I have various sets of 4 rechargable AA or AAA batteries and a number of appliances (camera flash, bike flashlight, hand flashlight, portable phone handset, wireless keyboard/mouse, etc.) which require 2, 3 or 4 batteries. All of them are Ni-MH, some ordinary, some of the eneloop brand (Sanyo first generation or Panasonic make). Altogether I have 20 batteries in sets of four.

For charging I use a charger with separate circuitry for each battery, four loading status displays and a discharge function (the charger can either charge or discharge, cannot charge one battery and discharge another at the same time).

I've been told some time ago to follow these rules:

  • Full charge, full discharge whenever possible,
  • one to three 'refresh cycles' from time to time, less so with the eneloops,
  • don't combine different capacities or brands or newer batteries with older ones.

My question is what should I do to make best use of the batteries while being able to grab some and use them for whatever I need at the time (not having a set designated to a particular single use).

I ask this because the way I use the batteries contradicts some or all of the three rules above - namely I can't always get the same level of wear or I'd like to use batteries from different sets which sometimes lay idly when the rest is used somewhere else etc.


NiMH batteries are much more tolerant of partial discharge/recharge cycles than the old NiCd ones, so I wouldn't worry about whether or not they are being run flat.

The third rule is the important one. If you mix dissimilar batteries, then one will always be a bit weaker. This will be the one that gets run flat quicker, and if left too long, the other batteries may end up pushing a charge through the flat battery. This recharges it the wrong way, damaging it and making it even weaker next time.

Also beware of batteries that have been left too long after being charged. Some of the charge will have leaked away, so it will be like using a battery of a lower capacity. All the batteries in a set should ideally be freshly charged.

  • \$\begingroup\$ Thank you for a nice answer! If I understand it correctly, it can actually make more sense to discard the weakest batter of the set and get a more durable set of three than to keep all four when one is more worn out than the others! \$\endgroup\$ – Pavel Aug 31 '16 at 19:41

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