What Types of Rechargeable batteries for Solar Panels

Solar Energy systems generate power during the day as the sun shines on the solar panels and depending on the system it will power your devices and have enough to store for later. Solar power can be used to recharge many types of batteries from consumer-level AA batteries all the way up to 48V batteries.  

Without batteries, you won’t be able to harness the full potential of your system. We look at the different types of batteries you can use to store power for your solar panels.

Batteries are made up of positive and negative terminal material, separated by an electrolytic medium (something that allows the flow of electrons from one terminal to the other).

The batteries will vary in chemistries, applications, and price points.


Lithium batteries are the newer type of batteries compared to the lead-acid (we cover them next) that are traditional.


Lithium-ion batteries are the most common types of battery that you’ll find on laptops and phones. The electrodes are lithium cobalt oxide (LiCoO2) and graphite with a solid lithium electrolyte.

Lithium-ion batteries are light with a high energy density but can also be recharged quickly and deliver a constant current.  

Lithium Polymer

Lithium polymer is still under lithium-ion batteries and are referred so because it uses high conductivity polymer gel/polymers electrolyte instead of a liquid electrolyte.

Lithium Iron Phosphate

Lithium Iron Phosphate are a type of lithium batteries that uses phosphate as the cathode. LIFEPO4 batteries have a longer life span with up to 2000 lifecycles and are safer. However, they have a higher self-discharge and are a bit heavier than Lithium-ion.

Lead Acid

Lead Acid batteries are the traditional types of rechargeable batteries used for off-grid power storage. You’ll find three types of lead-acid batteries in the market namely Wet or Flooded, Gel, and AGM batteries.

Flooded Lead Acid Batteries

Flooded Lead Acid batteries are an old-school type of battery that required maintenance by filling up with distilled water regularly. This is why they are referred to as wet or flooded. They are cheap but are very bulky and require ventilation as they emit gas.

Gel Batteries

Gel batteries are referred to as zero maintenance batteries. This is because the liquid from the wet batteries was replaced with jello-like material. The battery is also sealed so removing the labor of having to refill with water.

However, they will cost more and are sensitive to high currents.

AGM Batteries

AGM batteries, or Absorbed Glass Mat, like are also a type of lead-acid battery with another twist. They are referred to as “dry” or “starved” electrolytes. The batteries use a fine fiber between the plates to hold the electrolyte.

This makes them another maintenance-free type of battery and they are also great for portable applications. They are also more efficient and don’t freeze easily.

They are more expensive than the wet types but are definitely worth it for the upgrade.

Deep Cycle batteries are special-purpose batteries designed to provide a constant current for long periods.  Automotive batteries are designed to produce a high current for a brief period to start the motor. They are the recommended type to use in a solar system but the size will depend on your needs.

NiCd (Nickel-Cadmium)

NiCad batteries are made from Nickel-Cadmium and are a dry rechargeable type of battery.  NiCad is used in many electronic devices like power tools and emergency radios. They are used in solar lights but do not have the capacity required for a home solar energy system.

NiCd batteries have the shortest charge time and can deliver a high load current and are quite cheap. However, they require high maintenance as they suffer from memory effects and require a full discharge in order to maintain their capacity.

NiMH (Nickel-Metal Hydride)

NiMH has a higher energy density than NiCd and doesn’t suffer from the memory effect. However, the NiMH batteries suffer from considerable high-self discharge

Because NiMH batteries are more environmentally friendly they are favored more than NiCd batteries.

Effective use of these batteries in Solar lights. Solar lights use rechargeable batteries that are powered through a small solar panel fitted into the solar light. It is charged throughout the day to provide power all night long. They can be charged for more than 1000 times and used again.

However, in the initial stages, using these batteries can be a little difficult as their power drains out without any alarm or sign. Thus, you always need spare batteries which can help you continue with your work while the other set of batteries gets charged.

The rechargeable batteries have the same components as the primary batteries. They comprise of a positive electrode, a negative electrode, a separator, and electrolytes (chemical solution). But, unlike primary batteries, they can be easily recharged and used again anytime you want.

These LSD batteries can outlast normal alkaline batteries. The LSD batteries are available in AA, AAA, C, D, and also 9-volt sizes. Among them, the C, D, and 9-volt batteries are not very easily available

Types of Battery By Size

Name  Shape LengthWidth (Diameter)Volts
AA Cylinder50 mm14.2 mm1.5 V
AAA Cylinder44.5 mm10.5 mm1.5 V
AAAA Cylinder42 mm8 mm1.5 V
C Cylinder46 mm26 mm1.5 V
D Cylinder58 mm33 mm1.5 V
9V Rectangular Height 48.5 mm26.5 mm17.5mm9 V
123 Cylinder34.5 mm17 mm3 V
CR2 Cylinder27.5 mm16 mm3 V  
N Cylinder30.2 mm12 mm1.5 V
J Square with missing corner Height 48.5 mm35.6 mm9.18 mm6 V


Ways of Charging a Rechargeable Battery

Rechargeable batteries have positive and negative terminals, making them a “cell.” Most cells today are actually made up of multiple cells inside. The lead-acid battery consists of six separate cells combined in series to make 12 volts. Each cell is two volts, giving the entire unit a total of 12 volts. There are also three cells in the nickel-cadmium battery, making it nine volts.

Find out the voltage of the power source. DC power supplies can vary in voltage. Two places you will most often need DC power are in your car and in your boat. An alternator for cars produces 12 VDC power. Marine batteries are often powered by 24 VDC. Although USB uses DC, it also draws power from a wall socket. It is cheaper to purchase a plug-in charger if you need to charge your batteries indoors.

Pay attention to the voltage requirements of the battery you’re charging. Before attempting to recharge any kind of “sealed” lead-acid battery or lithium-ion, you should read the instructions for your specific unit. If you are not sure of what type of battery it is, DO NOT attempt to recharge it.

The output voltage of the power cord will determine the voltage required to charge the battery if you’re charging it on a device that doesn’t require you to take out the battery. The required charge voltage for a removable battery will be printed on the battery.

Charging a Battery Using Solar

The solar panel charges your batteries just as you might expect: by converting sunlight into electricity. It does this using photovoltaic cells, which produce an electrical current when exposed to light. This process is a little more complicated than it sounds – for one thing, the amount of sunlight that hits any given spot on the planet isn’t constant or steady.

Because of things like weather and time of day, there’s more direct sunlight on some parts of the planet than in others. That means that a solar panel in one location might produce more electricity than a solar panel somewhere else.

You can charge a battery using a solar panel in two ways; Directly and indirectly via a charge controller.  When charging directly you can use a small solar panel to recharge a cell or group of cells by applying an electrical current to the metal plates on of the cell through power from a solar panel.

This is done by taking a wire from the positive terminal and negative on the Solar panel and attaching it to each of the corresponding plates on the battery.  This will cause electrical current to flow into and through the cell, charging it.

You should not directly charge your battery with a solar panel that exceeds 5 watts. Due to sunlight intensity, the voltage of the solar panels will fluctuate and produce a very high voltage that can drive the amps to the battery quickly and overcharge it. Solar charge controllers will allow you to manage your battery and stop the solar panel from overcharging it.

If you attach an ammeter in series with your battery, the electrical current through your battery will be displayed on the meter. You can use that to determine if your charging system is working properly. A fully charged cell has an ESR of one ohm or less.