For a complete charge of a 12V LiFePO4 battery, a charger with a voltage ranging from 14V to 14.6V is necessary. If a charger with a lower voltage is used, it can still charge the battery, but it won't reach full 100% capacity.

Trickle charging is not acceptable for lithium batteries. Charging a LiFePO4 battery with a trickle charger not designed for this type of battery could lead to overcharging or damage due to the different charging requirements of lithium batteries compared to traditional lead-acid batteries.

The 14.6V 20Ah LiFePO4 battery charger is designed to charge LiFePO4 batteries. The low resistance in the Lithium cells allow the battery to accept the full output from the charger. With a constant 20A current, it takes around 100Ah/20A=5hrs to fully charge a 12V 100Ah LiFePO4 lithium battery.

Charging a battery to less than 100% and avoiding complete discharge always increases cell longevity. Similarly, maintaining operation within the 20%-80% state of charge (SoC) range will prolong the life of lithium batteries.

In the case of LiTime deep cycle lithium batteries, they can withstand over 4000 deep cycles at 100% Depth of Discharge (DOD), over 6000 cycles at 80% DOD, and more than 15,000 cycles at 60% DOD.

If the correct voltage limit is set for the LiFePO4 lithium ion battery you are charging, there should be no issue leaving a lithium ion battery on the charger overnight. LiTime Battery uses a LiFePO4 cell giving a nominal voltage of 12.8v and a fully charged voltage of 14.6v. A charger with 14.4-14.6v CC/CV output will do the job with consideration not to exceed roughly 1C maximum current output of the charger. As long as the CC/CV profile is used, the maximum voltage is at the correct level and the current is not excessive, you will achieve a safe and full charge on your battery.

For most applications, a charging time of 3-10 hours provides the longest lifespan for your LiFePO4 lithium battery. But if you have an application where you need rapid charging, you can choose a charger with a higher output current. For example, you could use a 40 amp charger with a 100Ah battery for a 2.5-hour charge time.

It depends on the voltages of your LiFePO4 lithium batteries. LiTime 14.6 volts charger is recommended for 12V LiFePO4 lithium batteries. And LiTime 29.2 volts charger is recommended for 24V LiFePO4 lithium batteries.

It is always important to match your charger to deliver the correct current and voltage for the LiFePO4 lithium battery you are charging. For example, you wouldn't use a 24V charger to charge a 12V LiFePO4 lithium battery. It's also recommended that you use a charger matched to your battery chemistry. Additionally, when charging a LiFePO4 lithium battery with a normal lead-acid charger, you would want to ensure that the charger does not have a desulfation mode or a dead battery mode.