Hello, I'm trying to design a circuit that has a battery charger that is powered from an AC regulator , has a constant load of around 4 amps, as well as an 8 amp load that will only last for approx. 1-5 seconds.

The Ac regulator can be adjusted from 12V to 14V with avg frequency 150hz, the battery is a 12v 5 ah lead acid battery.

My goal is a very minimal design, nothing too fancy. I was thinking a simple diode would do the job, and maybe fine tune the ac regulator voltage to output (after the diode) somewhere near 12.5-13.0 volts constantly charging the battery.

Will the load pull current from both the rectified source and the dc battery?
In that case do I need a high current diode? I think I have some 3 amp diodes somewhere but nothing that large. Any thoughts are greatly appreciated.

I drew a simple schematic of it below.

 

How do you plan to regulate AC ?

 

An ac regulator, i have one already

 

Sounds like a high wire act with a short ballance pole. Diode not needed as charger is always on. Using a sense resistor of say 1/10 Ω, measure battery current with charger at about 12 V. Battery current should decrease as charger is increased, when battery current reverses and battery is now charging, stop increasing when I is about 60 mA. Battery stands a chance of either under charging or over charging and is needed only to supply intermittant 8 A that we presume that charger cannot supply.

 

I was only thinking I needed a diode because my ac signal acts as the charger. There is no charging circuit, just a raw 12-14 volt regulated signal. And yes you are correct, I'm adding an 8 amp horn to my moped, and figured I would just gut out all the old wiring and convert the whole thing to dc.

 

If the AC is isolater from the DC, I would use a full wave bridge rectifier. Try to keep battery at about 13.6V while running.

 

I think the ac reg is capable of being isolated. My only concern is the load trying to pull amps from the charger as well as the battery. Will it pull most of the amps from the battery? Or do i need high amperage diodes.

 

Bridge rectifier should be rated at least 5 A RMS & 50 V. The battery acts as a large capacitor, with load drawing from AC & battery, with AC beeing dominet so that battery stays charged.

 

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