Question about Maxxtro Mobile Power KV-300 Power Inverter 300W

I've been using a power strip where I've cut the plug and put a plug with a + and - connector without the ground. When I travelled, my children were able to connect their computers and cell phones to the power strip and charge them. I myself have taken a multi-socket where I cut the plug and put a plug with a + and - connector without the earth. When travelling the children were able to connect their computers and mobiles to charge.