Cordless phones usually have a display that indicates the battery status (the remaining capacity). In order to ensure a reliable indication, important information is used, such as supplied from the built-in charging circuitry. If a battery is charged out of the phone the necessary information from the circuitry is missing and the phone may not properly display the status of the battery.

Hearing aid batteries are zinc-air-batteries. To function correctly, they need oxygen from the surrounding air. They have a coloured sticker (or “tag”) which need to be removed 20-30-minutes before using the battery, so air can enter the battery allowing it to reach full power.

Please check the smoke detector manual. In our opinion, almost every smoke detector will work with NiMH batteries, but please note: smoke detectors are equipped with a "battery empty alert", which emits an acoustic and visual sign when the battery is low. By using an alkaline or lithium battery, the signal may sound for a longer time (e.g. 3-4 weeks) whilst using NiMH batteries may only sound for 1-2 weeks.

Over 99% of battery operated devices which work with 1,5V alkaline or zinc-carbon batteries will also work with NiMH batteries. Alkaline batteries are normally around 1.5V and by NiMH batteries are about 1,2V nominal voltage, but this isn’t the whole story. The voltage of a new Alkaline battery starts at just over 1,5V, but when you use it the voltage drops slowly to only 0,8V. A fully charged NiMH battery is about 1,4V and stays at 1,2-1,3V until the end of its capacity and then quickly drops to under 1,0V.

Some older devices require at least 1,3V to work. These, then, only work for a short time with NiMH batteries. Another reason could be that the battery display of devices such as digital cameras is set for Alkaline battery voltage and therefore displays NiMH batteries as empty.