Timtool said:
I guess this would be nice so more power hungry tools can be used with as decent battery life as we have been getting from drills.
Otherwise i don't see the point, Li has allowed to make cordless tools so much lighter and easier to operate. The real evolution will be when they manage to keep the same weight and volume for a 10Ah as for a current 3Ah, now they basically double the capacity by making it twice as big. [huh]
There's more to it, actually, it's the same reason why 10-cell (normal sized) packs can handle more amps than the 5-cell compact packs.
18v is achieved with 5 cells in series, the compact cells are a single bank, meaning a 20 amp draw total draw at 18v nominal is a 20 amp draw on all 5 cells. In a normal sized pack, a 20 amp draw at 18v nominal is split across two banks of 5 cells, making the amp draw per cell 10 amps. In a 3x5 cell configuration, the amp draw is 6.667A/cell.
This is advantageous mostly because the cells perform better at a lower draw. As the amps drawn per cell goes up, the lower the voltage drops given the same charge level and same battery condition. i.e. If you hit a cell with 10A when fully topped off, you'll usually see 3.7v, whereas the same cell will put out 3.9v at 5A. This means your overall net consumption will be lower, since the batteries are not pushed at hard to achieve the same performance.
The other advantage is since cells can only be pushed to a specific amp draw, it can support higher draw equipment split amongst more cells.
As jonathan posted, there's another way to solve this, which is with cells that have lower internal resistance, and huge endplanes to handle the amp load, as Metabo have done. It splits the difference between the gigantor pack that Milwaukee decided upon, versus the standard 2x5 cell config we've all come to known.
