight and phone balance to 1500 mAh each (that’s ignoring, for now, transmission losses)
3 Would the flashlight transfer, as far as transmission losses allow, the full 3000 mAh to the phone
4 Something else
I ask because I am tempted to buy a flashlight / powerbank for emergency use. But I want the Straightdope on this.
If the flashlight is designed correctly, it will have an output circuit designed to charge whatever is connected. This could be a specific port or a switch control. So it should be able to transfer most of its stored power to the phone in this case.
There are plenty of devices out there that do this, no reason why a flashlight couldn’t work correctly. Check the reviews.
There are portable chargers/powerbanks available that only act as portable chargers. They give you a lot more charge for the dollar and are probably the better way to go. In something the size of a smart phone, expect closer to 30,000 mAH.
Another option is the crank chargers. Also a lot of solar chargers now.
I had seen the pure powerbanks which got me thinking that one could be useful. But I don’t go camping so really it would only have any utility to me in a real emergency. Which thankfully for me is rare to non-existent.
The appeal of a flashlight powerbank is it could get regular use as a flashlight plus if I had two decent batteries then, in theory, I could charge my phone at least once or twice if there really was an actual emergency.
Any emergency lasting beyond one full charge of a phone and I’m probably dead anyway.
Fair enough. Though I lived through an 11 day power outage just 10 years ago with Sandy. Also a pair of 5 day outages with Irene and in 2020 a wind shear that savaged my old town.
I now live in a town with better power infrastructure. They were down 30 hours when I was down 11 days.
I have an emergency radio/weather radio that can also function as a flashlight (two different light sources), and for its rechargeable battery has a solar charger, crank charger, and USB charger. It can also be used to charge other items via USB. It’s quite versatile. Admittedly, also limited in some ways.
However, as noted a dedicated power bank intended to charge up then discharge to charge other devices will function in that role more efficiently than the multi-use radio I have.
A lot depends on how the device is designed.
It can also run off non-rechargable batteries but I haven’t tried that yet and I don’t know if the charging-other-devices thing would work well with that.
If you’re using it as a flashlight it will reduce the power available to recharge the phone and vice-versa.
Other options are a cord that plugs into the “cigarette lighter” on your vehicle that lets you charge phones and other devices that way. That might be more suited to your needs.
As it happens my car has a built in USB socket as standard. I have never tried using it for charging anything and don’t know whether a USB converter in the cigar lighter (or 12V accessory port as it’s called) would be better in that regard.
I do know it takes several hours to charge a 18650 in a decent quality battery charger plugged into the mains. But the sockets in my car provide another existing option.
I’ve used the 12V accessory port in my car and in my pickup (both pre-USB vehicles) often to charge phones. And the power bank of a friend who uses her phone so much a full charge won’t last a full day.
I didn’t know about flashlights with a bonus power bank feature, but I have thought about buying one of the many power banks with a bonus flashlight feature.
Keep in mind that, when a phone is being charge, the “charger” is not in the power source (e.g. USB power adapter, powerbank). The phone simply needs to be connected to a source that supplies 5 VDC and at some minimum current capability. The “smarts” for the charger are in the phone. Same goes for other things that are charged from a USB connection, including cameras, flashlights, and powerbanks.
I have both a flashlight which can be used as a power bank, and a power bank that can be used as a flashlight. The flashlight is a bit smaller than a traditional C-cell flashlight, but I don’t know how much power it holds. It works great as a flashlight, and can slowly charge a phone until the flashlight is completely dead. It’s a poor power bank because of the slow charging and small battery.
The power bank is 20,000mAh or so and can quickly charge 3 devices until its battery dies. It also has a built in LED flashlight. Because of the weight and brick-like shape of the power bank it is an inconvenient flashlight. However, during a recent power outage I ran the light on the power bank for 1.5 hours, and the battery level stayed at 3 out of 4.
I have a similar power bank, though its capacity is just 12,000 mAh (I see that newer models are now 16,000 mAh). It has a small built-in LED flashlight but that’s just an incidental feature. It’s intended to be a power pack, not a flashlight.
It’s not something I use often, but it’s been very handy in emergencies. When we had a power outage here for a couple of days due to storm damage to a power substation, the phone eventually went out, too, and I only had my cell phone. The power pack was great for recharging the cell phone, as well as my Kindle so I could at least pass the time reading in the dark.
The cool thing about it, as with most of these types of units, is that it also has a jumper cable that can jump-start a car or even a moderately large truck, with a claimed peak current output of 400 amps. One time when my car was parked in the garage for over a week with a weak battery, I was worried it might not have enough power to start. Hah! The battery had failed so totally that it wouldn’t even make the dreaded clicking sounds. But this gadget started it just fine. And yet it only weighs around a pound and is small enough to put in your pocket. It’s amazing how much energy Li-ion batteries can hold.
Thanking everyone for the information. I think I now know most of the facts. Still unsure about what to do but that’s on me and my indecisiveness.
One more question perhaps @echoreply can answer. If your phone is completely dead and you connect it to the flashlight. Will the phone operate (almost) immediately drawing power directly from the flashlight? Or do you have to wait until the phone has been internally charged up enough?
Same as for any other charger. It will take a little while but at least for my phone probably only 5 min.
Basically, for any decent powerbank, there’s no difference between plugging into a powerbank or mains - either way it can supply as much juice as the phone can take.