Max cigarette lighter inverter question

Hi. 3 full days without power here and no estimate on restoration, and I want to plug in am air mattress pump so we can sleep in the basement where it's about 25 degrees cooler. The specs for the pump are 135 W and 1.2 amp. I see the car outlet says 120W and 10A max. So can I buy a 150 W inverter without blowing a fuse or otherwise damaging the car?
Is it some combination of Watts times Amps?

2011 Prius 3

Thanks guys!!

Not really

Watts = Amps times Volts; hence Amps = Watts divided by Volts

The pump pulls 1.2 amps at 110 volts = ~135 watts.

Your Prius supplies 10 amps at 12 volts = 120 watts.

If you try and get 135 watts out of the Prius (even assuming the inverter is 100% efficient), it's going to try and pull a current calculated as 135 watts divided by 12 volts = 11.25 amps, and the fuse will likely blow.

Oh. :-(

Thank you for the explanation.

You could try 100 degree weather, no power, but I've got my Prius.... | PriusChat. This is assuming you can run the pump off AC or the pump can be connected to the 12 volt via terminals.

If I were to do this, I'd definitely be in ready mode if powering anything and I'd probably want to use the terminals in the back, not in the front. Don't know how kindly the wiring to the jupming points under the hood would take to a sustained load.

Agreed. I think an outlet wired as you describe, with an appropriate fuse in line, would be the safest solution.

Connect directly to the 12V battery using a clip to cig. socket adapter (if you can find one when the stores are closed). Camping supply stores should have this. There is a fuse in the cig. plug to protect you.
Have the car in "ready" so you don't drain the 12V battery. We're not talking about a lot of current here, just more than the "accessory" socket can handle.

When you connect to the battery remember the rear-most terminal is negative (black usually) and the front-most terminal is positive (red usually).

Of course you -could- inflate the mattress by mouth. Just take your time.

Hi
We r desperate now
Is blowing a fuse all the damage that could occur to the car?
It's a new mattress, sothe AC pump is the only method. We Have a foot pump but can't use it in this mattress.
It takes 90 sec from enpty to fully inflate and
I'd say it's 60% full already before my comuterbattery
Backup died. So I don't need to run it very long.

The fuse may blow very quickly, protecting the car. I wouldn't want to overload the wiring, in the event the fuse blows slowly.

Just get an inverter that can clamp onto the 12 volt battery terminals. Make sure you get the polarity right. Be careful where the clamps touch to avoid inadvertent short circuiting.

Power up the car in READY mode and go. Forget the cigarette lighter. Going beyond the fuse's rating isn't a good idea.

If you get a high enough output inverter, you can do what sl7vk did and power other stuff too. If you do decide to use the Prius to help power stuff for an extended time, make sure you have ventilation (e.g. open garage door) to avoid a deadly carbon monoxide buildup.

Ok we'll drive around and see if anything is open

That inverter hooks up to the battery in the trunk area, right?
I hate this. This is definitely beyond my comfort level

Thank you for the help

^^^
Yep. From memory, there's less in the way of the 12 volt battery on the Gen 3 that you have vs. sl7vk's (and my) Gen 2.

The negative terminal is connected via cable to the frame of the car. So again, be careful where the clamps go and about what they touch. You DO NOT want to short circuit the 12 volt battery (e.g. by letting the clamps touch when connected, having some metal directly connect/bridge the two terminals, etc.)

Examples of previous discussions:
Use the Prius as a 12-volt generator during a power failure? | PriusChat
Prius as a power source? | PriusChat
Questions about hooking up inverter in car | PriusChat

V8Cobrakid recommends adding a fuse. I dunno. I'm no EE but my inverter already has a fuse.

Since Friday night I was without electricity (like so many here in the DC Metro Area) and I didn't have access to the internet. Monday morning I had this bright idea of using the Prius to run my DSL modem and accessing the internet. At about 7:30am I hooked up an old 12vdc/120vac inverter (rated 400wpeak/200w sustained) to my Prius' 120W cigarette lighter power plug and I used a very long extension cord (from the Prius to the inside of my home) to connect the inverter to a power strip which powered a laptop (65w), a DSL modem (40W), and a cellphone recharger (12W). Initially, I was really proud of myself that it worked, too! Unfortunately, it ran for about 10 minutes and then the power went out. Using my Garmin's GPS 12Vdc car adapter LED power light indicator - I realized that the Prius' 120W cigarette lighter power plug 15 amp fuse blew ( there are two separately fused 12VDC ports - the second 12vdc power port inside the center console was working) . Initially I was thinking -- This cannot be! I was still within the 120W limit! -- However, in hindsight it is likely that the inverter itself had an additional power load which push the load over 120W. Well - when I took out the 15 amp fuse -sure enough it was busted! About two hours later - the electricity came back on. It didn't take anything more than a trip to the auto parts store and a few glances at the owner's manual to replace the 15amp fuse - but it was a hassle. After replacing the 15 amp fuse ... I realize I should have limited the load on the Prius to just the DSL modem ... When Toyota says 120W max they really do mean max - if my experience suggest anything it is that the electrical load should not even get close to the cigarette lighter 12v power port's 120W max rating...

A long cable will drop the DC voltage and the inverter will compensate by increasing the current draw. Best to convert to AC -in- the car with short leads to the battery and then run an extension cord (120VAC) to wherever you want the power.

Connecting to the battery is not dangerous. Just remember the rear-most terminal is negative, the same as the chassis. The front-most terminal is positive. Don't short this to the chassis (or anything else). It's only 12V. -Some- people can get a shock from this but not many.

Gone to 2 stores- no inverters around. On to Plan T...
Thanks for the help. We will prob order one online for the next outage

We got power!! Yay! Anyway, we'll order an inverter from amazonfor next time

^^^
Best to order one that has comes with both cigarette lighter plug and clamps, in case you need to use anything that's beyond the amperage of the cigarette lighter fuse. I need to find the clamps I'm pretty sure my inverter came with...

In addition to some overhead, the inverter conversion is not 100% efficient. That 117W output requires something in the range of 130-150W on the input.

If a 12vdc/120vac inverter is directly connected to(via clamps) the 2010 Toyota Prius OE 12vdc aux battery what would be the safest max voltage/sustained-continous voltage load that one could draw from it (for about about 2 hours)? What kind of fuse would u use to protect it with?

Yep.

Does anyone have one they recommend? I looked at a bunch on amazon, and none seems to have consitent good reviews. Go for the $45 Cobra 800w or true Sine Wave xantrex for $150?
Or i wonder if i'm better off getting something like a duracell powerpack 600 and not even using the car...? Then I wonder if I should just buy a spare battery and use a battery tender, which I still need to buy for the prius, and an inverter, and make my own powerpack?

The maximum safe draw from a Prius 12V system is about 20Amps, which translates to about 200 Watts. The car would have to be in "ready", otherwise you would quickly drain the battery. You -can- do twice that, but I wouldn't recommend it to anyone but those who understand what they're doing.

What to buy?
It depends on what you are going to plug in. You don't need a true sine wave inverter for a mattress pump, but it would be better for sensitive electronics. The true sine wave inverter will be less efficient than a "standard" inverter which has a modified square wave output. Most computer (laptop) power supplies are happy with the standard inverter, as they are switching supplies and don't need a sine wave input. The inverters usually run at about 95% efficiency.

So now you are facing a dilemma. What are the chances of a power failure? How much are you willing to spend for security? You may want to check out small generators. Some of them are very quiet and cost about what you are contemplating spending. Particularly the Hondas. They are much more powerful than what you can safely draw from a Prius or any other 12V system. If you do go the generator route, you will want a secure place to put it with good ventilation. I understand there were a few deaths in this emergency from generator exhaust fumes. You will also have to maintain the generator (and the battery if you go that route). Draining the fuel, keeping fresh fuel on hand, etc.

It will be an exercise in emergency preparedness that you will have to continue indefinitely.