In this article, we’ll explain how to program your Blue Sky Energy solar charge controller for use with Lithium Iron Phosphate (LiFePO4) batteries. First of all, we strongly recommend asking for specifications and/or the recommended charge profile from the manufacturer. If manufacturer specifications are unavailable, the charge profile below is compatible with most 4S or 8S LiFePO4 batteries on the market.
LiFePO4 cells like to be charged between 3.55V and 3.65V per cell (VPC). Once the charge voltage is achieved, the battery is nearly fully charged. The remaining charging time is used by the battery to balance its cell voltages.
For a 4S LiFePO4 battery, we recommend a multi-stage charge profile with a charge voltage of 14.4V (3.6VPC), 30 minutes Absorption time in order to balance the lithium cells, and then dropping to a float voltage of 13.6V. Since the resting voltage of a fully charged lithium cell is usually initially above 3.4VPC, the controller will provide little to no current to maintain a fully charged battery. Once the battery becomes ~2% discharged, the voltage will fall to the float voltage (or below) and the charge controller will resume operation. Since the resting voltage of a fully charged Lithium Battery settles a little over time, it may be advantageous to reduce the float voltage to as low as 13.4V if the battery is not to be actively cycled/used. Here below are the specific settings for general use with 4S LiFePO4 batteries.
Check out the Learning Center for video tutorials covering a variety of topics related to optimizing your system. For programming your SB1524iX, SB2512iX-HV, SB2512i-HV, SB3000i, SB3024iL, and SB3024DiL with your IPN ProRemote, watch this video and refer to the instructions below.
NOTE: The Blue Sky Energy SB1524iX and SB3024iL/SB3024DiL can be programmed also for 8S LiFePO4 batteries (24V-nominal) by doubling the Absorption (Acceptance) and Float voltages values above.
NOTE: If you are replacing your lead-acid battery with a new lithium battery and have previously set your batteries to be “Equalized”, you should disable this capability on the charge controller by selecting “EqE” (Master equalize enable/disable) OFF through the display of the SB3000i and SC30 or by selecting OFF the dip switch of the other BSE controllers as described below:
The SB3000i and SC30 can be programmed directly using their onboard displays. Take a look at the video and the instructions below for more details.
For additional details please refer to your instruction manual. Manuals for all Blue Sky Energy products are available at the Sunforge Learning Center.
In conclusion, we strongly recommend following the manufacturer guidelines for battery charge profile settings. If these guidelines are unavailable, you can program your charge controller with the profile outlined above, which is suitable for most LiFePO4 batteries present on the market.
As always, drop us a line for more information.