The most common batteries used in solar energy storage typically are made with one of two chemical compositions: lead acid or lithium ion. In most cases, lithium ion batteries are the best option for a solar panel system, though other battery types can be more affordable.
1. Lead acid
Lead acid batteries are a tested technology that has been used in off-grid energy systems for decades. While they have a relatively short life and lower DoD than other battery types, they are also one of the least expensive options.
2. Lithium ion
ithium ion batteries are lighter and more compact than lead acid batteries. They also have a higher DoD and longer lifespan when compared to lead acid batteries. However, lithium ion batteries are more expensive than their lead acid counterparts.
Frequently asked Questions are:
· How long will my batteries last before I need to replace them?
o A typical solar battery has a lifespan of between 5 and 15 years
o This depends on a few factors, how many times or cycles the batteries are depleted and recharged the DoD (explained below), the type of charge controller and the settings used to optimize your charge and discharge cycle.
o Here at Foscam we pay close attention to the recommended depth of discharge, or DoD. DoD is the percentage of the battery’s stored energy you use. For example, your battery’s capacity is 13.5 kWh, and you use 10 kWh of its charge. The depth of discharge would be 74%.
o DoD is important because pushing your battery beyond its recommended DoD can significantly shorten your battery’s lifespan (the lower the DoD, the longer the life span and vice-versa). Manufacturers will assign each battery type a recommended maximum DoD. If your charge controller is not correctly configured you can kill your batteries in a few months, one setting does not fit all.
· How long will my batteries last without sun (dark run time) before they are flat?
o Foscam’s kits are designed to be used with the supplied equipment, that’s because we carefully match the connected equipment’s total power needs to the battery’s supped along with the panels recharge capacity. If you add or change the power consumption by adding more or different equipment it will affect the dark runtime.
o For example using our standard 12ah Solar System and connecting 1 Foscam camera we calculate a 30hr to 40hr run-time (Winter solstice), if you now add a POE CPE device like a TP-Link CPE510 to the pole then you run time drops to 20hr to 31hr run-time (Winter solstice). That’s a 10 hour reduction.
o Keep in mind that the minimum you need is 12 hours (summer solstice, Southern hemisphere), , that will only cover you for a one night, if the next day is very overcast and rainy then your system will go offline.
o It a trade off of price and weight v runtime, but most users accept that there will be a few days in year that they will be offline.
o If runtime is important to you then look at our 24Ah kit
· Can I connect my own equipment to the Foscam solar kit?
o We give you a USB 5V, a 12V regulated and a 12V unregulated hand off. You can connect any additional equipment (max 600ma) to a Foscam standard system, but we then cant can’t grantee guarantee runtimes as advertised / stated as we have no idea of the power requirements of your equipment.
o If you require a 48V POE handoff the look at our High Site gateway kit.
Lithium-ion batteries – life span
The predominant questions on any battery powered device are undoubtedly: how long will it last and what is the warranty. Warranty is certainly important, though not the only factor to consider when evaluating your solar battery options: price, performance, and durability should all be taken into account.
Similar to your laptop or cell phone battery, solar batteries degrade over time: as you continue to use and charge your battery, it loses the ability to hold a charge.
However, it’s important to not evaluate battery warranties based on charge – discharge cycles alone; because solar batteries gradually lose their ability to hold a full charge as they age, a cycle towards the end of your battery’s life will store and produce less energy than the output of a cycle immediately after installation.
Standard manufacturer warranties for lithium-ion batteries covering both performance and defects is one year, but extended warranties are available for purchase from some manufacturers. A warranty beyond 10 years does not make sense because so much of the battery would need to be replaced after year 10. As a comparison, a lead acid battery (such as in your car) and a gel battery (such as in your alarm system, UPS or automatic gate), has a life span of 3 to 5 years. For big installations, insurance can also be purchased by the user. Operations and maintenance of batteries is complicated because the normal tendency of the operator is ‘install and forget’. Rates of deterioration of the battery depend on how the battery is used.
Why choose LiFePO4 deep cycle batteries?
The life of a lead-acid battery is greatly affected by the DOD. A lead-acid battery is likely to fail quickly on a user as it normally only allows 25% to 40% (up to 60% sporadically) DOD.
In contrast, a LiFePO4 (Lithium Iron Phosphate) battery, which is newer technology, has a deep-cycle discharge, so it can reach 2000 cycles with 100% DOD. Lithium batteries can also be discharged at a specific C-rating. With a working temperature of 25° C and a discharge rate of 0.5C, a LiFePO4 battery can reach 4000 to 6000 cycles.
With a working temperature of 25° C (a higher temperature affects the figures quoted below) and a discharge rate of between 0.2C and 0.5C (the battery C Rating is the measurement of current in which a battery is charged and discharged at), a LiFePO4 battery can reach 1000 to 6000 cycles. Compared to lead-acid batteries which have a life cycle of between 500 and 2100 cycles, the advantages of deep-cycle lifepo4 batteries are the following: Eco-friendly; Good high-temperature resistance; higher DOD.
What is DOD (Depth of Discharge)? The Depth of Discharge (DOD) of a battery represents the percentage of the battery that has been discharged relative to the overall capacity of the battery.
A battery’s “cycle life,” the number of charge/discharge cycles in its life, depends on how much battery capacity is typically used. Rather than completely draining a battery to its maximum DOD, a user will be able to attain more cycles in their battery regularly discharging it with a lower percentage of charge.
For example, a battery may have 15,000 cycles at a DoD of 10%, but only have 3,000 cycles at a DoD of 80%.
With the Foscam solar systems, the aim is for a large number of cycle lives, and a stable discharge performance whilst giving the user the best possible ‘dark time’ (no solar charging available). The more equipment added to the solar system, the higher the DOD.
Compared to lead-acid batteries, the advantages of deep-cycle lifepo4 batteries are the following:
- Good high-temperature resistance
- Good safety characteristics
- No memory effect
- Higher-capacity compare with same size lead-acid battery
- Longer cycle life than other lithium-ion batteries
- Ideal drop-in replacement for lead-acid batteries
- Lower total cost of average use