
This is a topic I love to look into once or twice a year. In my experience, I tried some knock-off batteries, thought I saved a lot of money, but the performance was so bad that I ended up returning them.
Although it might look like you are getting a great battery at a much reduced price (and who would be against that?) what I found out is that the knock-off batteries I bought had about half the run time of the original brand batteries. That might still be a good deal, but I also consider the warranty period of value to me.
Looking at the Amazon reviews, the negative reviews only, I found case after case where a person was unable to return a battery to the company for replacement after the Amazon 90-day return period but before the 1-year warranty on the battery had expired. Even though the seller advertises a 1-year warranty, good luck on getting a replacement after the Amazon return period has expired.
Essentially, you are getting a 90-day warranty on some of these knock-off batteries compared to the standard 3-year warranty backed by the original tool brand. An original $90 battery with a 3-year warranty backed by the tool company will cost you $30 per year. A $22 knock-off battery with only a 90-day Amazon return period to count on comes out to $88 per year. Which is the better deal. Again, read the negative comments on Amazon to see how many knock-off battery companies vanish within that first-year warranty period or will not replace a defective item.
There was a YouTube video just posted that tested the performance of some knock-off batteries and looks at how dangerous some of these knock-off batteries can be. If a Lii-ion battery shorts out on you, do you want to risk burning down your garage or house? One of these knock-off batteries had no protection and could have started a fire.
In all fairness to knock-off batteries, the tests in this video showed that none of the knock-off batteries had the capacity of the original. But at a much-reduced price, it might be worth it to you to get some knock-off batteries and save some money up front. For example, the runner up in the performance category of these knock-off batteries was the Labtech. You could buy 4 Labtech batteries for the price of one original battery. The combined run time of 4 Labtech batteries would give you 3X the run time of a single original battery. That Labtech battery was tested out as safe with overload protection that worked.
Most of my jobs with batteries do not run the battery all the way down. Maybe I lose a bar or two of battery run time on the job. I would rather have 4 Labtech knock-off batteries in 4 different tools than having to swap out one original battery on each and every tool.
Unfortunately, I don't know of any way to get info if a knock-off battery is safe and how much real wattage you can get out them. Dollar for dollar you might get a good deal on a knock-off battery - as long as that battery is safe. If you can find a company that honors the 1-year warranty if the battery becomes defective, then you might have good reason to try them out.