Can I replace a 7Ah battery with a 9Ah?
When it comes to replacing a 12V 7Ah battery with a 12V 9Ah battery, it is generally safe to do so. The higher capacity of the 12V 9Ah battery means it can provide longer backup power or run time compared to the 12V 7Ah battery. They are all the same physical size and of the same voltage. The only difference is that the 9Ah will last nearly 30% longer between charges compared to the original 12V 7Ah amp batteries. No harm will come to your system from increasing amperage.
Can I replace a 3000mAh battery with 5000mAh?
You can always replace faulty batteries with higher mAh, different from the defaults. That is, the myth that high-capacity batteries in phones are unsuitable for replacement is not entirely correct. Using a physically larger battery or one with different voltage may cause software calibration errors or even swelling. Replacement Scenarios: Same phone model: usually safe.