How many amps can I put through a 12v power socket? "Poor Man's Goal Zero"

[trae]

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Eh, I think those "all in one" "power packs" are more for people who want to be able to charge their phones or tablets. And 12ah isn't much - Hell I can go down to HF and get a "portable jump starter" with a 17ah battery for less than $60:
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https://www.harborfreight.com/3-in-1-portable-power-pack-with-jump-starter-62306.html
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Those little "power packs" have deceptively high "mAH" ratings but you have to dig into the details to see that the "40000 mAH battery" is measured at 3.8v. As you pointed out at 12v the battery is more in the 12ah range.
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In fact, when I was at HF a couple weeks ago I came across their solar stuff. Here's a 35ah battery that is small enough to fit into an ammo can:
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https://www.harborfreight.com/12-volt-35-amp-hour-universal-battery-68680.html
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Combine it with a simple PWM controller and the appropriate input/outputs and it would probably do everything I need as well.

Fair enough. I’m not suggesting that this can’t be done, I’m just looking for a lazy way out. The HF unit you linked appears to be only chargeable via Ac where’s the battery box I linked has all the electronics included. In any case I guess we are starting to split hairs both will work just fine


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[ducktapeguy]

I'm also looking into making a similar portable battery box as an alternative of installing dual batteries into multiple vehicles.

In order to limit the charging current to the auxiliary battery, what about the old trick of putting a lightbulb in series with the charging wire? The bulb would act like a variable resistor, acting almost like a short at low currents and limiting current to the max amperage of the bulb? I'm no electronics expert, but seems like a workable, if inefficient, solution. I'm thinking a 100W bulb would limit charging current to about 8A even with the aux battery at almost a dead short, and just act as an extra inline fuse when the battery is almost topped off. Could also work as a very rudimentary charging indicator, depending on the brightness you have a rough idea of how many amps you're drawing.

EDIT: Actually, after thinking about it some more, you probably don't want to use a 12v bulb because in normal use the max voltage difference is probably closer to 4-6V.