How to Replace Old Rechargeable Batteries in Outdoor Solar Lights
Rechargeable batteries are great thing - they last for a long time, they are rather cheap and are reliable. But, after some time, they lose capacity due to numerous reasons and they need to be replaced. In most devices and gadgets, it can be done withing seconds.
Outdoor solar lights are exposed to high temperatures during summer, low temperatures during winter, to the rain, wind etc. All those elements negatively impact durability and performance of rechargeable batteries in solar powered lights.
Although such lights are mostly very cheap, they should not be thrown away - just change rechargeable battery and your solar light will have few more years of life ahead.
Changing batteries is easy - turn off the lights, open battery cover (usually no tools are required) and check battery size, type and capacity.
On the photo above - one cheap AA NiMH, 1800 mAh. When replacing batteries, always use batteries of the same physical size and chemistry. Capacity of the new battery can be higher than older batteries, but higher capacity also means more expensive batteries.
I had several Duracell rechargeable NiMH batteries rated at 2450 mAh - such batteries are kind of overkill when compared with cheap NiMH batteries often found in outdoor solar lights, but I had them and I put the to good use.
Although new NiMH batteries have no memory effect and have very low self-discharge rate, it is good practice to charge them first, before actually using them.
If you have smart charger/discharger, fully charge and then discharge the batteries 2-3 times using low currents and use them only then.
Manufacturers often claim that such practice is not required, especially not with new batteries, but I do it anyway - it can't harm the batteries and can only help. Just my 2c.
Put the new batteries into the battery's slots, close the slots and turn on the lights.
LEDs should be off - to turn them on, cover upper part of the lights with hands or some cloth. Since batteries are charged, LEDs should be on.
After verifying that all the lights are operating properly, put them back on their positions.
When night comes, your old solar lights will work even better than before - and provide you with rather hard conditions for good photography! :)