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Ryobi 4Ah vs 4Ah HP for brushless tools


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Hey guys, I recently picked up a set of brushless tools from ryobi and it came with the regular 2ah batteries. One of the tools is 7 1/4” brushless circular saw. I’m tempted to grab the regular 4ah batteries for ryobi day promo (2x 4ah batteries + free tool up to $79.99) since I don’t think the 2ah will get me really far with the circular saw. However, should I grab HP batteries instead since it heard it will provide additional boost to brushless tools or are the regular 4ah ones enough?



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I don’t have this saw so all appropriate disclaimers apply, but YouTubes I’ve seen tend to find Ryobi’s brushless circular saw is much more prone to stalling out in everyday cutting if running non-HP batteries, to the point where reviewers find the saw a little underwhelming if run that way. These would have been 4Ah units. There are 3Ah and 4Ah batteries that are HP that some online comparisons show as yielding discernibly better performance than the non-HP 4Ah on high-draw tools, but just by impressions I suspect most people would still want more. I do have other Ryobi tools, and generally speaking they have more mechanical friction than more expensive brands, which to me should be expected. They are built to a price point, and there’s nothing wrong with that, but it is what it is. If I were to purchase this saw, I would look to primarily use my 6Ah or 9Ah HP batteries on it. If you have to run smaller as a matter of immediate budget, just be prepared to be patient with the saw and cut slow and easy.

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All of the various cordless tools are using one of two models of Panasonic cells in their battery packs. 1-3 Ah is 3 cell, 4-6 is 5 cell (different model), and so on. Recently they have started using an upgraded model with more Ah and lower internal resistance so we see say a 5 Ah become 6 Ah, 3 Ah becomes 4, etc. The brushless motors are pretty similar too ultimately which is why we see similar specs across brands. Brushless motors have a rare earth permanent magnet rotor (expensive) and DC stator controlled by the tool electronics. Torque is almost directly inversely proportional speed (horsepower is constant) at a given voltage. So at peak horsepower (torque times speed) if the battery voltage is high enough the tool is at peak output and is thermally limited by the motor. If however battery voltage is too low to support that, the motor stalls. Battery voltage might be nominally say 18 V. But that’s with no load. The battery internal resistance causes voltage to sag as load increases. 1.5-3 Ah batteries have pretty much just 3 cells in series. At the “mid size” 4-6 Ah we have two cells in parallel in the string. At the 8-12 Ah size batteries it’s 3-4 cells. At the 4-6 Ah size range using high torque tools (saws, larger drills, impact wrenches) they tend to stall at 25% charge or less on older batteries but not so much on “HP”. On 1-3 Ah it’s generally a problem even at full charge. Milwaukee for instance recommends not running their table saw without an 8-12 Ah battery pack.

The small packs are fine on lights, staplers, screwdrivers, that sort of thing. All the tool companies try to promote the “all batteries fit all tools” idea but there are real problems using smaller batteries.

So I think either 4 Ah battery will work much better but you might actually get more torque from the 6 cell standard 4 Ah battery vs. the 3 cell 4 Ah HP battery at full charge but it might stall more at low charge on the 6 cell 4 Ah battery. I started only buying the “mid” size batteries for all tools for that reason. The 1-3 Ah batteries are light but clearly underpowered. I’d be hesitant to buy the 4 Ah HP for that reason.

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  • 1 year later...

Paulengr: Not sure where you are getting your cell counts from.  Standard 18v LiIon battery packs use at least 5 3.6v batteries in series. (5 x 3.6V = 18V)


This is the case with both Ryobi's low profile 1.5Ahr & 2.0 Ahr batteries. The entire battery's capacity, as well as max & usable current, being limited by the specs of the cells themselves. The 2.0Ahr battery simply has higher capacity cells.


To get around that, the mid height 3.0 Ahr & 4Ahr batteries add a second bank of 5 cells in parallel.  That both doubles the overall battery capacity (using the exact same 1.5-2.5Ahr cells) as well as their max & nominal current. 


So when using a high current tool, like a circular saw, half inch drill with a large bit, lawn mower etc., you get more available current while also putting far less stress & strain on each cell, which helps to extend battery life as well.


The super tall 6Ahr & 9Ahr batteries add even more banks of 5 cells in parallel, giving yet more increases in capacity and high current draw performance.  Not sure, but I believe the 9Ahr batteries use 4 banks of 5 cells with cells spec'ed at 2.25Ahr each @ 3.6V.


High Performance (HP) cells do things a bit differently, by adding additional circuitry & battery contacts that only really work with HP Brushless tools designed for them (with an extra set of contacts as well).  This even allows a specially designed 2Ahr battery to be high performance, but only in an HP Brusless tool.  If you use it in a non HP tool, not only are you not getting any extra performance, you may be limiting the performance of a high draw tool and damaging your pricier HP battery. 



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