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Presented here charger makes it possible to charge one or two accumulators NiMH. Both accumulators are charged totally independently from each other. Average charging current is about 0,5A (peak 1A).
The charger is based on DS2712 in parallel configuration.
Originally the construction was inspired by the schematic in this project: LINK, although it was slightly changed so that it fits housing Z-32A.
Final version of the schematic and PCB:
And how it looks inside:
2Ah accumulators can be fully charged using this charger within 5 hours.
The charger indicates the end of charging by blinking diodes (one diode per accumulator).
The charger requires 5V min 1A supply, it is equipped with a standard DC socket 2,5/5,5mm. It can be powered by power supply Sunny SYS1421-0605-W2E (5V 1,2A).
When building this device, you can face the following problems:
- unavailability of good quality containers for batteries. Typical containers have very weak contacts. The charger may indicate charging error on them due to the high internal resistance of the battery, but in fact it is the external resistance on the container contacts. For this reason, you have to make a solution using plates and screws.
- transistor visible in the schematic as Q0 can overheat and heat the thermistor, what causes precocious disabling the rapid charging – remember to add a plate.
- for the same reason sometimes you have to limit the charging current from 2A (effective about 1A per accumulator) to 1A (0,5A per accumulator).
Link to original thread (useful attachment) - Dwukanałowa ładowarka dwóch akumulatorków NiMH na DS2712