Re: AGM battery charging
I did a lot of research before I forked out 200.00 each for my two AGM's. Essentially the AGM is a flooded battery just like a lead acid so normally your engine alternator should produce enough rectified DC voltage/current to charge the battery. To bring them to full charge your charging system needs to be capable of outputting at least 14.1 - 14.4 volts. Once they are fully charged the charging source should be capable of going into float mode which keeps the batteries at around 13.8 volts. This requires that your engine charging system also has a voltage regulator. The rectifier only converts the A/C produced by the alternator to rectified DC. It does not regulate the voltage.
The best and most efficient way to accomplish this is by installing an onboard charging system and a 12vdc/120vac inverter that will produce enough wattage to run the charger. To figure that out simply check the specs on the charger and find the current requirements. Then multiply that times 120 and you'll have the power in watts. (P=IxE). I have a 2500 watt inverter that runs off the engine's 50 amp alternator and produces enough power to run my onboard charger. When I get back in I plug the charger into shore power and finish them off overnight.
This works great and my batteries are still in great shape after a full season of hard fishing.
One word of caution, if you are running at an idle and your alternator is not producing enough current to handle the load of the inverter, it will suplement it's needs with current from the starting battery. You could end up with a nearly dead starting battery after a period of time. I put a switch on the inverter so that it only runs when I want it too!
As a side note, this also gives you 120vac which might tempt you to use it for other 120vac appliances. It you do, use a floating ground. In otherwords, don't ground to the hull or the motor or any other conductor you might come in contact with. This is safer and won't turn your aluminum boat into a poster child for electrolysis prevention.
Humor - Paint your un-primered aluminum boat hull with a copper based abative hull paint and do away with your batteries altogether, you'll be riding inside one.
Respectfully
Steve Schefer
Santa Rosa, CA.
