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NotMicro is offline NotMicro
2016-06-01 , 10:10
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#1
I wonder if I can use stronger charger (with higher current) to use with my N900. I am thinking about AC-60 by Nokia (1500 mA). Could it be dangerous for my phone or battery?
 
juiceme is offline juiceme
2016-06-01 , 10:22
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#2
Originally Posted by NotMicro View Post
I wonder if I can use stronger charger (with higher current) to use with my N900. I am thinking about AC-60 by Nokia (1500 mA). Could it be dangerous for my phone or battery?
No, it will be perfectly safe.

There's some basic physics at work here; you need to understand the meanings of the ratings given to electronic devices.
  • 1.) Voltage is something that you need to be careful with; if a charger is rated at 5.0 output volts (like all USB chargers are since it says so in the spec) then it can supply exactly that voltage to a device that requires 5 volts.
  • 2.) Current rating tells you the maximum current that the charger can supply to the device. Note that it is the device that takes the current, so if it can just take 900mA for example, that is what it takes even as the charger could supply 1500mA
 

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pichlo is offline pichlo
2016-06-01 , 10:22
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#3
Will my light burn more brightly if I replace a 10A fuse with 16A?

Come on, people, it is not that difficult. The charging current is determined by the lower of the two limits: the charging circuitry in the phone and the rating of the charger. A stronger charger with the same phone will have no effect whatsoever.

EDIT: Thanks, juice, for a more detailed answer. You beat me to it
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juiceme is offline juiceme
2016-06-01 , 10:50
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#4
Originally Posted by pichlo View Post
EDIT: Thanks, juice, for a more detailed answer. You beat me to it
No problem

As long as we are on the subject, let's keep this going and try to teach people a bit. Might come handy at some point.

So. There are three basic measurable electrical properties usually involved, and 2 basic physical laws, Ohm's law and Kirchoff's second law.

Generally; when circuits are connected together so that energy is transferred from a source circuit to a drain circuit the following principles apply;
  • The output voltage of the source and the internal impedance of the drain determine the current that flows in the circuit, and the transferred power is the product of the voltage and the current; I=U/R, P=U*I
  • If the output voltage of the source is higher than what the drain is expecting, there will most probably be damage to the drain device.
  • If the input impedance of the drain is lower than what the source expects, there will most probably be damage to the source device

In both of the 2 last bullets the end result might be that you will have smelly blue smoke coming out from either the source or the drain.
This is why people in Electrical Engineering business often say that circuits work by smoke. When the smoke escapes, the circuit no longer works.
 

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aegis is offline aegis
2016-06-01 , 12:40
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#5
Originally Posted by pichlo View Post
A stronger charger with the same phone will have no effect whatsoever.
Not entirely true.

Quite a few phones these days come with a 'standard' charger that's rated at 5V 1A or 1.5A or whatever and the phone will only draw that.

But, they may support Qualcomm Quickcharge standards despite the phone only coming with a basic 5V USB charger. Quickcharge bumps the voltage up to as much as 20V and current to 3A if you have a compatible charger.

Also there's issues with some phones getting 'confused' by some USB chargers and requiring 'fast charge' cables which essentially just short the two middle pins on a USB cable to convince the charger it's not an old iPhone. The N9 for instance just fails to work with many 'standard' USB chargers and battery packs designed for iDevices. I've still got a couple of dongles that shorted the middle pins that I carried around with me so that I could use other people's chargers.

And lastly, I've lost count of the number of people I know who think any old USB socket is going to be good enough and don't realise that the max draw on some cheap chargers is only 500mA and they've been using one for ages without realising a better charger would help.
 

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juiceme is offline juiceme
2016-06-01 , 13:48
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#6
Originally Posted by aegis View Post
But, they may support Qualcomm Quickcharge standards despite the phone only coming with a basic 5V USB charger. Quickcharge bumps the voltage up to as much as 20V and current to 3A if you have a compatible charger.
Yes, so true but this is a non-standard extension which is not compatible with USB 2.x specification. (IDK about USB3, maybe that's incorporated there...?)

Luckily there's a protocol between the charger and device for negotiating the supported charging parameters, the newer chargers are not going to blindly push up the voltage to the high limit
 

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pichlo is offline pichlo
2016-06-01 , 14:37
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#7
Originally Posted by aegis View Post
Not entirely true.

Quite a few phones these days come with a 'standard' charger that's rated at 5V 1A or 1.5A or whatever and the phone will only draw that.

But, they may support Qualcomm Quickcharge standards despite the phone only coming with a basic 5V USB charger. Quickcharge bumps the voltage up to as much as 20V and current to 3A if you have a compatible charger.
Yes, I had thought about that but did not want to murk the waters too much for the OP. He only asked about the N900, after all.

But yes, for the sake of completeness, thanks for pointing that out.
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aegis is offline aegis
2016-06-01 , 16:44
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#8
Originally Posted by juiceme View Post
Yes, so true but this is a non-standard extension which is not compatible with USB 2.x specification. (IDK about USB3, maybe that's incorporated there...?)

Luckily there's a protocol between the charger and device for negotiating the supported charging parameters, the newer chargers are not going to blindly push up the voltage to the high limit
I would guess that the vast majority of chargers out there do not follow the USB standard. iDevices are so prevalent that you've often got to check any 3rd party battery/charger supports "Android" which is usually code for not using iDevice style voltage sensing on the middle pins.
 

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handaxe is offline handaxe
2016-06-01 , 20:40
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#9
Am I way off the mark with recalling that LION batteries do best with a slow charge rather than fast, so a lower Amp charger whilst slower is "kinder" to the battery?
 

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juiceme is offline juiceme
2016-06-01 , 20:56
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#10
Originally Posted by handaxe View Post
Am I way off the mark with recalling that LION batteries do best with a slow charge rather than fast, so a lower Amp charger whilst slower is "kinder" to the battery?
You might be correct there. However I suppose that to be destructive the charging current needs to be significantly higher than C/1.
 

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