Slow charging to extend battery life? How?

Fairphone recommends slow charging of the battery:

Quick charge and fast charge are possible and convenient, but does not extend the lifetime of your battery. Slow charge does.

Also write:

A charger and cable for the Fairphone 4 must have the following specifications:

For slow charge

  • 5 volts (5V)
  • The minimum current should be 1 ampere (1A, 1000mA).

For quick charge

  • Maximum output of 4 amperes (4A, 4000mA). Note: the cable must also support 4A to charge at total capacity

I bought the Dual-port 30W Charger and the USB-C 3.2 Long Life Cable from FP. The charger has the same values on it for both the USB-A port and the USB-C port: 3.0, 2.0, and 1.5 ampere with different technical values associated with each. I’m confused by the amperes and they don’t help me.

Normally, you would use the USB-C port of the charger, which is 30W, and charge the FP4 to 50% in 30 minutes.

I’ve read that higher wattages generate more heat and the heat is what damages the battery.

Can I just use the USB-A port (18W) and will that achieve the goal of saving the battery? Will this charge slower and with less heat without damaging the battery or the FP4 in any way? Or is it better not to do this and only use the USB-A port for smartphones that require an 18W port?

Doesn’t really matter which port you choose, neither will slow charge the FP4.

If I remember my last tests correctly, the phone didn’t charge with more than 18W anyway, so both ports should give you similar fast charging performance. If you want to charge it slower however, you’ll have to use a less powerful charger or limit the current in software.

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I guess @hirnsushi knows better: How about charging it on a computer USB outlet? That’s what I am doing with my FP3 to slow down charging.


Yeah, a USB port works great, if your computer is a laptop and not a power hungry desktop machine using hundreds of watts… :upside_down_face:
I just use an old 1000mA charger from my previous phone, those used to be bundled with everything so there’s always one left when they eventually break. (at least they’re getting reused before they are recycled)


Well, in my case it’s an (early 2009) MacPro that does the trick (charging slow). Surprisingly, my even older (2005) iPod charger charges all Fairphones quicker than the big machine.

Not directly related to the Fairphone.

I have a new laptop where I can set the max charge in the BIOS. I had it set to 78% which limits the volatge the battery will get too, not how slow it charges.

However there is data stored each time the battery is charged to show the wear on the battery, strangley if I charge to 100% now and then it seems the battery is healthier. I have noted another user on the forum that always charges to 100% and their records are the best I have seen.

So to avoid heat you will require a slow option, like a USB A 3 on a computer that only gives 0.9A so may taken 5hrs to charge from 0 to 90%.

I live off grid for 40 years and have used various batteries for just about everyhting and have never got a ‘good’ life no matter what I do, I still try though :roll_eyes: More embarrasing is that I am a qualified radio electrician and when I directly question the manufacturers for info etc. including Fairphone I get what I can only regard as dumb answers.

Sure the hearsay is be careful, makes sense, but how careful is carefull and what is your use scenario.

Don’t worry too much, as I do :slight_smile:

One old idea that is not supported in li-ion batteries, though I query that, is that batteries can stagnate, so it may be usefull now and then to fully charge and let it warm a bit.

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Thank you very much for your answers! :smile:

I will charge the FP4 via my notebook (USB-A 3 = 5 V, 0.9 A, 4.5W). And only when I am in a hurry, I will use the charger with the 30W connector.

On occasion, I will also look again, whether there is somewhere in iodéOS a setting where you can select slow charging.


There also exist Chargie devices that work together with an app on your phone. Basically, they tune the charging current depending on the battery temperature and allow you to set the charging limit in order to avoid your battery being constantly charged over the top when you charge overnight.

I cannot say how well it works in actually saving the battery life, but as for the useability - I have started using it recently, and it’s very easy and convenient to use.

Technically if the phone is worrking properly it cannot be charged ‘over the top’ but it can be held at a high voltage, which may make it warm and possibly impact it’s longevity.

But note, the battery is guarantted for two years by default, and I wonder if the extension to five includes the battery. Effectively saying Fairphone don’t see it as much of an issue.

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Nice idea. But I have already solved it without additional hardware and software. Slow charging (e.g. via the notebook or a charger with only 1 ampere) automatically ensures that the battery does not get very warm. I use iodéOS. There you can set under Smart Charging when the charging should be stopped. I have set 80%. :slight_smile:


Strictly speaking, you are right. What I mean by saying “over the top” is that it keeps the battery charged, and the common wisdom is that Li-ion batteries do not like to be fully charged, nor fully discharged - their properties are best preserved when they are about 50% charged. (See, e.g., Lithium-Ion Battery Care Guide: Summary Of Battery Best Practices - CleanTechnica).

Fairphone warranty explicitly does not cover battery performance deterioration (Warranty - Fairphone). I would guess it covers the case when your battery suddenly stops working. But if in a couple of years the battery keeps working, albeit with halved capacity, that’s not covered. The only remedy then is to order a new battery.


I see. Nice. I prefer not to root the phone if I don’t have to, though - and Android only allows software to stop charging if rooted.

BTW, does Google Pay work for you after installing the custom OS? (This is one of the main reasons I prefer not to root.)

you dont need root for Iodes smart charging and no without GApps Google Pay does not work (irrespective if rooted or not) and installing a custom Rom does not mean you root your phone


I see, thanks for the info.

As @yvmuell wrote, the FP4 is NOT rooted after finished installation with IodéOS.

IodéOS was primarily made for those who care a lot about privacy. That means, for example, that you just don’t want to use Google. If Google Pay and perhaps other Google things are important to you, IodéOS is not for you. It doesn’t matter. Everyone is happy with something else. For me, it fits very well and I am happy that Iodé can do smart charging and that this is solved very easily for me. :slight_smile:

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I see. I guess it is not for me then, I prefer to trade a bit of privacy for convenience.

But… Thanks for the explanation, @LibrePhoner!

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