Geo-TH,In
Well-known Member
Guido, explain this to me like I'm a first grader. No secret I've been a fan of 18v dewalt tools for past 20 years. I like they way the tools hold up for my purposes, but hate Dewalts Ni-cd and Li-ion. So I buy Ni-Mh batteries off ebay. Last order I spent a little more for a square deal 3 year warranty and cheaper than battery plus rebuilding them with Ni-cd cells.
Some of my original Ni-Mh batteries won't take a charge using the special dewalt charger designed for all 3 battery types. So I use an old .25 amp black and decker charger to keep those batteries charged and use them in the pole barn. BTW my oldest battery is my best one. I've been thinking there is something wrong with the temperature sensor (thermistor)inside the battery. Well I decided to use my shop radio to slowly discharge the Ni-Mh batteries in an attempt to erase their memory. When voltage gets to a low the radio shuts off.
To my surprise, when I plugged the radio back into the 110v the batteries now will take a charge from the radio. My question is why? In the summer thermistor's resistance goes down at temp goes up. In the cold pole barn, just the opposite, temp goes down resistance goes up. I decided to measure the resistance of the thermistors in all my batteries, both good and bad batteries. Most range from 29K to 100K. One of my bad batteries will now take a charge and the thermistor's resistance is infinity. So what's the need for the thermistor, except for having it there to tell charger battery is too hot to charge? What shuts the dewalt charger off? Obviously not the thermistor. Does it measure the current and the battery voltage to determine when it time to shut off?
geo
Some of my original Ni-Mh batteries won't take a charge using the special dewalt charger designed for all 3 battery types. So I use an old .25 amp black and decker charger to keep those batteries charged and use them in the pole barn. BTW my oldest battery is my best one. I've been thinking there is something wrong with the temperature sensor (thermistor)inside the battery. Well I decided to use my shop radio to slowly discharge the Ni-Mh batteries in an attempt to erase their memory. When voltage gets to a low the radio shuts off.
To my surprise, when I plugged the radio back into the 110v the batteries now will take a charge from the radio. My question is why? In the summer thermistor's resistance goes down at temp goes up. In the cold pole barn, just the opposite, temp goes down resistance goes up. I decided to measure the resistance of the thermistors in all my batteries, both good and bad batteries. Most range from 29K to 100K. One of my bad batteries will now take a charge and the thermistor's resistance is infinity. So what's the need for the thermistor, except for having it there to tell charger battery is too hot to charge? What shuts the dewalt charger off? Obviously not the thermistor. Does it measure the current and the battery voltage to determine when it time to shut off?
geo