While a tool from your preferred brand may be more expensive than a bargain you’ve spotted, you’ll likely still be saving significant money if you just stick with the manufacturer you’ve already purchased from.
A power tool battery is designed to deliver as much juice as the tool needs to perform at its best, and contain enough charge to keep up that performance for a reasonable amount of time. How long exactly depends on the capacity of the battery itself, and the tool it’s being used in.
Branded batteries are also very expensive, and can set you back over $100. It’s often fairly cheap to purchase a tool on its own without an included battery, with an 18v drill from a top brand tending to run between $60 and $100. But purchasing a power pack to go with it can really break the bank.
Off-brand power packs are available online at what looks like a tempting price, but there’s no guarantee they will deliver the amount of power your tool needs to function properly, hold a reasonable amount of charge, or last very long.
The good news is, a brand’s batteries usually work with its entire tool line. So if you have one cordless tool from Milwaukee, Makita, DeWalt, Ryobi, and others, then your next cordless tool purchase should really be from the same brand. That way, you can have one or two expensive battery packs and use them to power your entire tool set.