What is your battery voltage?
My guess is the battery is low and the voltage might go up to 13.0 after a few hours to charge the battery. What was the battery voltage before plugging in the converter? If say 10.9 volts, then 11.5 is actually pretty good improvement.
You might also have a tripped circuit breaker or fuse between the battery and converter. This can also happen if the fuse is smaller than the new converter output, IF the battery was low enough charge to accept more amperage than the wire and fuse is rated at. . .
So tell us the battery voltage, and we will get back to you. If battery is less than 11.5 volts, plug it back in and wait until morning, and check the voltage again. If over 12.8 volts, then a dead battery caused the low voltage, and it should be normal by afternoon!
Fred.
