Charging / Current Draw by fairphone

Hello, The Fairphone instructions tells me to use a 5V 1000mA charger. I would like to know if a 5V 700mA charger (wall plug) that I already have, would be OK to use? I’m a bit concerned because if I remember my Ohms Law correctly we have I = V / R, so if the fairphone needs say 800mA the phone will try and take more current than the charger can take - which may cause the charger to fail.

  1. Am I correct in the above assertion?

  2. Could using a lower amp charger cause damage to fairphone or it’s battery?

Presumably the amount of current the phone tries to take from the charger is dependent on the resistance state of battery and therefore is variable.Would it therefore be safer to have a higher amp charger (say 5V 1200mA) than a lower amp charger, i.e. so the charger is not under constant strain from a high power draw from the battery?

You might have guessed, I’m not electronics expert, but I would like your opinions on this - am I being overly cautious? Am I correct in my thinking above? Are there safety concerns? I know someone who has used a 700mA 5V charger on their Fairphone - with no obvious ill effect but is there a theoretical promlem that she might not have realised? She said she’d never even thought about it…maybe I should have just done the same :smile:

All the best,


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Hi, there is an article here about the battery and charger information.

You will find if you use an 800mA charger that it will take a longer time to charge your phone. It will support chargers up to 1000mA which is the maximum current the FP can draw. It won’t damage your phone or battery to use a lower mA charger though.


Hi Chris_R, thank you for your quick response and for the helpful link. Cheers, Eddie

I don’t think that a 1000 mA charger will supply 1000 mA under realistic circumstances. IIRC current is dependent on voltage which is most difficult to be held stable. (As Slinky cited Ohm’s law correctly resistance is the most constant.) From this it could mean that I should use a 1.2 A charger or even higher.
I only bought a 1 A charger because the handbook says so. Now FP draws about 800 mA.

That said a small charger will not hurt the electric consumer. (Unless it’s a really bad one which might get hot.)
But I will buy a bigger one (2 A and up, need one for my tablet anyway) and see what happens.

Would charging with a 2000 mA charger decrease the lifetime of the battery? I’m thinking about buying an adapter like this:
with two USB-Ports (has a maximum of 2400 mA), so that I could charge two smartphones at the same time when necessary.
I read that the speed chargers will decrease the battery’s lifetime. Could this be the case if I’m charging my Fairphone mainly with this adapter (with only the Fairphone plugged in to charge)?

I think caution is the word. You may overload the battery by trying to charger at a higher mA than the device can handle. It could present a fire risk if the battery become overly hot.

While I agree to be cautious, from what I understand nowadays all chargers should have a limiter. Also, the said charger is said to have “max. 2400 mA”, which I would read as ‘can provide, if device pulls that much sauce’.

We might get some info of the FP tech department how much mA the FP actually uses if a charger with more than 1000 mAh is deployed. There should be a limiter in the phone as well, to my understanding.

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I don’t think you can overload the battery. There’s an internal charging logic which takes care of the charging - the charger is just a “stupid” device providing electricity. Even if you used a 10 Amps charger, the phone wouldn’t use more juice than it can bear (unless there’s a design problem :wink: ). I’ve charged mine with chargers ranging from 500mA to 3000mA - no problems at all.

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Yup, that’s what I meant: there should be a limiter. Maybe the techies will, at some point, answer how much the battery actually receives; from the info available, I guess it’s =5V / 1A.

I use my old HTC charger which outputs 5V / 1A. Haven’t had any problems with that.

I contacted the Fairphone support team with that question and sent them a link to this thread. I got the following answer:

Theoretically spoken this should not matter as moviemaniac says Quote-(There’s an internal charging logic which takes care of the charging - the charger is just a “stupid” device providing electricity.)
However we do recommend using a normal 1000 mA charger just to be safe.

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I will use an old computer PSU to provide me with 5V/2A.
PC power supplies should be quite stable and I will try it first with old devices.
Anybody thinks this is a bad idea? :smiley:

I think the main issue is that you do not provide too high a voltage.

I charged my old (case-broken) phone and it really reached 2 A. Normally it’s about 800 mA and charges about 3.5 hours. PSU or phone weren’t getting warm but it was still scary since it fully charged in 1.5 hours!
I’ve read lithium cells like it slow and I don’t think that this will give me any advantage. The normal charger 5V/1A is quite enough!