3 Main Battery Types
Lead Acid Batteries
These are the best option for a small scale solar system if cost is the main factor and weight is not a concern.
Lithium Ion
If a lightweight system is your main design factor then lithium batteries may be your best bet. Before using lithium batteries please understand how to handle them safely as they can potentially be more dangerous than lead acid batteries. Tesla's power wall battery pack uses lithium ion batteries to store their solar energy and charge the Tesla Electric Vehicles. For large scale systems where cost isn't an issue, Lithium Ion batteries are the best option.
Nickel Cadmium
Nickel cadmium batteries are rarely used in small scale solar systems due to various reasons. For more indepth reasons visit this website.
These are the best option for a small scale solar system if cost is the main factor and weight is not a concern.
Lithium Ion
If a lightweight system is your main design factor then lithium batteries may be your best bet. Before using lithium batteries please understand how to handle them safely as they can potentially be more dangerous than lead acid batteries. Tesla's power wall battery pack uses lithium ion batteries to store their solar energy and charge the Tesla Electric Vehicles. For large scale systems where cost isn't an issue, Lithium Ion batteries are the best option.
Nickel Cadmium
Nickel cadmium batteries are rarely used in small scale solar systems due to various reasons. For more indepth reasons visit this website.
Battery Selection Variables:
Nominal Voltage - 6v, 12v, 24v, or 48v
When shopping for batteries you may see that there are different nominal voltage options. Your nominal voltage choice is based on the maximum power that you will be drawing. The lower nominal voltage you choose the bigger your wire will have to be because a lower voltage system requires a higher current to meet the same power requirement. I would suggest at least using a 12V system for small setups. If your power demand is much larger then I would advise using a 24V or 48V system. You can use a 12V system for large power demands, but the size of your wire can become so large that you have to weld your connections. I will show the equations and sample calculations in the future to show you at what power I would advise using a higher nominal voltage. Realize that you can combine multiple 6V or 12V batteries to meet a 24V or 48V nominal voltage requirement, so you do not have to buy a 48V battery for a 48V system. You can use 4 12V batteries instead of 1 48V battery. Compare the costs of 1 48V battery compared to 4 12V batteries with all needed connections and wire to make your decision.
Storage Capacity - Amp Hours
The main factor in choosing a battery is its storage capacity, measured in ampere hours. "An ampere hour (abbreviated Ah, or sometimes amp hour) is the amount of energy charge in a battery that will allow one ampere of current to flow for one hour". It may sound complex and technical but the calculations are simple. Storage capacity allows you to know how long your battery can go between charges. Ideally at minimum you would like your battery to last throughout a whole night while the sun is down.
I used 2 - 12V 18Ah batteries together for a total of 36Ah. I did this because they were on sale, and I thought it would save me a few bucks. In hindsight, it was more expensive since I didn't factor in the extra wire and connectors that were needed. Be sure to check the weight of the batteries and make sure you can reasonably move them for maintenance if needed.
Sealed VS. Unsealed Lead Acid Batteries
I would suggest sealed lead acid batteries because these are less likely to spill hazardous materials and require much less maintenance. Unsealed batteries are the cheaper option. I designed my battery bank to be portable, so unsealed batteries were not a viable option.
Sealed batteries are commonly either an AGM (absorbed glass mat) or stabilized GEL type. I would recommend AGM since that is what I have experience using. Please contact me or do more personal research if you have further questions.
When shopping for batteries you may see that there are different nominal voltage options. Your nominal voltage choice is based on the maximum power that you will be drawing. The lower nominal voltage you choose the bigger your wire will have to be because a lower voltage system requires a higher current to meet the same power requirement. I would suggest at least using a 12V system for small setups. If your power demand is much larger then I would advise using a 24V or 48V system. You can use a 12V system for large power demands, but the size of your wire can become so large that you have to weld your connections. I will show the equations and sample calculations in the future to show you at what power I would advise using a higher nominal voltage. Realize that you can combine multiple 6V or 12V batteries to meet a 24V or 48V nominal voltage requirement, so you do not have to buy a 48V battery for a 48V system. You can use 4 12V batteries instead of 1 48V battery. Compare the costs of 1 48V battery compared to 4 12V batteries with all needed connections and wire to make your decision.
Storage Capacity - Amp Hours
The main factor in choosing a battery is its storage capacity, measured in ampere hours. "An ampere hour (abbreviated Ah, or sometimes amp hour) is the amount of energy charge in a battery that will allow one ampere of current to flow for one hour". It may sound complex and technical but the calculations are simple. Storage capacity allows you to know how long your battery can go between charges. Ideally at minimum you would like your battery to last throughout a whole night while the sun is down.
I used 2 - 12V 18Ah batteries together for a total of 36Ah. I did this because they were on sale, and I thought it would save me a few bucks. In hindsight, it was more expensive since I didn't factor in the extra wire and connectors that were needed. Be sure to check the weight of the batteries and make sure you can reasonably move them for maintenance if needed.
Sealed VS. Unsealed Lead Acid Batteries
I would suggest sealed lead acid batteries because these are less likely to spill hazardous materials and require much less maintenance. Unsealed batteries are the cheaper option. I designed my battery bank to be portable, so unsealed batteries were not a viable option.
Sealed batteries are commonly either an AGM (absorbed glass mat) or stabilized GEL type. I would recommend AGM since that is what I have experience using. Please contact me or do more personal research if you have further questions.
I used two of the 18 Ah batteries pictured on the left for my battery bank. One of these weigh 12lbs and would be great for a small semi-portable setup with low power demand. This battery sells for $33. Click the link to view the Amazon product details. |
On the left is a 35Ah battery which is about twice the storage capacity of the previous option. It sells for $65 on Amazon. Click the link to view product details. |
For larger solar setups, I would recommend using one or more of these 100Ah batteries. This option sells for $165. In the future, I intend to use multiple of these connected together in a 48V nominal voltage system to power my off-grid structure. |