AC Battery Chargers
This discussion centers on battery chargers that convert 120 volt AC power to 12 or 24 volt DC. There are a few different varieties available. In our opinion this is the least desirable option for charging batteries in a remote power application, but is often the only option if you are not willing to tinker with antique or home built equipment. Options for AC Battery Chargers: Build Your Own! We converted a dead Heart Interface inverter into a super powerful battery charger by extracting the transformer and connecting it through a large bridge rectifier. Hardware Store Chargers (auto parts store, too) These chargers function quite well, but are not very efficient compared to the new solid-state variety. They are very easy to find, any hardware store or auto parts store will sell you one. And they work fine, BUT--the ratings are generally inflated by quite a bit. This is a problem with the new low-cost inverters available from Taiwan, too. It might SAY 1000 watts on the case, but that's not what you are getting. Shame on them! Usually what you really have is a 30-amp charger in a big case that's mostly empty space. Let WEIGHT be your guide as to the true amp rating of this sort of charger--big ones should be extremely heavy because of the transformer inside. Also, this transformer tapers the charging current into your batteries. When the batteries are nearly empty, the charger will put out nearly its full current, which will gradually get lower and lower as the batteries fill. Surplus Industrial Chargers Made for charging forklift batteries, these machines are brutally expensive when new, and a great bargain if you can find them used. Some are set up for 24 volts. This can be a problem with both efficiency and heat buildup if used to charge 12 volt batteries. Inverters with chargers built in This sort of charger is very convenient--when your generator gets up to speed, the inverter automatically switches your house over from battery to generator power, and uses the excess capacity from the generator to charge your batteries. While not as efficient as a solid-state charger, these are usually quality components. If the inverter's charger is rated at 50 amps, you can bet that it produces that rating when the batteries are empty. We've never seen one of these chargers that suffers from "ratings inflation" like the hardware-store variety above. Since it's transformer based, it will automatically taper off the charging current as the batteries fill. Solid-state chargers The latest thing in battery charging, these chargers are lightweight (no transformer) and very efficient, but expensive. The only 2 brands currently available are from Todd and Statpower. And if they say "50 amp," you'll get 50 amp into empty batteries.. Charging current is controlled electronically for best efficiency. One note--with Todd chargers (the brand we use here), be careful to unplug the charger from the generator when starting or stopping it, otherwise the charger can be damaged over time.