Mike - wow, this is all SUPER helpful, I really appreciate all the education!
Ok, so the Bluetti's AC charger is labeled like this:
Input: 100-240VAC, 50/60Hz, 7.5A Max
Output: 58.8V, 8.0A
Does that give you the info you need?
I definitely don't want to stress the alternator - this is a 1991 VW after all! And I really have no need for it to charge rapidly while driving, the trickle is great. Ideally I would get some sort of a trickle through the AC charger - again that way I wouldn't have to disconnect the solar cables and reconnect the DC charging cable before every drive, and vice versa when I get to camp. But if that's the only option, you do what you gotta do. To your point, I certainly could mount a couple of solar panels on the roof to get charging while driving (and parking, etc), and then patch in an extra portable panel that I can move around to chase the sun while at camp. Actually I bought flexible panels for that very reason, and may wind up going that direction at some point. I'm just also aware that the sun isn't always shining (or it's shining behind a thick layer of smoke....), and being able to get a trickle from the alternator seems prudent, if possible.
Thanks again!
Harwood
Ouch! The Bluetti AC charger can pull "7.5A Max" at 120VAC = 900 Watts. So even that 700W inverter I linked above, would be insufficient. 900 Watts is akin to a small coffee brewer or microwave oven. You would need a 1000W inverter, to avoid running it full out = more money, heavier cables and a bigger alternator, still. ?
There's no way to "throttle" the Bluetti AC charger so that it can pull only the fused cigarette lighter socket's 10 or 15 Amps at 12V when connected to a smaller 300W inverter, for example. The Bluetti charger will only overload a smaller inverter, forcing it to cut off.
So... I recommend pursuing a solution to your original problem - getting the Bluetti's 12V charging cable to work as expected. Your alternator will thank you. ?
Note that even my DIY, fan-cooled, 12V-to-24V, DC-to-DC converter box has to be directly connected to the car battety, while driving to keep the alternator cool at higher RPMs - and it's only delivering a charge rate of 220W at the Bluetti EB240 (pulling just under 20 Amps at 12V, so using the 15 Amp, cigarette lighter sockets is out ofthe question).
Keep in mind, too, that replacing a 15 Amp fuse with a 20 Amp fuse only invites overheated wiring and the possibility if an expensive repair job, if not a fire.
One last thing, while searching for 12V extension cables. Those that contain the cylindrical BUSS fuses within the makle cigarette lighter connector tend to quickly overheat, right there at the fuse holder, if the cable and connectirs are factory-rated for 20 Amp loads, even with a 20-amp fuse installed by the manufacturer. I've personally experienced extension cables rated at 20A and equipped with a 20A fuse, getting so hot at the fuse holder - WITHOUT blowing the fuse under a 19A load, that you can barely hold the make connector in your hand! This happens because the guage of the wire used to make the SPRING that holds the BUSS fuse in place is TOO SMALL, even if using 12 AWG conductors in the cable itself.
So... I STRONGLY recommend using male cigarette lighter connectors (in extension cables or otherwise, when pulling more than about 15 Amps) that accept BLADE fuses of the aporopriate rating - instead of BUSS fuses that use the thin wire springs.
But you won't have to worry about this with your "trickle-charging" rig, pulling less than 15A.
Mike