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Mobile charger with slightly higher output than required-how safe?

theDarkness

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Posted September 17, 2011 at 12:49PM

I have a mobile phone, a samsung sgh5620, which uses a 3.7 V, 1000 mA battery. My mains charger went missing, so I am wondering if I should chance any of these third party ones currently on sale via ebay? Most of these chargers state their output to be higher than my phone specifications above (although they are supposedly still for this phone)- eg a 5V output instead of 3.7, with a higher current (1200 to 1500 mA instead of 1000mA).

I always thought for current that my phones battery whilst charging will only take what it needed, but a voltage higher than 3.7V using a 5V, might damage the battery, or wear it out faster? Can anyone correct me on this if not? If so, then it would seem that alot of these identical online mains adapters are sold for multiple phones of different brands, as long as the connection fits. How safe is a higher spec adapter? I know my old nokia adapter also fitted my current samsung phone, and it also had a higher output in voltage and current than what the phone was rated at. Thanks

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dms_05

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Posted September 25, 2011 at 11:19AM

I think you will find that 5v is the standard for 3.7v cells. If you plug you mobile into your computer USB it will be delivered 5v and it's a recommended way to recharge phones. My smartphones power supply is 5v and it has a standard 3.7v lithium cell.

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theDarkness

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Posted September 26, 2011 at 1:20AM

I thought that the official mains plug would be able to give out exactly what was needed (3.7V) and not 5V.. unless 5V may be the minimum output that a mains plug may give out? If thats the right way to look at it, Im not sure. I was trying to find out what output (voltage or current) would be more likely to wear out the life of a charging battery more-eg an unofficial adapter gave over twice the voltage or current that a rechargable battery it was used with needed. My mobile is rated at 3.7V 1000mA DC, yet the popular unofficial mains charger (that I bought) is rated as having an output of 5V 1200mA DC. I suppose it will just take longer to charge, but I wasnt sure if a slightly higher voltage might be damaging-thanks

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lindastone6020

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Posted September 26, 2011 at 7:44AM

if the mobile charger with slightly higher output than required,it is not safe when charging. and it is bad for your phone at the same time. so you had better get one charger, the volt of which is compatible your phone. that is a wise choice. browse this site http://www.awholesalecompany.com/ and see wheter there is a charger in the voltage you need?

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dms_05

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Posted September 27, 2011 at 10:00AM

Basic Physics tells you you need a higher voltage than the nominal output of a battery. For example your car 12 volt battery is recharged by the alternator (or free standing battery charger) at 14.7 volts. This is because of an effect that produces a 'back emf' during the charging cycle. If you chose to use a charger of 3.7 volts output then you will get only a partial charge on a 3.7 volt battery. The charging procedure is performed at constant voltage with current-limiting circuitry (i.e., charging with constant current until a voltage of 4.2 V is reached in the cell and continuing with a constant voltage applied until the current drops close to zero).

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theDarkness

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Posted September 28, 2011 at 12:27AM

The mobile can charge on USB, and its mentioned as 5V standard:

http://en.wikipedia.org/wiki/USB_toys

so as long as the voltage is identical and the output type is the same as the device (both ac or both dc) I should be ok, but what about the current?

I have another device that has a third party adapter which gives out 0.2 voltage more, which shouldnt make a difference, but the current outputted is twice the mA that it requires. Is that safe? I used to think that a device may only ever take what it required in current, even if its adapter outputted far more mA than necessary, and that an adapter with a lower mA than the device would just take longer for the device to charge fully-does anyone know if thats true? any electricians around ;) thanks for the replies btw

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tomboard

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Posted October 20, 2011 at 1:10PM

I always thought for current that my phones battery whilst charging will only take what it needed, but a voltage higher than 3.7V using a 5V, might damage the battery, or wear it out faster? Can anyone correct me on this if not? If so, then it would seem that alot of these identical online mains adapters are sold for multiple phones of different brands, as long as the connection fits.

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theDarkness

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Posted October 23, 2011 at 7:50PM

The answer may also have to take into account that some modern devices (especially mobiles) may be able to regulate themselves and only take in the voltage or current that they require. As for adapters in general giving out slightly more in voltage than their actual spec, if true, my replacement 5V adapter may well be giving out over 7V. Since my mobile only requires 3.7V this may not be so good in the long term regarding lifespan of its battery if I continue to use it, but I would like to try and find out if there is a safety zone, for my 3.7V 1000mA mobile, should I simply avoid plugs that are over so much in voltage and mA?

The average consumer has little electrical knowledge, so the likes of amazon and ebay will probably have many people selling replacement plugs and telling you they will work and are safe, when in reality all they know about the product is likely to be that the adapters connection fits your phone. Im sure the majority are likely to be cheap replacements of average to low quality which could indeed do more bad than good, and even damage the phone or reduce its lifespan at worst, if the output is vastly greater than your phone requires.

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