What's the battery technology? What is the vendor's charging recommendation? What other design requirements have you not yet disclosed?
If it's lead acid, why not just get a golf-cart charger? You can't possibly build one (with unit pricing at retail) for less cost...given your level of experience.
Almost certainly not, but maybe. What battery type?
It can be two of each, or four N-channels. If you're charging from a direct-current source then you only need two MOSFETs.
You really, really, don't know enough to even start designing this. Normally you'd build a switching supply. You'd monitor the battery current and voltage, and control the charging current and/or voltage by modulating the duty cycle of the switching.
That depends on what you're doing. In a switching supply they are being rapidly turned on and off. The duration they're on vs. the total cycle time (the "duty cycle"), the supply voltage, and the load voltage all determine current.
In general they don't. If you're building an off-line switcher you generally rectify the incoming AC to DC, then use the resulting DC to power your electronics.
From the sounds of things you really need to learn more about electronics before you start trying to figure out a reference design.
The 2008 ARRL Handbook has a project for a 13.8V off-line switcher; many of the principles are the same as for your battery charger (in fact, there's a good chance that with the proper control electronics that circuit could be used to charge 12V lead-acid batteries).
I would suggest that you get onto the various semiconductor web sites and look for applications notes. "Off line power supply", "switching power supply" and "power factor correction" are all search terms that may get you useful applications notes.
If it's lead acid and you do build the charger, then you can't just go constant current -- you need to do a constant current charge up to a specific voltage (the nominal value of which escapes me at the moment, it varies with temperature, and I'm not sure that it doesn't vary by specific battery type).
--
Tim Wescott
Control system and signal processing consulting
Charging a battery from a full-H bridge makes about as much sense as using a full-H bridge for motor _speed_ control, when it only should be used to change direction >:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
Polarity auto sense and the ability to perform load testing between the charge pulse to test the life of the cell/battery.
Btw, we have a charger at work that does that very thing, it has a H bridge circuit. you can plop the battery on the holder any way you wish, it auto senses polarity and knows which side of the bridge to charge it on and uses the opposite side as a pulsed load test as it is being charged.
Guess no one has never heard of auto sensing polarity chargers and load testing.
We have a charger at work that uses an H bridge, you can connect the battery any way you wish, as long as it has at least .5 volt or more, anything less, it assumes nothing connected and does not make an attempt to select a polarity and turn on.
during a low state battery, the unit switches the bridge for a load test to determine if the battery is accumulating useful energy, if not, it'll give up and flash a bad battery LED>
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.