I find it mind boggling that a large percentage of people believe there is a solar energy storage problem. I agree in some places in there world it maybe cost prohibitive but that doesn’t mean there isn’t a solution or it doesn’t work. But that’s not the root cause of why there are so many naysayers. It really comes down to education, and most are very uneducated when it comes to batteries and how to treat and maintain their battery bank. People often make the mistake of thinking or treating batteries as an energy producing device. They’re purely an energy storage device. Batteries do not create any energy whatsoever. When you treat your battery as an energy producing device you are asking for nothing but problems. There are a few other major areas where mistakes are made when it comes to battery banks for solar energy storage.
- Not enough PV. If you draw 10 kilowatt hours out of your battery bank you must have enough PV to put at least put in 20% more than took out. if you are using a flooded type battery you need to put at least 30% back (one of the many reasons I never recommend floods). When you have an undersized PV array your batteries will spend most of there time in an undercharged state which will lead to poor performance. Always make sure you have a enough PV to support your battery charging needs, plus whatever you need to support your home’s energy usage while charging your battery bank. Your batteries will thank you. As it is with all batteries you never want to overcharge them or leave them in an undercharged state, both will lead to the untimely demise of your battery bank.
- Miscalculations. I know it sounds like common sense but it’s a mistake that happens all the time. Users will think they have properly sized there battery bank when in fact they have no idea what there actual usage is. Their biggest mistake usually happens when they have improperly calculated their usage from DC to AC. Their next mistake is calculating everything at 100% and under optimal conditions. Followed by miscalculating the true usable ampere hour capacity of their battery bank. Many also do not monitor their usage and some just don’t care and think the batteries are there to provide an infinite amount of energy. These type of users also have a bad habit of adding energy hungry devices down the road without thinking how it will impact there battery bank usage. What happens is the end user ends up going way too deep into the depth of discharge and sending there battery bank to an early grave. Rule of thumb is not to go deeper than 40%-60% DOD, no matter what battery chemistry you choose.
- Wrong Battery Chemistry. People love buying the cheapest solution on the market without fully understanding or thinking about the repercussions. In the solar energy storage market that honor goes to flooded type batteries. Sometimes you get what you pay for and that’s exactly what you get when it comes to flooded batteries. Just looking at them they look cheap. Flooded batteries are expensive and a pain to maintain, not to mention they can be dangerous too. The majority are poorly constructed using the cheapest materials possible. Their biggest flaw is they just are not as reactive as their counterparts. By this I mean their charge and discharge profiles are poor. Next is absorbed glass mat or AGM batteries. AGM Batteries are maintenance free, about double the price of flooded types, and are usually constructed out of higher grade materials. Although more reactive then floods, like floods; AGM batteries need a high charge current and voltage to be properly maintained. This becomes problematic in a PV array due too that it is not always operating at 100%. The biggest issue AGM batteries have is that they do not have a very good cycle life. Finally there are gel batteries. Gel batteries are the most expensive in the lead acid family (about 10% more than AGM), but here you get what you pay for, and Gel batteries deliver the goods. Gel batteries are constructed using high grade materials and electrolyte. Gel batteries need the lowest charge current and voltage to be recharged, contrary to belief it does not mean that they charge slower than floods or AGMs. They are the most reactive chemistry in the lead acid family. Gel batteries get over twice the cycle life over AGM batteries. I’ve seen Gel batteries get over 3000 cycles at 50% DOD when properly maintained. Gel batteries also handle high ambient temperatures much better than AGM or floods. With their high cycle life and low charge characteristics make them the ideal battery for solar energy storage.
When you become educated about batteries and maintaining your batteries there is a solution to solar energy storage, it is here and now. Start with choosing the right battery chemistry and proper battery size. If you start with the wrong battery your entire PV system will never work as designed. Make sure you have enough PV to support your batteries. Double check your usage calculations, monitor and know your usage. When adding new electrical devices make sure your system can support them. Finally properly maintain your batteries by ensuring they are always fully charged before there next cycle of use. When these simple rules are not followed solar energy storage never works. When followed the end user will have a PV system that works as designed and will be one of the few in the know that there is an answer to solar energy storage, and in fact it is here and now!