I want to build a lead-acid battery charger which can reach an average charge current of 3 to 4.5A, and start with a prototype. The charger needs to be supplied by the mains, up to 250VAC, for example. I was looking for some circuits on the web and did selected the circuit below.
I want to check your considerations and recommendations about this circuit and the components that I have choose (list below). My list of components would be:
- D1, D2 = B560A, SMC package (60V x 5A schottky)
- M1 = AmpMeter or short-circuit
- Rx = 1R or 1.5R or 2.2R, 10W, wirewound
- R1, R2, R4 = 1K, 1210, 0.5W, 5%
- R5 = 10K, 0603, 5%
- R3 = 470R, 1210, 0.5W, 5%
- P1 = 5K PCB potentiometer, PN CT94EW502 (Digikey)
- D3 = SMD 1N4007, SMA package
- D4 = BZX84C5V6, SOT23 package
C1 = ceramic 10uF , 0805, 16V
SCR2 = NYC0102BLT1G (Littelfuse Inc.) https://www.digikey.com/product-detail/en/littelfuse-inc/NYC0102BLT1G/NYC0102BLT1GOSCT-ND/2705214
SCR1 = MCR12DSMT4G (Littelfuse Inc.) https://www.digikey.com/product-detail/en/littelfuse-inc/MCR12DSMT4G/MCR12DSMT4GOSCT-ND/964541
Both theses SCRs have sensitive gate current (low IGT), lower prices and available in high quantities on Digikey.
- Is it suitable to use SCR1 as sensitive gate? Or it will be better to use a standard SCR for this part?
- Also, would it be better to select a higher temperature grade for SCR1?
- Is it possible to make a low cost protective circuit in case inverted battery connection occurs?
- What would happen to the output voltage when the battery is not connected to the circuit? If we considerar that the floating voltage of the battery is 13.8V and we set the potentiometer accordingly, the output voltage would be limited to 13.8V when the battery is not present?
- Also, you can suggest other good circuit for the same purpose (3 to 4.5A average current charge), maybe also a switching circuit.
Next month I will buy again on Digikey, so if you have some recommendations, I can buy any component present there for tests, giving preference for price and quantity available.