1.2v NiMh 20mah button cell

[bryan]

Hello;

Have a 1.2v NiMh button cell from a digital wall timer that needs replacement. Can't find an exact equivalant, so wanted to replace it with a 120 mah 1.2v NiMh battery. Will this be ok?

 

[HiTech]

Should be fine. The difference may be in the ampere rating between the two and perhaps physical size.

 

[MrAl]

Hello there,

You'll also have to make sure it can charge properly if it is a different ampere hour rating. Different ratings have different charge requirements if they are too different. If it doesnt charge, you'll know something is wrong.

 

[Sceadwian]

NiMH's are commonly charged with a Delta V charging method, meaning charge circuitry monitors the voltage of the cell and cuts it off when the characteristic dip of a fully charged battery is noticed. Since youre new cell is 10 times larger the 'dip' might not be properly detected, which means the charging current will never stop possibly damaging the cell in the long term, although being 10 times the size it can handle 10 times the charging current of the smaller cell it's still not a good idea to leave them charging for long periods of time.

 

[bryan]

Thanks everyone. Did some searching on the net and am having difficulty even determining what this battery is. Markings on the battery are Sylvania 60BNK which some sites say 1.2v NiMh 20mah other sites state NiCad. The charging circuitry is a transistor, resistor, cap and what appears to be a diode(s), think one is a zener.

The battery is part of a digital timer, so turning off the charging is not an option. May be just easier to buy another timer.

 

[Sceadwian]

If the cost of the larger cell is lowenough might as well try it, shouldn't hurt, since it's so much larger than the original cell the largest problem you're going to have is it's going to take a very long time to charge if it's used, it will also last significantly longer.