I like this method best for estimating the state of charge of an LFP battery I’ve just received or just pulled out of storage. Usually this chart is tailored to your battery, so it should take precedence over the ones above.
Your LFP battery’s manual probably has a state of charge chart in it. I then compared this number to the 12V LiFePO4 state of charge chart above, as well as the one in the battery manual.īased on the charts, I’d estimate my battery’s state of charge was somewhere around 80%. To get an accurate estimate of your LFP’s battery capacity based on voltage, you need to disconnect all loads and chargers from the battery and let it rest awhile before measuring its voltage. I brought it out of storage and measured its voltage with a multimeter. I wanted to check its capacity after having stored it for 3 weeks. Use it to get a rough estimate of your battery’s remaining capacity.įor example, I own the Ampere Time 12V 100Ah LiFePO4 Deep Cycle Battery. Let the battery rest for a little while - I usually wait 15 minutes - and then measure its voltage with a multimeter.Ĭompare your measurement to the right voltage curve above, or the state of charge chart in your battery manual. (Don’t forget to disconnect your solar panels from your charge controller first!) To get an accurate estimate of battery capacity based on voltage, you first need to disconnect any loads and chargers from the battery. Because of these factors, it can be hard to estimate their state of charge from voltage alone. Plus, LiFePO4 batteries have a relatively flat discharge curve from around 99% to 20% capacity. Measure Battery Voltage with a MultimeterĬons: Must disconnect all loads and chargers and let battery restīattery voltage changes depending on charge and discharge rates. 3 Ways to Check LiFePO4 Battery Capacity 1.
You can connect cells in series and parallel to make LFP batteries with your desired voltage and capacity combinations. They’re best used for making your own lithium batteries. You can buy individual LiFePO4 battery cells online. They are fully charged at 3.65 volts and fully discharged at 2.5 volts. Individual LiFePO4 cells have a nominal voltage of 3.2 volts. They are made by connecting 16 3.2V LiFePO4 cells in series. They are fully charged at 58.4 volts and fully discharged at 40 volts. They rarely make sense for small-scale projects. 48V LiFePO4 Battery Voltage Chart VoltageĤ8V is more popular for larger solar systems. They are made by connecting eight 3.2V LiFePO4 cells in series. They are fully charged at 29.2 volts and fully discharged at 20 volts. You can either buy an off-the-shelf 24V battery or pick up two 12V batteries and connect them in series to make a 24V battery bank. 24V LiFePO4 Battery Voltage Chart VoltageĢ4V lithium iron phosphate batteries are another popular option for solar power projects. They are made by connecting four 3.2V LiFePO4 cells in series. They are fully charged at 14.6 volts and fully discharged at 10 volts.
They’re a drop-in replacement for 12V lead acid batteries, and a great upgrade. Here’s a printable version of the above chart:ġ2V 100Ah LiFePO4 batteries are currently some of the most popular for off-grid solar power systems.
12V LiFePO4 Battery Voltage Chart Voltage Consult the manual of your LFP battery for its specific discharge curve and voltage parameters. Note: These charts are all for a single battery at 0A. Here are LiFePO4 battery voltage charts showing state of charge based on voltage for 12V, 24V and 48V batteries - as well as 3.2V LiFePO4 cells.