How could this be done?

[kazoocruiser]

Here is what I would like to do. I would like to use my truck as a charging station to pre-charge a new 19AH 12v lead-acid battery. The battery will fit under the hood, so location is no problem.

According to the instructions, I need to have a 1 amp charge-rate for 19 hours.

[kipps]

Assuming the 1 amp charging rate is critical, the only way to make that happen is to adjust the input voltage until that 1 amp rate is reached. It's likely to need adjusting throughout the day, so there would need to be some sort of feedback loop to adjust the voltage and charging rate automatically.

I'm assuming a simple battery minder type charger would do perfect. Some auto parts stores keep their new to-be-sold batteries on these chargers all the time. If you're good friends with one of these stores, ask if they can plug your battery in for a day. Of course, if you bought the battery somewhere else(online?), I can understand you being a little embarrassed to ask them for favors...

The only route I can see to charge it cheaply and manually, would be to use a ammeter(from a early squarebody), a variable resistor, and a 15 volt power source of some sort(possibly an old fashioned non-automatic battery charger). Set the thing up in your basement on a saturday, and adjust it every hour to keep the ammeter in the 1 amp range.

[kazoocruiser]

Thank you for your response. If I hooked up the battery I need to charge in parallel with my existing truck battery, and left it alone, not running the engine, would that allow for a slow charge into the new battery without damage? Just hook it up, and leave it alone?

[kipps]

I have no way of knowing. Anything is speculation unless you have a ammeter in the circuit.

[sweetk30]

NEVER good to mix and match battery types and or cca specs and or mfd codes .

newer non lead acid battery types take a specific charger unless there up to charge and in a working vehicle.

mixing brands / cca / older to newer age / and so on can lead to problems in short order .

[kazoocruiser]

Originally Posted by kipps

I have no way of knowing. Anything is speculation unless you have a ammeter in the circuit.

I admit my ignorance regarding all things Ohm's Law.

I sure miss Radio Shack.

I wanted to convert a 4 D cell Mag-light to a rechargeable unit using the cigar lighter and the guy rattled off a how-to answer in less time than it took me to type this.

[Dead Parrot]

Parallel is a bad idea. If the flashlight is near dead, you would get a very large initial current from the truck battery into the flashlight. Lead acid batteries can both put out and accept large amounts of current, more then enough to melt the average non-battery cable wire. Why they are still used after all these years to power the starter.

Sounds like what you need is a DC-DC voltage converter powered by the truck battery. Feed the output of the converter into a current limited charger for your flashlight. Make sure to include a timer/auto shut off or you might need a jump to the the truck started.