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ISO Info about 12v car lighter to Recharge a 120v AC Electronic Device. Thanks!

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IDEngineer:
I just did a ton of research on a similar project so I have a few tidbits to offer. Might not be a complete solution but at least it's data for you to stir into the mix.

My son is an internationally ranked drone racing pilot and we travel (fly and/or drive, sometimes internationally) to a lot of races. His aircraft run on 4S/5S/6S LiPo packs and during practice he will burn through a pack every five minutes (two minutes in the air plus a couple minutes between sessions), which means we must have the ability to recharge these packs in real time. We use multichannel LiPo balancing chargers that consume ~100W per battery being charged, so we are quite often drawing 400+ watts to charge four batteries at a time. Availability of AC power is not reliable at many of these venues.

My first thought was a small (~1KW) gas generator, of which there are a few models that would fit into a standard rollaway suitcase; I figured this was an ideal solution because then we'd be totally self-sufficient even at remote events. Alas, the airline industry flatly refuses to carry gasoline engines in luggage, checked or carry-on, even if the engine is brand new and has never seen gasoline. Just a flat NO. (The one exception was during one of the larger hurricanes... a couple of airlines made a temporary exception for people who wanted to bring generators to help, but they required the box to be factory sealed, AND their staff would cut open the box at check in to confirm the unit was brand new without gasoline, AND you couldn't return with it.)

The other option was an AC inverter, as already mentioned in this thread. If we drive, we have our car... and if we fly, we have a rental car... so no matter what, we have a source of 12VDC and the ability to recharge it. I did a bunch of tests on inverters and determined that they really aren't kidding when they sell "pure sine" inverters. Several of our balancing chargers, and my Hakko soldering station, would not run on "standard" inverters but ran fine without complaint on those marketed as "pure sine". By "pure" they mean low-ish distortion, and most of them publish a spec that is generally <=3% THD. I haven't personally analyzed that but some online reviews suggest that number is reasonably accurate - and the "testers" I care about (our chargers and soldering equipment) are happy.

We now have a 1200W inverter that we take to meets. I picked up a cheap set of battery jumper cables from Harbor Freight and attached ring terminals to one end in place of one set of battery clamps, which allows us to connect straight to the battery terminals. We've used this setup on multiple vehicles at multiple events now and it works perfectly. We "batch charge" our packs so we don't have to run the engine 100% of the time; he burns through a few batteries, we start the engine and charge everything, then turn off the engine. We've done a couple of 2-3 day events this way (so the drain on the car is over an extended period of time) and never had any issues with draining the battery too far, failure to start the engine, etc. I did some heavy load tests to push the limits since the car is idling and not running the alternator at high RPM, and it was only as I approached 1KW of load (a big space heater plus chargers) that I saw any effect - and that effect was a drop in voltage coming off the alternator, which got down under 11V. Loads at or below 500W saw no change in input voltage, which means the alternator was able to keep up with the current draw even at idle RPM's.

If I had it to do over again, I'd drop the size of our inverter to ~600W. This would save size and weight, which are important in airline luggage. That said, our 1200W unit is under six pounds and the cables only add another pound or so. It's a pretty sweet solution.

Most "cigarette lighter" outlets on cars these days are rated for 10A and fused for 15A, so you should be able to draw ~120W that way and not have to mess with jumper cables at all. If your load really is 55W or less as has been suggested in this thread, you should be able to do that via the cigarette lighter and a 200-400W pure sine inverter that costs around $100. (Our 1200W unit cost under $200 shipped to our door via Amazon.)

Second possibility: A fuel-burning generator. Yes, I know you said those are frowned upon by many of your venues, but consider this:


https://www.ryobitools.com/outdoor/products/details/900-watt-propane-inverter-generator

Your original post suggested that "personal Coleman propane tanks" might be acceptable. This little generator runs on exactly that! You screw a little propane bottle right into it and away you go. It also comes with an adapter for standard BBQ tanks, and there are kits to recharge the small tanks from the large ones, so this approach would give you a ton of options and flexibiliity. This Ryobi lists for $300 but I've seen folks online say it goes on sale for under $200 occasionally, so with some prudent searching you could make this quite affordable. The Ryobi isn't the only "mini propane bottle" generator I've seen, either, so look around.

There's two options for you to consider. Hope this helps!

james_s:
What sort of vehicle are we talking about? It's very common in RVs and boats to have separate starting and house batteries, the latter is used to power accessories and they are isolated so that you cannot drain the starting battery by running other things. Depending on the type of vehicle and the sort of locations you use, you could conceivably mount 100W or more solar panels on the roof and generate enough power to charge the speaker and run a small fridge without having to run the engine constantly. When more power is needed, idling the engine to charge the batteries does not burn a great deal of fuel and most car engines are fairly quiet.

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