[TheForge] Inverters & MIG Welders

Fri May 25 11:36:02 EDT 2007

Aubrey,
I would expect adding a second battery to substantially boost the power 
available. Again, you'll have to watch the size of the cables, and match 
them to the current drawn. However, I have no advice to offer on the 
right way to do this. I'd have to research it. But I believe many 
diesels are done this way. So this is an established configuration, or 
at least should be an easily learned process.

As far as the differences between a 3500 watt inverter and generator, 
the generator (assuming it was manufactured, and not homebuilt) would 
have a powerplant (the motor that drives it) would be sized to provide 
sufficient power to deliver the 3500 watts of electricity out of the 
generator.

The inverter is taking 3500 watts from another source (your truck) and 
converting it to another "form" for your welder. You need to make sure 
your truck can deliver that amount of electrical power. If it can't, you 
won't get 3500 watts out the other side. And since no conversion is 
100%, you'll lose some in  the process. So to get 3500 watts out, you 
may need to put like 3700 watts in.

Judging from the kinds of heat sinks I've seen on even modest sized 
converters, I'd expect that the loss in the conversion is significant. I 
have a small one, 225 watts, and I'll bet I lose at least 10% (I've 
never measured, this is just a guess)

Paul

Washington, Aubrey O. wrote:
> Paul,
> Thanks for your thoughts.  Nothing about electricity/electronics is too basic or too obvious for me!  So, you won't insult me by telling me something others would consider obvious.
>  
> Would there be an advantage to installing a second battery in the truck?  I assume there are right, wrong, and disastrous ways to do that, too.
>  
> I assume that a 3500 watt generator and an inverter rated at 3500 watts are different in some important ways.  Can anyone explain to me what those differences would be?
>  
> Aubrey
> 
> ________________________________
> 
> From: theforge-bounces at mailman.qth.net on behalf of Paul
> Sent: Fri 5/25/2007 9:03 AM
> To: Sponsored by ABANA
> Subject: Re: [TheForge] Inverters & MIG Welders
> 
> 
> 
> While I don't have any direct experience trying to do this, but since no
> one else has offered any advice, I'll take a shot at it.
> 
> Some of these points may be obvious, but since you asked, I'll throw out
> everything that I'd consider.
> 
> I'm deliberately being imprecise here, just rough numbers to evaluate if
> it's reasonable...
> 
> Even at 130 amps, your truck will turn out less than 2 kilowatts of
> sustained electrical power. Since you'll lose some power in the
> inverter, your 115V output will probably be less than 15 amps.
> 
> Your battery can probably provide enough additional power for surges, so
> you may get more, but exactly how much, I don't know. Managing your
> welding duty cycle may make this useable, but I'd add a fuse to the
> battery connection so you don't fry your battery.
> 
> Next point, you will likely have to connect an inverter this big
> directly to your battery, and use some #6 or heavier wire, ala heavy
> jumper cables.
> 
> I'd also expect an inverter this size to be pretty expensive (at least
> by my definition of expensive) so it won't be a cheap experiment.
> 
> I think this would be really taxing your truck's electrical system.
> Let's face it, arc welding is pretty close to a dead short, albeit a
> current limited short.  I've been considering a portable setup, but I
> have a 3500 watt generator (4300 kw peak) and I'm hoping that will work...
> 
> 
> Paul N.
> 
> 
> Washington, Aubrey O. wrote:
>> Now that I've got my 115V MIG welder ordered (Millermatic 140), I have another related line of questions for the group.
>>
>> I have a new Toyota Tacoma with the 130A alternator on it.  I've been considering installing a power inverter on the truck so I can run power tools, etc.  Here are my questions:
>>
>> Are there any cautions or dangers involved in installing or using inverters?  Can they damage my truck's electrical system in any way?
>> Inverters come in lots of different wattages.  Is bigger always better? 
>> Is it practical to consider running the MIG welder off the inverter?
>>
>> Thanks for any advice or information.
>>
>> Aubrey
>>
>>
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