I see how the cycles on my MacBook increase every week but I use my Mac from a power adapter about 80% time. And my battery doesn't discharge lower than 70%.
How I can fix it? I tried using a power bank, but all of them stop power after 100% and shut down automatically, without supporting low power like a wall charger.
One cycle represents a cumulative discharge of 100%. This could be 10 discharges of 10% each.
It is therefore entirely normal that cycles will increase with usage, and there is nothing to fix.
Also, the cycle count is not a fixed mortality clock, with the battery dying on the count of 1000. It's just an indication of the usage. Some batteries may hold their charge for longer; some may fail earlier.
Can you try AlDente? It prevents your Macbook from charging above or below a certain level. While it might not work, since you appear to be having an issue where your power back shuts off when "power source: power adapter; battery not charging". But maybe, give it a try. And if you do get the hardware issue fixed & you can keep that state, then AlDente will mean you get 0 cycles on your battery unless you take it off the charger (My macbook ive had for a month has 3 cycles, the exact amount it came with from the store since I use this app).
Not sure if this is exactly what you're asking, but I've successfully used both a Xiaomi Mi Power Bank 3 Pro (20,000 mAh) and a Baseus mini JA (30,000 mAh) power bank. The first one has a 45 W USB-C output and would deplete quite quickly if used from USB-C; but note that using the USB-A output with a USB-A to USB-C cable also works, and limits charging current to about 10 or 12 W -- indeed this is how I used the Xiaomi power bank, and in my usage, it didn't actually charge my MacBook Pro, but rather just slowed down (considerably) the rate of discharge. In addition, it took much longer to deplete, as one would expect due to the slower charging rate.
The Baseus one has a 15 W USB-C output, a 10 or 12 W USB-A output and a 5 W USB-A output. I currently use it from the 15 W USB-C output, and again it doesn't charge my MBP but merely keeps it from discharging, or slows the rate of discharge to a crawl. It also lasts very long.
Do note, however, this is all speaking from the perspective of an Intel 15" MacBook Pro, which consumes much more energy than, say, a MacBook Air M1. If that's what you have, then the Baseus power bank should be an excellent choice -- the 5 W output should more or less balance the charge and discharge rates, depending on your actual usage patterns, whereas it would take some heavy load to balance a 15 W USB-C output.
Note that if your goal is to maximize your battery lifespan, you should (as suggested in another answer) use an app like AlDente and limit charging. Batteries age more quickly if they're at high state of charges all the time. Limiting the charge to anything below 100% is better than 100%, even 90% should extend the lifespan, and 80% should have excellent results. 60% extends lifespan the most and is what I personally use -- and note you can temporarily increase it any time if you'll be away from a wall socket for long and need the extra battery life. Anything below 60% makes no sense and will actually start to reduce lifespan again, albeit by a different chemical process than the one that acts on a near-100% charged battery.
