How to Use a Diode to Stop Battery Drainage

How to Use a Diode to Stop Battery Drainage

Diodes are used in electronic circuits to prevent electrical current from flowing in more than one direction. They are also used to push electrical current from one point in the circuit to another, such as is the case in a solar cell charging circuit. When a diode is used as a means to control the direction of current flow, it is referred to as a "blocking" diode. When solar panels are exposed to light, these panels generate electricity and can charge a battery. If a blocking diode is not present, the solar panels can also drain the battery when the solar panels are not exposed to light.

Things You'll Need

Protective eyewear
Electrical pliers
Soldering iron
Secondary cell (rechargeable) battery
Photovoltaic (solar) cell (equal voltage to the battery)
1N4001 diode
Electrical wire
Electronic (rosin core) solder


Instructions
Put on the protective eyewear. Cut three pieces of wire, and strip each wire of 1/2 inch of insulation at each end. Using the electrical pliers, attach one end of the first wire to the negative terminal on the battery. Attach the other end of the first wire to the negative terminal on the solar cell assembly.

Connect one end of the second wire to the positive battery terminal. Connect the other end of this wire to the cathode lead (which is marked with a line) on the diode, and solder this connection.

Connect one end of the third wire to the anode lead on the diode. Solder this connection. Connect the other end of the third wire to the positive terminal on the solar cell assembly.

How to Build a Battery Isolator

How to Build a Battery Isolator

Automotive battery charging circuits are designed to recharge and maintain a single battery. However, automobiles with custom audio systems, electric winches or other high-drain devices may require a second battery to power these devices.


One of the problems with connecting two batteries directly to an automotive charging system is that if one battery is weaker (provides less electrical current at the same voltage) than the other, the charging system may be taxed beyond its design parameters for providing power. This also has the undesirable consequence of draining the “good” battery to equalize the charge in both batteries.


One way to charge both batteries without overtaxing the charging system is by using a battery isolator. A battery isolator is constructed using two diodes, which act as one-way electrical check valves for the charging system.



Things You'll Need
Solder-type lug terminals (3)
High-current diodes (two; RF1501TF3S or equivalent – See “Resources”)
Soldering iron
Electronic solder
Electrical wire (insulated copper, minimum 8 AWG thickness)
Electrical pliers
Permanent marker


Instructions
Cut three, 2-foot-long pieces of wire and strip one-half inch of insulation from each wire end.

Solder a lug terminal to one end of the first wire, and mark the side of the lug terminal with the letter “A.” Solder the free end of the first wire to the anode leads on both diodes.

Solder a lug terminal to one end of the second wire, and mark the side of the lug terminal with the number “1.” Solder the free end of this wire to the cathode lead on the first diode.

Solder a lug terminal to one end of the third wire, and mark the side of the lug terminal with the number “2.” Solder the free end of this wire to the cathode lead on the second diode.