Batteries are the energy reservoir in solar power systems, and it is important to choose the size and type of battery carefully.
The different types of batteries include:
1. Flooded batteries
These low-cost, high-quality wet lead-acid batteries are ideal for photovoltaic, attended applications. These small 6 and 12 VDC deep cycle batteries are the backbone of any autonomous power system and will deliver up to 1500 cycles at an 80 % depth of discharge.
Originally a kind of gel battery was produced in the early 1930s for portable valve (tube) radio LT supply (2, 4 or 6V) by adding silica to the sulfuric acid.
Unlike a flooded wet cell lead–acid battery, these batteries do not need to be kept upright. Gel batteries reduce the electrolyte evaporation, spillage (and subsequent corrosion problems) common to the wet cell battery, and boast greater resistance to shock and vibration.
Chemically they are almost the same as wet (non sealed) batteries except that the antimony in the lead plates are replaced by calcium, and gas recombination can take place.
AGM batteries differ from flooded lead–acid batteries in that the electrolyte is held in the glass mats, as opposed to freely flooding the plates. Very thin glass fibers are woven into a mat to increase the surface area enough to hold a sufficient amount of electrolyte on the cells for their lifetime.
AGM batteries are more resistant to self-discharging than conventional batteries within a wide range of temperatures.
As with lead–acid batteries, in order to maximize the life of an AGM battery, it is important to follow the manufacturers charging specifications and the use of a voltage-regulated charger is recommended.
4.Lithium Iron Phosphate(LIFEPo4)
LiFePO4 stands for Lithium (Li) Iron (Fe) Phosphate (PO4), and is the specific type of lithium battery that we build here at Dakota Lithium. LiFePO4 batteries are highly regarded for their resiliency and long life compared to other lithium battery chemistries.
Here’s a few more reasons why we love LiFePO4:
- Lithium Iron Phosphate (LFP) is the safest and most stable lithium battery chemistry. Unlike other lithium batteries. LiFePO4 does not catch fire or explode.
- LFP is Cobalt free. Cobalt is a rare earth element that is sourced from war torn Congo. Money from Cobalt mining in the Congo fuels conflict. Cobalt is the blood diamond of the battery trade.
- LFP is affordable. By using common chemical compounds LFP batteries are a lower cost energy storage solution compared to other lithium chemistries.
Battery Box Ventilators
Reasons to use a battery box ventilators include:
Positive venting of hydrogen gas.
• Stops back drafting.
• Puts the smell outside.
• Keeps batteries warmer in cold climates.
• Keeps the battery tops and terminals cleaner.
• Uses very little power.
• Excellent results for over 15 years.
Battery Charge Controllers
PWM SOLAR CHARGE CONTROLLER
A PWM solar charge controller stands for “Pulse Width Modulation”. These operate by making a connection directly from the solar array to the battery bank. During bulk charging, when there is a continuous connection from the array to the battery bank, the array output voltage is ‘pulled down’ to the battery voltage. As the battery charges, the voltage of the battery rises, so the voltage output of the solar panel rises as well, using more of the solar power as it charges. As a result, you need to make sure you match the nominal voltage of the solar array with the voltage of the battery bank. *Note that when we refer to a 12V solar panel, that means a panel that is designed to work with a 12V battery. The actual voltage of a 12V solar panel, when connected to a load, is close to 18 Vmp (Volts at maximum power). This is because a higher voltage source is required to charge a battery. If the battery and solar panel both started at the same voltage, the battery would not charge.
A 12V solar panel can charge a 12V battery. A 24V solar panel or solar array (two 12V panels wired in series) is needed for a 24V battery bank, and 48V array is needed for 48V bank. If you try to charge a 12V battery with a 24V solar panel, you will be throwing over half of the panel’s power away. If you try to charge a 24V battery bank with a 12V solar panel, you will be throwing away 100% of the panel’s potential, and may actually drain the battery as well.
MPPT SOLAR CHARGE CONTROLLER
An MPPT solar charge controller stands for “Maximum Power Point Tracking”. It will measure the Vmp voltage of the panel, and down-converts the PV voltage to the battery voltage. Because power into the charge controller equals power out of the charge controller, when the voltage is dropped to match the battery bank, the current is raised, so you are using more of the available power from the panel. You can use a higher voltage solar array than battery, like the 60 cell nominal 20V grid-tie solar panels that are more readily available. With a 20V solar panel, you can charge a 12V battery bank, or two in series can charge up to a 24V battery bank, and three in series can charge up to a 48V battery bank. This opens up a whole wide range of solar panels that now can be used for your off-grid solar system.