I get these for free at work when the batteries die. We went to a building-wide inverter with protected outlets in strategic places, so corporate refuses to replace or repair the portable units. The batteries in these things don't last very long anyway.
The hacked inverter was a APC 350 ES. APC says it's a "stepped approximation to a sine wave." It fools my Kill-A-Watt meter, so it must be fairly close to mains power.
Before, showing the APC and a car adapter cord saved from another inverter. This adapter has no internal fuse. I prefer this, more on that later.
Backside open showing battery removed and battery connectors showing. Five #2 phillips screws hold the back down.
The internal infernal buzzer
These are annoying, so I put a dab of silicone sealer in the hole on top. If it was removed the unit might show an internal fault and refuse to start on batteries.
Where the line cord went in. I used wire snips to cut the cord at the spot welds on the outlet bus.
The internal 40 amp car spade fuse. It's soldered to the board. I left it that way.
External inline fuse added with standard spade connectors and shrink wrap. This fuse is 30 amps. It will blow before the one inside. 30 amps should be enough anyway, since this is plugged into the power tap of my van. The fuse to the van power tap is probably 25 amps, I haven't checked.
Electric tape wrap over 4 click ties on the inside where the 120v circuit breaker used to be. This hole is the right size for the wire exit to the car plug. The click ties prevent the cord from being pulled out.
Finished product fast charging my portable drill battery. There is a procedure for using it off-grid. It is plugged in then the power button is pushed. It's a momentary switch. Wait for some beeps (since it is off-line), then plug in your load.
