How to store your solar batteries in winter: Complete Guide 2025

Winterizing solar batteries is crucial to maintaining the performance and longevity of your solar kit. With the onset of winter temperatures, your lithium batteries need special care to maintain optimum efficiency and avoid premature damage.

Why is winterizing solar batteries essential?

Solar batteries, whether lithium or lead-acid, undergo considerable stress during cold spells. Low temperatures directly affect their storage capacity, charging efficiency and overall lifespan. A poorly winterized solar battery can lose up to 30% of its capacity, reducing its lifespan by several years.

The risks of poor winter storage

• Reduced capacity: up to 40% loss of performance in very cold weather
• Premature degradation: crystallization of electrolytes in lead-acid batteries
• Charging problems: Difficulty recharging lithium batteries at temperatures below 0°C.
• Additional costs: Early replacement requires new investment

Types of solar batteries and specific wintering requirements

LiFePO4 lithium batteries: the benchmark technology

LiFePO4 lithium batteries, like the Delong Top Energy 5.12kWh available from Wattuneed, offer excellent resistance to cold, but require special precautions:

"The Rousseau family, owners of a solar installation with Pylontech batteries for 3 years, have seen a 25% increase in the life of their batteries thanks to methodical winterization in their heated garage."

Lead-acid batteries: extra precautions

Although less efficient than lithium batteries, lead-acid batteries are still used in some installations. Winterizing them requires special care, as they are more sensitive to frost and sulfation.

Practical guide: How to winterize your solar batteries effectively

Step 1: Pre-winter preparation

1. Check state of charge: Charge your solar batteries to 60-70% of their maximum capacity.
2. Clean terminals: Remove all traces of corrosion or oxidation.
3. Check connections: Tighten all connections and check for leaks.
4. Performance test: Measure voltage and actual capacity

Step 2: Choosing a storage location

The ideal winter storage location for your solar battery should meet the following criteria:

• Stable temperature: preferably between 10°C and 20°C
• Dry environment: Relative humidity below 60%.
• Adequate ventilation: Air circulation to avoid condensation
• Freeze protection: Never negative temperature for lead batteries

Recommended storage solutions :

• Heated or semi-heated garage
• Dry, temperate cellar
• Insulated machine room
• Garden shed with thermal insulation

Step 3: Winter maintenance

A well-maintained solar kit over winter guarantees optimum performance when the sun comes back out:

Mandatory monthly checks

1. Voltage check: Measure the open-circuit voltage of each solar battery
2. Maintenance charging: Recharge if voltage falls below 50% of capacity
3. Visual inspection: look for signs of corrosion, leaks or swelling
4. Temperature control: Monitor ambient conditions in the storage room

"Our professional customer, Mr. Beaumont, a photovoltaic installer, recommends a fortnightly check for critical installations and confirms that this method achieves the 15-year lifespan advertised on Delong batteries."

Comparison of storage solutions by technology

Optimization of the entire system during winter

Hybrid inverter and battery configuration

Your solar inverter plays a crucial role in the winter management of your solar batteries. Wattuneed hybrid inverters, compatible with all major battery brands (Victron, Deye, WKS), offer advanced thermal management functions:

• Intelligent charge management: automatic temperature adaptation
• Frost protection: automatic charge shutdown below 0°C
• Programmed equalization: Preventive cell maintenance
• Remote monitoring: Monitoring via mobile application

Recommendations by user profile

Individual beginners (3-6kWh system)

Recommended configuration :

• Battery: Delong Top Energy 5,12kWh (968€)
• Inverter: Deye 5kVA hybrid
• Storage: Garage or tempered cellar
• Maintenance: Simple monthly check

Professional installation (10-20kWh)

Optimized configuration :

• Batteries: 1 x Delong Top Energy 15 kW/hseveralin parallel
• Inverter: 10kVA three-phase system
• Storage: Air-conditioned technical room
• Maintenance: Bi-monthly professional protocol

Expert/Installer (20kWh+)

High-performance solution :

• Batteries: Pylontech US5000 scalable modular system
• Inverter: Redundant architecture with multiple hybrid inverters
• Storage: Dedicated infrastructure with thermal regulation
• Maintenance: Real-time monitoring and predictive maintenance

Economic analysis and return on investment

Optimal winterization costs

Investment in high-quality winterization represents 2-5% of the total cost of your solar kit, but can extend the life of your solar batteries by 30-50%:

• Storage room insulation: €200-500
• Auxiliary heating system: €150-300
• Monitoring equipment: €100-250
• Preventive maintenance: 50-100€/year

Long-term profitability

"The case study of Lefebvre & Associés, a company that has been using our solutions for 5 years, shows savings of €2,800 over 10 years thanks to methodical winterization of their 15kWh Delong batteries."

Restart after winter

Spring restart protocol

Restarting your solar kit after wintering follows a rigorous procedure:

1. Complete inspection: visual check of all components
2. Connection test: Check for electrical continuity, ensuring that all connections are tight and free of play.
3. Performance measurement: Capacity and efficiency test, ideally checking error logs, state of health if available in logs
4. Progressive load: Gradual return to rated capacity
5. Commissioning: Reconnect to solar panel andsolar inverter

Warning signals to watch out for

Certain indicators may reveal problems during wintering:

• Abnormally low voltage: Possible excessive self-discharge
• Extended charging time: Capacity degradation
• Unusual heating: Internal cell problem
• Cell imbalance: BMS recalibration required

2025 trends and innovations

The solar battery market is evolving rapidly, with innovations that simplify wintering:

Emerging technologies

• Adaptive BMS: Automatic management according to ambient temperature
• Integrated heating: pre-heating systems before charging
• Advanced chemistries: New cold-resistant LiFePO4 compositions
• IoT monitoring : Connected monitoring and preventive alerts

Price trends in Belgium and France

2025 tariffs show stabilization after the 2024 drop:

• LiFePO4 batteries: €200-300/kWh (stable compared with 2024)
• Thermal management systems: 15% decrease thanks to volumes
• Maintenance services: Professionalization of the sector

FAQ - Frequently asked questions about wintering solar batteries

Can solar batteries be left outside in winter?

We strongly advise against leaving solar batteries outside in winter. Sub-zero temperatures can irreversibly damage the cells, especially in the case of lead-acid batteries. Lithium batteries are more resistant, but their performance drops drastically below 0°C.

How often should I check my batteries in winter?

A monthly check is recommended for private customers, and fortnightly for professional installations. This check includes voltage measurement, visual inspection and control of the storage environment.

Should batteries be completely disconnected in winter?

No, it's best to maintain a light connection to thehybrid inverter to allow for automatic maintenance charging. Total disconnection can lead to damaging deep discharge.

How much does professional winterization cost?

The cost varies according to the size of the system: €100-200 for a 5kWh residential system, €300-500 for a 20kWh system. This includes preparation, optimal storage and return to service.

Do new batteries need to be winterized?

Yes, even new solar batteries benefit from proper winterization. This practice from the very first year establishes good habits and maximizes battery life from the outset.

Wattuneed services and support

At Wattuneed, we support our customers at every stage of their solar project, including the optimum winterization of their solar batteries. Our technical expertise and comprehensive product range guarantee solutions tailored to every need.

Our services include :

• Customized study of your existing installation
• Winter optimization recommendations
• Preventive maintenance training
• Technical telephone support
• Extended warranties on our lithium batteries

Contact us today for a free diagnosis of your installation and personalized winterization advice. Our experts will work with you to maximize the profitability and lifespan of your solar kit.

Contact information :
Wattuneed
Rue Henripré 12
4821 Andrimont
Belgium
Phone : +32 87 45 00 34
Email: info@wattuneed.com

Investing in quality winter storage for your solar batteries guarantees the long-term performance and profitability of your photovoltaic installation. Rely on Wattuneed's expertise to optimize your energy autonomy, winter and summer alike.