We have a lot of toys. A large portion of these toys utilize batteries for at least part of their operation. A few years ago, I made the decision that we would switch to almost exclusively rechargeable batteries. As of this writing, I estimate that I have about 240 rechargeable AA batteries and 132 rechargeable AAAs in my house. I will share with you some of what I have learned.

The case for rechargeable

Rechargeable batteries have a lot going for them. The most important points are as follows:

• A consistent, dependable battery supply. We’ve all experienced it before. Beth is one year old, and instead of playing a lively tune, her favorite toy produces a garbled, off-key mess of sound when she pushes the magic button. She’s confused and upset, but you don’t have the right kind of battery available. With the proper strategy in place, which I will go over later, you can easily avoid this situation when using rechargeables.
• Long-term savings. Rechargeable batteries are much more expensive than traditional alkaline cells. I typically spend about $3.00 per AA battery. In contrast, a typical alkaline AA costs about $0.35 – $0.50, when purchased in bulk. That means that you would need to recharge a battery between 6 – 10 times before you start to see savings from it, assuming that the two options provide the same amount of usage time (capacity).
• No more leaking batteries. NiMH batteries do not leak. Let me say it again. They don’t leak! In my mind, this is a huge win.

The case for LSD

I did some research on rechargeable batteries. Most rechargeable batteries these days use NiMH (Nickel Metal-Hydride) technology, but there are two different types of NiMH battery: the standard NiMH cells, and a newer technology called “low self-discharge” (LSD) NiMH cells. Until very recently, these newer batteries have been somewhat overlooked for the following reasons:

• They were more expensive than standard NiMH cells, though this may no longer be the case.
• They have a lower capacity than standard NiMH cells. The capacity of a battery is measured in milli-amp hours (mAh), and a standard Energizer AA NiMH cell is rated at about 2500 mAh. The LSD cells that I buy are rated at only 2000 mAh.
• They have been marketed as “pre-charged” batteries. So what? I can buy them and immediately put them into something without needing to charge them first. Is that really much of a benefit?

Then what is the actual benefit of LSD cells? Why am I willing to pay more for a lower-capacity battery? The secret is that LSD batteries hold their charge for a long time. Standard NiMH batteries tend to lose up to 20% of their capacity in the first day after they are removed from the charger even if they are not being used. After the first day, they then continue to lose up to 4% of their charge per day. The result of this leakage is that your 2500 mAh capacity cell could be reduced to only about 1600 mAh after sitting on a shelf for only a week. People who have encountered only the standard NiMH technology come away from the experience with the distinct impression that rechargeable batteries don’t last as long as their alkaline counterparts.

LSD batteries, on the other hand, can retain 70% – 80% of their charge after an entire year of sitting on the shelf. This is why they can be marketed as “pre-charged”. The rate of leakage is significantly lower.

Putting it into practice

Here are some tips that I have come up with for using LSD NiMH cells in a toy-heavy, child-oriented household:

• Focus on a single brand. After some research, I settled on the Eneloop (Sanyo) brand of batteries. At the time, it was generally considered to be the best at providing consistently high output in demanding applications. It’s possible that the landscape has changed in the last few years, and other brands may be much more competitive. I have used the Sanyo batteries in a very wide range of applications for years now, and I am 100% satisfied with their performance. I have no desire to experiment with other options at this time.
• Focus on AA and AAA. You can buy very inexpensive C and D spacers that allow you to use AA cells in situations that require C or D cells.
• Use a slow trickle charger. There are faster (15 minute) chargers available, but they can damage the batteries after a while. Batteries get hot when charged quickly, and  heat damages batteries. I use a BC-700 from La Crosse Technology. Again, I did my homework before selecting this specific model.
• Use a faster charger for emergencies, and to resurrect “dead” batteries. Some batteries get discharged so much that a trickle charger won’t recognize them. For these cells, I put them into a cheap Energizer charger for about 20 seconds and then my main charger will charge them without a problem.
• Keep at least 10-20 spare each of AA and AAA. You never know when several toys will need replacement in a single day. Since charging takes a good 10-20 hours with a trickle charger, it’s good to have plenty of stock on-hand.
• Keep your extra batteries charged and ready to use. When a battery comes out of a toy, it goes right into the charger, or into the “on deck” circle if the charger is already full. When the charger indicates that the batteries in it are fully charged, remove them and put in any other cells that are waiting to be charged.
• Buy extra batteries in anticipation of large events such as birthdays and Christmas.
• Be “religious” about your homogeneous battery selection. Use only the rechargeable battery that you have selected, and don’t allow other types or brands to work their way into your fleet. I even go so far as to throw away the batteries in any toy that ships with cells from the factory.

– danBhentschel