When I first used solar to charge my car battery I was working in the dark, so to speak — I chose quite a large solar panel and just hooked it up. Bad idea! Before thinking about charging batteries with solar you need to know the following:. Both examples assume a current of 5. Battery sizes can mean two different things — the electrical capacity or the physica l dimensions expressed as types such as the most common designations 24, 24F, 25, 34, 35, 51, 51R, 52, 58, 58R, 59 and When taking about solar charging, we refer to the electrical capacity in Ah.
Modern vehicles have an amp-hour capacity of between 40 to Ah , while some bigger diesels can go up to Ah. Car batteries are quite special. They are constructed to deliver a lot of current in amps for a short period, just long enough to crank an engine until it fires. For 10 or 20 seconds an auto battery might supply up to amps. Once the engine fires, the alternator quickly charges the battery fully and maintains it ready for use.
As the current increases the capacity of the battery reduces and it will supply much less than the advertised 50Ah. Deep cycle batteries are different from car batteries, This type of battery can deliver medium level currents for some hours without harming the battery. As with auto batteries, the higher the current draw, then the less overall capacity can be drawn in total.
Increase in temperature will also reduce the overall capacity. Deep cycle batteries are ideal for applications that need sustained current draw for lighting, TV,etc and also be available for supplying things not used all the time, such as water pumps. For this reason they are used for marine situations and RVs.
Marine-type deep cycle batteries are a tougher breed and can also crank an engine, so they are a kind of hybrid between the two types. A useful guide to the DOD, or Depth of Discharge , of a 12 volt lead-acid battery can be found by measuring the terminal voltage with a simple multi-meter.
I think this is a bad way to determine your battery health. The real test of a good battery is how the terminal voltage reads when the battery is delivering current. The charge controller has overcharge protection, meaning it will stop the charging once the battery is full. Tip: This circuit diagram would work for many other solar panel sizes e.
According to our solar panel charge time calculator , it takes around hours of direct sunlight for a 5W solar panel to fully charge a 50Ah 12V battery. For example, a 20W solar panel can charge a 20Ah 12V battery in around 17 hours of direct sunlight. A 50W panel can do it in around 8 hours. For more help on finding the right size solar panel for your solar charging setup, check out my post on what size solar panel will charge a 12V battery quickly.
You connected a solar panel to a battery via a charge controller. And the solar panel is now charging that battery. Car batteries are also 12V batteries. So, using the same solar panel and charge controller, I was able to make a solar car battery charger. Hi, I'm Alex. I started Footprint Hero to help people reduce their environmental impact.
My current obsession is DIY solar power projects, which I've been building since Yes, you can. Though it might be simpler to just buy a 10W 12V solar panel than connecting two 5W panels in parallel. How long? That depends on how big your battery is. It seems that with just 5W, you can go without a charge controller.
A standard volt battery is designed to receive a charge at around 12 volts, which equates to watt-hours. If the battery receives a higher charge than 12 volts, it will start producing hydrogen and oxygen and gassing. If this gassing continues, the battery will eventually be destroyed. The solar panel needs to be placed at an angle to the sun to ensure that it captures the most photovoltaic cells from the sunlight to convert into usable alternating current AC.
If the panel is laid flat, it will take longer to charge the battery. When a solar panel receives direct sunlight, it can charge faster, while cloudy days slow charging cycles down. A solar tracker is a good piece of equipment to have when charging a battery with a solar panel. Alt Energy Options is an Amazon Associate. As an Associate, we earn commissions from qualifying purchases. The site also maintains other affiliate relationships. Full affiliate statement here. The four main stages involved in the process of charging batteries using solar energy are the bulk phase, absorb stage, float stage, and equalization stage.
The bulk phase is the primary stage of charging and occurs when the solar panel draws energy from the sun and converts it into alternating current AC. During the bulk phase, the solar panel converts as much energy as possible and transfers it into the cell in the form of amperage. The voltage in the batteries begins to rise as a result of this transfer as they absorb the electricity.
The second stage of battery charging with a solar panel is known as the absorb stage. This second stage of the process is achieved when the batteries reach a charge of between This number can be pre-set on the charge controller to ensure the battery does not overcharge and get damaged.
The third stage is known as the float stage and begins when the charge controller lowers the voltage to a specific pre-set value to avoid damaging the battery. The last stage of the battery charging process is known as the equalization stage and is a controlled overcharge stage that is done periodically. Charging batteries using solar energy is slightly different from charging batteries using mains power because the energy drawn from the sun is not always consistent.
Solar panels need full and direct sun to work at maximum efficiency and supply enough alternating current to fully charge a battery.
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