Solar Light Batteries: Which Replacements Fit Garden Lights?

Replacement batteries for solar garden lights must match the old cell’s size, voltage and chemistry. Many lights take a 1.2 volt rechargeable AA or AAA, either NiMH or NiCd, and NiMH is usually the better swap. Some lights use a 3.2 volt lithium (LiFePO4) cell instead. Never use alkaline batteries, which are not made to be recharged.

Read the old battery before you buy

The label on the old cell tells you almost everything you need. Look for four things:

• Size. AA and AAA are most common. Some lithium cells, such as the 14430 size, are made in an AA shape.
• Voltage. 1.2V means NiMH or NiCd; 3.2V means a lithium iron phosphate (LiFePO4) cell; 3.7V usually means a lithium-ion cell.
• Chemistry. Printed as Ni-MH, Ni-Cd, LiFePO4 or Li-ion.
• Capacity. The mAh figure, such as 400mAh or 800mAh.

If the label has worn off, check the light’s manual or the inside of the battery door. The manual for Energizer’s Solar Recharge pathway lights, for example, names AA 800mAh nickel metal hydride (Ni-MH) rechargeable cells as the only type to use.

Why alkaline batteries do not belong in solar lights

A solar light charges its battery every day, and it cannot tell what is inside. Alkaline and carbon-zinc cells are not built to be recharged. The Energizer pathway light manual says plainly not to use alkaline, standard carbon-zinc or NiCd batteries in its NiMH lights, so even NiCd is ruled out for some models. Follow your own light’s manual where it is stricter than the general rules here.

NiMH or NiCd for solar garden lights

NiMH and NiCd cells are both 1.2 volts, so a NiMH cell of the same size usually drops into a light built for NiCd. Energizer’s NiMH handbook says NiMH has significantly higher capacity than NiCd, avoids toxic cadmium and fits easily into products designed for NiCd because the two are so similar.

Capacity is the one catch. A small panel may not fill a much larger cell on short winter days, so a big jump in mAh may not bring the extra run time you expect. Staying near the original rating, or a modest step up, is the safe choice.

Low self-discharge NiMH cells such as Panasonic’s eneloop suit lights that sit through cloudy spells. Panasonic says eneloop keeps 70% of its capacity after 10 years in storage and is rated for use from -20°C to 50°C (-4°F to 122°F). Panasonic’s FAQ also explains that its older 2,100 cycle rating came from earlier IEC test conditions; under the stricter 2017 standard the figure is about 600 cycles.

3.2V lithium (LiFePO4) solar light batteries

Some lights use a 3.2 volt LiFePO4 cell made in an AA shape, so it is easy to mix up with a 1.2V AA. A light built for 1.2V cells is not designed for that voltage. Lake Lite, which makes solar dock lights, sells 3.2V LiFePO4 cells in the 14430 size for its own lights and warns that an incompatible cell may reduce performance or damage the fixture.

Buy a LiFePO4 cell only when the old cell says 3.2V or LiFePO4, and match its size. The same chemistry runs larger portable power stations, as our LiFePO4 vs NMC guide explains.

When new batteries do not fix a solar light

If a light stays dim with fresh cells, the battery may not be the problem. Wipe the panel, since dust and pollen cut charging, and check for new shade from a tree or wall. The Energizer pathway light manual suggests three sunny days in direct sunlight when a battery is not adequately charged. Our outdoor solar section covers placement in more depth, and the same rules about sun and angle apply to larger panels in how to charge a solar generator. The same checks apply to solar post cap lights and solar lanterns.

Some lights are simply worn out: a cloudy panel cover or a failed circuit board ends their life. Replacing them can cost less than chasing the fault.