Something Handy to Avoid
When you have one cigar lighter-type outlet but more than one 12-volt DC device that needs to be run at the same time, a Y-splitter can be a handy solution. Once you insert its plug into your outlet, it then offers a couple of sockets that you can use to advantage. Splitters are inexpensive, and are easy to use.
They are also problem-prone. I’ve had to discard a handful of them when they’ve failed and, as a result, offer here a few tips to use them properly.
The problems stem from two issues. First, cigar lighter connectors are a bad way to electrically power devices. Cheap connectors have plenty of electrical resistance, and will overheat with even modest loads, especially if they are not firmly engaged. They can fry and melt under a modest 60 watt load, which many laptops use when on and charging. Connectors that are left plugged in should be checked regularly for tightness, especially if vibration from vehicle movement has occurred. Excellent-quality connectors may brag about 180-watt limits, but you’ll never see that in practice.
This type of connector is universally used not because it works well, but because of technical inertia. It worked for lighting cigars and cigarettes in automobiles, using a device that uses resistance to get hot enough to set things on fire, basically. It pulls a lot of power for a few seconds, gets really hot, and shuts off. The “do anything” creativity so prevalent in the thirties through the fifties helped the cigar lighter outlet get pressed into service for everything from electric shavers to coffee warmers and beyond. These days, it’s electronic gizmos. Dedicated power outlets in cars have become popular, though they are not 100% interchangeable with plugs intended for cigar lighter outlets. In any case, care is still needed, especially since the plugs on most devices are the cheapest, worst possible design in order to keep costs low and keep the device cost-competitive. This is especially true of splitters, since they all strive to be the cheapest one on the market. That’s what we gravitate toward.
Second, nearly all splitters use 16 or 18-gauge wires. This is very thin wire for the power that is often pulled through them, and chokes down the voltage that the device sees. This is less of a problem than the bad connectors themselves, which will nearly always overheat first. If you hold a connector and it feels warm, then that connection is wasting energy. If it feels hot, then you are heading for a meltdown. All that resistance is not good. Your toaster at home deliberately uses too-small wires to get them red-hot so that you can burn your bread. That’s using resistance for a good cause.
Resistance in a splitter causes the same result, except that the heat causes its components to disintegrate. When your device pulls power through a high-resistance connection, voltage lowers and amperage increases. This stresses all the wiring from the battery to the device, and it may not do the device itself much good, either.
If you’re locked into keeping this type of connector, the best thing to do for anything that draws much over 40 watts is to avoid using splitters at all. Assuming that your rig’s wiring up to the outlet is sound, wire up another outlet, preferably using a Marinco Marine or similarly-serious outlet.
For low-power devices or, if you are stuck with using a splitter with more worrisome ones, try a splitter which is one-piece, having no external wiring. This doesn’t help the connector quality issue, but may decrease internal resistance. There’s only one wired splitter I’ve come across so far that survives higher loads. That is, I have yet to feel one heat unduly or see it fail. That’s the Roadpro Platinum Series fused cigarette lighter adapter. I think they make them with a choice of two or three dust-capped outlets. The contact on the nose of its plug is backed up by a spring, which ensures that this pin holds contact with the outlet it’s inserted into. The fuse is 10 amps, and I recommend that you do not upsize this.
It’s easy to assume that a fancy-looking splitter must handle more power, but don’t be fooled. If you have some experience with frying splitters and have found a good one, please include it in your comment!