Charging From a Laptop?

I recently got hold of two 18650 batteries, but not the charger that they were supposed to come with.

They have micro USB charging ports, which got me thinking.

A computer's USB ports should be current- and voltage-controlled, because it has to work with so many different devices. If I plug a battery into the computer's USB, it should work just as well as a charger.

But I wanted to ask the experts here before I did it, because releasing the Blue Smoke makes batteries not work anymore.

So, am I right, wrong, or just silly?

The problem won't be with your batteries, the problem could be that the computer's USB circuitry might overheat and die. Computer USB ports aren't really designed for constant high-current charging. It might work fine, or it might burn out. If you're charging at 500mA or something, no problem. But 2000mA might become a problem.

Not worth the risk, my opinion.

Are you saying that each battery has a micro usb charging port?

BigusLightus said:

Are you saying that each battery has a micro usb charging port?

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Yeep!




And a built-in charge indicator LED!




Thanks to @WalkIntoTheLight for giving me a number. These are 2600mAh batteries, so that's a no-go.

I have a really nice pair of batteries that I can't use because the vendor that sells them would rather try to get me to return the batteries than just cough up the charger. That's about right for how things go, for me.

Shorttime said:

Thanks to @WalkIntoTheLight for giving me a number. These are 2600mAh batteries, so that's a no-go.

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Actually, WalkIntoTheLight was referring to the charging CURRENT (mA) not the battery capacity (mAh). The Streamlight SLB26 18650 2600mAh battery with built in micro USB charging socket (https://www.streamlight.com/products/detail/index/sl-b-26-usb-battery) will charge fine from a PC's USB output.

As WalkIntoTheLight mentioned, If you're charging at 500mA or something, no problem.

If you look at the data sheet from the link, you will see that they state that via USB, it will take around 5 hours to charge. So the 2600mAh batteries are charging at around 0.5A. So your PC's USB is fine.

It would be good to know how these batteries run in the long term though, if you don't return them. They are a bit expensive downunder (a pair of them goes for around AUD$80).

keithy said:

Actually, WalkIntoTheLight was referring to the charging CURRENT (mA) not the battery capacity (mAh). The Streamlight SLB26 18650 2600mAh battery with built in micro USB charging socket (https://www.streamlight.com/products/detail/index/sl-b-26-usb-battery) will charge fine from a PC's USB output.

As WalkIntoTheLight mentioned, If you're charging at 500mA or something, no problem.

If you look at the data sheet from the link, you will see that they state that via USB, it will take around 5 hours to charge. So the 2600mAh batteries are charging at around 0.5A. So your PC's USB is fine.

It would be good to know how these batteries run in the long term though, if you don't return them. They are a bit expensive downunder (a pair of them goes for around AUD$80).

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Oh! Um. Gimme a minute to remove this shoe, that has somehow found it's way into my mouth, again....

Thank you for clearing that up, @keithy. I'm new to really paying attention to specifics of batteries, although as a Sparky, you would think this would be in my professional wheelhouse. Live and learn, right?

I'm looking forward to trying them out as well, especially since the pair of one-shot CR123s that are running the light right now have passed the time limit for running in High mode. I'm not going to break the blister pack until these jaspers stop trying to get me to return them, though.

Confusing that no mention of the availability of phone chargers that are meant for charging, could be used. A compatible cord should be easy to find. The USB port on a computer is for exchanging data, not charging outboard flashlight batteries. Yes it can be done, but risking a $500- $1200 computer's USB port functionality is something that needs to be mentioned.

KITROBASKIN said:

Confusing that no mention of the availability of phone chargers that are meant for charging, could be used. A compatible cord should be easy to find. The USB port on a computer is for exchanging data, not charging outboard flashlight batteries. Yes it can be done, but risking a $500- $1200 computer's USB port functionality is something that needs to be mentioned.

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There have been threads before on onboard computer charging and there are always those of US that lost a computer due to it. Yes, I had a computer die from charging batteries in a USB port. I wouldn't do it and I would recommend finding some other means to charge them. I agree with Kitrobaskin on this one. Just use a dedicated charger.

keithy said:

If you look at the data sheet from the link, you will see that they state that via USB, it will take around 5 hours to charge. So the 2600mAh batteries are charging at around 0.5A. So your PC's USB is fine.

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Good catch on the current. In that case, there should be no problem using a computer's USB 3 port. They're designed to handle portable external hard drives, which can use around 1 amp when copying files. 500mA, no problem at all.

The electrical load from an external drive is not going to be like the current going to a depleted 18650, so let's be a responsible source of information here. If someone has no other way at the time to recharge a battery of that size, it should most likely be ok to charge a few times. But continual use? Not necessary when other cheaper ways can easily be at hand.

KITROBASKIN said:

The electrical load from an external drive is not going to be like the current going to a depleted 18650, so let's be a responsible source of information here.

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I disagree. Have you never done a full backup, using an external drive? It takes hours, at pretty-much full power the entire time. The drive heats up a lot, so there's a lot of current going into it. It should be reasonable estimation of charging a battery at 1 amp. At 500mA, the OP will have no issue using the USB port of a computer.

If he was using some kind of dumb-charger, that just sucked as much current out of the USB port as it could, then yeah, I'd worry.

i charge such cells from laptop, as well as power banks. i have 18650 from ylp, 26350 from acebeam, never had any problem, laptop usb wont overload, it just wont put out more current than it was designed for. people run coffee mug warmer off laptop usb, as well as external drives, ... in fact some drives come with double plug wire, in case 1 usb outlet wont provide enough current.

Huh.

All right, well, there seems to be some difference of opinion. Which is not unexpected: this is the internet.

While I'm inclined to believe that a laptop USB would do the job, there are enough people with stories about bad things happening, that I'm going to err on the side of caution. Since dedicated chargers exist, I will wait until I have one, even if I have to feed my light another pair of CR123's.

Thank you, flashaholics! Most helpful.

Why not just use the brick and USB charger you probably already have for a phone or bluetooth speaker or headphones or any of the myriad other USB charged items we have in the house?

^^^ Exactly.

I'm all for safety advice but for these batteries this is from the manufacturer from their data/fact sheet:

The Streamlight® SL-B26™ protected Li-Ion USB rechargeable battery pack with integrated micro-USB charge port is an economical alternative to disposable CR123 cells for the latest Streamlight. flashlights that are designed to accept both. The integrated USB charge port with LED status lights can recharge the battery in 5 hours. Input power source can be any Streamlight USB power adapter or a PC USB port.

Charge Time: 5 hours using the Micro-USB input. Charge time may be increased when connected to a PC (some PC's may have limited output).

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A few of the other more reputable companies like Nitecore and Klarus also make these protected 18650 cells with built in microUSB charge port. Some of these will charge with max 1A through the microUSB socket but the Streamlight appears to only charge at 0.5A through the built in socket.

Of course it would be as easy to use a dedicated USB power supply wall plug, but the original question was whether this could be safely charged by PC. The answer is still yes.

I've tested the USB output currents of my various older TVs (all around 6-10 years old) as well and they mostly are between 0.5A-0.9A. So I would even say one of my old TVs could charge this cell while it is powered on.

I looked at these 18650s with built in charging sockets as a way to not have to carry a separate charger when in the bush/backcountry for a few weeks and using my portable solar panel and powerbank. I like that they can still be charged/discharged with regular Li-ion chargers as well as the built in USB socket. But for me its still cheaper to carry a quality protected 18650 and use my Olight UC cable charger.