On-board Battery Charger
 

As many of you FAS-ers have experienced, my alternator isn't running enough to keep my battery charged. I bought a chager at Harbor Freight, but I don't have the discipline to drag it out every night. My plan is to keep the charger on-board in the engine bay, and have a dedicated length of extension cord that I can simply plug into the nearest exterior outlet when I park in the driveway.

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The unit has some stand-offs to keep the fan clear for adequate airflow. Since the fan side of the unit will be facing the inside of the engine bay, I wanted to remove the stand-offs.

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Stand-offs coming off.

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Relocated indicator lights to be visible from fan-side as they would otherwise be covered when the unit was mounted.

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handle removed, lights relocated, stand-offs removed. I'm going to just let it do it's job normally for tonight, and tomorrow find a good spot for it.

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sounds like a solar battery charger would be another good option for you if this does not work

I also have an onboard charger. It was recommended to me by the distributor (who knows his stuff) to not put the charger in the engine bay due to heat.

I had considered that, and figured that since most of the actual operation of the charger would occur at night w/ the engine off it might be ok.

BUT...the engine bay idea didn't work out anyway (I should have expected as much with an econobox). I mounted it right in front of the driver's side front tire, in the bumper cavity where cold air intakes are usually designed to run. I was shocked by how clean it was in there. I think I introduced the first dirt that area had seen in its 7+ years.

Maybe I've misunderstood the instructions, but it seems when I kill 120V power to the unit, under charging mode, it will stay in charging mode, with the cooling fan running, until I remove the 12V clamps. However, if I just attach the 12V clamps to the unpowered unit, just the trickle charge light will come on. I guess I'll just install an in-car switch to kill the 12V side..?

what you need to do is find an older charger that is nothing more than a 120 volt to 12 volt transformer and a full wave bridge rectifier, and not all of the other "sensing" junk, if you want to keep it hooked up all the time to the 12 volt system. Yard sales, junk yards, flea markets are a good place to look for the "old school" type of chargers.

Well, I guess I'm too naive to let go of all the sensing junk. I'm a gear-head not a sparky.

The sensing 'junk' keeps your battery alive longer. Not really junk IMO.

Mine does not have any sensing stuff on it - basic. It is, however, only a 15 watt unit. Running all night long is just right to top off the battery but not to overcharge it.

I have mine on board. It's on the side, between the air intake and the fender. The intake box separates it from the main engine compartment. Also, it only cost me $7, so I can replace it if it fails from the heat.

Quick, dirty, works. If you want the elegant solution, Daox has that covered.

Get a relay with a 120V coil, then have it connect the charger only when AC power is connected.

What you want is a charger that is designed to stay hooked up to the battery, they tend to cost a little more because they also tend to be in a sealed weather tight box but they are pretty common for trolling motor batteries, motorcycles that sit over winter or hot rods that tend to sit for months at a time.