Electrics question - inverter amps

Hi, quick question for the electric guys. I have an old inverter in the car (can be run from a cig lighter socket), 500w peak / 300w cont. What will be the max amps drawn on this? I am assuming not too much if it comes with a cig lighter connection. Cheers

I would think the cig lighter wiring/socket/fuse would be your limiting factors.

Hi, going to connect direct to battery, but just wanting to know the max amps it will use if possible. Cheers

I would do it this way:

300W/12V = 25A, without any losses of the inverter. If the efficiency of the inverter is 80% then I would expect 30A. 500W would be 42A.

This would drain a 45Ah battery in theoretical 1.5hours, in reality probably more like 3/4 h and after 1/2hour or less the car might not start anymore.

I hope this answered your question.

In addition I would add a fuse as close to battery as possible and make sure, that the cables from the battery to the inverter a thick enough. If the cable length is 2m then I would go with 16mm2 or 6AWG. Maybe, if the cable is shorter also 10mm2 might be ok but a thicker cable is never bad. This is so that the losses are not too big and the cable do not get too warm.

25A assuming 100% efficiency - which it won't be. 500W peak is approx. 42A.

Now here was my confusion. I got the above answers when looking on Google, but then wondered why these low power inverters come with a lighter plug? Will running an inverter plugged in here not do some damage?

I've used an inverter on a boat but that was powered off 4x 90ah batteries and a complicated wiring system, quite effective. What a Jimny battery can achieve I shudder to think. Chris

I think it is safe to assume they shouldn't come with that type of plug then. Will be going to a 2nd battery (will put something on here when finished!)
Cheers

The cig socket fuse is 15a (180w), so the invertor isnt being used at its peak, or is lying about its abilities. If the cable fitted to it is relatively small (2.5mm say) then its probably best to fit a fuse according to that, If you can replace the cable then, as others say, use a larger cable (6mm would probably be about right on a 30a fuse). You want tri-rated flex or welding cable, rather than some domestic 230v twin & earth stuff mind

I would bet more that the invertor is unlikley to be able to produce the indicated power, and certainly not for long. A common thing with electronics like this.