Solar lights for the home and garden come with pre-installed, pre-charged batteries from most (safe to say, all) manufacturers when you buy them online or directly at stores. What many people don’t realize is that these rechargeable batteries will eventually run their course and lose all of their effective capacity after about 2 years of nightly use. These solar light batteries are almost always replaceable. And it is important to get the correct rechargeable batteries when the time comes.

Here are what you need to consider:

1. Chemistry. If your lights have either NiMH or NiCd rechargeable batteries, then you can replace them with either of the two. However, we recommend using the NiMH (Nickel Metal Hydride) chemistry as the Cadmium in NiCd (Nickel Cadmium) batteries is classified as a toxic material and must me recycled/disposed of properly. NiMH batteries can be thrown in the trash, but we do recommend recycling them wherever the services are available (some big box stores have bins at the front of their stores where you can leave your old rechargeable batteries).
2. Capacity. This is the specification listed on your batteries as mAh (or, milliAmp hours). This is effectively the amount of energy the battery is capable of storing/supplying on a full charge. Some solar lights will have a higher energy demand, so would thus require the higher capacities starting at 1000 mAh and going up to 1300 mAh and topping out at a very high 1600 mAh capacity per battery. If your light uses 2 or more rechargeable batteries, you want to be sure that the capacity is the same with both batteries in each light. For example, if you use a 300 mAh and a 1000 mAh NiMH rechargeable battery in a solar light that had an original mAh rating of 1000 mAh, then the charging current may be too high for the 300 mAh rechargeable battery and will damage it. Conversely, using these two battery examples in a light that originally had 300 mAh batteries will mean that the 300 mAh will charge to its optimum capacity, but the 1000 mAh battery will never reach its full potential and will only supply 300 mAh worth of energy. You can use higher rated mAh rechargeable batteries as replacements, but we recommend staying as close as possible (above) the original rating because higher capacities cost more and will not stay on any longer at night compared the original ratings. Using 2 or more rechargeable batteries of the same capacity will not additively increase the specification (so, 2 of the 1000 mAh series will not equal 2000 mAh). But it will increase the Voltage, which is our next point.
3. Voltage. This is very important when replacing the NiMH or NiCd chemistries. Both of these chemistries are typically rated at 1.2 Volts per battery. Using 2 or more of this series will additively increase the Voltage. So, using 2 NiMH AA 1000 mAh 1.2 Volts will result in a system that is 2.4 Volts at 1000 mAh capacity. If your light uses 1 NiMH rechargeable battery, then replace it with 1 of the same chemistry. DO NOT use a Lithium battery (even if it has the same mAh rating as the original NiMH battery) as Lithiums have a higher Voltage rating (typically 3.2 for solar lights). This higher Voltage will wipe out the components of your solar lights in a matter of seconds (we tested it, and the LEDs of our NiMH light was a goner in about 5 seconds).
4. Size. This is the easiest specification to keep constant. If your lights came with AA size rechargeable batteries, then you will want to stay with that size. Same goes for AAA rechargeables. And watch for the fractional sizes on the market such as 4/5AA and 2/3AA. These are not very common, but they are out there and will need that exact specification in order for the light to work properly.

Sound confusing? It can be. But if you just stick with the same specifications as your original rechargeable batteries, then you are in good shape. In a nutshell, you can:

• Use NiMH in place of NiCd (we recommend that)
• Use higher mAh capacities (not too high, though) when the original capacity is not available
• Stay with the exact same Voltage as your original batteries
• Stay with the exact same Size as your original batteries

Remember to check the connections in the battery box and clean them when they get dirty or corroded. A light steel wool will usually knock off the larger particles and a little WD40 sprayed on a clean soft cloth will help to wipe way any leftover material. The less chemical action you can perform on the battery terminals, the better.

Remember to change out those older solar light batteries and stay illuminated this summer! Great thing about solar lights for your home is that they are 100% renewable energy lights, 100% of the time!

Solar on!