I have a standard 200 watt power inverter which I have used to power a sound system off of my Econoline e250 on multiple occasions with no problem. I tried to run a 4hp rigid shop vac off of it and the cables to the inverter got so hot they melted the plastic on the top of my battery a bit. Is there a chance I could have damaged my alternator?

  • More than likely you damaged the inverter.
    – Moab
    Commented May 14, 2018 at 16:25
  • Inverter is running just fine. Car ran fine for a day and a half afterwards until it just stopped working. Car started when a jump kit was on it, but would die immediately after we took the cables off. Like not even struggling kinda dead. No sound but the keys turning kinda dead. Now we put in a 14 volt battery and it's charging that just fine. Thoughts?
    – Philip
    Commented May 14, 2018 at 16:38
  • 3
    4 hp is equivalent to about 2800W so more than 10 times the output of your inverter... Not a good idea...
    – Solar Mike
    Commented May 14, 2018 at 16:38
  • Yes. But could it damage the alternator?
    – Philip
    Commented May 14, 2018 at 16:46
  • I know I made a mistake. I'm asking specifically about whether it could have done damage to the alternator. E only ran it for around 15 minutes
    – Philip
    Commented May 14, 2018 at 16:50

2 Answers 2


To be direct, yes it could ... but most inverters I've seen are fuse protected and/or have a thermal cutout on them. If the inverter was drawing too much juice, it could possibly damage your alternator, but it's highly unlikely unless there was an unseen issue with the alternator in the first place. If it did damage your alternator, I'd highly suggest you get a different inverter as it will cause issues for you in the future. If it did cause alternator damage, the built in safety devices failed and will do so in the future. That it worked at that much wattage in the first place is beyond me.


Yes, it could, but you said the car would then not start or charge, and seems OK now you have installed a new battery. In my opinion it's more likely that you have damaged the battery. Batteries are designed to supply hundreds of amps but only for brief periods - you asked it to do that for 15 minutes.

  • 2
    So are suggesting a 200W inverter can run a 4hp (2800W) shop vac? Really?
    – Solar Mike
    Commented Jun 15, 2018 at 15:05

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