ELECTRIC QUESTIONS

Most likely measured with a Kill_A_Watt meter, very handy device

Thermo electric, is handy picnics and driving no ice, alternator keeps it going

But it's a huge power sucker when camped someplace with no electric hookup

It also only cools about 40 degrees below ambient
Which is okay in winter , air temp 65 , inside cooler might reach 25, will keep below 40 for safe food
But when the air temp is 95, inside cooler will never get below 55F , and maybe not even that low

If I had to take a guess on how much current it would draw if you plugged in dirct I would say his
2 amps times 0.9 = 1.8 However you might need to multiply by 0.9 (90%) again in which case it would be 1.62 and it could be even less if you turn inverter off.

It is thermo electric.
Wow, it's called having 2 batteries. Who woulda thought?
Watts and amps were measured with one of those devices that gives watts and amps being used on AC. Don't know what it's officially called.

he called it an AC-DC fridge using 200w
its reasonable to think think this is a thermo electric cooler,
NOT a compressor driven fridge (although it is possible)
the power use seems high for a DC driven compressor fridge
he did not post MFG brand or model

Simply multiply the AC amps by 10.

If you are pulling power from the battery, whether by running it directly from the battery or on an inverter that is pulling from the battery, you will be pulling almost 20 amps from the battery. There is no way around that. It is basic physics. Actually, using an inverter is worse, because you also lose almost an additional 10% due to inverter inefficiencies.

As far as running wires to a second battery to charge it while driving, many of us do that. We call it having 2 batteries. We wire a pair of 12v batteries in parallel, or a pair of 6v batteries in series. Use the biggest wires you can find. I, personally, would not want anything smaller than 0 gauge.

200 inverter watts is 17 amps from the battery. Maybe a little less if plugged in direct. This is too much power for the cigar outlet.

Use #6 wire to parallel charge the batteries. You may need more than two batteries if camped off-grid.

The cooling system needs 200W to operate (and maybe a bit more for compressor start) in 120Volt mode. It may draw less if in 12V mode. If it does need 200W to operate, that is about 17 amps. you would need at least a AWG 12 wire for that ampacity.

Yes, you can connect another battery and you should. A typical marine hybrid battery has a capacity of 85 AH, 42AH of that is usable and then the battery needs to be recharged. So, using one battery, you could operate the cooler for 2.5 hours continuously. A second battery will double that to 5 hrs. If you have a compressor driven chiller, it will have a duty cycle (not run continuously). That may be as low as 1/4. You may get 20 hrs of run time with two fully charged 85 AH batteries.

For more direct advice, post what you have and particulars of what you want to do.

where did you read the number ? on the power supply that you plugged into the inverter

to make 2amps at 120v you use at least 16.2 amps of 12v power

its going to use almost the same amount of power wired directly to the battery

going direct to battery will reduce the use 10-15%.. thats all you will save..

that is the extra being used in the double conversion, DC to AC back to DC

the 100w 120v light in the previous post won't work on 12v
but he means a 12v 100w light would use almost 10amps

watts is watts.. 2amps at 12 volt would only be 24w..your electric fridge is not going operate on 24w it will need about 16~17 amps 12dc to make that 200w it does use

wheteher or not you use an extra battery, is determined by how much battery life you need when not moving
the alternator will still be supplying the extra needed power to both power the fridge and recharge the batteries in question

Sorry you have to do the basic formulas. If the formula is not understandable as posted I can maybe explain it differently.