The profile setting on a solar charge controller sets up the power output parameters to charge the battery bank in the most optimal voltage and current based on the battery chemistry used. Lead-acid, Absorbent Glass Mat (AGM), and Lithium Iron Phosphate (LFP) type batteries have different optimum charging parameters.
The battery manufacturer defines the charge controller settings, such as charge voltage and current, to ensure optimal charging conditions and battery longevity. The settings are specific to each brand and type of battery and must be adhered to, to maintain your battery warranty.
Battery manufacturers list their recommended charging parameters on their product websites or supply them as part of the support documentation when purchasing the device.
important Charge Controller parameters;
- Battery Voltage 12V/24V/48V
- Charge Controller Capacity 10A/20A/30A/….150A
- Charge Rate – Manufacturer specified
- Charging Voltages – Manufacturer specified per stage
- Absorption Voltage
- Float Voltage
- Equalization Voltage
- Absorption Duration
- Maximum absorption rate (30 minutes/100Ah of battery capacity)
- Voltage Compensation for Low Temperature
- Low Temperature Cut Off
- Load Output Profile – Maximum Battery Life
- Smart Networking Enabled/Disabled
Let’s review these parameters and understand what they mean and what role they play?
How Do Charge Controller Settings Work?
The battery manufacturer defines the charge controller settings according to the type of battery chemistry and battery bank setup.
The parameters are programmed for the battery charging parameters, load output parameters, programmable relay settings, external device settings, firmware update settings, Bluetooth enabled/disabled, and networking setup.
Battery manufacturer websites and user manuals typically provide the charge controller settings required for optimal charging and battery protection. If this data is not supplied, the manufacturer’s technical support contact can be requested for it.
See also: What A Solar Charge Controller Does (Explained)
The most critical settings For Charge Controllers:
- Absorption Voltage:
- Float Voltage:
- Equalization Voltage:
- Re-Bulk Voltage offset:
- Absorption Duration: (Adaptive/Fixed)
- Maximum Absorption Time:
- Tail Current:
- Equalization Current Percentage:
- Automatic Equalization: (Disabled / Equalize every X Days)
- Equalization stop mode: (Fixed Time / Automatic on Voltage)
- Maximum Equalization Duration:
- Temperature Compensation (mV/°C):
- Low-Temperature Cutoff (optional):
Also, request the method of programming for these settings to be supplied. Most smart MPPT charge controllers can be programmed via a mobile application interface. Older models have switch dials that must be set in certain combinations to achieve the desired settings.
A simple e-mail request to the battery manufacturer technical support requesting the above settings should prove effective.
Also, please provide them with a brief description of your solar systems, such as the type and number of solar panels and the make and model of the charge controller.
How To Set Up A Charge Controller – Example
I will discuss an example of how the settings are loaded for a Victron Smart Solar Charge Controller via the mobile application interface. Mobile applications are the easiest way to interface with the charge controller and to set parameters and monitor performance.
- Download and install the mobile application on your smartphone
- Open the mobile application on your smartphone
- Select the Charge Controller to be programmed on the “Device List.”
- Select the Settings Cog in the upper right-hand corner
- Select the “Battery” menu
- Enter the values specified by the battery manufacturer for Battle Born LiFePO4 Batteries.
- Battery Voltage (12V/24V/48V)
- Maximum Charge Current (30A) – 50A maximum per 100Ah battery capacity
- Charger Enabled
- Battery preset – User defined
- Expert mode Enabled
- Absorption Voltage – 14.60V
- Float Voltage – 13.50V
- Equalization Voltage – 14.40V
- Bulk Voltage Offset – 0.10V
- Absorption Duration – Adaptive
- Maximum Absorption Time – 6 hours – 30 minutes per 100Ah battery capacity
- Tail Current – 2.0A
- Equalization Settings
- Equalization Current Percentage – 25%
- Automatic Equalization – Disabled
- Equalization Stop Mode – Fixed Time
- Equalization Duration – 4 hours
- Manual Equalization – Select (Start Now)
- Voltage Temperature Compensation – Disabled
- Battery Limits – Low-Temperature Cutoff – Disabled
- Once the settings are loaded, they are automatically saved and active.
The charge controller settings have now been set, and you can activate the system to start charging the batteries.
Monitor the charging via the mobile application and use a voltmeter to verify the output voltage going into the battery bank.
Why Careful Recording Of Charge Controller Settings Are Important
Battery manufacturers will warrant their products for as much as ten years. Still, the burden of proof is on the owner or installer to show that the proper installation procedure and charge controller settings were used.
The quality and durability of modern Lithium Iron Phosphate (LiFePO4) batteries are so good that battery manufacturers use durability as a key selling point.
The high cost of these batteries is easily offset by the numerous benefits versus conventional flooded batteries.
Lithium Iron Phosphate Vs. Lead-Acid Batteries – Key Comparison
| LiFePO4 Battery | Lead-Acid Battery | |
| Battery Capacity | 100Ah 12V | 200Ah 12V |
| Depth of Discharge | 100% | 50% |
| Self-discharge rate | 2 to 3% per month | 33% per month |
| Battery Life | 3,000 to 5,000 cycles | 500 – 1,200 cycles |
| Weight | 31 lbs | 144 lbs |
| Warranty | 10 years | 3 years |
| Purchase Price | $1,000 | $450 |
| Battery Protection | Internal BMS | none |
A comparison between LiFePO4 (LFP) and Lead-Acid batteries gives the stark contrast in performance and durability between the two battery types.
Battery Capacity
The battery capacity of the LFP battery needs only be equal to half of that of the Lead-Acid battery as the allowable depth of discharge on an LFP battery is 100% versus only 50% on the Lead-Acid battery.
Only half the stated battery capacity can be used due to the deterioration of the electrolyte chemistry if the capacity falls below 50%. All batteries lose charge over time, even when not in use. The monthly discharge rate of the LFP is ten times less than the Lead-Acid battery.
Battery Cycles
LFP batteries also weigh 70% less than their equivalent Lead-Acid models and boast a manufacturer warranty that is typically seven years longer.
Although the upfront purchase cost of the LFP battery is about double that of a Lead-Acid battery, the benefits are numerous, and the cost per kWh is significantly better.
Battery Cost
Due to the significant upfront cost of batteries, the batteries must be charged under the optimal conditions as specified by the battery manufacturer. Batteries can constitute 50% of the total cost of an off-grid solar system.
Whether you are using low-cost Lead-Acid or expensive Lithium-Ion batteries, the charging settings are key to getting the optimal lifespan and value from the battery bank.
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