Bed outlet power without key in the ignition?

That's funny! And believable. Earlier today I grabbed my 6.5 amp circular saw & 6.5 amp Ryobi angle grinder & tried to power them (one at a time) with the bed outlet @ the 100w setting. Nothing happened. I then started up my truck & tried again. Each tool ran perfectly at high speed.
400W divided by 120 VAC is 3.33 amps then why was it able to power both of those tool? Sorry but I just don't understand how that works.
The label on the Ryobi reads 120 V AC, 60Hz, 6.5 A

 

try cutting a PT 6x6

 

I'm sure that will take forever. I did cut a 4x4 pressure treated wood post. I did take my time with it. It was slow but it worked & the inverter never shut off.

 

Exactly. It thought is was a great feature even though (as an engineer) I knew the outlet was NOT of great capacity. I tried to run an older refrigerator off of it during a power outage thinking that the 'frig wouldn't drawn much - wrong!

If you're lucky, it might power a work light or a small coffee maker.

 

Simple - tools are rated on their maximum amperage draw under load. Free-running draw will be substantially less.

 

Zombie thread, but there's a high likelihood you'll damage your AC powertools running them on a dirty inverter. They aren't meant for inductive loads.

 

The answer is because AC is not a straight forward as DC is.
The formula for DC is: Power = (Amps)(Volts) -> W=(I)(V)

For AC there is an extra factor in there called the power factor that varies based on the type of load.
Specifically for single phase AC (like the inverters in our trucks): Power = (Amps)(Volts)(PF) -> W=(I)(V)(PF)
Where PF typically ranges from 0.5 - 0.99

So if we rearrange for Amps: I=(W)/(V*PF)

Then assume that power and voltage are constant I=(400W)/(120V*PF) we see that Amps can change based on the PF.

So thats why

 

whoa - how about a resurrection of this post after 5 years? =)

looking for feedback on an idea. i have one of those 12v fridges i want to run from the bed outlet. what are your guys' thoughts on using one of those solar trickle chargers to keep the battery charging and/or topped off? yes, i plan on leaving the key in the ignition turned to enable the on-board inverter and such. will this ruin the battery in any way?

 

Why not just use 12V? Run a dedicated feed with appropriate fuse. Add a switch if desired.

Using the inverter is inherently inefficient: truck DC > AC > back into DC at the fridge. Plus with the key on, the truck accessories will be drawing power (and you need to leave the keys in your truck all the time). The electrical demand will be higher using this method

 

this is the kind of straightforward answer i was hoping for! thank you. i never would have thought about other possible devices that would be sucking power when the key is turned to acc.

 

here's the end result! i chose this spot because the 12v fridge plug is more protected from bumps in cargo shifting while driving. there's an on/off switch built into the left display (although i learned that it only toggles the power to the USB ports and not the 12v outlet... grrrr)

i routed the wires along the rear passenger side frame, then the wire run turns toward the driver side just in front of the bed. i was a little apprehensive of it running so close to the exhaust at that point, but i managed to zip tie it far enough away to where it shouldn't be affected. then the wire run follows the frame on the driver side, then up into the engine compartment just behind a rubbery flap in the front driver side wheel well. the wires are encased in that plastic wire loom protective stuff throughout all the undercarriage. i got a little too excited about finishing that forgot to install the in-line fuse. that'll be for another time i guess.

i connected the solar panel to the pos/neg and left the panel on my roof, while also leaving the fridge plugged in... everything seems like it's running harmoniously.

i was too lazy to take pictures of the whole process; sorry!

with these new wires, truck bed lights, solar panel charging leads, and also an under-hood lamp.... the battery terminals are looking a little too busy. although i'm scared to do much electrical work, i'm thinking it's time to do one of those fuse blocks next.

 

What I ended up doing is getting a new key and getting it cut but not programed. Put new key in, turn 2.5 clicks and then use old key to lock doors as fob won't when a key is in

 

That's the route I took: ran a dedicated 12V through a circuit breaker to the bed cubby, added a fuse panel, USB and 12V Lighter socket, it also provides power for the topper lighting. Powering the fridge straight off 12V uses about 15~30% less wattage, the truck must convert D/C to A/C at the inverter then the Fridge's power brick does the same thing in reverse as you mentioned, each of those devices are in the 80-85% efficient range. Most fridges now have a low voltage cutoff to prevent running down the vehicle battery, I've found it runs for days with no impact to the engine turning over when starting. I know it's not ideal running a constant load on a cranking battery so I watch it and have options. I've measured the fridge's power draw, it pulls 42W when the compressor kicks on and nothing in-between compressor cycles, mine is under a topper and in a thermal cover and doesn't run very often. I recently got home from a camping trip sick as a dog and left the fridge running in the truck for 3 days in 90s temps and the truck cranked normally 3 days later and everything food-wise was just as I left it. I used to run the fridge off a power bank that charged off the inverter in order to keep it running at stops, it meant I had to remember to turn on the inverter everytime I started the truck. Running off DC I plug it in to bed outlet and leave it that way over a 3 day camping trip with no issues. I carry a power bank if needed and a charged up jump pack just in case the LV cutoff doesn't work.