Impact of high-power USB-C chargers on Li-ion battery longevity

Question

Context: I have a 24 Ah 65 W power bank. I use a USB-A 5 W charger and it takes over 12 hours to charge it. Considering buying a more expensive USB-C fast-charger + cable, as this power bank can take a "30 W USB-C charger, taking only 4.5 hours" to charge.

Question: I’m curious about the effects of using faster-charging USB-C chargers on Li-ion battery health. Specifically, I’d like to know if opting for a higher power charger (say, 30 W or 60 W) damages the battery more over time. Below are articles from Battery University which mention "ultra-fast charging" and its effects, but I’m seeking insights from the expert community here.

1. Does faster charging (higher power) significantly impact Li-ion battery
2. Is there an optimal “sweet spot” for power-choice & fast charging times that balances convenience with maintaining battery health?

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• https://batteryuniversity.com/article/bu-401a-fast-and-ultra-fast-chargers
• https://batteryuniversity.com/article/bu-409-charging-lithium-ion%C2%A0
• https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

Answer 1

Charging current (i.e. charging rate) will have an effect to cell life.

The problem is, you are given a commercial product with no info about the cells inside it.

It may be that USB-C 30W charging is the normal it is rated for, and it's not any near ultra-fast for your cells.

And the USB-A 5W charging is just the slow charging because generally you can't pull more from USB-A without some fancy chipset to know it can draw more current.

And it does not matter if you have a 60W or 30W charger. Your product wants 30W from it.

Answer 2

Yes, faster charging times degrade Li-ion cells faster. However, (depending on the actual cells used) that only becomes noticeable when charging at constant current / constant voltage in less than 2 hours. Fast charge algorithms (not CCCV) can be smart and charge faster with little degradation.

You asked about a sweet spot. Since you did not give us any information about your cells or your application, the best I can offer is that a 2-hour charge time is the generally-accepted sweet spot.

Answer 3

The general rule of thumb is that you should charge any type of battery as slowly as you can afford - so if you can charge this overnight, do so, don't use a faster charger just because you can.

Answer 4

First, what should happen. You have a charger, a cable, and batteries to charge. Each device should be reporting correctly how many watts it can handle. If your battery pack reports it can handle 100 Watt and you attach it to my laptop charger it will burn. If it reports it can handle 5 Watts it will charge very, very slow. Neither should happen. If you get the cheapest cable you can find which reports correctly that it only handles five watts it will charge safely but very slowly. And if your battery pack reports correctly how fast it can charge, then this part is safe.

On the other hand charging your batteries fast, but within the limits, it might reduce the lifetime. It’s up to the manufacturer to take that into account. If the manufacturer figures out that lifetime is reduced over 18 Watts and cares about it than they can limit the charging speed. If they don’t care lifetime will be reduced.