Winter Battery Maintenance Tips

As temperatures begin to drop in winter, special precautions must be taken to store, preserve and/or keep batteries in operation through the winter season. Each situation may be different.

·        Dry charged batteries at the John Deere dealer – John Deere dry charged batteries need no further concerns until activated with acid.

·        Recently activated or already “wet charged” batteries - Wet batteries require a completely different care through the winter season since they will become perishable items unless the precautions listed below are taken.  However, we must first know what is expected from the battery through the cold season.  Will the battery mounted on the vehicle be used to start it or is it in the vehicle for seasonal storage only?

Batteries in vehicles used for starting during cold season need to go into the season as fully charged as possible to be able to crank a cold engine and to keep them from freezing.

Batteries below 70% state of charge have greater difficulties in starting a cold engine. This is because batteries produce less energy at lower temperatures while attempting to crank a cold engine with more viscous oil, drag, etc.

The output of the battery decreases at lower temperatures and lower states of charge (SOC) as seen on the graph below.

Example:   A 100% SOC battery at°F will produce 100% of its cranking ability but at 50% SOC at the same 0°F temperature will only produce 50% of its rated capacity.  Also noticeable is that warmer batteries can have greater outputs.  Example:  A 50% SOC warmer battery at 60°F can equal the output of a fully charged battery at 0 °F.

·         Important Note: Avoid battery freeze ups

There is danger of electrolyte freezing due to the fact that the electrolyte in lead-acid batteries goes more and more towards water as the battery gets more and more discharged.

The graph below shows the dramatic difference:  A fully charged battery will not freeze until the temperature drops below -80°F while a 0% charged battery may freeze at +5°F.

A good quality battery charger must be used to prevent batteries from freezing by bringing the cell specific gravities above 1.265 SG as a minimum.  In the absence of a hydrometer, a simple voltmeter can tell if the battery is charged or not.

The picture below shows the typical rested voltage values for a 12 volt battery open circuit voltage (OCV) and what it means.

A typical voltage on a rested (8 hours or more without charge/discharge) and fully charged battery is expected to be about 12.60V-12.80V.  Lower voltages indicate successive levels of discharge as shown.  Higher voltages than 12.8V may indicate a temporary surface charge or higher charging voltages imposed on the battery as indicated.

Batteries installed in a vehicle for storage during the cold season have similar concerns and the same precautions apply.

·         Make sure that the battery being placed in storage is fully charged prior to being put away, especially if the vehicle will be in an unheated area.

·         Batteries self-discharge over time but lower temperatures will slow this process. This means that contrary to general belief, it is beneficial to store batteries in low temperature conditions.

·         Because the installed battery will more likely be discharged by the electrical and electronic components over an extended time, disconnecting the negative ground cable or using a DC disconnect if available is highly recommended. This connection must be properly restored at the end of the storage season.

·         The use of a trickle charger left on the battery is a good idea but unnecessary if the battery is already charged and the ground cable is not connected. A small trickle charger will however compensate for external vehicle accessories discharging the battery if the battery is left connected.

Following these practices will insure a successful start every time for any kind of vehicle and will prolong the life of the battery.