# Charge through USB?



## tpatana (Dec 8, 2015)

I wonder why the cameras don't charge through the USB connection? I'm now on small trip and was too lazy to bring charger, so it'd be great even if it'd slowly trickle charge through USB, I could easily leave it charge overnight.

Short answer is that the camera don't have the charging HW installed, so next question is that why not, they don't really take up that much space in cell phones, and similar amount of charging current would be already plenty.

Any cameras that do this?


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## lion rock (Dec 8, 2015)

Consider heat generated by charging circuit and battery during charging. Lithium batteries are not entirely completely safe, either.
Batteries voltages are usually above 5 volts and require a higher charging voltage which USB devices can't provide.
-r


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## 3kramd5 (Dec 8, 2015)

My A7R2 charges over USB.


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## grainier (Dec 8, 2015)

Because voltage/current is not high enough to charge it over reasonable amount of time.


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## Valvebounce (Dec 8, 2015)

Hi tpatana. 
It could be because the battery for 5DIII 7D etc is 7.2V 1865mAh and USB puts out a maximum of 1000mA at 5V so a charge to capacity would require voltage step up tech in the body and if I'm right 18hrs if the USB voltage was 7.2V (or the camera 5V) so I'm thinking something in the order of 24 hrs? Either that or my reasoning is flawed and this is BS! ;D

Cheers, Graham.


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## tpatana (Dec 8, 2015)

lion rock said:


> Consider heat generated by charging circuit and battery during charging. Lithium batteries are not entirely completely safe, either.
> Batteries voltages are usually above 5 volts and require a higher charging voltage which USB devices can't provide.
> -r



Voltage you can always step-up, that's no problem. Heating/safety can be one reason.


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## tpatana (Dec 8, 2015)

Valvebounce said:


> Hi tpatana.
> It could be because the battery for 5DIII 7D etc is 7.2V 1865mAh and USB puts out a maximum of 1000mA at 5V so a charge to capacity would require voltage step up tech in the body and if I'm right 18hrs if the USB voltage was 7.2V (or the camera 5V) so I'm thinking something in the order of 24 hrs? Either that or my reasoning is flawed and this is BS! ;D
> 
> Cheers, Graham.



7.2*1.865 = 13.4 Wh

5V @ 1000mA would charge that in <3h, or assuming typical losses/efficiency, probably about 4h.


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## grainier (Dec 8, 2015)

tpatana said:


> 7.2*1.865 = 13.4 Wh
> 
> 5V @ 1000mA would charge that in <3h, or assuming typical losses/efficiency, probably about 4h.



LP-E6 takes 2.5 hours to charge, the charger, LC-E6 is 8.4V and 1200mA, so ~10 Wh, meaning that you need to transfer 25 W for a full charge, so in your scenario, 5 hours is more like it. FWIW, my phones are fast charge capable, and even with 2.1A adapter I have not seen the current top 800mA.


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## Mt Spokane Photography (Dec 9, 2015)

Some cameras do charge via USB, but high end cameras usually do not. Some of the Sony's are the exception.


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## Valvebounce (Dec 9, 2015)

Hi tpatana. 
As I said, may be BS by way of flawed reasoning! :-[

Cheers, Graham. 



tpatana said:


> Valvebounce said:
> 
> 
> > Hi tpatana.
> ...


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## Valvebounce (Dec 13, 2015)

Hi tpatana. 
I know this isn't quite what you were looking for, but it might go some way to solving the problem as in you could leave this permanently in your laptop bag to make sure it went with you. Of course you may already know of these but I just discovered it! 

Cheers, Graham.


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