Lithium Iron Phosphate batteries are amazing. They are exceptionally durable and efficient, and offers the best cost per kilowatt of usable energy considering their full lifespan. In short, good quality LifePo4 batteries have the following characteristics:
They are typically rated between 3,000 to 4,000 full discharge cycles before they reach 80% of their rated new capacity. That is more than 10 years of life if you use them every day, and keep in mind even at below 80% of their original capacity you should still be able to use them.
Charge and discharge efficiency is typically 97%+. You only lose about 3% of energy when charging or discharging. In comparison, lead-acid batteries are less than 85% efficient.
They have low internal resistance, and typically don't heat up when being used.
They require no maintenance.
They can be discharged fully (down to zero percent) without being damaged.
They weigh considerably less than lead-acid batteries of the same energy size. (Have a high energy density.)
They are safe, and do not combust in fire when damaged or abused. (A lot safer than their pure lithium based cousins that are used in cell phones and laptops
The above good characteristics do come with one big disclaimer: You need to look after your batteries! It is not a difficult ask, since LifePo4 batteries are fairly robust, and they always do come with their own Battery Management System (BMS) that prevents worst case scenario damage by cutting off and protecting batteries when you are doing something seriously wrong.
However, from the perspective of an owner of these batteries, to ensure maximum longevity, the below list of tips and info will make sure your investment is well cared for and provide a long and reliable service life.
Do not charge them in below freezing temperatures. This causes crystal sprites to form on the anode and could result in rapid damage, and even internal shorts. Most BMSs will cut off charging when the ambient temperature falls below zero. (In South Africa this is seldom an issue, and even in cold regions a proper enclosure will typically keep the ambient air above zero.)
Avoid storing them in very hot conditions, such as above 35 degree Celsius. If you store them in a poorly ventilated room or shed that gets excessively hot, you may find they degrade quicker than expected. The odd hot day here and there is not an issue, but their lifespan will shorten if they experience extremely hot conditions on a regular basis.
Try to not keep them at 100% full or 0% empty for extended periods. The battery does experience some internal chemical and physical stresses when completely full or empty. A short period (like a day) in this state is not an issue and will have no negative impact. However, if your battery is completely full or empty for weeks on end, it will degrade faster.
It is recommended to cycle your LifePo4 batteries up and down and occasionally allow them to reach full charge. This is especially important to allow the internal battery cells to balance. If you use your batteries daily (like in a solar system), then a good target is for the batteries to reach full charge at least once a week. Again, avoid keeping them at full charge for too long.
LifePo4 batteries are sensitive to voltage and your voltage charge and cut-off settings need to be correct. This is stating the obvious, and probably the first thing you need to set if you are configuring your charger and inverter. The battery BMS will typically cut off charging and/or discharging if voltages go completely out of range, but it is still important to set this correctly. Each manufacturer has slightly different voltage recommendations, which also depends on the overall battery bank (system) voltage - 12, 24, 36 or 48 volt (or more). As an example, a 48 volt LifePo4 battery could have a bulk (maximum) charge of 56.8 volt, and a cut-off (minimum) voltage of 46.0 volt. You must keep voltages within the recommended range for your specific brand of LifePo4 batteries.
Avoid charging or discharging your batteries too rapidly (at too high of an amperage). Again, each brand and size of battery will have a different specification, which is usually measured in amps. For example, if your battery is rated at 100 amps continuous current, and you are running a 48 volt system, that implies you must not charge or discharge your batteries at a wattage of higher than 4800 watt continuous load. Most batteries will not mind considerably exceeding the limit for short periods of time (i.e. less than 60 seconds), but if you exceed the limit often, you will shorted the lifespan.
Most of the above factors the Battery Management System will help you monitor and protect your batteries. However, often the BMS only kicks in at extreme conditions. If you truly want your batteries to last for 15 years+, it takes a bit of common sense and logic. Make sure you are not sailing too close to the limits too often!
We hope this short guide helps when considering how to setup, store and use your batteries. Unfortunately, most installers don't go through the effort of double checking setup and battery conditions, or advising and training the owner. Batteries are often (non-intentionally) being damaged by just a lack of knowledge and visible data on usage conditions, resulting in a much reduced battery lifespan.
EneFrame of course takes away this issue by making sure all our batteries are remotely monitored all the time. You will be notified of anything that is causing even the slightest harm to your batteries. Through active web monitoring and management, combined with a leading BMS and A-grade cells, you can be sure your EneFrame batteries will exceed their expected service life.
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