400W inverter not charging power tool battery charger
https://www.thedieselstop.com/threads/what-i-learned-about-the-spiffy-new-400-watt-inverter.619330/


  The stock inverter is a bit of a joke. Won't power my laptop or my dewalt batter chargers.


The stock 400W inverter of the Ford uses a modified sine wave...or rather...a square wave that looks like something called a sine wave.



Many chargers use the line voltage to regulate and with a sine-wave like this there's a lot that can happen. The harmonics this kind of square wave can create are immense. Effectively, the charger is tuned for 50 or 60hz. This kind of subpar inverter will mismatch the frequency in many charger circuits. (ex. 150hz instead of 60hz) This mismatch can create over-current saturation in the transformer of the charger, or in the regulation, thus pulling more than 4A on the line. (Fuses for your type of charger are usually 4-5A from my experience.) The bottom line is that usually the charger will draw too much current, so the over-current protection will trip on the Inverter. 

If there's a better way of explaining then please do say. I'm just saying what I think is happening. All open for a true answer if this isn't. 

Given 400W is barely enough for most tools, I suggest just upgrading it to something more powerful, with a true sine wave if possible.