5 ms·

I have switched to using NiMH rechargeables almost exclusively now, even for low power devices (e.g. remote controls, clocks). The problem I have encountered wi

I have switched to using NiMH rechargeables almost exclusively now, even for low power devices (e.g. remote controls, clocks). The problem I have encountered with alkaline batteries is that they leak chemicals which can destroy the electrical contacts and sometimes the entire device. I've never had a NiMH rechargeable battery leak in the roughly 15-20 years that I've used them. But I have seen so many alkaline batteries leak that I don't trust them anymore. Maybe it's my imagination but alkaline batteries seem to leak far more often today than 10-20 years ago. Is it just me, or are Duracell brand batteries worse than others in terms of leaking? The traditional argument for not using rechargeables on low-power devices is that the self-discharge rate for the rechargeable battery is higher than the power consumption of the device itself. However, some NiMH batteries (e.g Eneloop, https://eneloop101.com/ https://eneloop101.com/) seem to use a special chemistry that results in only a 30% discharge after 10 years. I use the Eneloop brand pretty much exclusively. I think the extra cost of the rechargeable batteries have more than paid for themselves by avoid the damage caused by leaking alkaline batteries. The cost of NiMH batteries are now low enough that they may be far cheaper than alkaline batteries for almost all applications.

leggomylibro 7y ago
The difficulty that I have with NiMh batteries is that it is very difficult to tell when they are done charging, and they are less tolerant of overcharging and "trickle charging" than the NiCad chemistries which preceded them. Most chargers will just assume that you've discharged them fully between uses, and perform a "full" charge cycle when one is plugged in, maybe with a temperature sensor to stop if they get too hot. You can't really use resting voltage as a gauge, and it's tricky to find a good charger which can reliably detect the small and brief "dip" in voltage which occurs around the time that the batteries are fully charged. They're great batteries, and I also prefer them for applications where the batteries get fully drained before being plugged in, but they can still be iffy for applications where you only discharge them briefly and want to keep them "topped up". For those applications, these days you can buy 1.5V lithium cells in AA/AAA form factors with built-in microUSB charging ports. But those are lithium-based, so you have to be careful about thermal runaway. Life is a balancing act full of compromises...
- jacobush 7y ago
  NiCad is the devil though but I assume you didn't advocate them, just missed a property of them.
  - leggomylibro 7y ago
    Right, good point, at least NiMh batteries aren't full of cadmium.
    - durandal1 7y ago
      And has no memory which is a huge advantage.
      - aidenn0 7y ago
        NiCd memory effect is way overblown. It requires nearly identical cycles each time and has only ever been observed in high-capacity aerospace cells. [edit] Repeated overcharging can cause changing voltage curves that are (apparently) also referred to as memory effect, but NiMH cells are also prone to this.
- bxparks 7y ago
  The NiMH chargers that I've seen have a negative delta-V detection and a timer shutoff. I've had problems charging the Eneloops when used on devices that drain the battery too much. When they are inserted into the charger, the voltage seems to rise too quickly and and somehow confuses the charger so that it stops charging early. In those situations, I've resorted to charging those batteries twice. First time, charge for 5-10 minutes to raise their voltage. Then remove and reinsert the batteries to charge a second time using a more normal voltage curve. Maybe it's a quirk of my charger. I didn't know about lithium AA/AAA rechargeable batteries. Interesting. I see that most are rated at 1200-1500mAh (AA) and 400-500mAh (AAA). These are only a little over 1/2 the capacity of the NiMH that I normally use. I guess the charging circuitry takes up room in the battery.
  - 7y ago

leggomylibro 7y ago

The difficulty that I have with NiMh batteries is that it is very difficult to tell when they are done charging, and they are less tolerant of overcharging and "trickle charging" than the NiCad chemistries which preceded them. Most chargers will just assume that you've discharged them fully between uses, and perform a "full" charge cycle when one is plugged in, maybe with a temperature sensor to stop if they get too hot. You can't really use resting voltage as a gauge, and it's tricky to find a good charger which can reliably detect the small and brief "dip" in voltage which occurs around the time that the batteries are fully charged. They're great batteries, and I also prefer them for applications where the batteries get fully drained before being plugged in, but they can still be iffy for applications where you only discharge them briefly and want to keep them "topped up". For those applications, these days you can buy 1.5V lithium cells in AA/AAA form factors with built-in microUSB charging ports. But those are lithium-based, so you have to be careful about thermal runaway. Life is a balancing act full of compromises...

jacobush 7y ago
NiCad is the devil though but I assume you didn't advocate them, just missed a property of them.
- leggomylibro 7y ago
  Right, good point, at least NiMh batteries aren't full of cadmium.
  - durandal1 7y ago
    And has no memory which is a huge advantage.
    - aidenn0 7y ago
      NiCd memory effect is way overblown. It requires nearly identical cycles each time and has only ever been observed in high-capacity aerospace cells. [edit] Repeated overcharging can cause changing voltage curves that are (apparently) also referred to as memory effect, but NiMH cells are also prone to this.
bxparks 7y ago
The NiMH chargers that I've seen have a negative delta-V detection and a timer shutoff. I've had problems charging the Eneloops when used on devices that drain the battery too much. When they are inserted into the charger, the voltage seems to rise too quickly and and somehow confuses the charger so that it stops charging early. In those situations, I've resorted to charging those batteries twice. First time, charge for 5-10 minutes to raise their voltage. Then remove and reinsert the batteries to charge a second time using a more normal voltage curve. Maybe it's a quirk of my charger. I didn't know about lithium AA/AAA rechargeable batteries. Interesting. I see that most are rated at 1200-1500mAh (AA) and 400-500mAh (AAA). These are only a little over 1/2 the capacity of the NiMH that I normally use. I guess the charging circuitry takes up room in the battery.
- 7y ago