Replacing Solar Light Batteries: NiMH, NiCd or Lithium?

To replace a solar light battery, open the battery door, read the label on the old cell and buy a rechargeable one with the same chemistry, voltage and size. NiMH can replace NiCd because both are 1.2 volts. A 3.2-volt lithium cell only goes into a light built for lithium. Recycle the old cell; never trash it.

Getting that match right is most of the job. The rest of this page covers how to confirm the battery is the problem, how the four chemistries compare, how to swap safely, and where the old cells go.

Is the battery really the problem?

Rule out the easy causes first: the switch, a shaded or dirty panel, or a porch light shining on the sensor. Our solar Christmas lights troubleshooting guide walks through those checks.

The battery is the likely culprit when the set still turns on at dusk but fades within an hour or two, even after a sunny day. Gama Sonic, a solar lighting maker, says its batteries are designed to last about 3 to 5 years (roughly 1,000 to 2,000 charging cycles) and then need replacing.

What to read on the old battery

Pull the cell out and note four things printed on it:

1. Chemistry: Ni-Cd, Ni-MH, Li-ion or LiFePO4
2. Voltage: 1.2 V for nickel cells, 3.2 V or about 3.6 V for lithium
3. Size: AA, AAA, 14500 (AA-sized lithium) or a wired pack
4. Capacity: in mAh

If the label is worn off, check the manual or the maker’s website before buying anything.

NiMH vs NiCd vs lithium: which battery for solar lights?

	NiCd	NiMH	Li-ion (typical)	LiFePO4
Nominal voltage	1.2 V	1.2 V	About 3.6 V	3.2 V
Capacity in same size	Lower	30 to 50% more than NiCd	Varies	Varies
Memory effect	Strong	Reduced	See maker	See maker
Self-discharge	Low	Higher	See maker	See maker
Cold	Operates in extreme cold and heat	Extreme cold reduces performance	Check maker’s charging range	Do not charge below 32°F (0°C)
Toxic metal	Cadmium	None	None	None
Swap into a 1.2 V light?	Yes	Yes	No	No

Sources: Ufine Battery for NiCd and NiMH comparisons and LiFePO4 voltage; Duracell for cold and NiMH; Wevolver for typical Li-ion voltage; Bioenno Power for LiFePO4 cold charging.

NiCd

Ufine Battery, a battery maker, describes NiCd as tolerant of extreme cold and heat, with low self-discharge. The trade-offs are a strong memory effect and cadmium, which is toxic and must be disposed of under strict rules.

NiMH

NiMH offers 30 to 50% more capacity than NiCd in the same size and has no cadmium, according to Ufine. It loses charge faster when idle. Duracell notes that extreme heat or cold reduces battery performance, which matters for lights that sit outdoors all December.

Li-ion and LiFePO4

Some newer solar lights use lithium cells, often a 14500 size that matches a AA. Ufine lists LiFePO4 at 3.2 V nominal with a full charge near 3.65 V and high thermal stability. Wevolver notes that other lithium-ion cells run about 3.6 V nominal.

Smart Living Home & Garden, which sells a 3.2 V 14500 cell for its solar lanterns, puts the rule plainly: if the original battery is 1.2 V, do not order the lithium one. Match the voltage on the old cell in both directions.

Bioenno Power warns that charging a LiFePO4 battery below 32°F (0°C) can cause lithium plating, which reduces capacity and can create safety risks. If your lights use lithium cells and your winters are hard, check the manual for a low-temperature rating.

How to replace the battery, step by step

1. Switch the light off and bring it indoors to a dry table.
2. Open the battery door. Many are held by small screws.
3. Note which way the old cell faces before removing it.
4. Wipe the contacts dry. If a cell has leaked, wear gloves.
5. Insert the new cell the same way. Do not mix old and new cells in a multi-cell light; Duracell warns that mixing can reduce performance and cause leakage or rupture.
6. Close the door, switch on and set the panel in full sun for a full day before judging run time.

Some lights have a sealed battery or a wired pack with a plug. Check the maker’s site for an exact replacement before buying a generic pack.

When a new set makes more sense

If the panel is cracked, the battery is sealed in, or the contacts are badly corroded, replacing the whole set is usually simpler. Before you buy, read up on how solar Christmas lights perform in winter and how long they stay on at night so the new set fits your conditions.

Solar Christmas light sets if yours is past saving

Browse current solar Christmas lights on eBay, new condition only.

Shop solar Christmas lights→

• Warm white
• Multicolor
• 100+ LEDs
• With remote

Opens eBay in a new tab. Check condition, seller feedback and returns on the listing.

Battery safety and disposal

Old rechargeable batteries do not belong in the trash. The EPA says nickel-cadmium, nickel-metal hydride and lithium-ion batteries can go to specialized battery recyclers, participating retailers with take-back programs, or local household hazardous waste collections.

To find a drop-off point, use the locator from The Battery Network, the program formerly called Call2Recycle. It lists more than 20,000 drop-off locations and also asks you to bag or tape terminals. Duracell’s FAQ adds that all rechargeable batteries should be recycled.

For choosing a better set next season, see our guide to the best solar Christmas lights.