Hi,

I'm currently design a Ni-MH charger, and I'd like to protect it from a Alkaline batteries charging.

What the best way to implement the protection?

Thanks!

Mikel (mandropov@yahoo.com)

 

hi

the best protection for your nicad charger is YOURSELF. a charger will never distinguish what kind of battery it is charging, whether rechargeable or non. it will even charge your car battery.

 

I'm with mozikluv on this one, it is a case of the operator using the charger correctly. If you do not with it to used for charging Alkaline batteries, make sure you place a warning on the unit where anyone who uses it (other than yourself) knows.

 

It's been a long time since I visited this forum. More than 5 years are passed since I asked a question here.

For anybody interested in a solution, here is an answer: the way to detect Alkaline batteries in charger is monitoring its charging curve (constant current charge) during first few minutes. Even with a low charging current applied, the voltage on Alkaline battery will rise to its initial value (mature cells), while Ni-MH cell' charging curve will rise very slow (almost unchangeable during first 2-3 minutes with a low charging current). Then, if the voltage is raised immediately, the charging process should be terminated. Otherwise, the charging battery is probably Ni-MH. Low current for few minutes into Alkaline battery shouldn't damage it (i.e. the battery wouldn't leak). Of course, such a charger should be controlled by uCU (or very complicated discreet HW).

 

It's been a long time since I visited this forum. More than 5 years are passed since I asked a question here.

For anybody interested in a solution, here is an answer: the way to detect Alkaline batteries in charger is monitoring its charging curve (constant current charge) during first few minutes. Even with a low charging current applied, the voltage on Alkaline battery will rise to its initial value (mature cells), while Ni-MH cell' charging curve will rise very slow (almost unchangeable during first 2-3 minutes with a low charging current). Then, if the voltage is raised immediately, the charging process should be terminated. Otherwise, the charging battery is probably Ni-MH. Low current for few minutes into Alkaline battery shouldn't damage it (i.e. the battery wouldn't leak). Of course, such a charger should be controlled by uCU (or very complicated discreet HW).

Thanks for posting the solution!

I have a battery charger which when you put in alkalines shuts off in about 2 seconds. So maybe there's a faster way of doing it? Perhaps it is just detecting the relatively high cell voltage of 1.5V, and relying on your described method for determining if it's an alkaline for voltages lower than 1.5V.

 

Thing is I've got devices that don't even start signalling for alkaline battery replacement until they get down to 1.3V or less. My guess is that Mandropov's suggestion is correct so 2 seconds isn't always going to be long enough to detect that.