How long to charge Electronic Headset?

[ulflyer]

I have an old Bilsom Marksman electronic headset that I've put a new 9V rechargeable battery in. The charger is listed as 10Ma for 9V. It has no light to indicate when charging is complete. How long should I leave it plugged in?

The new battery had very little charge on it and I inadvertently left it plugged in overnight. It seems to have plenty of charge now but suspect that was more than needed or advisable.

I've long since lost any instructions that came with it.

 

[rcmodel]

Charge at C/10 (ten percent of the battery's rated capacity per hour.) For example, if you have a 100 mAH battery, you would charge it at 10mA for 15 hours.

Look on the battery for ma rating.



rc

 

[GBExpat]

My Dad's (rough) Rule of Thumb was to figure that charging would only be ~80% efficient, so plan with that in mind.

BTW, rc's 10mA for 15 hours for a 100mAH battery covers that.

 

[ulflyer]

Thanks guys. My battery is 250mA so my charging it overnight, around 15-20 hours leaves room for more safe charge in case I forget to unplug it sometime. Not sure how much charge it had, but it was very little as it would barely power the headset.