I have a vector 300 amps that will not charge or hold a charge.This is the first time i needed a jump and did not work!It must be a MANUFACTURER DEFECT.What to do? Your Customer I would like a replac

I know how you feel because I had the same problem with mine until I read about the procedure.
Most of those Jump start chargers unfortunately require that you charge them when you buy it and then maintain the charge at least once a month.
There is usually a light on the charger to indicate that the charger is fully charged.

The first answer is the correct one, Every device that utilizes a sealed lead acid battery such as your vector MUST be regularly maintained or you will destroy the battery in it, Just like the battery in your car. if you leave it sit until it goes dead and then recharge it, it will only last a few cycles and then loses the ability to hold a charge due to plate sulfation . Carrying a wetted cell (automotive battery) as a back up is foolish at best. First off you risk spilling sulfuric acid in the trunk or any time you use it. Next, you may as well just replace the bad battery and fix the electrical issue causing the problem to begin with. And if this is an "outback"situation, have a battery isolator and switch over installed along with a second battery. so that you can run two batteries. switch over as needed, use a starter solenoid and a switch to use the second battery as a jump battery, and the system will keep keep both batteries charged