Solar batteries: Your independent and reliable energy source

Which technology is the right one for solar batteries?

Each battery technology has different advantages that qualify it as a solar battery. While wet batteries are inexpensive and can deliver high currents at the same time, AGM solar batteries are somewhat more expensive, but are maintenance-free, leak-proof and also somewhat more cycle-resistant than the classic lead-acid battery. If you are looking for even more durability and robustness, GEL solar batteries are a good choice, but you should also bear in mind the significant price increase compared to wet or AGM solar batteries. The absolute premium version is available with lithium solar batteries: Not only do they have an extremely long service life, they also deliver greater efficiency, higher usable capacities and faster recharging behavior. However, these outstanding properties are also reflected in the price.

A comparison of battery technologies

Wet batteries (lead-acid)

Wet batteries, also known as lead-acid solar batteries, are an established and cost-effective technology for storing energy. They consist of lead plates immersed in a liquid electrolyte of sulphuric acid. An important aspect of wet batteries is that they require regular maintenance, especially topping up with distilled water, as the electrolyte can evaporate during the charging process. They also emit gases during charging, which is why good ventilation of the installation site is necessary. To maximize their service life, wet batteries should generally not be discharged below 50% of their capacity.

Advantages of wet batteries:
  Low initial cost
  Robustness against extreme temperatures
  Ability to deliver high currents
  Well-established and reliable technology
  Relatively tolerant to overcharging

Wet batteries are well suited for cost-sensitive off-grid systems where sufficient space is available and regular maintenance can be carried out. They can also be an option for backup systems that are rarely used. They can also be used in environments with large temperature fluctuations, where robustness is more important than service life. 

AGM batteries (Absorbent Glass Mat)

AGM solar batteries are a further development of lead-acid technology. With this technology, the electrolyte is bound in a glass fiber fleece between the lead plates, making the battery leak-proof and maintenance-free. The sealed design eliminates the need for topping up with water, and gas development is reduced compared to wet batteries. AGM batteries perform well at low temperatures and are more resistant to vibrations and shocks. They can be discharged deeper than wet batteries (up to 80% of their capacity) and recharge faster.


Advantages of AGM batteries:
  Maintenance-free
  Leak-proof and can be mounted in various positions
  Good performance at low temperatures
  Faster charging than wet and GEL batteries
  Better cycle stability and longer service life than wet batteries
  High resistance to vibrations and shocks
  Low self-discharge rate

AGM batteries are a good choice for grid-connected solar systems with backup requirements, smaller off-grid systems, mobile applications such as RVs and boats, and for systems in colder climates.

GEL batteries

GEL solar batteries use an electrolyte that is converted into a gel-like form by the addition of silicon dioxide. This design also makes them leak-proof and maintenance-free. GEL solar batteries are characterized by a very good deep discharge capacity (up to 70% of their capacity) and a longer service life compared to AGM solar batteries. They perform well at high temperatures and have a low self-discharge rate. However, their charging speed is slower than AGM solar batteries and they are more sensitive to overcharging.


Advantages of GEL batteries:
  Maintenance-free
  Leak-proof and can be mounted in various positions
  Very good deep discharge capability
  Longer service life and higher cycle stability than AGM batteries
  Good performance at high temperatures
  Low self-discharge rate
  Safe operation with lower risk of battery blowout or explosion

GEL batteries are particularly well suited for off-grid solar systems that experience frequent deep discharges, systems in warmer climates, backup systems with irregular use, and applications where long life and high reliability are important.

Lithium batteries (especially lithium iron phosphate)

Lithium solar batteries, in particular the lithium iron phosphate variant (LiFePO4), represent the most modern and often most efficient technology for solar power storage. They offer a very high energy density, resulting in more compact and lighter systems. They have an extremely long service life and high cycle stability (often over 4000 cycles) and can be deeply discharged (up to 100% of their capacity) without significant loss of performance. They also enable fast charging processes and are highly efficient. Another important advantage is their high level of safety, as they are less susceptible to thermal runaway compared to other lithium-ion technologies. Maintenance requirements are minimal.

Advantages of lithium batteries (especially LiFePO4):
  Very high energy density
  Extremely long service life and cycle stability
  Low weight
  Fast charging process
  High depth of discharge
  High level of safety
  Low maintenance
  High efficiency
  Wide operating temperature range