Winter Battery Care for Off-Grid Seasonal Cabins

Essential Tips for Lithium-Ion Battery Systems, like EG4

Solar production in winter can be as low as 10-20% of summer output in many regions across Canada. This is mostly due to shorter days with lower sun angles, and weather factors like snow cover.  That means off-grid cabins and homes require diligent energy management in the winter—especially when you plan to be away for long periods of time with no auto-start generator. 

Taking the time to set up your EG4 batteries and inverter for winter is no different than draining your water lines, turning off your propane, and putting antifreeze in your toilets. It can mean the difference between coming back to a functional system or facing costly replacements. Here are some practical tips to keep your batteries in tip top shape during the colder months to ensure they are ready to power up nicely upon your return:

1. Reduce Standby Power Draw
Idle consumption can gradually drain the batteries over time, especially when there’s minimal solar input during winter. Reducing unnecessary loads will extend the battery’s endurance. Most inverters, including the EG4 6000XP, has a standby consumption of about 50W.  At this consumption, 50W * 24hrs means you have to generate at least 1.2kWh of solar per day to compensate. If your solar system isn't big enough to generate that amount of power, turn off your system completely. Otherwise, turn off cirucuit breakers to all non essential loads. Lowering idle power requirements minimizes discharge and helps conserve your battery’s State of Charge (SOC) throughout the winter months. 

2. Set the Optimal Battery SOC Before You Leave
You can optimize battery health over extended periods of non-use by starting with the right State of Charge (SOC). Lithium iron phosphate (LiFePO₄) batteries, like EG4 models, are sensitive to extreme charge levels when left unused for weeks at a time.

a. Aim to store LiFePO₄ batteries at 60% SOC: This level is the “sweet spot” to prevent unnecessary chemical reactions that degrade battery cells. Before leaving, check that your batteries aren’t near full capacity or nearly drained. Extended periods at these extremes can strain the battery and reduce its lifespan.
b. To charge or discharge your battery, set the Discharge Cut-Off to 60%, turn off the solar switch, and run some heavier loads. Once at the target SOC, turn the entire system off. At this level, your battery may still discharge on it's own at a rate of about 1% per month.

3. Battery Charging Limits at Low Temps
EG4’s indoor and outdoor wall-mounted batteries come equipped with integrated heaters that activate automatically when the battery temperature hits 0°C. However, if solar power is insufficient to power both the heater and keep the battery above 20% SOC, the BMS will shut off the heater and prevent block charging. If temperatures drop below -20ºC the BMS will put the battery in temperature protection lockdown. Charging/discharging will automatically resume once temperatures warm up.

4. State of Charge Calibration: When lithium batteries are not cycled for long periods, the Battery Management System (BMS) can lose accuracy in calculating the SOC as a percent. This effect is common across all lithium batteries including cell phones and electric vehicles. For example, EV manufacturers generally advise charging only up to about 80% regularly to preserve battery health. However, because electric vehicles contain thousands of individual cells, the BMS will occasionally bring certain cells to 100% to recalibrate and maintain an accurate overall state of charge, ultimately extending the battery’s lifespan. Residential batteries require a bit more manual.  TIP: Before you leave, set the EG4 battery discharge control to "Volts" and Discharge Cut-Off to 52V in the winter.

5. Automatic Generator Start
Your EG4 Inverter has the ability to start and stop your generator automatically, but not all generators are capable of this.  Some can be retrofitted, but if it requires a mechanical choke, those moving parts can be unreliable. We understand that purchasing a new generator isn’t practical for most people, but whenever possible, we highly recommend using a good 240V inverter based generator that has 2-wire auto start capabilities.

Final Thoughts
By setting a minimum voltage level for storage, limiting extreme temperature exposure, reducing idle power draw, and using an auto-start backup generator, your battery system will be ready to welcome you back for well more than 10 years.

Have questions about specific settings or want more tips for optimizing off-grid battery care? Please reach out [email protected]