Lithium batteries charge much faster than sealed lead acid (SLA) batteries. You might wonder how much quicker and what it means for you as an end user. Can a regular SLA charger be used to charge a lithium battery?
Charging Absorption Differences between SLA and Lithium
Charging an SLA battery can be time-consuming. For example, a 12-volt, 20-amp-hour deep cycle SLA battery took about 6.5 hours to reach a full charge, while a 12.8-volt 20-amp hour lithium iron phosphate battery achieved full charge in just over 2.5 hours.
A charging cycle for SLA batteries consists of three stages: constant current, constant voltage, and float charging.
In the constant current stage, a 20Ah deep cycle SLA battery reaches 80% State of Charge (SOC). The constant voltage stage completes the remaining 20%, taking about 50% of the total charging time.
Finally, a float charge is maintained to prevent over-discharging from self-discharge.
A lithium charging cycle consists of two stages: constant current and constant voltage.
In the constant current stage, the battery reaches 99% capacity (SOC of 99%) in 96% of the charge time. A 12.8V 20AH lithium battery nearly fully charges in under two hours. The constant voltage stage adds just 1%, taking only 4% of the charge time.
Additionally, lithium batteries don’t need float charges due to their low self-discharge rate.
Lithium Absorption on an SLA Charging Profile
When considering a lithium battery as a drop-in replacement for an SLA battery with an SLA charger, it’s important to understand the potential effects.
Charging a lithium battery on an SLA charger at 13.8V allows it to reach 95% capacity in about 90% of the charging time, while at 14.6V, it reaches 99% in 95% of the time.
Charging a lithium battery on an SLA profile increases the time from about 2.5 hours (using a lithium profile) to 5 hours. However, as shown in the chart below, the lithium battery still charges faster than an equivalent SLA battery on an SLA profile.
You can use lithium batteries in an SLA charger if it lacks de-sulfation mode or dead battery detection features. De-sulfation pulses can damage or shut down the lithium battery’s BMS, and dead battery detectors might misinterpret a protected lithium battery as dead.
SLA chargers typically operate at voltages between 13.8V and 14.7V, allowing lithium batteries to charge faster than SLAs. Lithium batteries reach full charge quicker and achieve higher states of charge within this voltage range.
Will A Normal SLA Charger Damage A Lithium Battery?
Using an SLA charger on a lithium battery can be acceptable, especially if it lacks a de-sulfate mode.
In daily cycling applications, degradation is unlikely, though the lithium battery may not reach full capacity (e. g., a 20AH lithium battery might not achieve 20 amps with an SLA charger). If infrequently used and left on float for extended periods, it’s best to disconnect the battery before storage.
Lithium batteries perform optimally at 50% state of charge (SOC). Holo Battery recommends using chargers suited for each battery’s chemistry and checking lithium batteries for low voltage every 3-4 months.
