How To Charging Deep Cycle Custom Lithium Iron Phosphate RV Battery Packs

How To Charging Deep Cycle Custom Lithium Iron Phosphate RV Battery Packs 

When shopping for a battery, we often equate the quality of a unit with the brand we buy. A battery from a bigger, well-known brand will guarantee better wear. 

Not always! 

Maintenance and handling come to play an essential role in extending the life of your battery too. This includes the methods of charging and storing the power cells. 

Yes! You heard it right. 

Compared to lead-acid models, lithium-ion chemistries are low maintenance. In this article, we talk about charging lithium iron phosphate batteries. 

A Compatible Charger 

Experts typically recommend choosing a charger designed for a LiFePO4 chemistry. This is because the voltage limits vary according to the battery type. 

You can also use the charger intended for lead acid units; however, that depends on whether it is sealed or flooded.Sealed lead acid profiles such as AGM and GEL models operate within the same voltage limit and hence are safe to use. However, chargers for flooded lead acid batteries can be problematic. They average a higher voltage limit which impacts the function of the Battery Management System (BMS).The higher voltage limit sends the system into protection mode. 

In the end, the charger should match the battery for its voltage and current requirements. The battery specifications and the charger instructions provided by the battery manufacturer are a good place to start. 

Charge Profile 

The two charging stages common to a lead acid battery and a lithium-iron phosphate battery are the constant current and the constant voltage. The major difference is that the higher rate of charge that can be applied to a lithium-iron phosphate battery reduces the overall charge time drastically. 

The constant current stage charges the battery to 60%-70% of its capacity. It takes about an hour for a LiFePO4 battery as against four hours in a lead acid variant. The second stage, the shift to constant voltage, requires under an hour to bring the battery to its full capacity. This is in contrast with the 6-7 hours required by a lead acid battery. 

Thus, considering the final figures, a lithium-iron battery can be charged to 100% SOC in 2-3 hours, allowing one to repeat the charge and discharge cycles several times a day. 

Lithium-iron phosphate cells do not need a float charge to preserve a full capacity. Given the low self discharge rate of lithium-ion chemistries, they can function at full capacity after sitting unused for as many as 6 months. 

Storage 

One needn't worry about the battery getting damaged as a result of being stored at a partial SOC. In fact, lithium iron phosphate batteries must not be stored at full charge. 50% is the ideal state of charge for storage for the short and long term storage. The latter however will require some maintenance charging. This includes discharging the battery completely and recharging it back to 50% SOC every six months. 

Overcharging impacts battery performance. While a lithium-iron phosphate battery can tolerate an overcharge of up to 0.7V above the voltage threshold, it is best avoided as it breaks down the electrolytes. 

Follow these tips to charge your lithium-iron phosphate battery to boost performance and get the best out of your investment.