Toyota PU

Today I started the Toyota Pick up engine using the jump starter on the battery charger. The little portable battery that is supposed to jump start an engine didn't even get it to turn over! I charged this piece of junk yesterday, had a green light today. Followed the instructions, but it was worthless. I have only had this unit for a few months, very frustrating as it is about the 4th or fifth unit of this sort (all were different brands) that didn't work for more than a few weeks after purchase. I hope to figure out the trick, but for now, I use a unit that plugs into wall power. Still need to fix my little generator.