What Is Float Charging?
Batteries used for standby emergency power supply for uninterrupted power supply, telecommunication centers, and many more instances are always charged (floated) at a constant voltage.
Therefore, the question remains, ‘What is float charging?’.
Hopefully, the article below will help answer the question.
What Is Float Charging (Battery Maintainer)?
A battery used for standby emergency power supply for UPS and telecommunication devices is constantly floated at a constant voltage.
Normally the float value is between 2.2 and 2.3 V per cell, and the constant potential (CP) value is enough to keep the batteries fully charged while compensating for the power lost in the last discharge.
Further, the CP charge covers self-discharge processes occurring when the battery is idle.
Unlike a trickle charger, a float charger charges your device until it hits 100%, stops charging, and switches to standby mode.
However, over time as your battery dies, the float charger resumes to charge your device to 100% and switches to standby mode.
Thanks to the abovementioned features, you can leave your battery on a float charger for as long as you’d like.
Batteries function at the optimum rate when fully charged, and with the float charger, you can ensure your battery is always at 100%.
If you’re charging a fully charged battery at the rate of discharging, it is referred to as trickle charging.
The key difference between a trickle charger and a float charger is the circuit in the floating charger that prevents the battery from overcharging.
Battery Charger
How Does a Float Charger Work?
A float charger will continually charge your battery at a preset voltage regardless of the state of charge.
Also, the device isn’t disconnected from the charger.
There are a couple of factors to consider, such as power outages and optimum temperatures, to get the ideal voltage settings for your float charger.
Remember that capacity is also an important deciding factor in the voltage settings.
Some chargers might have a boost facility to help prepare the battery for future power shutdowns in case there’s frequent power shedding.
The charging conditions include the following:
- Charge Period: Continuous, regardless of the SOC
- Initial Current: Max 20 to 40% of the rated capacity
- Charging Type: Constant potential at 2.25 to 2.30V per cell, with temperature compensation of – 2mV to 3 mV per cell
Several manufacturers suggest charging lead acid batteries at temperatures ranging between 150C to 300C and that you don’t require any temperature compensation if the ideal temperature ranges between 00C to 400C.
However, you can consider a built-in temperature compensation to increase charge efficiency.
A temperature compensation of -2mV to -3mV per 0C per cell is ideal.
Below is a guide to temperature compensation.
| Temperature in 0C | Float Voltage | |
| Optimum | Maximum | |
| ≥ 49 | 12.8 | 13 |
| 44 – 48 | 12.9 | 13.2 |
| 38 – 43 | 13 | 13.3 |
| 32 – 37 | 13.1 | 13.4 |
| 27 – 31 | 13.2 | 13.5 |
| 21 – 26 | 13.4 | 13.7 |
| 16 – 20 | 13.55 | 13.85 |
| 10 – 15 | 13.7 | 14 |
| 5 – 9 | 13.9 | 14.2 |
| ≤ 4 | 14.2 | 14.5 |
Difference Between Float Charging and Boost Charging
| Boost Charging | Float Charging | |
| Functions | A float charger functions to maintain a battery’s voltage. Therefore, it charges a battery at a rate the same as its discharge and stops once it is at full charge. Charging resumes once there is a drop in battery voltage. | High charging rate( an initial maximum current of 30 to 40 percent of rated capacity in amperes), normally full load capacity of the charger. |
| Current limit | In an emergency if the AC supply crashes in an emergency, the battery will meet the DC load. Later the battery is discharged after serving the load and will need to boost charging to charge the battery at once if the battery is working with high load requirements. Also, if the AC fails while boost charging, the boost charger ensures no break in the DC supply to the load. Therefore, it’s a no-break power supply system. It doesn’t need to be constantly online. | If the AC supply crashes in an emergency, the battery will meet the DC load. Later the battery is discharged after serving the load and will need to boost charging to charge the battery at once if the battery is working with high load requirements. Also, if the AC fails while boost charging, the boost charger ensures no break in the DC supply to the load. Therefore, it’s a no-break power supply system. It doesn’t need to be constantly online. |
| Output voltage | High output voltage (14.4 to 14.7 v, A variation of ± 3 %) because the battery draws high amongst manufacturers, stipulating a high charger current. | It has a low output voltage (2.25 to 2.30 V, A variation of ± 1 %) |
| Application | Low Ife is no limit for float charge current | It is primarily used to avoid overcharging the battery. You can keep a device connected indefinitely without damaging its battery. It has a separate rectifier, transformer, and controls. |
Conclusion
Hopefully, after reading, you understand float charging and the difference between boost, float, and trickle charging.
For all your charging needs and any queries, feel free to contact Cloom Tech.