How Long Does A 12
How long a 12v battery lasts depends on a variety of factors its amp-hour rating, the size of the solar panel that is charging it, and what load youre putting on it.
Lets take a 100ah 12v battery as an example.
Lets say youre using a 200-watt panel to charge your battery. This means that youll be able to charge your battery fully in less than a day under ideal conditions.
A 100ah battery technically has 50ah of power available before recharging is required , and so if you are putting a heavy load on it you can expect it to last a day or so.
If you are using the battery for lighter loads charging mobile phones, just using it for backups, or running a few LED lights, you can get away with using a smaller solar panel as the battery wont go dead in a day.
How Many Solar Panels Are Required To Charge A 12
Lets have this example:
You have a 12-volt solar panel system installed, and youre required to supply 100 ah of charge to your batteries per day. Lets assume that you have eight sun peak hours in your region a day. This means that youll require 1,200 watt-hour.
So, if we divide 1,200 watt-hours by 8 hours, we get 150-watts solar panel. Solar experts recommend overrating your requirements by a minimum of 20 percent thus, youll require 180-watts of solar panels.
How To Use A Solar Panel To Charge A Lead Acid Battery
First of all, you need to get yourself a solar panel and a voltmeter. Make sure you get a standard size panel and avoid buying the larger ones.
When you connect the solar panel to the battery, you will see the voltage rise, and when it reaches to near 14V, it means the battery is fully charged.
When the battery is fully charged, remove the connection. You dont want to overcharge the battery or charge it too fast. Make sure to check the batterys owner manual to see how many amps your battery can handle.
If you are familiar with trickle charging, there are some solar chargers that are designed for the sole purpose of maintaining the batterys charge level.
They dont produce too much voltage to damage the battery. In other words, if you keep your vehicle on idle for too long, get a trickle charger.
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What Other Equipment Do I Need
You will also need a charge controller or regulator to monitor the flow of current between the solar panel and battery. Weve noted that solar power is erratic in terms of low light levels and the angle of light hitting the panel directly and may also be affected by ambient temperature .
A 12V battery needs at least 13.6V to charge, which is the level of charge required from the solar panel. In ideal sunshine conditions, a 12V solar panel may output 17V or more. If you plug this directly into your charging battery, it is likely going to cause some damage to the battery.
The charge controller is designed to take those 17V+ from the solar panel and moderate it to a voltage that is safe and usable to charge your 12V battery. In doing so, it also protects your solar panel from overcharging the battery and promotes longer battery life.
Conversely, if the sunlight conditions deteriorate, the solar panel may shut down, and your on-charge battery may start to discharge. So, a solar charge controller/regulator is something like an on-off switch that allows power to pass through when the battery needs it and cuts it off when the battery is fully charged.
Who Will Suit A 100 Watt Solar Panel System
Theres no getting away from it: a 100 watt solar panel set up is quite small.
Unless you intend wild camping in your motorhome, you may have reliable access to shore power.
Your demand for an off grid power source could be really low, so a 100 watt set up maybe the perfect size for you.
If your budget doesnt stretch to anything bigger, starting small is a great idea.
Build the system with scaleability in mind and you can add panels and batteries in the future as your needs grow and budget allows.
Perhaps you have a small campervan, RV or motorhome and dont have the space on your roof for anything more.
You could consider extra juice from a portable solar panel system but thats for another post.
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Questions Chat With Us
Wil has been a part of the solar industry for over 20 years as an electrician, solar installer, support technician, and more. He’s also been living off-grid since 1996. Wil and the rest of the Unbound Solar team are here to answer any questions you have about designing a system that will fit your needs.
Watt Solar Panel Wiring Diagram
Theres a few points worth clarifying about this wiring diagram before you get into the detail:
- The wiring diagram shows only the supply side installation of a 100 watt solar panel system. It goes as far as charging the battery. For the load side detail, check out our post on campervan wiring.
- It excludes charging the battery from shore power or the alternator.
- For information on how to fit the battery, see our post on campervan batteries.
- The diagram also excludes an inverter. You may not need one and even if you do, a 100w solar set up is possibly too small to provide the energy you need for it.
- The 100 watt solar panel wiring diagram assumes only 1 x 100w panel is being fitted. If you happen to be fitting 2 x 50w panels instead, see our 200 watt solar panel wiring diagram to see how to wire the panels in series.
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How Many Solar Panels To Charge A 50ah Battery
To figure out the size and number of solar panels required, you need to convert amp hours into watts and find out the battery voltage.
The conversion is battery amp hours x voltage = solar panel watts required
In this example you have a 12V battery like the Mighty Max 12V 50ah. It is completely discharge and has to be recharged.
50 ah x 12V = 600W
You need a solar panel that can produce 600 watts in total power. With 5 hours of sunlight the solar PV system has to produce at least 120 watts an hour. A couple of 300W Renogy solar panel kits will be enough to get the job done.
A 150W solar panel can recharge the battery in 5 hours, so can a 200W, 250W, 300W etc. A 50W solar panel is too small, and a single 150W solar panel would need six hours. With 250W and 300W panels the most widely used, it will not take long to recharge a battery of this size.
Any of these panels will do, but a 200W, 250W or 300W is the most practical. The fewer solar panels to install the better. If the conditions are ideal the battery will go from 0% to 100% in an hour.
If you are not in a hurry you can use a smaller solar panel. It will take several hours to charge, but if time is not an issue it is a good option. However it is best to charge the battery as fast as possible because the weather can change.
What if My 50ah Battery is 24V? The conversion still works, but instead of 50 x 12 = W this time it is 50 x 24 = W. It is the same rule for 48V batteries as well.
50 x 12 = 60050 x 24 = 1200
Do I Need A Charge Controller To Charge A Battery Using Solar Panels
The problem with solar panels is that their output depends on sunlight. In other words, it fluctuates during the day. For instance, the output is at its highest during peak sun hours , then it gets very low at dusk.
For this reason, a charge controller is needed to prevent the panels from overcharging the battery, which wont only permanently damage the battery and reduce its lifespan but also can cause the battery to catch fire and explode.
Its important to mention that you dont need a charge controller in case of small maintenance solar panels such as trickle charge panels, as the panel output would be too low to overcharge the battery.
In general, if the panel produces less than 2 watts for each 50Ah, then you dont need a charge controller.
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Size Of The Solar Panel
Solar panels come in all kinds of shapes, sizes and weights. The general rule is that the bigger the panel the more that wattage but thats not necessarily true. Two panels of the same size can have a very different output in the same conditions. This mostly goes down to the technology and efficiency which well discuss later in this article.
Width and length
Manufactures of Solar Panels use standard sizes to build solar panels used in roof systems in homes and business. For residential solar panels you expect to find them measuring about 65 inches by 39 inches and those on the commercial side are a bit longer going up to 77 inches by 39 inches.
Though the width and length slightly vary, many organizations manufactures these systems in standard sizes. The size used for the residential connections is 65 inches by 39 inches. On the other hand, for the commercial uses is 77 inches by 39 inches.
Now on the portable solar chargers that are now more popular nowadays the width and length is up to the discretion of the manufacturer and use of the panel. You can find a 1cm panel on a calculator, or 2 by 2 inch inch panel on a solar light while most portable solar chargers will come at around 11.1 × 6 inches.
Depth
The solar panels depth normally ranges between 1.5 inches to 2 inches with portable ones having a depth of 0.71 inches. Again this is also influenced by the technology used.
Example : 12v 200ah Deep Cycle Battery
Lets say you have the following solar charging setup:
- 12V 200Ah deep cycle lead acid battery
- MPPT charge controller
Here are estimates of how long itll take to charge the battery with various solar panel sizes:
For a 12V 200Ah deep cycle lead acid battery paired with an MPPT charge controller, use a 5W or 10W solar panel to trickle charge the battery. Use an 80W solar panel or bigger to fully charge the battery in a week or less of sunny weather. Use a 800W solar array or bigger to fully charge the battery in a day or less of sunny weather.
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Can You Connect A Solar Panel Directly To A 12v Battery
Technically, you can connect a solar panel directly to a 12v battery as long as its not more than 5-watts, but connecting any higher-rated panels is not a good idea.
Solar panels will produce varying voltage outputs depending on the amount of sun hitting them, and this dipping and spiking of the voltage can quickly damage your battery.
Solar panels can generate up to 20v, which is much higher than the 12v required by a 12v battery. This can lead to overcharging, permanently damaging your battery.
The best course of action is to use a charge controller or regulator between the panel and battery, as this regulates the charge current and keeps your battery healthy.
Choosing A Battery For Your Camper Or Rv: The Cliff Notes
- Economical choice: Flooded lead acid. This is the oldest technology in the bunch. If maintained properly, they still are the cheapest short-term and long-term. Maintenance is more involved and must be managed more carefully due to ventilation and liquid acid inside. It is not hard to do, but for small amateur systems they arent as appealing.
- Low maintenance: AGM Deep Cycle. Over the long term, this is the most expensive battery because they wear out faster than the other two. In the short term, they are cheaper than lithium. They are common and all around a good starting point for most amateur installers.
- Premium choice:Lithium LiFePO4 These batteries are just around the corner from being the best choice for everyone. Unfortunately, the high up front cost is a barrier to many.
Read Also: How Does Buying Solar Panels Work
Charge Solar Battery: Best 12 Volt Solar Panel
Charge 12v Battery With Solar technology is the best money saving off-grid power solution. Portable solar charging 12v battery has benefit to supply electricity when you are in a campaign or in a remote area.
This portable solar charger for 12v batteries is an extreme source of electricity to active your devices right way.
People who may not have access to a power source right way, solar power battery charging technology works better than others.
Make sure when you get a Solar panel charges that is powerful enough to charge the device you want in an adequate amount of time.
The silent operation of charging with solar panels retains the blissful tranquility of your remote hideout.
Energy Consumption Of Devices Or Appliances Over Time
To calculate your power requirements to make sure that your solar panel system is capable of running your home electrical grid. You also have to consider how much power your appliances or devices will consume over a period of time. Considering this aspect will give you an idea of how much power your system should deliver to run your home 24/7. Power is measured in Watts, and you have to get the value of power consumption over a period of time which is measured in WH.To calculate for the power of your home devices will consume over time you have to multiply power consumption by the number of hours the devices will be used.
Power Consumption Over Time = Power X Hours of Use
For a better picture, to compute for the power consumption of a TV that uses 20 Watts of power used for 5 hours a day. It will be mathematically represented on the equation indicated below.
TVs WH = Power Requirement X Hours to be Used
TVs WH = 20 X 5
The TVs WH = 100 WH
This means that if you are going to use a TV with 20 Watts power requirement for 5 hours a day, its total power consumption over time will be 100 WH. To calculate your total home power consumption, you can do this computation for every single appliance or device at home then sum up all the results you will get. This will lead to an accurate value of how much power or energy your entire home electrical grid will consume.
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Will The Number Of Solar Panels Decrease Charge Time
In most cases, no. If you have 2 x 150-watt solar panels, that is still going to be delivering 300-watts of power to the batteries. This doesnt change.
That being said, there are some situations where having multiple solar panels as opposed to one big one could benefit you.
As we said before, shade is a bad thing for solar panels. If you are parked in the shade, then the solar panels wont be working to their maximum capacity. Because of this, a lot of people will actually place solar panels at different positions on their RV.
This means that if one solar panel loses its ability to charge effectively, the other solar panel may be able to work at peak performance. Charge capacity would still be reduced, but by nowhere near as much as having a single solar panel set up.
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You need to provide the capacity in Ah as well. Lets say it is a 10Ah Battery or 120 Watt hours. You should only be using ~half of that capacity or 60 Watt hours. Charging that 60 Watt hours from a 15 Watt panel will likely take about 6-8 hours in good sun.
Hi Im looking for help, I have a 72volt 35ah battery i also have a 300 watt solar panel . how long would it take to charge from empty to full?
It may not work at all. The voltage from the panel typically needs to be higher than the voltage of the battery unless there is some sort of charge circuit that boosts the voltage of the panel. You should look at the voltage output of the AC charger that comes with the ebike. You should certainly not connect the panel directly to battery terminals.
From what you say, it sounds like your bike battery is 2.5KWh . That is a pretty big battery. In good sun, it would likely take about 16 hours. It depends on how the peak charge rate coming out of the panel.
Im confused by this equation, as you flip it when you are doing the calculation. You state that its Power panel watts / Battery Watt Hours x 2, but then when you show your work you flip that division to Watt Hours / Watts x 2.
Battery Capacity / Panel Power X 2 is correct.
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