Introduction

LiFePO4 chemistry lithium cells have become famous for various applications in recent years due to being one of the most robust and long-lasting battery chemistries available. They will last ten years or more if cared for correctly. Please take a moment to read these tips to ensure you get the most extended service from your battery investment.

Tip 1: Never overcharge/discharge a cell!

The most common causes for premature failure of LiFePO4 cells are overcharging and over-discharging. Even a single occurrence can cause permanent damage to the cell, and such misuse voids the warranty. A Battery protection System is required to ensure it is not possible for any cell in your pack to go outside its nominal operating voltage range,

In the case of LiFePO4 chemistry, the absolute maximum is 4.2V per cell. Though it is recommended that you charge to 3.5-3.6V per cell, there is less than 1% extra capacity between 3.5V and 4.2V.

Overcharging causes heating within a cell, and prolonged or extreme overcharging can cause a fire. EV Works Takes no responsibility for any damages caused by a battery fire.

Overcharging may occur as a result.

• Lack of a suitable battery protection system

• Faulty infective battery protection system

• incorrect installation of the battery protection system

EV Works takes no responsibility for choosing or using a battery protection system.

At the other end of the scale, over-discharging can also cause cell damage. The BMS must disconnect the load if any cells are approaching empty (less than 2.5V). Cells may suffer mild damage below 2.0V but are usually recoverable. However, cells that get driven to negative voltages are damaged beyond recovery.

On 12v batteries, the use of a low voltage cutoff takes the place of the BMS by preventing the overall battery voltage from going under 11.5v no cell damage should occur. On the other end, no cell should be overcharged to no more than 14.2v.

Tip 2: Clean your terminals before installation

The terminals on top of the batteries are made from aluminum and copper, which over time builds up an oxide layer when exposed to air. Before installing your cell interconnectors and BMS modules, clean the battery terminals thoroughly with a wire brush to remove oxidation. If using bare copper cell interconnectors, these should be cleaned too. Removing the oxide layer will significantly improve conduction and reduce heat buildup at the terminal. (In extreme cases, heat buildup on terminals due to poor conduction has been known to melt the plastic around the airports and damage BMS modules!)

Tip 3: Use the proper terminal mounting hardware

Winston cells using M8 terminals (90Ah and up) should use 20mm long bolts. Cells with M6 terminals (60Ah and under) should use 15mm bolts. If in doubt, measure the thread depth in your cells and ensure that the bolts will get close to but not hit the bottom of the hole. You should have a spring washer, a flat washer, and the cell interconnector from top to bottom.

A week or so after installation, check that all your terminal bolts are still tight. Loose terminal bolts can cause high-resistance connections, robbing your EV of power and causing undue heat generation.

Tip 4: Charge frequently and shallower cycles

With lithium batteries, you will get longer cell life if you avoid intense discharges. We recommend sticking to 70-80% DoD (Depth of Discharge) maximum except emergencies.

Swollen Cells

Swelling will only occur if a cell has been over-discharged or, in some cases, overcharged. Bump does not necessarily mean the cell is no longer usable though it will likely lose some capacity.