Using 18w phone charger to charge my MacBook pro, any harm to the battery?

[Jacobcullen]

I recently found out that my Moto phone charger which android 9 supports fast charging for my Android phones can also charge my MacBook pro 13inch at a slower pace. It is a much lighter and smaller in size charger so I plan on using it when traveling. I have one question though: is it going to affect the battery life cycle if I use it regularly in stead of the 61w one?

[HarryT]

I'm moving this to the Apple forum, where such questions belong.

[pwalker8]

I suspect you are going to get a number of different answers on this. I don't really think it matters how you change it, but then again, I'm not a battery engineer. I would suggest asking on one of the Apple support forums at Apple or simply via the contact us at apple.com.

[OtinG]

It probably doesn't affect the charging cycle, but with the screw-ups lately from Apple's design teams, who knows. Lithium batteries are much more forgiving than lead acid or NiCad or NiMH batteries, especially in memory retention. It sounds like the underpowered charger you are using is trickle charging the MacBook. That is, charging rather slowly over a long period of time. Modern devices with modern batteries tend to be fairly cooperative with battery charging sources that are not an exact match to the one they provided in the box. I would make sure that it completely charges the battery every time though because what will effect a lithium battery is the total number of charge cycles it can handle in its life expectancy before it gives out. After you charge a lithium battery enough times, it will eventually wear out. So make the best of all those charge cycles by charging it to 100% capacity each time so you don't have to charge it again as soon. That cuts back on the charge cycles which ultimately extend the battery life.

[DaleDe]

Generally speaking it is always ok to use a Lithium ion battery charge that offers more current so long as the Voltage is the same. The device will pull from the charger what it needs and no more. If the charger is as less current then there will be no more to pull. It is sometimes the case that Apple will supply a charger that is less current than the device can use and you will charge faster with a bigger charger, especially bigger Apple chargers. Apple chargers do have some ability to cut off the charging when full power is reached but which as a plus but the batteries themselves are safeguarded from over charging.

Dale

[tomsem]

I’ve done this with my MacBook Pro on occasions when I mislaid its power supply. An 18W charger is helpful in keeping the battery from draining at its normal rate (in absence of external power) but not enough to charge. It gives you extra time before you have to charge in other words, and it is able to charge the battery when system is in standby (say overnight). I am not a battery expert but I don’t think there is any damage potential. I don’t know if there’s a lower limit on ‘useful’ wattage: does a 5W charger help proportionately less? Or maybe they do not exist...

[HarryT]

Originally Posted by tomsem

An 18W charger is helpful in keeping the battery from draining at its normal rate (in absence of external power) but not enough to charge.

Just as connecting an iPad to a standard 5W USB port will not usefully charge it, but will prevent it from discharging.

[pwalker8]

Originally Posted by HarryT

Just as connecting an iPad to a standard 5W USB port will not usefully charge it, but will prevent it from discharging.

I'm pretty sure that many of the Apple devices, such as the iPhone, iPad and macbook pro, will sense if it's connected to power and if so, will use that rather than the battery. I generally use a mophie powercase with my iPhone and that tends to keep the internal battery from being worn down over time. I use to do it with iPads, but I haven't been able to find a battery case for the iPad in a number of years.

[dura]

Just the other day an iPhone charger I also used for my iPad 10.5 Pro burned through with some fireworks. I'm not sure but perhaps the little iPhone charger was not build for heavier appliances? If so, using na iPhone charger for a laptop could be dangerous.