Power Inverter question.

[MuddyButt]

I have a 2500 watt power inverter installed in the back of my 4runner behind the rear seat. I was just wondering if I keep my car running while I use it and don't max it out (I've never used over half of its potential power, even with an electric griddle) will I run the risk of doing damage to my alternator? also have a normal sized battery in it still will it do anything else other than just run the battery out?

 

[UnderFire]

The factory alternators are pretty good at running at full capacity for long streches of time, but eventually it will take it's toll on the alternator, also get a digital voltmeter of some kind, you want to make sure you aren't getting too much voltage drop, generally anything under 13v is bad, but if you're dropping under your battery's resting voltage with the engine off, it's really hard on everything.

 

[MuddyButt]

The factory alternators are pretty good at running at full capacity for long streches of time, but eventually it will take it's toll on the alternator, also get a digital voltmeter of some kind, you want to make sure you aren't getting too much voltage drop, generally anything under 13v is bad, but if you're dropping under your battery's resting voltage with the engine off, it's really hard on everything.

Not sure what you mean by voltage drop. The guy at Auto Acoustics that installed it finally responded and said I shouldn't have to worry about anything because they used a heavy gauge wire and 2 fuses For both of the power wires they installed he told me "as long as the car is running it should be okay" Still skeptical but I haven't had any problems yet so I guess I should be okay.
I was only wondering because I'm going camping soon and will be using the inverter a lot.

 

[UnderFire]

Not sure what you mean by voltage drop. The guy at Auto Acoustics that installed it finally responded and said I shouldn't have to worry about anything because they used a heavy gauge wire and 2 fuses For both of the power wires they installed he told me "as long as the car is running it should be okay" Still skeptical but I haven't had any problems yet so I guess I should be okay.
I was only wondering because I'm going camping soon and will be using the inverter a lot.

It's pretty simple really, the more load you put on the electrical system (Amps draw) the lower the voltage throughout the system gets, The alternator is only supplying about 60A constant in our 4Runners, which usually isn't enough to fully keep up with very much of an extra load, so you're bound to get some voltage drop since you're making the battery use some of it's reserve capacity to cover the rest.


With nothing electrical on and just the engine running, it should be anywhere from 13.8-14.4V, the more electrical things you turn on the lower it will get.

I don't think voltage drop is the technical term for it, I just know that's what it's referred to as in the car audio world.

You can install the volt meter at any point that sees direct 12V power, the voltage will be pretty much the same throughout the system, just make sure it has it's own circuit or it could give a false reading.

You're thinking voltage drop over a distance of wire based on how many amps are being drawn through the wire and gauge/distance of the run, that is what voltage drop actually means in the electrical world, but not what I'm trying to explain.

 

[MuddyButt]

Thanks man!

 

[MuddyButt]

It's pretty simple really, the more load you put on the electrical system (Amps draw) the lower the voltage throughout the system gets, The alternator is only supplying about 60A constant in our 4Runners, which usually isn't enough to fully keep up with very much of an extra load, so you're bound to get some voltage drop since you're making the battery use some of it's reserve capacity to cover the rest.
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60 amps seems like a lot. I don't think I'll even be using anything over 15 amps most I've used is probably 11. Do you by chance know how many amps Max I could use? I understand the 4runner will be using a lot of those 60 amps for electric stuff like my daylight running lights just wondering if you knew how much would be left over. Hopefully this will be my last question.

 

[Mgyver1]

60 amps seems like a lot. I don't think I'll even be using anything over 15 amps most I've used is probably 11. Do you by chance know how many amps Max I could use? I understand the 4runner will be using a lot of those 60 amps for electric stuff like my daylight running lights just wondering if you knew how much would be left over. Hopefully this will be my last question.

As far as your amps, are you figuring in amps at 110v from your inverter or at 12v from your vehicle power? 15a from the 12v side is about 3 regular 55 watt lights. 15a from your inverter on the 110v side is about 138a from your vehicle.

The reason I ask is because you said you don't use half it's potential, which half it's potential is 104a from your vehicle. My figures are based off of 12v (not 14.4) and don't account for the loss of converting the voltage, because it takes electricity to make electricity

 

[MuddyButt]

As far as your amps, are you figuring in amps at 110v from your inverter or at 12v from your vehicle power? 15a from the 12v side is about 3 regular 55 watt lights. 15a from your inverter on the 110v side is about 138a from your vehicle.

The reason I ask is because you said you don't use half it's potential, which half it's potential is 104a from your vehicle. My figures are based off of 12v (not 14.4) and don't account for the loss of converting the voltage, because it takes electricity to make electricity

Electricity hurts my brain... I've used a griddle plugged into my inverter that says it uses 1300w 120v which is like 10.83 amps I believe. I'm not even sure what that means but to my limited knowledge it means it requires that amount of input to run but I suppose that's what it uses at max temp because the higher I turned the heat the more power it said it was using and it never said I was using more than half of the inverters potential.

 

[UnderFire]

Electricity hurts my brain... I've used a griddle plugged into my inverter that says it uses 1300w 120v which is like 10.83 amps I believe. I'm not even sure what that means but to my limited knowledge it means it requires that amount of input to run but I suppose that's what it uses at max temp because the higher I turned the heat the more power it said it was using and it never said I was using more than half of the inverters potential.

This calculator will be helpful with figuring out a ballpark of how much draw you are putting on the system.

BatteryStuff Tools | AC to DC Amperage Calclator Through An Inverter

Also, make sure to add another 15% at least onto the number it gives you because inverters are not 100% efficient.

I've drawn 200A+ Constant off of my electrical system, but I also have a rewound alternator and extra battery, They might not be necessary for you, it all depends on the health of your stock system and how much draw you really end up putting on it.

 

[Mgyver1]

Electricity hurts my brain... I've used a griddle plugged into my inverter that says it uses 1300w 120v which is like 10.83 amps I believe. I'm not even sure what that means but to my limited knowledge it means it requires that amount of input to run but I suppose that's what it uses at max temp because the higher I turned the heat the more power it said it was using and it never said I was using more than half of the inverters potential.

Yes the 10.8a is correct at 120v. You need to figure what it will be at 12v because ultimately that's where your power is originally coming from. Remember that watts is watts no matter the voltage, the amps is what changes depending on the voltage. So if your alternator puts 60a at 14v at idle, your alternator is only putting out 840 watts whether it's used at 110v or 12v. Between your ECU, spark plugs, headlights, etc, those watts get accounted for quickly. Your battery is what picks up your alternator's slack but only for so long.

 

[jeremyc74]

Electricity hurts my brain... I've used a griddle plugged into my inverter that says it uses 1300w 120v which is like 10.83 amps I believe. I'm not even sure what that means but to my limited knowledge it means it requires that amount of input to run but I suppose that's what it uses at max temp because the higher I turned the heat the more power it said it was using and it never said I was using more than half of the inverters potential.

As a general rule you can take the current draw on the 120V side, and multiply it by 11.5 to find out what you're pulling from the vehicle battery.

In the case of your griddle it's pulling about 125 amps.