Connecting a Car Battery to a UPS Uninterruptible Power Supply I mentioned in the article that I need to modify the SMPS power supply to charge the car battery.. The charging adapter should be small, so I can handle it with the appropriate current limiting and voltage setting of the Laptop adapter.. I finished the job in a shorter time than expected, I used the strange part, the brand of the Laptop adapter is familiar 😀
The output voltage of the adapter can be adjusted between 15V…24V, the voltage changes with the plugs attached to the cable end (there is resistance inside the plugs) of course, the plugs are lost and the output cable is cut anyway. Fortunately, even if the plug is not plugged in, it gives its lowest voltage, which is 15V, this made my job easier. Also, I didn’t need to modify it to lower the voltage, 15V is enough
I need to limit the current to charge the car battery with the laptop adapter, the adapter gives 8A, 5A limitation would be enough. I added the simple single transistor circuit that I mentioned in the article Battery Charging Flyback SMPS Modification, I connected 1 0.33 ohm 5W and 0.22 ohm in parallel for the shunt resistor, and a current limitation of approximately 5A was made.
You can use this system in classic, not too advanced flyback SMPS devices. UC384X, or similar SMPS control integrated circuits, those using integral SMPS integrated circuits such as Viper12, Viper22 are very suitable. But if they have advanced structures, they may be difficult, the laptop adapter I applied is not complicated. There is an 8-pin control integrated circuit, mosfet on the primary level. Opto in the secondary, TL431 simple structure..
Battery Charge Laptop Adapter Modification Schematic
SMPS Current Limiting, the system used for battery charging is already a method used in devices on the market. Below is a 5V 1A application made with Viper12;
I also used this battery charging modification in the Mosfet flyback power supply circuit (ATX Standby) shown in the diagram below for 7aH battery charging (700mA limitation was made). First of all, the TL431 voltage adjustment was made according to the high voltage winding, then the current limiter was added, it works without any problems…. You can use the SMPS modification for LED dimming in addition to battery charging.
ATTENTION Laptop, notebook adapters work with voltage, be careful. Use a fused power line, protective glasses.
