You can buy a lead-acid activator online, but developing your own is much more fun. This DIY lead-acid battery activator can restore the capacity of lead-acid batteries that are declining in performance.
Lead-acid batteries are widely used in vehicles, uninterruptible power supplies (UPS), renewable energy applications, and more. While handy for various applications because they can deliver power in a short amount of time, these batteries often lose efficiency when the process of sulfation impedes the chemical reaction necessary for charging and discharging. A solution is to use a DIY lead-acid battery activator to revitalize and restore the capacity of lead-acid batteries that have experienced a decline in performance.
The Circuit
You can buy a lead-acid activator online, but it can be more fun to develop a solution at your workbench. Back in 2017, Elektor presented a circuit intended for just that. The principle was straightforward. The battery was loaded with a current of approximately 100 A for a period of 100 μs, which was repeated every 30 s.
The circuit's sections: supply, MOSFET circuit, potential divider with jumpers, and control and display.
Check out Jan Lichtenbelt’s circuit. The design incorporates a microprocessor to output a 100-μs long pulse to a MOSFET every 30 s. The different sections can be clearly seen from top to bottom: supply, MOSFET circuit, potential divider with jumpers, and control and display via the microprocessor.
"A shunt is connected to the battery in series with this MOSFET, which is protected against reverse polarity connections by a diode. The theoretical peak current when a shunt of 50 mΩ is used is about 100 A for a 6-V lead-acid battery. The voltage measurement at the battery terminals is done with a separate set of wires, so that the large current flow doesn’t distort the reading (four point measurement). Both circuits are separated from each other, and they’re only connected together at the terminals using battery clips."
IC2 is a Microchip Technology PIC16F1847 microcontroller.
Current is calculated by measuring the voltage across the shunt, and the processor handles pulse generation.
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The nearby graph shows the restorative effect in a worn lead-acid battery (12 V, 7 Ah) with a 10.3 V terminal voltage. The circuit’s designer explains: “After just four or five pulses the internal resistance has halved and is getting close to its eventual value. In a 12-V lead-acid battery of 7 Ah, we find that the temperature dependence of the internal resistance is about –0.7 mΩ/°C. It changes in value from 34 mΩ at room temperature to 62 mΩ in the freezer (–18 °C).”
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