Choosing a charger for BUKNUWO 12.8V 100Ah batteries in series
Connecting LiFePO4 batteries in series raises the voltage of the bank while the capacity stays at 100Ah. The charger has to match that higher bank voltage. A charger intended for one 12.8V battery cannot charge an entire 2S, 3S, or 4S bank.
For BUKNUWO 12.8V 100Ah batteries, the charger voltage depends on the number of batteries in the series string:
|
Battery setup |
Nominal battery bank |
LiFePO4 charger voltage |
|
One battery |
12.8V 100Ah |
Approximately 14.6V |
|
2S |
25.6V 100Ah |
Approximately 29.2V |
|
3S |
38.4V 100Ah |
Approximately 43.8V |
|
4S |
51.2V 100Ah |
Approximately 58.4V |
Confirm these values, the permitted charging current, and the maximum series configuration in the manual for your exact battery model before choosing the charger.
Why charger voltage is higher than nominal voltage
The 12.8V rating describes the battery's nominal voltage. Charging requires a higher voltage. If one battery uses approximately 14.6V while charging, the charger voltage rises in proportion to the number of batteries in series.
For example, four batteries have a nominal bank voltage of 51.2V:
4 x 12.8V = 51.2V nominal
Their corresponding charging voltage is approximately:
4 x 14.6V = 58.4V
This is why a 48V-class LiFePO4 bank built from four 12.8V batteries normally uses a charger around 58.4V. Before building a 4S bank, verify that the specific BUKNUWO model supports four batteries in series.
Use a charger with a LiFePO4 CC/CV profile
Choose a charger designed for lithium iron phosphate batteries with the appropriate constant-current and constant-voltage, or CC/CV, charging profile.
Lead-acid chargers may use equalization or desulfation modes that are not suitable for LiFePO4 batteries. Use one only if those functions can be disabled and the charger can be configured correctly for the battery bank.
Choose the charging current for one battery
Series wiring increases voltage, but it does not increase the bank's amp-hour capacity or charging-current capability. The same current flows through every battery in the string.
A bank made from four 12.8V 100Ah batteries is 51.2V 100Ah, not 51.2V 400Ah. The charger output current must stay within the recommended charging-current limit of each battery and its BMS.
Do not select charging current by adding together the current limits of the batteries in a series string. Check the limit for the individual battery model and use that limit for the complete string.
Prepare the batteries before connecting them
Use batteries with the same model, capacity, and voltage. Their age and condition should be similar, and they should be at a similar state of charge (SOC).
Charging each battery individually to a similar state before assembling the series bank can reduce the chance that one battery reaches high-voltage protection before the others. Once the bank is assembled, use only a series arrangement approved for the battery model.
Charging the complete bank or one battery at a time
For routine charging, one properly matched LiFePO4 charger can be connected across the main positive and negative terminals of the complete series bank. A 2S bank uses approximately 29.2V, a 3S bank uses approximately 43.8V, and an approved 4S bank uses approximately 58.4V.
Individual charging can be useful when batteries in the series bank have become unbalanced. A 14.6V charger is suitable for one 12.8V battery, but it must not be connected across an entire 2S, 3S, or 4S bank.
Before charging, verify polarity and confirm that the charger voltage, current, and LiFePO4 profile match the complete bank. The specifications for the exact BUKNUWO model remain the final reference for supported series configurations and charging limits.
Frequently Asked Questions
What charger should I use for two BUKNUWO 12.8V 100Ah batteries in series?
Two batteries create a 25.6V 100Ah bank.
Use a LiFePO4 charger with a charging voltage around:29.2V
What charger should I use for three batteries in series?
Three batteries create:
38.4V 100Ah
Use approximately:43.8V LiFePO4 Charger
What charger should I use for four batteries in series?
Four batteries create:
51.2V 100Ah
Use approximately:58.4V LiFePO4 Charger
Can I use a 14.6V charger after connecting two batteries in series?
Not across the entire series bank.
A 14.6V charger is intended for a single 12.8V LiFePO4 battery. A 2S 25.6V bank requires a charger matched to the full bank voltage, approximately 29.2V.
Does series connection increase Ah?
No.
Four 12.8V 100Ah batteries in series create:
51.2V 100Ah
not 51.2V 400Ah.
Series increases voltage; parallel increases Ah capacity.