Carbon Pile Load Testing a Shorai Battery
One of the most reliable methods of testing the voltage under load performance of the Shorai LFX battery is with an adjustable carbon pile load tester. The tester uses carbon stacks to simulate the draw a battery experiences under starting conditions. A battery with good starting performance will show a higher voltage measurement under load.
Most Carbon pile load testers modify the amount of resistance by twisting a knob that is connected to a threaded post. Rotating the knob clockwise will compress the carbon discs together to lower the circuit resistance and permits higher current flow. Unscrewing the knob counterclockwise will reduce the number of carbon discs that are in the stack which increases the circuit resistance to lower the flow of the current (Amps). If the knob is unscrewed completely, it will disconnect the circuit, and result in no current flow.
Before testing the voltage under load, your battery must be fully charged to 14.4V. This voltage can easily be achieved by using a balance type charger like the Shorai BMS01. If the battery has been deeply discharged below a resting voltage of 12.86V (~20% SOC), it is important to balance charge the battery before load testing. If the LFX battery is over-discharged, it can be recovered by cycling the battery between the load test and a slow charge saturation/cell balance process.
The Battery Council International testing protocol states that a battery should be loaded with 1/2 of its rated CCA for a period of 15 seconds. For example, the Shorai LFX14L2-BS12 battery has a CCA rating of 210 Amps, so it should be tested at 105 Amps for 15 seconds. During the test, Current and voltage levels of the battery are measured. The battery passes the voltage under load test if the voltage remains above 9.6 volts at 50 degrees F or higher. Lithium battery performance will increase as the case becomes warmer. In colder temperatures, a second load test will deliver a better representation of how the battery will perform under starting conditions.
When testing a Shorai LFX battery, it is important to take appropriate safety measures:
1. Always wear safety glasses and protective clothing.
2. Testing should take place away from flammable materials.
3. The testing area should be in an open space with good ventilation and/or an exhaust fan.
4. In the case of a load tester or battery malfunction, pouring a bucket of sand over the test area will control a thermal event.
5. Stop testing if the test battery's temperature exceeds 140 degrees F, or if the voltage drops below 9.6V.