Whether you are preparing your vehicle after seasonal storage or simply keeping your vehicle in tip top shape, your battery is a critical part of your charging and starting system and needs attention. At a minimum the battery should be inspected, connections checked and battery fully charged.

Maintenance Actions

  1. Visually inspect the battery for signs of damage; plastic case is cracked, warped or swollen. If the battery is damaged, do not attempt to charge or start your vehicle. The battery needs to be replaced.
  2. Verify battery terminals are clean and terminal screws are properly secured (torque to specification [45in-lbs] per the installation & maintenance manual).
  3. Measure the voltage at the terminals.

• If at or above 13.28V- nothing needs to be done.

• If below 13.28V, the battery needs to be charged prior to an engine start attempt with an appropriate charger. Jump starting your battery in this situation is not recommended for it can damage it. Use a plug-in charger to safely and slowly bring the voltage back up to the appropriate level. Here is a link with details about charging the battery: How to Charge an EarthX Lithium Battery – EarthX Batteries

• If below 10.5V, it is possible the battery (or cell) is damaged. Only use the EarthX approved Optimate charger to slowly recharge the battery from this over-discharged state. Do not force the battery to accept a charge as it can result in cell rupture, release of flammable vapors, and smoke/fire. If successfully charged with the Optimate charger (up to 14V), remove the charger, and let the battery sit disconnected from the vehicle for 24 hours. If the battery self-drains to below 13.3V within 24 hours, it should be replaced.

  1. After fully charging the battery with an appropriate charger the voltage should be greater than 13.9V (if measured at end of charge cycle). Within two days the voltage may drop but still be 13.5V or more. And even a week later it should still be greater than 13.3V. If the battery is below these thresholds, the battery is not “holding a charge” and should be replaced.

Even with proper care and maintenance, all batteries will lose cranking amps and capacity over time. The cranking power (amps) can be judged by how fast it spins the engine, but the capacity requires a dedicated test.

Capacity Test

The most accurate way to determine the service life of your battery is to verify the battery capacity. Annually measure the batteries capacity and compare this to original capacity. Once the capacity is less than 80%, it is time to replace the battery. A battery with greater than 80% of its original “rated” capacity is consider fit for continued service. Example, the original battery capacity is 16Ah. Once the battery measures 80% of this capacity (16Ah * .8 = 12.8AH) it is time to replace it. (general rule of thumb).

There are two test methods that can be used to measure the capacity of your battery. The first method given below only requires your vehicle, a timer and a volt-meter.

Test Method #1 (with timer and voltmeter):

a. Fully charge the battery with an appropriate charger.

b. Turn on all electrical loads and start a timer. The same load must be used in subsequent years for accuracy.

c. Record the time (annual time) to drain the battery to 12.0V.

d. Plug information into this formula:

(annual time/ original time) *100= % of capacity remaining

Example: original time = 90 minutes, annual time is 80 minutes. (80/90)*100 = 88.89%
Greater than 80%= good battery
Less than 80%= time to replace.

e. Fully charge the battery with an appropriate charger.

Test Method #2 (with timer and DC current meter):

a. Fully charge the battery with an appropriate charger.

b. Turn on all electrical loads and start a timer. The same load must be used in subsequent years for accuracy.

c. Measure and record the battery’s discharge amps using a DC clamp-on current meter at the positive terminal of the battery.

d. Using the measured amps in the previous step and the battery’s nameplate rated capacity (in Ah), calculate the time to discharge the battery to 80%.

Time to Discharge 80% (Hours) =
(Rated Capacity in Ah * .8) / Measured Discharge Amps

For Example (16 Ah Rated Capacity, 5 amp measured discharge rate)

Time to Discharge 80% = (16 * .8) / 5 = 2.56 hours

e. Terminate the test after the number of hours calculated in the previous step has expired or if the battery is over-discharged (shuts off discharge current). If the battery is still supplying power at the termination of the test, then the battery’s capacity is greater than 80%. If the battery’s capacity is greater than 80% of it’s rated or capable of supporting the aircraft’s emergency load for the required amount of time, then the battery has passed the test.

f. Fully charge the battery with an appropriate charger.


Source1: EarthX Lithium Battery User’s Manual
Application Note AN-2003 – Rev A