Hammocan question

[KF0AWL]

I picked up a complete Hammocan cheap as a conversation piece for when I do presentations.
It came with a wall charger that plugs into Anderson PP and it got me to wondering.
The wall plug is a inverter obviously to charge the Lead Acid but would it charge if I adapt a plug from the car lighter port to Anderson PP since its both 12 volt? Just like a car battery 🤔

 

[mmckenna]

The wall plug adapter is a rectifier, takes AC to DC. If it's a good one, it's regulated.

You could use a cigarette lighter cord to charge it, but to do it correctly, you'd need to see what the specs are on the battery. Vehicle DC power can vary, and you'd need to make sure it didn't go above what the battery is speced for on the float charging.

Best bet would be to make a regulated DC-DC converter and use that to properly float the battery.

Or, just hook it up without a regulator, and it would probably work pretty well with some minor impact on battery lifespan.

 

[KF0AWL]

It has a digital volt meter on it, so if I keep a eye on that n shut off at 12 it would be ok would it not?

 

[mmckenna]

It depends entirely on the chemistry of the battery. Take a look at the battery itself and look up the specs on the manufacturers website. They'll usually give a maximum 'float voltage' level and a maximum 'equalize voltage' level.
For what you are doing, keeping the input voltage below the maximum float voltage level will give you the longest life out of the battery.
To do it right, it can get pretty complicated...
Float voltage is the voltage that you can constantly feed into the battery to keep it charged. Doesn't matter how long. Float voltage levels will depend on the exact chemistry. Since the chemistry of the starting battery in your car may be different than the battery in the can, you may need to be careful. Also automotive "12 volts" isn't 12 volts. It may vary quite a bit, even up in to the 14 volt range. The battery may be fine for short bursts of 14 volts or so, but long term it can cause damage.

Equalize voltage is a higher voltage that can be used to equalize the cells. It can be used for short times and only periodically. Not all battery manufacturers will recommend equalize charging of a battery, since it can be damaged if not done right.

Add in temperature compensation, and it gets even more complex, but no need to make it that complicated for a cheap battery...

Take a look at the manufacturer specs, and then compare that to the "12 volts" that your car really puts out. If your cigarette lighter or whatever you tap into for your source doesn't exceed that, then you are good to go. If it does exceed that, then you may want to add a charge controller. A good option might be a solar charge controller. They'll usually take the higher voltage of an open circuit solar panel (~18 volts or so) and control it down to a steady 13.8volts or so. I've used those at some remote locations to keep batteries charged for repeaters off solar panels.
Only thing to be concerned about is some of those use a very choppy wave form and can cause RFI, but if you are just charing your battery and not running radios at the same time, it won't be an issue.