Solar Panels for lithium battery
In this blog I will break down the different battery types available to use with your Solar Panels. Lead acid batteries have large capacities and are often available in many places around Australia. A lot of people ask me "which battery should I use with solar panels?" I always recommend using sealed AGM lead acid batteries wherever possible and will describe in this blogs the benefits of using this type of battery with iTechworld portable solar panels.
Starter vs. lithium Batteries
Starter batteries are designed to deliver short, high-current bursts for starting a vehicle engine, and are designed to discharge only a very small part of their capacity. If you were to use a starter battery as a way of running your caravan/motor home/camper trailer it would corrode very quickly, the plates and the chemistry are designed to stay nearly 100% fully charged most of the time. They cannot handle the discharge and charge needed when running your RV on Solar Power.
For solar charging applications, I always recommend an iTechworld lithium battery. Cheap knock off batteries are available via eBay but come with very little warranty and fake specifications which means you can never be sure of what getting.
Typical car batteries can be used but will not be suitable long term. iTechworld lithium batteries are designed with larger capacity. They are designed to be charged and discharged by solar and can handle the strain of using most of its capacity.
iTechworld lithium batteries HERE
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How much solar power do you need?
So you want to set your rig up for Solar but you are not sure what size of set up you need? This blog is designed to give you the tools needed to be able to work out exactly what are you are drawing from your rig's batteries and what type of solar set up you need. Knowledge is key when setting up your rig for solar so the more information you have on each and every one of those home comforts devices you plan to take away with you the better. If anyone has a question pop it in the comment section below. I will try my best to answer everyone.
How to work out Watts, Amps and Volts
A larger solar panle will collect more energy in less time, but just how big does the solar panel need to be?
The power consumption of appliances is usually given in Watts. To calculate the energy you will use over time, just multiply the power consumption by the hours of use. For example:
10 watt device used over 3 hours equals 10 x 3 = 30 Watt
How to convert Amps to Watts
The energy in Watts is equal to the electric charge in Amps times the voltage in volts:
Watts = Amps × Volts
If your device doesn’t have the Watts labelled on it, then it should at least have the input Volts i.e. 240V and the Amps AC it draws such as 240V – 1.5A. You can then use the equation Watts Volts x Amps so 240v x 1.5amps = 360 Watts.
How to convert Watts to Amps
The electric charge in Amps is equal to the energy in Watts divided by the voltage in volts (V):
Amps = Watts / Volts
Find the electric charge in Amps when the energy consumption is 300 watts and the voltage is 240 volts.
300 Watts / 240 volts = 1.25 Amps
Do I need a battery?
Solar panels are commonly used to charge a battery – not to charge a device directly. There are a couple of reasons for having batteries. Solar panels might not generate enough wattage to directly power an appliance, but they can build up a higher wattage via a battery. Secondly a battery can regulate the power going in to the appliance at a constant rate. When solar panels are charging a battery it is usually at a varying rate which could harm an appliance if not regulated.
Battery capacity is measured in Amp Hours (e.g. 120Ah). You need to convert this to Watt Hours by multiplying the Ah figure by the battery voltage (e.g. 12V) – see calculations above.
AH refers to amp hours. This rating is usually found on deep cycle batteries. If a battery is rated at 100 amp hours it should deliver 5 amps of power for 20 hours or 20 amps of power for 5 hours.
When choosing a battery, keep in mind the equipment you will be powering and the time in which they will be running. Theoretically a 100Ah battery can deliver 5 amps over a 20 hour period (and so on). Taking into account the average small campsite - with a small 45W fridge running for 6 hours, 3 hours of 15W lighting and 20W of other electronic equipment - the minimum consumption to be expected is 335W. Take this wattage and divide it by the voltage, 12V, gives 28Ah. With the aim of leaving 50% in the battery brings the requirement to 56 Ah per day. A smarter battery setup would be to use an iTECH120 lithium battery. This new type of battery is a fraction of the weight of old style AGM batteries. AGM batteries usually weigh 35kg but and iTECH120 battery weighs just 13kg. You can also use more of the battery capacity in an iTECH120 - 80% which means its usable Amp Hour rating is similar to a 200 Amp Hour AGM. Read more about the iTECH120 HERE
What size solar panel do I need?
Solar Panels power generation is commonly given in Watts e.g. 120 Watts. To calculate the energy it can supply the battery with, divide the Watts by the Voltage of the Solar Panel.
120 Watts / 18v = 6.6 Amps
Please note that Solar Panels are not 12v, I repeat Solar Panels are not 12v. Any one who works out the Amps of a solar panels using 12v as the voltage calculation does not understand solar or has been misinformed. All solar panel voltages should be marked in the item description of our website or on the unit itself.
Check out the iTechworld Solar Panel range HERE
The power inverter converts your storage battery power into the 240 volts AC that runs your appliances. Unless you only run 12 volt DC appliances you will need a power inverter to supply your AC.
There are 2 types of Inverters
Pure sine wave and Modified sine wave.
The Pure Sine Wave matches the power to that of which you get from your Electricity Supplier, its clean and you can run any appliances safely even sensitive equipment.
The Modified sine wave used to be considered a dirty power but some aren't as bad as they used to be, you can use this inverter type for things that don't have sensitive electronics for example fridges, cookers, pumps, You may have to be careful with some appliances such as laptops and TVs so check first.
Check out the iTechworld range of inverters HERE
All Solar Panels 30 watts and above need a Solar Charge Controller/Regulator. A Charge Controller/Regulator is necessary to protect the batteries from over charging and supply them with the proper amount of energy to promote long battery life. If the charge isn’t regulated it can have a damaging effect on the battery being charged.
Check out the iTechworld range of Charge Controllers/Regulators HERE
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Determine which items you consider essential to have access to when you are the road.
Consider such items as fridges, microwaves, air con units or fans, lights and other small appliances as well as medical devices such as oxygen machines.
- Determine the wattage you will need to power the items you wish to access simultaneously. This is the continuous watts. This will determine the size of generator needed. For example, a 3000 continuous wattage generator will power a fridge, small air con units, microwaves and household items.
Place your generator outside in an open area.
It should be located away from doors or windows to prevent carbon monoxide from entering your living area. Make sure the area is dry. If using during rainy weather, place it under a canopy or other covering.
- Consider that generators will make noise. You may want to experiment with different locations. 7-10 meters away is usually a good starting point.
Follow manufacturers' instructions for recommended fuel and oil and for starting and running instructions. A typical 3000-watt generator will hold 6-7L of fuel and will run for approximately 6 hours.
Plug appliances and other items into the generator using a heavy-duty outdoor extension cord that is grounded. You can then plug power boards into the extension cord indoors. Charge your caravan batteries using generator power via the battery charging cables provided.
- Shut generator down and let cool before refuelling.
- Use only the oil listed in the instructions.
- Store fuel in an approved container in a locked shed or another safe area.
- Seek advice from iTechworld if you are unsure of wattage needs.
- Consider starting wattage as well as running wattage when purchasing a generator. Appliances require greater power on initial startup. Check appliances for wattage info.
- Note that Watts/KiloWatts is different from KVA.
- To prevent theft, consider running a metal ring into the ground and secure the generator with a chain.
- Make sure fuel is clean and no water or other liquids have been kept in the jerrycan.
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Before you start harnessing the elements to heat, cool or light your home, caravan, tent or truck, it is worth considering your motivation as it will determine what systems are best for you. You will also need to assess your site as you may not have suitable resources. Are you able to connect or remain connected to the national infrastructure as a backup? Do you need to have an uninterrupted power supply (UPS)? Are you relocating daily or is it a more permanent arrangement? What is your budget?
We recommend that you focus on what you consider to be essential and then be prepared to compromise if nature temporarily leaves you a bit short. Establish what are your MUST and WANTS are. Once you have established your MUST and WANTS you can calculate your energy requirements and usage. We also recommend that you develop a modular and scalable approach so that the system can be easily changed as your requirements or financial circumstance changes.
The photovoltaic (PV) cells of a solar panel harvest sunshine in the form of photon rays and converts them to direct current (DC) electricity. The life of a solar PV system is impressive as there are no moving parts to convert the solar energy into electricity.
How Solar Panels Work
Each solar panel is a remarkable lattice of layers of silicon-based cells. When the sun’s photons hit a layer of silicon that has free outer electrons around the atoms, these move to the layer beneath, which comprises atoms with electrons missing. The resulting flow causes a small current, but because there are many cells linked together, the whole panel produces a useable voltage of DC electricity. It remains as DC current it is going straight to a battery. This is a 12V system.
Solar PV systems are specified as having a ‘peak power capability’, because they depend on how much sun shines on the panels. The systems do still make electricity on overcast days, though obviously make more power on a sunny day.
Solar panels are extremely useful for charging batteries and so are ideal for powering “stand-alone” or “off the grid” systems that are remote from mains supply. For a stand-alone system, it is important to be sure that your solar panel can provide enough energy to power whatever you intend to use it for. As long as your panels are a suitable size and you have sufficient batteries you should seldom have an occasion when there is not enough power. You should aim to have enough stored energy for those “just in case” situations.
In a battery, a chemical reaction occurs and then electrons travel through a wire from one terminal to the other, and the result is Direct Current (DC) electricity. Batteries are particularly useful for standalone systems as they are fairly cheap and power can be stored and used when needed. If you wish to store electricity that you have generated in the battery bank then deep cycle batteries are designed to deliver less current for a longer period of time. Once flat they are designed to be recharged.
Car batteries can be used but they are not suitable as they are not designed to be fully discharged. The deep cycle batteries are designed to be recharged once flat and will last longer.
The amount of energy that a battery can supply is specified in ampere hours (Ah). So, a 12-volt battery that is specified as 100Ah can theoretically deliver 1 amp for 100 hours or 100 amps for 1 hour.
Multiplying the volts and amps, gives you the power (watts) the battery will produce.
So for our 12 volt battery it is possible to have:
- 12 volts X 1 amp = 12 watts for 100 hours
- 12 volts X 100 amp = 1200 watts for 1 hour
Back in the real world, these numbers don’t quite add up as you can’t expect to get more than 80% capacity from your battery, i.e. 80 Ah.
The smaller deep cycle batteries are not designed to deliver masses of current so you shouldn’t really drain more than about 10 -15 amps (that’s a device of about 120 – 180 watts). So if a pump needs 60 watts to function we divide 60 watts by 12 volts, which gives 5 amps.
If you use the pump for 2 hours a day, a fully charged battery therefore lasts about 8 days.
How to work out Watts, Amps and Volts
Common sense states that a larger Solar Panel will collect more energy than a smaller solar panel, but what size is correct for your needs?
Most power consumption of appliances is given in Watts. It is a relatively simple calculation to work out power your energy use, just multiply the power consumption by the hours of use. For example:
100 watt device used over 5 hours equals 100 x 5 = 500 Watt hours (Wh)
Converting Watts to Amps
If you want to figure out if your 100W solar panel is capable of running a fridge that draws 2A, then it’s a matter of one formula. You cannot directly convert watts to amps, since watts are power and amps are the current. It’s kind of like trying to convert litres to kilometres. But because the voltage in a 4WD is fixed at 12V then converting the watts into amps becomes achievable via the following equations:
So in the event of the 100W solar panel, 100W / 18.97V = 5.28A. That shows that the 100W solar panel can provide a maximum unregulated output of 5.2A whilst the fridge is drawing just 2Ah. A common mistake people make with solar power is taking the wattage of the panel and dividing it by 12V, this is the wrong calculation to make as no solar panel is 12V they are generally between 18V and 21V. False statements about 120 Watt panels being able to produce 10 Amps per hour are un true, un realistic and an unfortunate selling point used by people in the industry who do not fully understand solar power. To combat the “cowboys” out there all iTechworld solar panels have the full power ratings clearly marked on each and every panel we produce.
If you would like to find out more about Solar Power then please do not hesitate to get in touch.
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