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20v versus 36v runtime?


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Since dewalts 20V batteries are actually only 18V. The two batteries would contain the same energy but it is output differently and the tools will have a different efficiency. The 36V (dewalt will call it 40V) will likely use the energy faster for a more powerful tool which may result in fewer cuts per charge although they would be faster. It all depends on the tool but they do contain the same power

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Both batteries have thesame capacity. 72 watthours of power.

18v x 4.0 amps is 72 watt hours.

36v x 2.0 amps is also 72 watt hours.

Now.... It all depends on the tool they are used in.

A 36 volt Rotary Hammer will be more powerfull then the 18v Rotary Hammer and this also use up more power.

So if you compare a 36v Rotary with a 2.0 amp battery ----> 18v Rotary with 4.0 amp the 18 should in theory go longer. ( although the 36v Rotary will work faster because the 36v motor provides more power)

The exception: i do not know if dewalt had this but Bosch has a ' compact 36v Rotary '.

This is actually their 18v Rotary but then adapted to take a 36v battery.in this example the motor in the tool only needs/ draws thesame current as an 18 volt tool. Meaning it will work as long( and as powerfull) with a 36v/2amp as bosch's 18v Rotary with a 18v/4.0 amp.

Hope you understand me :D

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True what they said over, but a little note about efficiency: 

When you make your cuts, the load will alter the efficiency of your motor.

To low load and the efficiency falls, but a load that pushes the motor way to hard (for example by pushing the saw to hard, or use it on a to thick piece of wood) is just as bad.


A 36V saw will  inherently have a bit higher electric efficiency becouse of lower amperage that gives lower electrical losses and heat. But it also usually has a bigger motor/blade. Which in turn will need a higher load to be efficient, since it got more mass to spinn, bigger blade etc... 


What I'm trying to say, if the Wh rating on the batteries is the same, it will probably come down to what you are trying to cut. If you cut thin softwood plates, the 18V ("20 V") unit will probably win. If it's to cut larger pieces of lumber or thicker plates, or hardwood, the 36V machine will probably be  the winner in runtime. 

But again, the Wh is usually higher on 36V tools, and in that case, it will probably win either way. 


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the rotary was updated, but its based on the 20v version.


the newer battery(dcb361 2.0ah) is just a new plastic shell for the most part.

the older dc9360 batteries have used 3 different cells over the years.  the original came with A123 cells, then went to samsung cells, then sanyo cells.  the sanyo cells have almost double the amp hours of the samsung, so dewalt only put have the number of cells inside the battery, with the rest of the case having false filler cells.  thats why the newer battery feels lighter.

dewalt did come out with a more powerful battery (dcb360 4.0ah), by filling the whole battery shell with cells, but this battery seems to only be available in europe.


the original A123 cells



samsung cells



latest sanyo cells(red).  the black are just plastic fillers















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