2013Batteries/Power forum
Using diodes when wiring two battery plates in parallel
13 years old. Gear and prices may have changed since.
DisputedParticipants disagreed and reached no conclusion. Read the findings as positions, not as an answer.
What the thread found
- A diode should be installed on the positive line from each battery when wiring two batteries in parallel to prevent one battery from charging the other through backflow of current.
- Without diodes, the battery with lower voltage or charge will trigger its protection circuit and stop supplying power.
- Nickel-metal hydride batteries do not naturally balance load between parallel units and require diodes to prevent damage.
- Lithium-ion batteries handle parallel configurations more safely than other chemistries even without diodes.
- A Schottky diode rated for high current capacity can minimize voltage drop compared to standard diodes.
- Using diodes introduces approximately 0.7 volts of voltage drop per diode in the circuit.
- Diodes do not reduce maximum amperage output if properly rated for the application.
- Two fresh batteries of the same type and voltage matched together can operate in parallel with reduced risk even without diodes.
Depends on
- The voltage drop from diodes becomes noticeable when maximum power output is critical for high-drain equipment like power motors and wireless transmitters.
- Battery chemistry type significantly affects whether diodes are necessary, with some chemistries safer than others in parallel configuration.
- Practical application requires matching the diode current rating to the equipment's power demands.
- Age and charge cycling of batteries can cause different voltage levels that make diode protection more important than with identical new batteries.