Batteries have their variety, both in terms of size and shape. Of these, the lead-acid battery is quite frequently used in the solar industry. The lead-acid variety also has its types. It is broadly classified into two categories – the flooded lead-acid battery and the sealed lead-acid battery.
Again the second type, that is, the sealed lead-acid battery has two groups – the Gel batteries and the AGM (absorbent glass mat) batteries. Read on to find out more about these batteries, compare between the AGM battery and the Lead-Acid battery and learn about the pros and cons of each.
Flooded Lead-Acid Batteries
This kind has been the standard battery in the solar industry for a long time. These are most durable, long-lasting and cost-effective amongst the lead-acid batteries.
The flooded lead-acid batteries contain an electrolyte that can move around freely in the battery encasement. On charging the lead plates react with the battery acid to store electricity.
These batteries require to be mounted erect so that there is no leakage of electrolyte. They are the most economic and if well-maintained will reach the potential lifespan. But you have to check the levels monthly and top off with distilled water so that the lifespan is maximized.
These batteries release toxic hydrogen gas at the time of charging and this needs to be enclosed and vented to the outside so that the gas does not get trapped resulting in a hazardous atmosphere.
Pros of Lead-acid Battery
- The lead-acid batteries are the most cost-effective
- These are long-lasting
- Best choice for backup power applications, grid and utility energy storage
Cons of Lead-acid Battery
- These batteries have to be mounted erect to prevent leakage
- These get damaged in regular movement
- These require regular maintenance
- With these batteries, you need to check the levels periodically and top off with distilled water
- These batteries release toxic hydrogen gas during charging which needs to be vented out so that a hazardous atmosphere is not created
- Extreme climates have a deterrent effect on these batteries as the electrolyte solution inside may freeze or evaporate
Sealed Lead-Acid Batteries
The sealed lead-acid batteries are quite similar to the flooded version except that there is no access to the inside compartment. As such the electrolyte is sealed inside and you do not have to add distilled water. The amount of electrolyte is just enough so that the battery can live a calculated number of cycles. These batteries are also called VRLA (valve-regulated lead-acid) batteries as these have a small valve that allows the gases that occur during charging to escape. The two types of sealed lead-acid batteries are here under –
1) Absorbent Glass Mat (AGM) Batteries
Absorbent Glass Mat batteries are a variety of VRLA battery which is most popular as these can work in a wide range of conditions. Here the electrolyte is suspended in a thin fiberglass mat which is situated between the lead plates. This helps in the battery to be resistant to vibration and thus is the ideal choice for RV and other mobile applications.
These batteries can be mounted in any orientation and can be seen mounted in their sides to facilitate wiring and placement.
But AGM batteries are comparatively expensive than the flooded lead-acid ones and are not so long-lasting also. But they require very little maintenance. Also, you need not deal with that much gas released during the charging phase.
These batteries are ideal for mobile applications, remote locations where regular maintenance is quite impossible, places where leaked acid can cause problems and where the batteries will have to withstand very cold temperatures.
Pros of AGM Battery
- The AGM batteries can be mounted in any orientation as there is no fear of leakage
- These need very little maintenance
- These are resistant to vibration
- Too much gas is not released during the charging phase
- These batteries can handle higher charge/discharge rates
- These batteries are most commonly found in off-grid power systems, renewable energy systems and are useful for electric vehicle service and uninterrupted power supply systems (UPS) and also for robotics, solar street lights, some ATVs and motorcycles
Cons of AGM Battery
- These batteries are more expensive
- These are not very long-lasting
- These batteries should not be over-charged or under-charged as that can affect their performance and life
2) Gel Batteries
This second kind of VRLA battery is quite similar to an AGM but uses a thick paste that allows the magic to occur than the fiberglass mat. The main difference between the two is the charge rates. The AGM batteries can handle higher charge and discharge compared to Gel batteries. Again the Gel batteries are more costly than AGM and last longer in hotter temperatures. So, if the temperature of the place where the battery is to be used is a concern, you may go for the Gel batteries.
These batteries are the most expensive and are thus not quite perfect for quite some specific solar applications. Gel batteries are quite often mistaken for AGM batteries and this can affect their lifespan. But they are again the most sensitive VRLA batteries and it is advisable to use the correct charging parameters when you are using a Gel battery. These batteries can withstand high temperatures and perform best with slow, deep discharge.