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 we find 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 mins 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 SunForge YouTube channel 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.
Here below the instructions to follow for programming a BSE charge controller with IPN ProRemote for a 4S LiFePO4 battery:
From the ENTER SETUP MENU of the IPN ProRemote display:
- Set (or change) your battery capacity SET BAT AMP-HRS to reflect the battery bank based on its nominal capacity (@ 20-hour rate)
- Set Charge Efficiency to 99%
- Set Charge Efficiency Mode to FIXED
- Set Monthly SELF-DISCHG (self-discharge) to 1% / Month
From the SET BAT CHARGE PARAMETERS MENU of the IPN ProRemote display:
- Set Absorption (Acceptance) charge voltage 14.4V. You could go as low as 14.2V to be less aggressive, but 14.6V is the absolute maximum
- Set Float charge voltage 13.6V. You could go 13.4V to be a little less aggressive, or as much as 13.8V to be more aggressive
- Set Equalization Charge to desired Absorption (Acceptance) voltage (14.4V recommended, see point 1.)
- Set Equalization Time to 0.5 hours (30 mins)
- Set Equalization frequency to MANUAL (one step below 10 days)
- Set the Temperature Compensation Factor -0.00mV/C/C* (lithium batteries do not require temperature compensation) or remove the Battery Temperature Sensor (P/N 930-0022-20)
- Disable the Float transition current by setting FLOAT CURRENT to 0.0A/ 100AH
- Set Absorption (Acceptance) charge time to 0.5 hours (30 mins)
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:
- SB1524iX, SB2512i(X), and SB2512i(X)-HV, DIP # 4 OFF
- SB3024(D)i, SB3024(D)iL and SB3024(D)iL-DUO, DIP # 5 OFF
The SB3000i and SC30 can be programmed directly using their onboard displays, take a look at this video for more details and refer to the instructions below:
From the SETUP CONTROL SETTING (by pressing the Setup button for 5 secs):
- Set the Absorption Voltage (AbS) to 14.4V. You could go as low as 14.2V to be less aggressive, but 14.6V is the absolute maximum
- Set the Absorption Time (Abt) to 0.5HRS
- Set the Float Voltage (FLt) to 13.6V. You could go 13.4V to be a little less aggressive, or as much as 13.8V to be more aggressive
- Set the Master Equalization Enable (E9E) to OFF
- Set the Temperature Compensation Factor (btc) to 00
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.