Which battery should you choose for solar panels?

We work with the four technologies that are currently the most suitable for self-consumption or off-grid installations. The difference between them lies not only in the purchase price, but also in the cost per cycle over their lifetime. LiFePO4 lithium batteries: the current standard for any new installation. Between 3,000 and 6,000 cycles, usable depth of discharge of 80–100 %, maintenance-free and with a charge efficiency of around 98 %. Available in 12V for motorhomes and marine use, 24V for medium-sized systems and 48V for domestic use. Brands: Victron Energy, Pylontech, Pytes and the high-voltage BYD batteries. AGM batteries: sealed, maintenance-free lead-acid. The most economical option for low consumption or occasional use. Between 500 and 800 cycles at 50 % of discharge: if discharged further, the service life drops sharply. A good option for a second home or a backup system that is used infrequently. Gel batteries: greater tolerance to high temperatures and lower self-discharge than AGM batteries. Suitable for hot climates and installations that remain unused for weeks at a time. Carbon and stationary OPzS batteries: for daily deep cycling on a tight budget, or high-capacity banks in re

How many batteries do I need for my solar panels?

The calculation is based on daily consumption, not on the panels’ power output. Add up the kWh you use each day, decide how many days’ supply you want to cover, and divide by the depth of discharge supported by the technology. A real-life example: a home that consumes 10 kWh/day and wishes to cover night-time consumption — around 40 %, or roughly 4 kWh — requires a lithium battery bank with a usable capacity of 5 kWh. With modules rated at 5.12 kWh at a 90 % depth of discharge, a single battery will suffice. With AGM batteries at 50 %, you would need a nominal capacity of 10 kWh to achieve the same result—in other words, twice the battery capacity. In a campervan, the reasoning is the same but on a different scale: a compressor fridge, lights, water pump and USB chargers account for around 600–900 Wh/day, which is covered by a 100 Ah lithium battery at 12V.

How long does a solar battery last?

It depends on the number of cycles, not on the calendar. A LiFePO₄ lithium battery with a cycle life of 6,000 cycles, charged and discharged once a day, will last around 15 years whilst retaining around 80 % of its initial capacity. A correctly sized AGM battery will last between 4 and 6 years. A well-maintained OPzS stationary battery can last for more than 15 years. The three factors that most significantly shorten the actual lifespan of a battery bank are discharging it below the level permitted by its technology, operating continuously at temperatures above 35 ºC, and leaving it in a partially charged state for long periods. Correct sizing from the outset is cheaper than having to replace the battery bank prematurely.

Which battery is recommended for your setup?

Campervans, vans and boats: 12V lithium. Lightweight, withstands deep discharges and recharges quickly from the alternator using a DC-DC booster. This is the setup we use on a daily basis. Off-grid homes with grid connection: 48V lithium in rack format. The Pylontech, Pytes and Victron models from the NG series offer capacities ranging from 2.4 kWh up to 20 kWh battery banks by stacking modules. If you plan to expand in the future, choose a brand from the outset that allows for parallel expansion. Off-grid home: here, the battery bank is the heart of the system and it is advisable to oversize it. Opt for 48V lithium if the budget allows, or stationary OPzS batteries if you are looking for maximum capacity per euro.