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Is it safe to charge tablet from phone via OTG cable if tablet's adapter is 5.2V (a bit above)?

Pranciskus
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  • Your question does not make sense to me. Charging one device from another only works if both devices use USB-C and the power providing device supports USB power delivery. For USB-C there is no such thing as an OTG cable, just us an USB-C to USB-C cable with USB-PD support. And why you mention the tablet (charging) adapter is totally unclear to me as it is not relevant at all. – Robert Dec 18 '19 at 18:19
  • "Charging one device from another only works if both devices use USB-C" - thanks, didn't know that. I ordered LG V20 with extended battery and I have Lenovo Tab 10. As musician, I have a lot of screen on time because I use tablet as sheet music. So I want to be able to charge my tablet from LG V20 extended battery. – Pranciskus Dec 18 '19 at 18:45
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    The LGv20 has a 3200 mAh battery and the Tab 10 one with 7000mAh. Charging the large battery using a much smaller one is not very effective. May be you should better look for a power bank. – Robert Dec 18 '19 at 18:49
  • I ordered this extended battery and I want to carry less things. – Pranciskus Dec 18 '19 at 18:51
  • IDK maybe I need to cancel it and find phone with micro-usb type B – Pranciskus Dec 18 '19 at 18:55
  • I just tried to charge my mom's C-Type Xiaomi Redmi Note 7 from Tablet and it works, why do you say it's not working? And C-Type OTG cable exists – Pranciskus Dec 18 '19 at 19:12
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    The cable you have linked to is just a plain USB-C male to USB-A female cable. OTG is specific to micro USB ports (one special pin is used to identify if a cable is an regular or an OTG cable). For USB-C there are no such thing like an OTG cable. You can just use regular adapter cables and it works as you already have found out. – Robert Dec 19 '19 at 08:28
  • Is this cable fake? Because it says OTG. If yes, will mouse, keyboard and etc. still work with phone that supports OTG using this cable? – Pranciskus Dec 19 '19 at 10:47
  • No it is not a fake - OTG of USB-C is just marketing nonsense. With USB-C there are no OTG cables anymore - or if you look at it from the other side every USB-C cable with an male USB-C plug and a female connector at the other end can be considered an OTG cable. – Robert Dec 19 '19 at 12:10

1 Answers1

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Yes, as long as it is supported by the tablet and you have compatible cables available.

USB Standards specify that charging voltage should be 5.00V ± 0.25V, i.e. 4.75V~5.25V.

Upper limit is 5.25V which is higher than tablet adapter voltage ; add to this the resistance offered by the cable and the input voltage will be well within safety limits.

How efficient it would be is upto you to verify as Robert pointed out in comments

beeshyams
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  • Thank you for answer! Another thing: if I charge like that, will I lose almost 50% of energy. Because when energy goes from battery to cable it loses ~25% and after that when goes to another battery will I lose another ~25%? – Pranciskus Dec 19 '19 at 08:05
  • Cable losses are not so high as you suspect. You can buy a good cable. For help see this answer. How much over all loss you would have needs to be tested by you. That said, power bank is a better option as suggested by Robert – beeshyams Dec 19 '19 at 08:46
  • I don't really understand why power bank is better option if I will have 10500mAh battery for my phone. Anyway, is loss by charging using phone will be higher than using powerbank? – Pranciskus Dec 19 '19 at 11:00
  • From your answer I understand that cable thickness matters. – Pranciskus Dec 19 '19 at 11:14
  • yes............ – beeshyams Dec 19 '19 at 11:17
  • Is it possible to know AWG of my current cables? – Pranciskus Dec 19 '19 at 13:13
  • So, if I want to use 1A charger without more loss than USB standards and with transfering function, it has to be 15cm long (AWG 28)? – Pranciskus Dec 19 '19 at 13:33
  • Sorry,busy so can't verify what you are claiming but please re-read and if you still have a question ask a separate question linking that answer as background. you can know the AWG either through documentation or physical measurement or ask somebody who deals in cables – beeshyams Dec 19 '19 at 13:51
  • Ok, thanks for help. – Pranciskus Dec 19 '19 at 15:08
  • Simply put go in for long, thick cable. Sample link is provided in that answer – beeshyams Dec 19 '19 at 15:19