Hello everyone,
I've got into RC hobby recently and my transmitter requires 8x AA batteries in series. I've got 8x 1100mAh NiMH AA batteries but don't have a dedicated 8 battery charger. For several years I was charging pairs of NiMH at 80-100mA for abt 18hrs and they served fine for years. Now that I have 4 pairs, charging has become a problem. Dedicated 8 cell chargers are very costly here in India and dedicated MAX NiMH charge IC's are not available either. All the transformers available are for 12v 500mA at the least which will kill my batteries soon, so I tried building 2 circuits to control the current. The first was this with values set for 100mA and 10V. On charging the batteries, the voltage was observed to be arnd 10.4v but charge current was less than 10mA. The circuit is working fine and supplying max current if I try to light a bulb but cannot charge the batteries properly. Next I built a common current regulator with LM317 and a 12ohms resistor to provide arnd 100mA but the same thing happened with a very low charge current. Now Im charging as pairs as I used to as I donot want to overdose with the 500mA transformer setup. should I try charging as 4 each or 4+4 as parallel or something? I just need to get a simple charging circuit, no fancy timers or auto chargers as the batteries will be monitored while being charged. Please help.
I've got into RC hobby recently and my transmitter requires 8x AA batteries in series. I've got 8x 1100mAh NiMH AA batteries but don't have a dedicated 8 battery charger. For several years I was charging pairs of NiMH at 80-100mA for abt 18hrs and they served fine for years. Now that I have 4 pairs, charging has become a problem. Dedicated 8 cell chargers are very costly here in India and dedicated MAX NiMH charge IC's are not available either. All the transformers available are for 12v 500mA at the least which will kill my batteries soon, so I tried building 2 circuits to control the current. The first was this with values set for 100mA and 10V. On charging the batteries, the voltage was observed to be arnd 10.4v but charge current was less than 10mA. The circuit is working fine and supplying max current if I try to light a bulb but cannot charge the batteries properly. Next I built a common current regulator with LM317 and a 12ohms resistor to provide arnd 100mA but the same thing happened with a very low charge current. Now Im charging as pairs as I used to as I donot want to overdose with the 500mA transformer setup. should I try charging as 4 each or 4+4 as parallel or something? I just need to get a simple charging circuit, no fancy timers or auto chargers as the batteries will be monitored while being charged. Please help.