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using another brands battery?


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i have just got myself a ryobi 18v mitre saw, bare tool. Its going to be used on sites which have no power supply for cutting small timbers like 3x2 for noggin's / supports for pipework, fixtures.


I have two good ryobi nicad batts that work the saw, but they are only 1.5ah. What i want to consider doing is making a adaptor to fit the saw that can allow me to use either dewalt xr, milwaukee m18 or makita 18v batteries. Dewalt would be bests as i have more than 10 batts. 


what problems am i going to face doing such a thing? what battery would be most suitable to use considering they have a type of cell protection on them?


any advise would be welcomed, especially if it saves me burning a good battery out trying a fruitless idea.

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The only thing i would hesitate about is that now these tools have override protection and alot more communication between the tool itself and the battery that trying to force one battery to work with a different line up of tools might not be the best idea.  I'm sure you could eventually get it to work but my concern would be for how long before it breaks.  If you can figure this out i would love to see some pics though.

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  • 5 weeks later...

Although I have not taken apart a lot of power tool batteries, I can make an educated guess as to the protection circuit. If I designed the tool, the protection circuit would be integrated into the battery via an IC similar to Texas Instruments bq77910 (integrated battery-protection and cell-balancing solution)

This (or similar) IC can handle a majority of the monitoring/control requirements modern LiPo batteries demand. Everything from over-temp, open cell, high peak voltage, undervoltage condition, charging, discharging, etc...

A battery is nothing more then a voltage source, the tool should have the voltage regulators and control hardware. Meaning... The tool will have a circuit board that regulates voltage (kicks the battery voltage up/down or converts it into AC, as needed). Usually the tool will have a speed control circuit (PWM or similar) and some other protections/monitoring components that automatically adjust speed in relation to current/temp?.

Additionally, your power tool battery-pack is nothing more then a bunch of AA batteries connected together. (A bit more complex but you get the idea) and most power-tool vendors use the same power cells.

I would guess that your only real concern is with the mechanical connection. Short of using a 3D Printer to build an adapter .... I'm not sure how you plain to connect a Dewalt batt to ryobi?

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