Sure, let’s say you have a typical car battery with a capacity of 60 amp-hours (Ah).
And let’s assume you have a small refrigerator that consumes about 100 watts of power when running.
To calculate how long the battery can power the refrigerator, we need to convert the power consumption from watts to amps.
Power (watts) = Voltage (volts) × Current (amps)
Assuming a car battery voltage of 12 volts:
100 watts / 12 volts = 8.33 amps
Now, we can determine the approximate runtime:
60 amp-hours / 8.33 amps ≈ 7.2 hours
So, with a fully charged 60 Ah car battery, you could run the refrigerator for approximately 7.2 hours before the battery is completely drained. However, it’s important to note that factors such as battery age, temperature, and other loads on the battery can affect actual performance.
if the car was running, the alternator would be charging the battery. would it be able to keep up with the drain of the fridge of just extend the time a bit?
Probably depends on the car + alternator, but it’s not so rare for modern gas cars to have AC outlets for backseat passengers, and the ones I’ve seen are typically rated 120-150W or so. Glancing at the power meter I have on my fridge, it uses ~110W while running and only runs ~10% of the time.
Theoretically the car probably can keep up while running, BUT
Compressor startup current may blow whatever fuse is protecting that circuit.
AND
Cars are very inefficient generators. You’d be wasting a bunch of fuel so I wouldn’t generally recommend it unless it’s an emergency.
That said, in an emergency it may be worth doing for like 20 min on / 1 hr off, so that you’re running the engine only when needed, but I’m not an expert, that’s just pure speculation.
If your dome light isn’t an LED, then you should replace it with one. It won’t completely fix your problem but it will give you 9 to 10 times longer to catch it.
There’s really no reason that every car doesn’t have a voltage cut off to protect the battery such that it can still start. Additionally, if they just included a super capacitor then even with a heavily discharged battery, it could charge up the super capacitor to then start the car.
But if we went around doing smart stuff like that then we could potentially wreck the entire lead acid battery industry and that would just be awful…
Looking passed the absolutely insane answer here, no one has even brought up the whole issue of AC vs DC. Batteries are DC, while your fridge that plugs into your wall running on AC. I know they make DC ones, but it isn’t like they are interchangeable.
Funny thing, most modern refrigerators use DC motors for their compressors so that they can run at variable speeds, so there’s likely an inverter that you could bypass if you know the appropriate voltage. The DC ones for RVs are the same internals, just without the inverter.
Correction: they still use AC motors, but those motors don’t use line AC. It goes line AC > rectifier > DC > inverter board > variable frequency AC to run the compressor motor.
Most RV fridges just use DC motors, but there are some that use VFDs and AC motors.
There are DC-AC converters you can use (might be called inverters in English idk), which are pretty interesting circuits. They are used all the time, e.g. to use solar energy
I’m not sure of the max load output on a car battery, but with a 15 amp 1800 watt dc to ac inverter, you probably can run a fridge off one. It probably just won’t last all that long.
From the owners manual: “There is a 115 Volt, 150 Watt inverter outlet located on the back of the center console to convert DC current to AC current. This outlet can power cellular phones, electronics and other low power devices requiring power up to 150 Watts.”
I don’t know if I’d plug in a fridge to that. I was wondering because my father in law’s truck has a similar outlet and I know he’s blown a fuse using it to power power tools.
My father in law drives a 2015 F150. That outlet on the center console is 120 Volt outlet supplies 400watts. But a fridge can be anything from 300 to almost 800. I’m not saying it’s impossible. And with newer trucks (especially the lightning and the F150 hybrid), I would believe it more readily. Ford is quick to market this in new trucks but I wouldn’t count on it with older trucks. I’m just pointing out that real work experience says your mileage may vary. Especially in places like Texas or Arizona where your battery is going through extreme heat cycles due to the weather from like February to November.
I wanted to say “look at the label but it should be fine” but then I did a quick google double-check and depending on whether you get US or EU results you get quite different answers: US 350 to 780W, EU 100 to 300W. Refrigerators have quite lower numbers but we wanted a fridge so let’s look at small refrigerators with proper fridge compartment (four stars, -18C), like… a Beko TSE1284N b100, 240 bucks not fancy not shoddy (Beko in a nutshell, honestly). Damn, why are they only listing kWh/24h and kWh/a. Whelp. No pictures of rating plates anywhere. Oh. According to Amazon “50W”, according to another trader 90W connected load, which makes sense if we understand those 50W as consumption load (or whatever those things are called in English).
So, yeah, look at the label and you should be fine. Don’t get that fridge though it’s 220V.
I measured my fridge. You could, in theory. Problem is that the motor in the fridge (and in power tools) is an “induction load”, meaning it draws a lot more power in a split second when starting. Inverters have to be built with that in mind, or just stronger (killowats range).
maybe they’re really into creepy sexist jokes and defending paedophiles and they figured RMS would overlook the licensing to support some fellow travelers…
Did this change? Many years ago I visited Vancouver and all their tobacco had graphical imagery of throat cancer and related conditions on the outside wrapper.
Depends on the province. Health is provincial jurisdiction, so things will vary. In MB, the packages have the graphical warning on the packages, but the stores all look like this (no packages on display).
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