How to Charge a Lithium Battery?

how to char a lithium battery

Charging and discharging a battery is a chemical reaction, but lithium-ion is claimed to be an exception. Lithium-ion batteries are subject to many characteristics such as overvoltage, undervoltage, overcharge and discharge currents, thermal runaway and cell voltage imbalance. One of the most important factors is cell imbalance, which changes the voltage of each cell in the pack over time, thereby rapidly reducing battery capacity.

You can charge the lithium iron phosphate battery at any time, just like a cell phone. Unlike lead-acid batteries, lithium iron phosphate batteries do not break down in a partially charged state, so you don't have to worry about charging them immediately after use. They also have no memory effect, so you don't have to fully deplete them before charging.

The ideal way to charge LiFePO4 batteries is to use a lithium iron phosphate charger, as it will be programmed using the proper voltage limits. Most lead-acid battery chargers do this job very well.

AGM and GEL charging curves are usually within the voltage limits of LiFePO4 batteries. Wet lead-acid battery chargers tend to have higher voltage limits, which may cause the battery management system (BMS) to go into protection mode. This will not damage the battery; however, it may cause a fault code to appear on the charger display.

For safe operation, lithium-ion battery cell level and pack level control variables need to be accurately maintained. These control variables are monitored and protected by the Battery Management System (BMS).

The BMS is an electronic device that acts as the brain of the battery pack, monitoring output and protecting the battery from serious damage. This includes temperature, voltage and current monitoring, fault prediction or prevention, and data collection via communication protocols for battery parameter analysis. Battery State of Charge (SOC) is the percentage of energy currently stored in the battery versus the nominal capacity of the battery. One of the important key functions of the BMS is battery balancing.

Of course, you can also use solar panels to charge your LiFePO4 battery, but be sure to choose the right controller, both PWM and MPPT controllers will work.

Since the SLA Target 12V panel produces about 18V at full solar load, such a 12v panel will provide sufficient voltage under all actual light conditions.

If you do not have a controller, you can also connect the battery to the solar panel. The internal BMS will protect the battery in most cases.

How to Choose Lithium Battery Charger?

Lithium batteries are not like lead-acid batteries, and not all battery chargers are the same. A 12v lithium battery fully charged to 100% will maintain a voltage of about 13.3-13.4v. Its lead-acid cousin is about 12.6-12.7v.

A 20% capacity LiPo battery will hold about 13V and its lead-acid cousin will hold about 11.8v at the same capacity.

So if you charge your Li-ion battery with a lead-acid charger, it may not be fully charged.

You can use an AC to DC lead-acid charger powered by the mains because charging efficiency and duration are less important and it can't have automatic desulphation or equalization mode. If so, do not use it as there is a high risk of damaging the battery or cells. This will significantly shorten the battery life. If it has a simple high capacity/absorption/float mode, then it can be used to charge the battery, but it must be disconnected after charging and not in trickle charge/maintenance mode. It must also have a maximum output voltage of 13v-14.5V. When it comes to DC-DC chargers and solar controllers, you must change them to LiFePO4 specific models.

How to Use the Charger Properly?

Most LiFePO4 chargers have different charging modes, set it like this:
battery type: LiFePO4
battery cells: 4S 
C (current): 10A (e.g. 0.3C for 30ah Battery)

Set the charger’s output current to no greater than ‘0.7C’ rating of the battery. A recommended charging current no greater than 0.5C will help to maximize the lifespan of the LifePO4 battery.

Battery Bank Charging/ Separate Charging

Our batteries have a voltage limit for battery BMS modules, allowing up to 4 batteries in series. And there is no parallel limit.

Charging connected cells together may result in one cell being full and the other not, as the BMS will cut off the current when it detects a high voltage when a single is full.

Example. 2*30ah batteries arrive at one customer unfilled, with different capacities and actual voltages when they enter storage, one at 13.2v (70%) and one at 12.9v (20%).

The customer put them in series and charged them together with a suitable charger. After a while, the monitor detected that one of the batteries had 13.6v when it showed full capacity status, the charging process was completed and the charger cut off the current to the battery pack to avoid overcharging.

However, in reality, the other 12.9v battery was not fully charged after the cutoff, so the customer found that the capacity did not reach his expectation when using the battery pack because the total output power was limited by the low voltage battery. .

Therefore, we recommend you to purchase a charge balancer. Or just charge it separately.

If you find that the total capacity of the battery pack is not as high as it should be when the pack is fully charged, you can disconnect the batteries and test the voltage of each battery to verify that some of the batteries are not fully charged. Process.

Can I Charge Lithium Batteries in the Cold?

Lithium batteries rely on chemical reactions to work, and cold can slow or even prevent these reactions from occurring. Unfortunately, charging them in cold temperatures is not as effective as in normal weather conditions, because the ions that provide the charge do not move properly in cold weather. There is one hard and fast rule: To prevent irreversible damage to the battery, do not charge it at temperatures below freezing (0°C or 32°F) without reducing the charging current. This is because lithium batteries can become lithium-plated on the anode when charged at high speed at low temperatures. This can lead to internal short circuit and failure of the battery.

Can I Leave Lithium Battery on Charging All the Time?

For lithium batteries with low maintenance charging programs and battery management systems, this is much better than letting them discharge for long periods of time. Whether it's a dedicated charger or a regular charger, under normal circumstances it has a charge cut-off voltage, which means it stops charging when it reaches a certain number of volts. The same is true for solar panel controllers, which can also be configured in this way. The solar panel is connected directly to the charge. If there is a problem with the BMS, it could be an overcharge.

Can I Use My Vehicle Alternator to Charge a Lithium Battery?

Yes, but not necessarily fully charged, as most alternators are tuned for the lower voltage requirements of vehicle lead/acid batteries (about 13.9-v). Lithium batteries require 14.4 to 14.6 volts to be fully charged. That said, you can get up to about 70% of the charge, depending on the depth of discharge and distance traveled when charging from the vehicle alternator.

It is best to use a DC to DC charger to help protect and extend the life of the RV battery and not overload the vehicle alternator. Most DC to DC charger models have the same three-stage charging mode that will safely charge the battery and prevent alternator damage.

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