long term trickle charging NiCad batterys

[Keith Soldavin]

I have an application where I am using a two cell 2300 mAh NiCad
battery as a backup power supply for a sensor. The system will be out
in the field and running off AC power most of the time but when the
power is disconnected that battery will keep the system alive. I want
to be able to recharge the battery and keep it maintained but I am
trying to avoid a smart charging system. Would it be OK to constantly
trickle charge the battery at a rate of around C/50 and not risk
overcharging? I'm not concerned about how long it will take to
recharge the battery nor am I concerned about shortening the battery
life significantly. I doubt this will be used for longer than a year
before the entire system is replaced. If the C/50 rate is not
appropriate then what charge rate would be acceptable for my
application?

Thank you
Keith

 

[Keith R. Williams]

I have an application where I am using a two cell 2300 mAh NiCad
battery as a backup power supply for a sensor. The system will be out
in the field and running off AC power most of the time but when the
power is disconnected that battery will keep the system alive. I want
to be able to recharge the battery and keep it maintained but I am
trying to avoid a smart charging system. Would it be OK to constantly
trickle charge the battery at a rate of around C/50 and not risk
overcharging? I'm not concerned about how long it will take to
recharge the battery nor am I concerned about shortening the battery
life significantly. I doubt this will be used for longer than a year
before the entire system is replaced. If the C/50 rate is not
appropriate then what charge rate would be acceptable for my
application?

A SLAC is likely a better solution than NiCd for this application, as
long as when they're used you don't discharge them to zero. SLACs love
to be left on float for years.