I have a long car trip planned with a couple of kids and have borrowed a 300 watt inverter to power a 53 watt TV and a 72 watt PS2. I have heard (anecdotally, of course) of people that have “ruined their alternators” by running an inverter. I can see how a battery’s life could be shortened by constantly running it down and then recharging but I’m at a loss to see how an alternator would be effected. I’m only going to run my inverter when the engine is running. I did a test run and my alternator guage didn’t budge when the equipment was turned on. Are there any precautions I should take?
You’re adding an extra load of about 9-10 amps, which is significant. It will place additional stress on the alternator and shorten its life to some degree. In particular, alternators tend to overheat and fail prematurely if they charge at close to capacity for extended periods, which they are not designed to do. It might be wise to avoid using the inverter simultaneously with other noticeable loads such as headlights, A/C, or blower on high.
Well, the AC won’t be a problem since we’re driving to Colorado in February. I can keep the fan on the blower down to the first 2 settings. We’re primarily driving at night so I don’t have much choice on the headlights.
Shouldn’t the additional load show up on my alternator guage? If it doesn’t, I’m not sure exactly what it is measuring.
Thanks.
Your alternator guage is showing the output voltage, not the load on the system. The voltage stays the same, the current is increasing. Hook up an ammeter and you will see a change.
I don’t think the alternator is in much danger.
Does the inverter wire directly to the battery (ideally) or does it plug into the lighter/accessory jack? If the jack, check the fuse for the lighter. Your ~120 watts is going to be 10 amps at 12 volts. The inverter is not 100% efficient so figure in a few more amps for that, too. If the lighter fuse is, say, 15amps, you might be approaching the blow current, especially if the fuse is shared by other stuff like the dome light or dashboard lamps.
Mine will run through the lighter. I’ll check the owner’s manual to see what else is on that circuit. The inverter has a 30 amp fuse on it but I’m sure my lighter fuse isn’t that big.
Now I’m torn on what to do. The lighter plug in my Explorer is on a 25 amp circuit all by itself. It also has an additional 20 amp auxiliary power plug so I would think that my electrical system can handle the ~10 amps that I need. My other choice is to drive my wife’s car (Honda CRV) with its Realtime AWD. The downside to that is that it has 2 power outlets that are each rated at 10 amps and are on separate circuits. So I would have to buy another inverter and run 4 and 6 amps through each of them. It does get better mileage but it is quite a bit smaller and has incredibly hard seats. (Honda calls them firm and supportive.) If I take the Explorer, I’ll have to get tire chains because I certainly don’t want to get them from a gas station on I-70.
My kids have used a TV/VCR in my 84 Ford extended cab pickup routinely, including at night with the AC on. The truck has the original alternator, and has never blown a lighter fuse.
Plug it in and don’t worry about it.
Many years ago, I was driving with someone in the dead of winter. It was cold, I had just started the car, and the window was fogging up. My friend told me to turn on the air conditioner. I replied with something along the lines of “are you freaking nuts? It’s 20 freakin degrees out there.” He said no, turn the defroster on, crank the heat up, but turn the air conditioner on too. I looked at him skeptically, but as soon as I did it the fog on the window vanished awfully darn quickly.
20 years ago this was just a neat trick that worked really well but few people knew about. These days, car manufacturers got wise, and many cars will automatically turn on the AC when you turn your defroster on.
I don’t think it has much bearing on your situation since I think your car’s electrical system can handle it anyway, but I thought you might want to know.
Personally, I’d take the explorer. The “firm and supportive” Honda seats clinched the decision for me.