Best Type of Solar Battery for an off-grid System

best type of battery for off-grid solar systems

I have recently been contemplating going totally off-grid. Not that I am an environmentalist or anything. I mean, I love the environment as much as the next guy, which means I hardly ever think about it unless there is a flood or another calamity. The reason why I have been seriously considering going off-grid has to do with the fact that there is hardly a grid to talk about in Zimbabwe. The infrastructure is there. However, drought and other factors have colluded to give people in the country to rolling blackouts that can go for as much as 20 hours! No matter how you look at it, ZESA just doesn’t seem to be able to catch a break. Anyway, what’s the best type of solar battery for people in the country?

Lessons from the hunt

While doing my research, I have learnt a lot about home solar systems. In fact, I can safely say I am now an expert! Okay, so I am a bit obsessive. But that’s for good reason. So called experts around the world typically do not know what they are talking about. Take the solar experts here as an example. I have spoken to a lot of them, and depending on the person, I either need a 1000 watt inverter or one that’s rated at 300 watts.

I usually notice the same thing when it comes to servicing my old Toyota Corolla. The people that claim to know everything about cars usually turn out to know nothing. If you take yours to have the oil changed, as an example, they will simply find an oil that’s rated for petrol engines. They will then use it on all petrol cars. Never mind the fact that the oils come in different ratings.

A friend of mine told me the story of how his car engine was destroyed after one of these oil changes. Apparently, they didn’t replace the oil filter well enough, and the car lost all of it’s oil while he was driving. Now the thing is a heap of junk sitting in some garage. The mechanics here also insist on changing the original spark plugs on cars with cheap Chinese knock-offs. The result is a drastic fall in the performance of most cars. Nobody has apparently told them that the spark plugs on most modern cars are rated for as many as 150 thousand kilometers! That is why I usually service my car on my own.

Available solar batteries

Anyway, enough about cars. Now, while doing research, I discovered that the following are the types of deep cycle batteries that are available for solar systems;

  • Flooded lead acid batteries.
  • Lithium ion batteries.
  • Sealed lead acid batteries
  • Gel batteries
  • Absorbed Glass Matte (AGM) batteries.

What are deep cycle batteries

All solar energy systems use deep cycle batteries. Deep cycle batteries are designed to be discharged to a greater depth than would be safe for automotive batteries. That’s not to say, however, a deep cycle battery can be fully discharged. In fact, you should probably use no more than 40% of the charge in a deep cycle battery if you wish to prolong it’s life. On the other hand, automotive batteries should only be discharged to a depth of no more than 10%. Now, let’s take a look at each of the types of solar batteries that are given above;

  1. Flooded lead acid batteries

These are the most common type of battery that can be found on the market (for both automotive and solar). They are usually the type of battery that can be found in cars. Now, flooded deep cycle lead acid batteries have been around for quite some time. And they remain fairly reliable. They are also one of the cheapest type of solar battery that you will be able to find on the market today.

Disadvantages of flooded lead acid batteries

The major disadvantage of flooded lead acid solar batteries comes from the fact that they are a bit difficult to handle due to the fact that they are flooded (they have liquid sulfuric acid and distilled water). There is always, therefore, a danger of spillage of potentially harmful fluids. Flooded lead acid batteries also require regular top-ups with distilled water. They also produce fumes during the charging and discharging cycles.

  1. Lithium ion batteries

Lithium ion batteries are the newfangled thing. They are the type of battery that’s in phones. Their biggest advantage lies in their greater energy density. More power can be stored in a smaller battery. They also last longer than all the other types of battery. You can expect to have yours for as many as 15 years, if claims by manufacturers are anything to go by. However, their major disadvantage is the issue of cost. Lithium ion batteries are the most expensive type of battery that can be found on the market today.

  1. Sealed lead acid batteries

Sealed lead acid batteries are maintenance free. What it means is that you do not need to top up the electrolyte. Otherwise, they are just the same as flooded lead acid batteries. One major advantage of this type of battery is that it can be stored in confined spaces. There is no need for ventilation, as is the case with their flooded counterparts. That’s because they produce far few fumes while charging and discharging.

  1. Gel batteries

Gel batteries are, in actual fact, a type of lead acid battery. However, they use a gel instead of a liquid electrolyte. The result is far greater portability. There is nothing inside that you can spill, and the batteries can be stored at odd angles. However, Gel batteries are notoriously fickle. Under or over- charge one, and it will die on you. If you roam around the streets of Harare, you will notice that Gel batteries are the most common among dealers. Maybe they are getting them as knockoffs from somewhere…

I had an argument with one man in a shop selling solar batteries about their reliability. I told him that Google had told me that they were not reliable. And he told me that Google had told HIM that they were reliable. He even produced a web page showing the advantages of Gel batteries when compared to sealed lead acid batteries. He had the document saved on his phone. Now, I didn’t have my own supporting documentary evidence from the internet. So I left in a huff because the guy was adamant that he was going to sell me a Gel battery even though I was equally adamant that I didn’t want one.

  1. AGM batteries

This is the final of the widely available battery types for solar installations. AGM batteries use a fiberglass matte that absorbs the electrolyte and is packed between plates in the battery. Their main advantage is the ability to withstand vibrations. They can also handle faster charge rates. AGM batteries are great in that they are not as fickle as their Gel counterparts.

Which solar battery type should I choose

Your choice, when it comes to deep cycle batteries, is going to be determined by your budget and the type of system that you wish to set up. Where funds are available, go for lithium ion batteries, which are much more efficient and can be discharged to greater depths without suffering damage. However, this type of battery is out of reach for many. Based on my research, the second best type of battery is the AGM battery. On the other end of the spectrum, I would stay away from Gel batteries. As mentioned earlier, they can easily suffer irreparable damage when improperly charged or discharged.

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