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Bert Kemp
04-22-2019, 11:54 PM
I have this rechargeable light that has a warning
"Do Not Charge Over 5 Volts the Battery Will Result in Damage"
So I went looking for a 5 V USB wall charger to charge this light but found none. What I did find was this

All USB cords carry the same 5V, regardless of if it's got a 30-pin head or a microUSB plug, whether it's first-party or third. That means DC chargers are now brand agnostic; if the volts, amps, and connectors are compatible, an Apple wall wart can charge an HTC just as easily as a Samsung.m

So would I be correct in thinking that I can plug this into any usb wall charger I have and not worry about damaging the battery because all cords only carry 5 V??

Ken Fitzgerald
04-22-2019, 11:58 PM
Bert,

that is my understanding.

I am building a couple end tables right now. The rear 5" of the top tips up and inside I am installing a surge protector with both 120 VAC outlets and USB outlets.


The MP3 player I bought for shop use, has a rechargeable battery in it and I use my Samsung USB charger and cable to charge it.

Jim Koepke
04-23-2019, 2:27 AM
In a different way, what Ken said.

My understanding is USB is a standard and if something wants to call itself USB compatible, it has to meet the standard.

Your rechargeable light may not have limiting circuitry built in. It might be a good idea to not leave it plugged in to a charger longer than it takes to charge it for a longer life.

jtk

Bert Kemp
04-23-2019, 2:53 AM
is there anyway to protect it from over charging outside of watching and see if the light goes out?

John K Jordan
04-23-2019, 8:08 AM
I have this rechargeable light that has a warning
"Do Not Charge Over 5 Volts the Battery Will Result in Damage"
So I went looking for a 5 V USB wall charger to charge this light but found none. What I did find was this

All USB cords carry the same 5V, regardless of if it's got a 30-pin head or a microUSB plug, whether it's first-party or third. That means DC chargers are now brand agnostic; if the volts, amps, and connectors are compatible, an Apple wall wart can charge an HTC just as easily as a Samsung.m

So would I be correct in thinking that I can plug this into any usb wall charger I have and not worry about damaging the battery because all cords only carry 5 V??

You mentioned volts. There are two things that describe power, the voltage and the amperage. All USB chargers are "supposed" to supply 5v DC. I haven't seen a charger that delivers significantly more than 5v but I certainly haven't tested them all! Note that this is a NOMINAL 5v, it can vary some and will work fine with a well-designed device. Look on the charger - the one I'm looking at now says 5.2v. (in microscopic print!) You can easily verify the voltage for a specific charger with a multimeter and some tiny wires for probes. For the micro USB connector, measure between 5V and ground:
http://pinouts.ru/PortableDevices/micro_usb_pinout.shtml

This says nothing about the current, the amperage. The USB spec requires power producing devices to supply at least 1/2 amp, 500 mA. Some can provide much more and some devices need more, specifically some Apple devices. I have some chargers with two ports, one for Apple devices that need more power, the second for other devices. Read all about the power that chargers can supply:
https://www.extremetech.com/computing/115251-how-usb-charging-works-or-how-to-avoid-blowing-up-your-smartphone

About your lamp? It's impossible to know how they built it, but in general a device that needs a certain voltage, such as the 5v from a USB charger, will only pull as much current as it needs. (limited by resistance, impedance for AC) Even though a charger can deliver more current, it's up to the device using the power to pull what it needs. This is the same with the AC power in your house - if a device only needs a few milliamps that's all it will draw; if the device draws more the line will supply more up to the limit of the breaker.

As for your lamp, if it came with a charger, use it. If not and you are concerned, get a charger rated at 500 mA. The output voltage and amperage will be printed on the charger. The microscopic print on the one I'm looking at now lists the output at 1.35 amps - that's 1350 mA.

A well-designed device will not draw more current than it needs so it won't melt down and catch fire! However, battery charging circuits can be different - depending on the type of battery (Lithium Ion, Lithium polymer, NiCad, NiMH, etc) the battery can indeed be damaged by charging too long even if the voltage and current is exactly right. A well designed (sophisticated) charging circuit will manage the current but a cheap one may not. If the manufacturer doesn't provide charging time instructions either it doesn't matter or they don't care!

Is this a light you need to rely on? If so, I'd get one with replaceable batteries and carry a spare set.

Note that I don't claim to be an expert on this - this is just what I've learned from experience designing/building/repairing electronic circuits as a hobby, and from reading.

JKJ

Alan Rutherford
04-23-2019, 10:47 AM
IMO anything rated for "5 volts DC" will work with any DC power source claiming to be 5 volts assuming the source can put out enough amps. That is, you can plug a 500 MA device into a 1 amp power source but don't use a 1 amp device on a 500 MA (1/2 amp) power source, and I like to leave some room for error.

I label chargers with the voltage and amps by writing it on white tape or using a white pen so I can read it more easily. I also copy the little diagram that shows the orientation of the positive and negative connectors if that's relevant. It's usually not with USB chargers or multi-pin connectors but is with 2-wire connections such as most 12 vdc sources . Look for the "C" with a line to the back of it and a line to the open side. The will be a "+" at the end of one of those lines and a "-" at the other.

James Tibbetts
04-23-2019, 11:45 AM
"if the volts, amps, and connectors are compatible" This is the answer to your question. The USB chord is an extension chord, nothing more.

Bert Kemp
04-23-2019, 12:15 PM
You mentioned volts. There are two things that describe power, the voltage and the amperage. All USB chargers are "supposed" to supply 5v DC. I haven't seen a charger that delivers significantly more than 5v but I certainly haven't tested them all! Note that this is a NOMINAL 5v, it can vary some and will work fine with a well-designed device. Look on the charger - the one I'm looking at now says 5.2v. (in microscopic print!) You can easily verify the voltage for a specific charger with a multimeter and some tiny wires for probes. For the micro USB connector, measure between 5V and ground:
http://pinouts.ru/PortableDevices/micro_usb_pinout.shtml

This says nothing about the current, the amperage. The USB spec requires power producing devices to supply at least 1/2 amp, 500 mA. Some can provide much more and some devices need more, specifically some Apple devices. I have some chargers with two ports, one for Apple devices that need more power, the second for other devices. Read all about the power that chargers can supply:
https://www.extremetech.com/computing/115251-how-usb-charging-works-or-how-to-avoid-blowing-up-your-smartphone

About your lamp? It's impossible to know how they built it, but in general a device that needs a certain voltage, such as the 5v from a USB charger, will only pull as much current as it needs. (limited by resistance, impedance for AC) Even though a charger can deliver more current, it's up to the device using the power to pull what it needs. This is the same with the AC power in your house - if a device only needs a few milliamps that's all it will draw; if the device draws more the line will supply more up to the limit of the breaker.

As for your lamp, if it came with a charger, use it. If not and you are concerned, get a charger rated at 500 mA. The output voltage and amperage will be printed on the charger. The microscopic print on the one I'm looking at now lists the output at 1.35 amps - that's 1350 mA.

A well-designed device will not draw more current than it needs so it won't melt down and catch fire! However, battery charging circuits can be different - depending on the type of battery (Lithium Ion, Lithium polymer, NiCad, NiMH, etc) the battery can indeed be damaged by charging too long even if the voltage and current is exactly right. A well designed (sophisticated) charging circuit will manage the current but a cheap one may not. If the manufacturer doesn't provide charging time instructions either it doesn't matter or they don't care!

Is this a light you need to rely on? If so, I'd get one with replaceable batteries and carry a spare set.

Note that I don't claim to be an expert on this - this is just what I've learned from experience designing/building/repairing electronic circuits as a hobby, and from reading.

JKJ

not a replaceable battery , its a cheap light but would like it to last. Lithium Polymer Battery 3.7v 500mAh
no charger included
The chargers I have I can't read the info on them to faded out. I'll go buy a new one rated 5v 500 thanks guys

Myk Rian
04-24-2019, 11:15 PM
If it will charge a phone, it'll charge the light.
Don't lose sleep over it. Plug it in and leave it for 5-6 hours.
A 3.7v system will have a charging circuit in it to limit the voltage supplied to the battery.