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Power Tool Brands Don’t Make Their Own Batteries

Edit:ShenZhen Dingkangda Technoloy Co., Ltd      Date:Mar 07, 2016

Power tool brands might make their own battery packs, but they don’t make their own batteries. Panasonic might be the only exception.

I spent the past two hours or so disassembling 18V 3.0Ah and 4.0Ah battery packs and examining datasheets, at least those I could find online.

All major power tool brands build their 18V (or 18V-class) battery packs with (5) or (10) 18650-size rechargeable Li-ion cells.

Bosch, Milwaukee, and Hitachi all use Samsung INR cells, Dewalt uses what appear to be Sanyo cells, and Makita uses what appear to be Sony cells. I haven’t taken a look at other battery packs yet.

A lot of power tool brands use the highest performance Li-ion cells available, although not necessarily the highest capacity ones, at least not yet. I have not disassembled other brands’ battery packs yet, but I anticipate that homeowner and DIY-grade brands use lower performance cells.

This should not come as a surprise to anyone, as there aren’t any good reasons why power tool brands would not use off-the-shelf Li-ion cells manufactured by major battery suppliers and OEMs. Even so, this isn’t something that most power tool users ever really think about.

While I can’t speak for power tool brands’ product managers and engineers, these are likely some the more significant factors that determine which batteries brand’s select to build their battery packs with:

Cost. When you’re talking about 5 or 10 battery cells per battery pack and tens of thousands of battery packs per year – if not more, cost is a very important consideration.

A product engineer or manager for a homeowner brand will not select a top-dollar Li-ion cell for their battery packs; they will select the cells which meet or exceed the needs of their tools. Cost is perhaps a more important factor for lower-cost tool makers than higher-end brands. It’s not feasible to sell a cordless tool kit for $65 if the battery costs $50 to manufacture.

Maximum discharge rate. One brand’s latest 18V battery packs are built with cells advertised as having a 20A max discharge rate (22A on paper), and their previous battery packs were built with cells rated with a 25A max discharge rate (23A on paper).

A homeowner brand will not equip their tools with Li-ion batteries rated for 20A+ max discharge rates, and pro-grade brands will not equip their tools with cells rated much lower than that.

As a reference reminder, a battery with a 2.0Ah rated capacity can deliver a 2A discharge rate for 1 hour. Thus, a 20A discharge rate would deplete the battery charge in 6 minutes.

When is the last time you saw a consumer-grade cordless rotary hammer? Angle grinder? Band saw? Consumer-grade cordless tools don’t have the same power requirements as pro-grade tools, and so they don’t require top-dollar battery cells that can deliver the highest maximum discharge rate.

Minimum operating temperature, or rather minimum operating temperature and battery performance at those temperatures. The best rechargeable Li-ion batteries I have seen thus far can deliver 60% of their rated capacities at -4°F, and 80% at 32°F at a 10A discharge rate. A 10A discharge rate would deplete a 2.0Ah battery in 12 minutes at room temperature (100% capacity).

Battery packs that probably won’t be used outdoors in all weather conditions don’t need cells with good cold weather performance.

Life cycle. Samsung’s recent INR batteries maintain 60% or greater charge capacity after 250 charge cycles. More life cycles means longer usability and less frequent replacement schedule.

Minimum/standard capacity. A 2.0Ah battery won’t necessarily deliver 2.0Ah charge capacity under load. 2.0Ah is the nominal capacity, but during high drain discharge, the actual capacity might drop.

Charging time. Higher performance batteries can usually be charged at higher rates, although active cooling is required to achieve the maximum charging rate.

There are of course a lot of other factors involved in selecting battery cells, but it seems that these are the 5 most significant ones that separate cells suitable for homeowner-grade power tools and those suitable for pro-grade tools.

Although power tool brands aren’t responsible for a lot of what they boast, a lot of engineering does go into battery pack design.

For instance, Dewalt’s 20V Max 2.0Ah battery pack is built with a rather sizable aluminum heatsink, and Milwaukee’s M18 battery pack looks to have the most built-in electronics.

Samsung, Sanyo, and other battery manufacturers are constantly working to develop new and better battery technologies. Except in a few cases, their off-the-shelf batteries are accessible to any and all power tool brands. In other words, if one brand came out with 3.0Ah compact and 6.0Ah extra capacity battery packs today, all others could follow within a reasonable amount of time.