Both solar batteries and car batteries are similar. They power important devices in our lives. You can also recharge after they are discharged. But can they be used in place for the other?
Car batteries and solar batteries perform the same type of work. However, they are made specifically to fit what they use. Therefore, you cannot use a car battery to power your solar lights. Why so? This guide will discuss how the two batteries differ and why you cannot use a car battery for your solar lights and vice versa.
Can a solar battery start a car?
Solar batteries and car batteries are both batteries and you can use them in place of the other right? The answer is no. If you have been thinking that you can use a car battery to power your solar lights, this post is for you.
Solar lights require a little amount of energy to start. This is not the case with car batteries. Car batteries generate a large current over a short period to start the car engine. Solar batteries produce a little amount of current over a long period. Below are some other reasons why you cannot use a car battery to light up your solar batteries.
What is the difference between a solar battery and a car battery?
| Specification | SLI batteries | Solar AGM batteries |
| Chemical reaction | Produces high current | Low current |
| Type of batteries | Four types | Two types |
| Cold-cranking Amp | 300-600A | 200-400A |
| Design | Thin lead oxide plates | Thick plates |
| Discharge rate | Low discharge | High discharge rate |
| Price | $120 | $80 |
Chemical Reaction
Both batteries have a chemical reaction that produces the energy that powers the respective devices. The main difference is the amount of energy produced.
- Car batteries require a large amount of current to start the engine. Only 20% of the energy in the battery is used to start the engine. The other energy that runs the car is generated by the car.
- On the other hand, solar batteries require little energy to power the lights. All the energy used in solar lights is harvested and stored on solar batteries.
Types of Batteries
- Cars use deep-cycle lead-acid batteries. These batteries are meant to be used and recharged. Car batteries are known as SLI batteries from their main uses to start, light and ignite.
Cars used four types of batteries that are grouped into two categories: wet cell and VRLA.
- Solar lights on the other hand use two types of batteries: Flooded lead-acid and Lithium-ion batteries. These batteries light up your home for years without dying.
Cold Cranking Amps
Cold-cranking Amps (CCA) is a system used to measure the amount of Amps produced by the batteries for 30 seconds at -18°c. Batteries with high CCA ratings have a high Amp burst.
- Car batteries have approximately 300-600A which enables them to start the engine.
- On the other hand, solar batteries have about 200-400A.
Since there are solar batteries that have CCA compatibility with car batteries, can you use car batteries for solar lights? In theory yes. However, other differences like the design and current determine the compatibility of the two.
Design of the battery
Both car and solar batteries are similar in design. The difference comes in the thickness of the plates.
- Car batteries have two thin plates submerged in sulfur acid to enable a chemical reaction that produces electrolytes. The thin plates ensure the battery runs for many hours without being drained.
- Solar AGM batteries on the other hand thick plates that can withstand the constant recharge of the batteries.
Discharge rate and life span
Since the two batteries have different plates design and CCA rating, their discharge rate also differs.
- Car battery’s thin plates influence the rate of discharge. You can use a car battery for up to 3months without the need to recharge.
SLI batteries can be used until they are 50% discharged then recharged. Which might take weeks.
- Solar batteries have a life span of up to 30 years of discharge and recharge cycle. The solar batteries discharge at night when in use and charge during the day.
Price
As said above in theory car battery may be used for your solar lights. But the price difference is a key difference between the two batteries.
- A standard solar battery costs about around $80-$110. While a car battery cost about $120
Can a car battery be used with solar panels?
Solar batteries and car batteries are similar. However, the differences influence how you can use each of the batteries. For example, the large current produced by car batteries is not ideal for solar lights.
Solar batteries have a storage capacity of up to 1000 hours while car batteries have a capacity of approximately 80hours. The reason why the car batteries do not discharge at a high rate is that they are used to start the engine only. Which will not be ideal for solar lights as they require the energy collected during the day.
Why car batteries are not practical for solar power use
Car batteries have thin lead oxide plates, they cannot withstand the constant recharge as solar batteries. The small capacity of car batteries cannot serve solar lights which use the energy collected during the day.
Can I use the solar battery as a normal battery?
If you cannot use car batteries for solar lights, is it possible to use solar batteries for car batteries?
Solar batteries produce little energy overtime to power solar lights. This is not the case for a car. To start a car engine along of power is required which may not be produced by the solar batteries.
Can a solar battery charge a car battery?
Car batteries are designed in a way you can use for a long time without the need to charge. Use electricity to recharge the car batteries as it produces the voltage needed to charge. Solar batteries are charged by weaker sunlight energy. You cannot, therefore, charge a car battery with a solar battery.
can I leave a solar trickle charger on all the time?
A solar trickle charger is the best alternative for charging your budget using solar energy. One advantage of having a solar trickle charger is that it is small and portable. You can also use them in any type of weather.
For battery life span, you should use the solar trickle for 16hours. In case there is too much heat from the sun, you can switch off the trickle to prevent overcharging.
Learn how to use a solar trickle charger from this guide.
Frequently Asked Questions (FAQs)
After how long should you charge a car battery?
Cars only use the power stored in the battery to start the engine. Since a car is a powerful device, about 20% of the power is used. The other power is generated when the car is in use.
To prevent the car battery from draining when starting the engine, charge when 50% of the power is used.
After how long do I charge a solar battery?
Solar batteries discharge rate differs depending on the type of battery and how well you maintain your battery.
Before buying the battery, ensure the manufacturing date is within six months. Batteries that stay on shelves without being used have a high discharge rate.
Ensure you clean the solar panel and the battery frequently to improve the life expectancy of your battery.
Normally solar batteries are charged during the day when there is sunlight and discharged at night.
Can you live the solar charger on indefinitely?
Solar batteries start to charge immediately there is sunlight during the day. At night the battery is discharging since there is no sunlight. Since the sun produces less energy than electricity, leaving the charger on cannot damage the battery.
In some cases, like when the battery has a hot spot, more heat is harvested meaning more energy there the battery might overcharge. To prevent overcharging, invest in a high-quality solar charge controller.
Can you charge the car battery with a solar panel?
A solar panel harvests a little amount of energy from the sun during the day. This is ideal for solar batteries as they have a large power holding capacity. You can therefore charge the battery for long hours without the fear it won’t light up your residence.
Car batteries on the other hand require high energy to charge. You will also use a large current to start the engine. Charging the car battery with a solar panel might be not effective when you want to use the battery after fee hours.
Conclusion
Using a car battery is only practical in theory. However, due to the different specifications named in our guide above, it is better to use the right battery for the right purpose.
Car battery uses a lot of currents to start the car’s engine. The energy used to start the car cannot be provided by solar batteries. You cannot, therefore, use a solar battery to start a car.
Solar batteries have large lead-oxide plates, while car batteries have thin plates. Thin plates of SLI batteries cannot withstand the constant discharge and charging as is the case with solar batteries.
Eng. Matthew Joseph Nandirio is the Founder of walkingsolar.
After graduating from the University of Houston in 2002, matt started working as a Solar Electrical Engineer for several multi-national solar energy companies.
He has a wide range of experiences including solar system requirement analysis, planning, maintaining, debugging and even solar device development through research.
He now shares his 20 years of expertise through his articles on the walkingsolar website.
Further, he is also the author of two books on Solar Technology, “Solar Power for Villages” and “DIY Solar System for Dummies”.
