You can use a lead-acid charger to charge lithium batteries as long as you can set the maximum voltage of the charger and as long as the charger does not have the automatic equalization mode activated. So can you use lithium in an SLA charger? Yes, as long as that charger doesn't have a desulfation mode or a dead battery detector. For reference, the desulfation function of SLA chargers is to recover an overdischarged SLA battery by using low amperes and high-voltage pulses. This desulfation mode can cause the BMS of a lithium battery to turn off the battery or even damage it due to the high-voltage pulse.
In addition, the dead battery detector may interpret a lithium battery that has gone into protection mode as a dead battery and may not be able to unprotect the lithium battery. To fully charge a 12 V LiFePO4 battery, a charger with a voltage of 14 V to 14.6 V is required. Most AGM battery chargers are within that range and would be compatible with Canbat lithium batteries. If you have a charger with a lower voltage, it may continue to charge the battery, but it won't charge it to 100%.
A charger with a higher voltage would not charge the battery and the BMS would go into protection mode due to its high-voltage disconnect function. Although many AGM battery chargers are compatible with LiFePO4, wet or flooded cell battery chargers are not compatible, as they are typically charged at a higher voltage. The charging time will increase when charging lithium in an SLA profile, going from about 2.5 hours with the 20 AH lithium battery charged with a previous lithium profile to about 5 hours with the same battery in the SLA profile. You can charge your LiFePO4 batteries after each use or when up to 80% DOD (20% SOC) have been discharged.
Dividing 100 Ah by 20 A would give you 5, and that's the number of hours needed to recharge the battery from 0% to 100%. When you charge a lithium battery in an SLA charger with a massive charge of 13.8 V (the typical floating voltage of SLA and a common voltage for simple chargers), it reaches 95% of its capacity in approximately 90% of the total charging time. At the higher end of the voltage range, used in most AGM batteries, the lithium battery will be 100% charged. If you have a 23 Ah LiFePO4 battery and you use a 23 A lithium charger, it will take an hour to recharge the battery from 0% to 100%.
Research has shown that you can extend the life of lithium batteries if you avoid charging them to 100%; however, the effect only has a pronounced impact if they are charged to less than 80%. The 48 V Canbat LiFePO4 batteries support up to 14 units in parallel, as they are designed for larger projects. However, the 12.8 volt, 20 amp per hour lithium iron phosphate battery took just over 2.5 hours to reach 100% SOC. If you use a more common LiFePO4 battery charger, such as a 5 A lithium charger, it will take about 4.6 hours to recharge the 23 Ah lithium battery from 0% to 100%.
At the lower end of the voltage range, the lithium battery will continue to reach 95% SOC faster than the SLA battery will reach 80% SOC. To learn more about the lithium and SLA charging profiles of lithium and SLA batteries, visit this blog post for more information. Installing a DC to DC charger is the recommended option when it comes to charging lithium with an alternator.
