Returning to work after the holiday break can be a bit of a letdown, but it’s even more frustrating if your fleet of vehicles won’t start. Every year, this is a common issue. The good news is that with some simple preventative maintenance, it’s entirely avoidable.

Why it happens

Modern light vehicles often come with smaller batteries - around 45Ahc - compared to the 90–100Ah batteries found in larger vehicles. Manufacturers are also incorporating “smart charging” features, which reduce charge rates to improve fuel efficiency. While great for economy, it means batteries need longer drives to fully recharge.

If your fleet is going to be unused for two weeks or more, you could face starting issues when you return. Batteries that are already partially discharged or below optimum capacity are particularly vulnerable.

Fleet Managers may worry that telematics devices can drain a vehicle’s 12-volt battery. In reality, these devices are engineered to draw very low current, and the real causes of 12-volt battery drain can be something else.

How to prevent a flat battery over the break

1. Charge before you leave: Ensure batteries are fully charged before the break. If possible, top up older batteries to give them the best chance of holding a charge.
2. Disconnect batteries if possible: For vehicles that will be idle for an extended period, work with your mechanics to disconnect the batteries. This guarantees they won’t drain while parked.
3. Check master switches: If vehicles have a master switch, make sure it’s turned off. An auto electrician can assist if you’re unsure.
4. Prepare for quick recovery: Have a mechanic or auto electrician on standby in the new year for jump starts. Investing in a jump start pack can save time and hassle.
5. Use smart power management: Devices like the Smartrak Timed Power-Off Harness can prevent electronics from drawing unnecessary power, disconnecting hardware automatically after a set period.

For electric vehicles (EVs)

EVs have different considerations compared with traditional internal combustion vehicles. Even when not used, both the high-voltage traction battery (the main battery that powers the motor) and the 12‑volt auxiliary battery (which powers lights, infotainment, telematics, and other electronics) can slowly lose charge over time.

To avoid issues when returning to work:

• Keep the traction battery partially charged: Most EV manufacturers recommend storing the vehicle with the high-voltage traction battery at 50–80% charge if it will be unused for extended periods. Avoid leaving it fully charged or fully depleted, as this can reduce long-term battery health.
• Maintain the 12‑volt battery if the vehicle sits idle: The 12‑volt auxiliary battery can discharge even when the car is off, due to electronic systems drawing power. Consider using a small trickle charger or battery maintainer to prevent it going flat.
• Use a smart charger for the traction battery if possible: Timed or programmable chargers help manage charge levels and prevent overcharging, while also protecting battery health over long idle periods.
• Check for software updates: Many EVs include battery-management software that helps preserve both the traction and 12‑volt batteries. Ensuring the latest updates are installed before long storage periods can prevent unexpected battery drain.

Start the New Year charged and ready to go

By following these steps, you can ensure your Internal Combustion Engine vehicles and EVs (all vehicles in your fleet) are ready to go in the new year, without frustrating flat batteries slowing you down.