Increasing amperage to inverter.

cigarette lighter plugs make a poor connection at best of times
hard wired with proper gauge wire gives the best connection
length of wire and gauge of wire both create electrical loss

 

The proper way is ro use welding cables and install corectly. overvoltage can cause the plugs to melt.

 

Thot 1500 sorry . Well current is lost thru poor wires. It comes down to the fact of how good your batteries are and how many you have. Cleaning your posts can make a huge difference.

 

if it's a fleet truck. then you have to have the shop install it to the battery pack. most trucking companies normally only replace one battery out of the 3 or 4 batteries on the truck. so that is most likely part of your problem with low voltage. so you might have one good battery doing the work of 3 or 4 batteries. and i do agree with everyone else. a cigarette lighter is a poor connection to run anything over a phone charger.

 

It is a 1500 watt peak inverter, Which means it can draw 125 amps. For a 10' circuit you are going to need a minimum #4 wire, #2 is preferable.

That large of an inverter needs to be hard wired properly. Don't use the cigarette lighter, you are just asking for a FIRE

 

It is not a 1500 watt inverter.
The 1500 watts is just a short duration peak surge watts rating. (typically under 10 seconds duration) BTW, the 10 sec is "generous".
His inverter is not designed to put out 1500 watts continuously, or anything beyond a temporary surge.
The 750 watts is the continuous wattage rating.

If the OP is only using 125 watts of 115 vac power out of his inverter, then a 10 ga wire is more than sufficient.
To use his inverter to its full 750 watt capacity, he needs a 6 ga cable, minimum.
As the other posters said, and I agree, cigarette lighter plugs are terrible ways of providing reliable/ample power.