Can you use regular batteries in solar lights?
Basically, no you should not use regular batteries in your solar lights, though there are one or two situations where you could.
See our reviews of the best solar lights, or keep reading to learn more about the importance of rechargeable batteries in solar lights.
Can I replace rechargeable batteries with regular batteries?
Generally, it’s not a good idea. If you use regular alkaline batteries in a device that tries to recharge those batteries (like a solar light), you are going to start seeing corrosion at the battery terminals. The corrosion will start to interfere with the flow of energy, eventually blocking it completely. You could try to clean away that corrosion using a soft brush and a solution of water and sodium bicarbonate (i.e., baking soda) but you would be running the risk of water seeping through the terminals into the inner workings of your solar light, at which point it’s pretty much game over. You lose.
And to make matters worse, by using regular alkaline batteries you will likely have voided the warranty of your solar light.
(You can replace rechargeable batteries with regular batteries in devices where the energy flow is a one way street. A simple flashlight, for example, draws power from the battery but doesn’t try to put it back. Solar lights are a two way street though – they will try daily to push energy into the battery, and that is where the trouble begins.)
What’s the difference between rechargeables and regular batteries?
Good question! All batteries got charged once, right? Why do NiMH and NiCd batteries get to do it again and again while alkaline batteries get just one shot?
If you’re a battery, getting recharged is a stressful process. Electrons are moving, liquids or gels are heating up and expanding, and pressures are building. Rechargeable batteries are made to handle these stresses, or to minimize them. Alkaline are not.
True, alkaline batteries survive that first charging process. But remember – that took place at the factory under carefully controlled conditions. Your solar light batteries have to do this day after day, under the sun, in variable humidity and temperature, without technicians in lab coats making sure they’re ok. It’s a tall order that requires different chemistry and physical structures in the battery.
Is it ever ok to use normal alkaline batteries in solar lights?
The only situation where we feel comfortable putting normal batteries into a solar light is when you need to troubleshoot or identify the cause of a problem.
Using alkaline batteries to identify the cause of a problem
For example, let’s say your lights have dimmed and are no longer lighting up your garden or porch the way they once did. Is the problem in the batteries or in the LED lights?
Hopefully the problem is the battery since this is the easiest fix. To test, remove the rechargeable NiMH or NiCd batteries that are currently in the light, and replace them with fresh regular alkaline batteries, of the same AA or AAA size, of course.
Now take your light into a dark room and see what happens. If the lights shine brightly again then you know the problem is the batteries and it’s time to replace them. If the lights remain dim (and they’re not simply dirty) then the problem is likely the LEDs or a connection in the circuit of the light. If this isn’t something you can fix then it may be time to start looking at a new light.
A less common scenario: Let’s say your lights have been getting dimmer and so you did the test described above to see if the rechargeable batteries were losing their punch. And let’s suppose that the normal alkaline battery did indeed restore the lights to their former glory.
Ok , so you go out and buy new rechargeable batteries and you get them charged up. But then you find that the problem persists. What’s going on?
At this point you know that the problem is neither the batteries nor the LEDs, and that leaves the solar panel itself, or the transfer of power from the solar panel into the batteries, as the most likely culprit. Solar panels are a pretty reliable technology, so this is not likely, but if this is where you are at it’s probably easiest to get a new set of lights.
Can I use alkaline batteries just for a short time?
If you’re waiting for replacement rechargeables and want to keep using your solar lamps in the meantime, then it is probably ok for a few days. Some people would say a week is ok, but we think you’d be pushing your luck, especially in hot weather. And while it’s a bit of a hassle, we would recommend removing the alkaline batteries during the day and putting them in at night, when you need them.
Rechargeable batteries for solar garden lights
Now that you know why you should be using rechargeable batteries in your solar lights, some new questions come to mind…
Are NiMH and NiCd batteries interchangeable?
NiMH (nickel-metal hydride) and NiCd (nickel-cadmium) batteries can indeed be used interchangeably. But pay attention to the voltage. If your system came with a 1.2V battery, then make sure that’s what you replace it with?
Which is better, NiMH or NiCd?
We recommend NiMH. NiCd batteries were a big leap forward when first mass produced in the 1950s, but NiMH is a superior technology and today is the more common choice. Advantages of NiMH over NiCd include:
- environmental friendliness: Cadmium is a toxic metal and so NiCd’s should not be disposed of in a landfill. NiMH batteries are much gentler on the environment.
- memory effect: Nickel cadmium batteries are prone to the memory effect, meaning that if they are not fully discharged before recharging, they will gradually lose their charging capacity. NiMH batteries are much less prone, and so better able to retain their original capacity.
- temperature range: NiMH batteries maintain solid performance over a wider range of temperatures than NiCd’s.
- higher energy density: NiMH batteries are about 50% more energy dense than NiCd’s, meaning a longer run time from a fully charged battery of the same AA or AAA size.
- cycle life: Cycle life refers to the number of times a rechargeable battery can go through the cycle of fully discharging and then recharging. Here, too, NiMH has the edge, especially with batteries that have higher amp ratings (mAh ratings, see below.) The advantage held by NiMH technology becomes even more pronounced when the memory effect is taken into account. (In other words, a large cycle life number in a NiCd battery loses some of its value if that battery begins to discharge for fewer and fewer hours per cycle.)
Given the advantages of NiMH, is there anything going in favor of NiCd’s? Not really, at least not in solar lights.
The one characteristic where the NiCd clearly comes out ahead is self-discharge rate: NiMH batteries have a self-discharge rate up to three times that of NiCd’s. This matters in, say, a clock, where the device uses little energy. The batteries would lose more energy to self-discharge than they would to actually powering the clock! But in solar lights where the battery is charging and discharging daily, this isn’t a cause for concern.
Can I use a higher mAh battery in solar lights?
Yes you can, as long as the voltage is the same in both batteries – typically 1.2V in a solar light NiMH or NiCd. But don’t overdo it. Replacing a 400 mAh battery with a 600 mAh will give you more hours of night light from a day’s worth of sunshine. But batteries with a higher mAh rating need more current flowing from the solar panel in order to charge as intended. If the solar panel isn’t cut out to provide the current for optimal charging of a 2400 mAh battery, then you aren’t going to get your money’s worth out of the 2400 mAh battery.
Can I use lithium ion batteries in my solar lights?
Absolutely! Many solar lights use lithium ion batteries, especially when powering brighter lights such as flood lights or security lights. However, lithium ion batteries are not sold in the standard AA and AAA sizes, so you are unlikely to find one that replaces your current NiMH or NiCd. Readers of this article are most likely looking at AA or AAA size batteries and so are probably best served by NiMH or NiCd rechargeables.
So, to wrap up: Can you use regular batteries in solar lights? We hope we’ve answered that question for you. For an even deeper dive into battery technology, check out this article. Or visit one of our other posts here at thesolartechnology.com.
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