QuestionQUESTION: I was wondering if I could use two separate 160 watt power inverters in separate DC receptacles (cigarette lighters) at the same time in the same car. I believe that it would not be a good idea to try and pull a total of 320 watts through the receptacles, but I was wondering if I could use each at the same time if I only placed half the continuous load on each. Are all DC receptacles in the car (Sienna - two in front, one in back) on the same fuse?
I know there are inverters with two receptacles, but I have two inverters that each have only one and I am trying to use one inverter for a PS2 (45 watts) and one for a TV (48 watts).
Thanks in advance for your help.
ANSWER: Hi Steve,
I don't have specific wiring information for a Sienna. However, based on what I've seen in other vehicles, it's likely that each socket is fused separately. I've occasionally seen a pair of front outlets on the same fuse, but in just about every case a rear receptacle will be fused separately.
From what you're describing, it sounds unlikely that the average current draw on the DC outlet circuit will be higher than 10 amps total. In this case, I don't think you'd have a problem even if both inverters were combined on the same outlet. I'd suggest turning on the TV first, then the PS2, as TVs often require a brief surge of power when they're first turned on.
Hope this helps!
Brian
---------- FOLLOW-UP ----------
QUESTION: Thanks for the response Brian.
Should I just worry about the amperage? I know they make inverters that are rated for far more wattage than mine (160), but, as I understand it, you can only pull around 150-160 watts through a DC socket (for more you have to hard wire it to the battery). I assume that is because of the fuse, correct? The battery can handle more wattage, but the fuse can't.
If that is the case, would I be able to up the fuse amperage? In other words, if the fuse is 15 amps, could I get away with using a 20 amp fuse? Or, would I risk melting the car's wiring?
Also, could I use a power strip with the inverter if I didn't exceed 80% of the rated continuous load or are there other risks?
AnswerSteve,
Current is the issue you have to worry about, but the limiting factor is likely to be the vehicle's cigarette lighter wiring, rather than the fuse.
In theory, the fuse should be the weakest link of the circuit, and it should fail before there's any possibility of damage to the wiring. In practice, most manufacturers use somewhat undersized wiring at the cigarette lighter compared to the size of the fuse in the circuit. A typical cigarette lighter fuse is rated at 15 or 20 amps, while typical cigarette lighter wiring is 18-gauge or 16-gauge at best. The ideal wire size for a 20-amp circuit is 12-gauge, not 16-gauge. The vehicle manufacturer can get away with this because the duty cycle of a cigarette lighter is usually short-term: when you push in a cigarette lighter, it heats up and pops out again within 30 seconds. Other devices that plug into the receptacle (like cell-phone chargers) are usually very low-current.
A high-current, constant power inverter load can really test the wiring of a cigarette lighter circuit. It should be able to handle a constant load of around 10 amps, but if you go much higher than that, you risk damaged wiring. Upgrading the fuse size won't help this situation. Plugging your inverters into separate outlets will help, because even when two receptacles share a fuse, they'll usually have separate wiring to the fuse box.
You can get a general idea of the current draw of the device by dividing the power rating by 12 volts. A 100-watt load requires about 8.3 amps of current from a 12-volt battery, but you have to add a bit because an inverter isn't 100% efficient: some power is converted to heat in the inverter itself. That's why I estimated around 10 amps for your PS2 and TV system.
If you're concerned about the current demand from your inverters, you might want to consider adding an after-market heavy-duty 12 volt receptacle, wired directly to the battery terminal with 14-gauge or 12-gauge wire (and appropriately fused at the terminal). One advantage to this setup is that you'd be able to place the new outlet in a more convenient location. However, with the devices you're planning to use right now, I don't think you'll have a problem if you just plug one into each of your front receptacles.
Hope this helps!
Brian
