I’ve been exploring options to power my cordless reciprocating saw using a Car Battery Tool because the standard tool batteries drain too quickly, especially when tackling demanding tasks like clearing thick bushes away from AC power. While DC-DC converters are available for stepping up 12V to 18V, their amperage ratings often seem insufficient for power-hungry cordless tools like saws, which can draw significantly more current than typical converters are rated for. I’ve read that saws can spike up to 70A, far exceeding the 15A continuous, 25A spike rating of a converter I considered.
Initially, I considered using resistors to split voltage and add the necessary 6 volts to run the saw, but I’m unsure about the appropriate type and capacity for this application. The 500W resistors designed for braking systems seem oversized and potentially unsuitable. My goal is to run the saw in bursts of about two minutes, with short pauses, for a total of around 30 minutes of work.
Another thought was adding a 6V battery, like a golf cart battery, and integrating it with my vehicle’s 12V system. However, I’m unclear on the rectifier requirements and whether the car’s charging system would overcharge a 6V battery in such a setup.
As an update, I tried running the saw directly from my car battery. The performance was initially poor until I upgraded to heavier gauge wires. This improved things to an acceptable level. However, I noticed a gradual decline in power, and I initially attributed this to the 105°F weather. Upon closer inspection, I discovered warm spots within the tool itself. Opening it up, I found some surprisingly thin internal wires. Space is limited, particularly around the variable speed switch, but I’m now planning to upgrade the internal wiring to see if this can deliver more consistent and robust performance when powered at 12V from a car battery tool setup.
