IOTA Engineering DLS-55/IQ4 12 VOLT 55 AMP 4 STAGE AUTOMATIC SMART BATTERY CHARGER/POWER SUPPLY

Connected to my 12v battery on the workbench my iota did not charge them. my cheapo charger charged them up fully. any ideas what's with the iota?

Is it ok to have the charger plugged in at the same time the vehicle is running and the alternator is charging, or does it need to be unplugged first?

What are dimensions? Does it have an ac plug?

Will the 75 amp charge faster than the 55 amp or is it just capable of 75amps as a power supply?