DC to DC Charging

[MNtal]

"It's not heavy. Your probably thinking an automotive battery, mine is much smaller."

"Honestly it was a goof off project gone wild."

That's exactly what I was picturing and it sounded like a pretty lousy thing to haul around.
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I have a 30mm Ammo can that could hold a car sized, heck probably a truck sized battery, but like I said that would be horrible, and that's what I was picturing in my head.
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I like DIY, carry on, it sounds like a fun experiment.

 

[Airmapper]

I was thinking, if you want to play around with this some more fairly inexpensively why not use a diode or MOSFET at the charging port to prevent discharge? (This is the electrical equivalent of a backflow preventer.)

Cool, if I get my head back into it I might try this.

I didn't think of a diode, that would be really simple if it works. Just got to make sure I don't plug it in backwards or I'd have a dis-charging cable. :sombrero:

 

[Rando]

If you want to play around with this, there are plenty of extremely inexpensive buck/boost voltage regulators on ebay that would easily allow you to set a constant charge voltage and charge current, independent of your alternator and power loss on the wires:
http://www.ebay.com/itm/Auto-DC-DC-...698321?hash=item33a5206f11:g:04wAAOSwgQ9Vke3d

I can't vouch for any of these, but for the price they may be worth exploring.

 

[pugslyyy]

Cool, if I get my head back into it I might try this.

I didn't think of a diode, that would be really simple if it works. Just got to make sure I don't plug it in backwards or I'd have a dis-charging cable. :sombrero:

A diode is the simpler of the two, but has a bit of a voltage drop across it (0.6V or 0.2V depending on type). A MOSFET takes slightly more work but will yield much less of a voltage drop.

 

[dBeau]

I've used this charger with good results. It can properly charge about any small battery you've ever seen and even some you haven't. I bought it because it takes 12v in and will boost the voltage if needed to get the job done. Mostly I use it for the 9ah 12v SLA "security" batteries. It can only do about 4 amps when charging at 14v but that should be fine for any SLA battery up to about 40 amp hours. The down side is that it's very configurable. You can easily configure it incorrectly and destroy your battery, or worse. The instructions that come with it could be better written.