Hi.
I have a 48 volt battery bank (675 Ah) supplying my Outback Inverters which are connected to my house wiring. I am looking for a way to charge the batteries until I get the cash to get some solar panels. Right now I am using one inverter to supply AC and another one only to charge batteries. The problem is that it will only charge at up to about 20 amps.
Are there plans somewhere that would show me how to build a regulated battery charger in the 100 amp range? If not a battery charger then perhaps a power supply? It would need to be able to go up to about 62 volts. So far I've only built little 12 volt, 1 1/2 supplies. If I can't get 100 amps can I get 50?
Would it be possible just to use a step-down transformer from 120 VAC to about 60 VAC or so and rectify it? Would one 12,000 uF capacitor be enough to smooth out the AC ripple? I've read that deep cycle wet cells do not like ripple.
Another possibility might be a DC generator and the voltage could be adjusted by engine speed. If I was to acquire a permanent magnet DC motor is there a simple way to determine how many amps it would put out at what voltage at what RPM? I've looked at many online and something in the 1725 RPM range seems like it would be easier on a small engine (and quieter if the engine is running at half speed) but so far I've not seen any motors rated at more than about 30 amps.
If all else fails I'd consider building a permanent magnet alternator from scratch. I've read about building PMAs for wind generators and it sounds like to get more current I would need to wind the coils with larger diameter wire and fewer turns to reduce resistance. All of the plans I've seen call for six coils but I'm thinking 9 might work better for higher current. Most of them also call for two rotors containing 12 magets each but I'm thinking that is just so there is more output at low wind speeds and if I'm using an engine then 1800 rpm or higher is not a problem so I was thinking six magnets might work. Anyone know it it can be built with 9 (or more) coils and fewer magnets?
Any other ideas?
Thanks.