Self-sufficient into the season - Part 2: Choosing the right supply battery

Not all batteries are the same! Depending on the application, there are different technologies that differ in performance, lifespan, and weight. Here are the three most common battery types:

AGM batteries – The robust classic

AGM (Absorbent Glass Mat) batteries are widely used and offer a good balance between price and performance. They are maintenance-free and, thanks to their sealed design, can also be used indoors.

✅ Robust & leak-proof
✅ Average lifespan (~600-800 charging cycles)
❌ Not deep discharge tolerant
❌ Heavy & large

Gel batteries – Long-lasting, but slow

Gel batteries use a gel-like electrolyte, making them particularly durable and resilient. They tolerate deep discharges better than AGM batteries, but take longer to charge.

✅ Long service life (~800-1200 charging cycles)
✅ Very resistant to deep discharge
❌ Slow loading speed
❌ Heavy & more expensive than AGM

Lithium batteries (LiFePO4) – The best choice for self-sufficiency

Lithium iron phosphate (LiFePO4) batteries are the most modern and efficient choice. They are lighter, charge faster, and offer a much longer lifespan than AGM or gel batteries. They are also virtually maintenance-free and retain their performance even at low temperatures (some NOVA models are equipped with heating mats for this purpose).
Another advantage is their high usable capacity: While AGM and gel batteries can only utilize about 50% of their capacity, lithium batteries can be discharged up to 90% without significantly affecting their service life. They also have an integrated battery management unit (BMS) that prevents overcharging, deep discharge, and excessive currents.

✅ High cycle stability (~3000-5000 charging cycles)
✅ 50% lighter than AGM/Gel
✅ Fast charging & deep discharge tolerant
✅ High usable capacity (up to 90% discharge possible)
✅ Integrated BMS protects against overcharging and deep discharge
❌ Higher purchase price
❌ May be sensitive to extreme cold (models with heating function recommended)

Calculate capacity - How many Ah do you need?

Before choosing a battery, you should calculate your daily energy consumption. This way, you'll know exactly how much storage capacity you need.

Formula for calculating consumption:

Power (W) x operating time (h) = consumption in watt-hours (Wh)

Some typical consumers:

• LED light (10W) for 5 hours → 50Wh
• Compressor refrigerator (50W) for 12 hours → 600Wh
• Laptop (60W) for 3 hours → 180Wh
• Kettle (1500W) for 5 min → 125Wh
  

👉 Total consumption per day: ~955Wh

Now we calculate the appropriate battery capacity:

• To convert Wh to Ah: 955Wh ÷ 12V = 79.6Ah per day
• For 3 days of self-sufficiency: 79.6Ah x 3 = 238.8Ah
• Safety reserve (25% more capacity): 238.8Ah x 1.25 = 298.5Ah

🔋 Recommended battery capacity: approx. 300Ah (for 12V systems)

If you're using an AGM or gel battery, keep in mind that you can't discharge it to 100% (only about 50% usable). One way to achieve the required capacity is to combine multiple batteries. For example, you can connect two 150Ah lithium batteries in parallel to achieve a capacity of 300Ah.

With AGM or gel batteries, you can also combine multiple batteries, but this increases the total weight considerably. A 300Ah AGM battery can easily weigh over 70kg, while two 150Ah lithium batteries together weigh only about 30kg and still offer the same usable capacity.

The weight of your battery plays an important role, especially if you plan to install multiple batteries and with regard to your vehicle's maximum payload! Lithium batteries offer a decisive advantage here, as they save weight and make it easier to distribute the batteries evenly throughout the vehicle. Those who travel a lot or are off-roading therefore benefit from a lightweight and powerful lithium solution that leaves more room for other equipment.

Lifespan, charging cycles & battery care

To ensure your battery lasts as long as possible, you should take care of it properly.

Charging cycles & depth of discharge

The lifespan of your battery depends heavily on how deeply it is discharged. Every battery has a limited number of charging cycles – a cycle represents a complete discharge and recharge of the battery. The deeper a battery is regularly discharged, the faster it wears out. Here are the differences between common battery types:

• AGM batteries: Can only be discharged to 50% before their lifespan is severely affected. With 600-800 charge cycles, they last significantly shorter than lithium batteries.
• Gel batteries: Slightly more deep-discharge tolerant than AGM, with a maximum discharge of 50-70%. They have a longer lifespan of 800-1200 cycles, but require a longer charging time.
• Lithium batteries (LiFePO4): These allow for deeper discharge of 80-90% without significant negative impact on battery life. With 3,000-5,000 charge cycles, they have a significantly longer lifespan, making them particularly suitable for long-term use.

Why is this important? If a battery can only be discharged to 50%, you need twice the capacity to obtain the same usable energy. This means higher costs, more space, and, above all, more weight—an important factor for touring vehicles with limited payload. Lithium batteries offer the major advantage of allowing you to use a smaller and lighter battery with the same usable energy.

Another crucial point is the constant voltage of lithium batteries: While AGM and gel batteries have a decreasing voltage as they discharge, the voltage of a lithium battery remains constant, which guarantees consistent performance for your devices.

Battery care tips:

A well-maintained battery lasts significantly longer and delivers reliable power. AGM and gel batteries are particularly susceptible to sulfation – a buildup of lead sulfate crystals that reduces charge absorption and shortens service life. This occurs when the battery remains partially discharged for long periods or is not fully charged regularly. Regular charging helps prevent sulfation and maintain battery performance.

✅ AGM/Gel: Fully charge regularly to avoid sulfation – ideally with a charge booster or a special trickle charger if the vehicle is not used for an extended period.
✅ Lithium: Do not store permanently at 100%, ideal is 50-80% charge
✅ Store batteries as warm as possible in winter (especially AGM/Gel batteries) – low temperatures reduce capacity and can damage AGM batteries. Lithium batteries with integrated heating are a sensible alternative.

Especially with AGM/Gel batteries, A suitable charging strategy is important. It's best to use a charging booster or a high-quality solar charge controller to ensure optimal charging.

Conclusion - Which battery is right for you?

Depending on the application, there are different ideal solutions:

• Occasional users (weekend trips): AGM or small lithium battery (~100 Ah)
• Long-term travelers & vanlife: Lithium battery (~200-300 Ah)
• Winter campers & off-road users: Large lithium battery with heating function (~300-400 Ah)

Anyone who wants to be permanently self-sufficient on the road will hardly be able to avoid a lithium battery. The higher purchase price is worth it due to the long service life and lower weight. However, these figures are only guidelines – the actual battery capacity required always depends on the specific devices you want to power. Therefore, a detailed consultation and a precise calculation of your individual energy requirements are the best way to find the optimal solution for your vehicle.

Outlook: Solar modules & charging technology - harnessing energy from the sun

Now that you know the right battery for your vehicle, the next question arises: How do you charge them most efficiently?

In part 3 of our series we look at:

• Which solar panels are the best choice for your setup
• How much solar power you need
• Whether an MPPT or PWM charge controller makes sense
• Stay tuned – this way you’ll be well prepared for your independent power supply on the go!