Overwintering on the Costa del Sol: motorhome battery care

From November to March, motorhomes and campervans from all over Europe come to overwinter on the Costa del Sol. The sun is out most days, yet plenty of leisure batteries are flat by February. It isn't bad luck: in winter your solar panel produces less while you use more. Here is what to check, how to keep the battery charged and what to do about the starter battery, so your winter in Málaga goes to plan.

Why leisure batteries struggle in winter, even here

On the Costa del Sol the problem isn't the cold. It's the daily balance between what goes in and what comes out:

• Short days, low sun. In December there are fewer than 10 hours of daylight and the midday sun sits only about 30° above the horizon. A flat roof panel catches that light at a steep angle and produces far less than in summer, even under a clear sky.
• Cloudy spells. Three or four grey, wet days in a row are normal between November and February, and that is enough to empty a battery that was already borderline.
• Longer evenings. In December it gets dark around 6 pm, and evenings are spent inside: lights, TV, laptop, phones.
• Heating. Even if it burns diesel or gas, the fan, pump and control unit draw on the 12 V supply for hours, and a diesel heater pulls a lot of current for a few minutes at start-up.
• Long stays off hook-up and without driving: the alternator isn't helping.
• Parasitic loads. Control panel, gas detector, router, inverter on standby: small, but round the clock.

The result is a battery that never gets a full charge. With lead-acid and AGM, that means sulphation and lost capacity week after week.

Check the resting voltage

Use a multimeter on the terminals after two or three hours with no charging and no load (first thing in the morning with everything off works well). As a guide for 12 V lead-acid and AGM batteries:

With lead-acid and AGM, the rule is don't routinely go below 50 %. If you wake up to 12.2 V or less every morning, the battery is either too small for your winter use or not getting enough charge.

With LiFePO4 lithium the voltage barely moves between roughly 20 and 90 % charge, so a multimeter won't tell you what's left. Go by the battery monitor with a shunt or the BMS app, which count the amps going in and out.

Ten-minute checks worth doing

Terminals and connections

Salty coastal air speeds up corrosion. A loose or corroded connection stops the charger from filling the battery. Clean with a wire brush, tighten and protect with terminal grease.

Charger and regulator set for your battery

The mains charger, solar controller and DC-DC charger must be set for your battery type: lead-acid, gel, AGM and lithium don't charge at the same voltage. A solar controller left on "flooded" with an AGM battery is a very common mistake.

Panel angle

If you're staying put for weeks, pick a pitch with no afternoon shade and, if your mounts allow it, tilt the panel towards the south. In winter it makes a real difference. There's more on this in our guide to leisure batteries with a solar panel.

DC-DC charger when driving

An hour on the road with a DC-DC charger puts back a good number of amp hours. With a smart alternator and no DC-DC, the leisure battery gets very little while you drive.

Parasitic loads when you leave it

If you leave the motorhome parked for a few days, use the leisure battery isolator or switch off everything you don't need at the control panel.

Don't forget the starter battery

When the vehicle sits for weeks, the engine battery drains too: alarm, ECUs and trackers keep drawing. And nobody looks at it until the engine won't turn over on the day you want to leave.

• Check whether your habitation charger or solar controller also maintains the starter battery. Some do, some don't.
• If not, connect a maintenance charger when you're on hook-up, or drive for at least half an hour every week or two. Starting the engine and idling for a few minutes isn't enough.

When to replace it and what to choose

Signs your leisure battery is at the end: it lasts much less than it used to on the same usage, the voltage collapses when the heater or inverter kicks in, it won't rise above 12.4 V at rest after a full charge, or the case is swollen.

There are two routes:

• Deep-cycle AGM: maintenance-free, robust and compatible with almost any setup. Plan on using about half its capacity.
• LiFePO4 lithium: you can use most of the capacity, it accepts faster charging and it's much lighter. In return, your mains charger, solar controller and DC-DC must be lithium-compatible, and it shouldn't be charged below freezing (rare on the coast, possible if you head up into the mountains).

To get the capacity right, first work out how many amp hours your campervan or motorhome needs, using your winter consumption. If you're weighing up lithium, read whether LiFePO4 is worth it in a motorhome and our guide to lithium batteries. All the options are on our page about leisure batteries for motorhomes and campervans.

Overwintering near Málaga: how we can help

We give advice in English, Spanish and German, by phone, on WhatsApp or at our shop at C/ La Orotava, 100 (Málaga). Send us a photo of your battery label and your charger and we'll tell you what suits your setup.

You can collect from the shop or we can deliver to the campsite or aire where you're staying. Some road distances from the shop:

• Málaga Monte Parc, Alhaurín de la Torre: 20 km · ~23 min
• Cala del Moral, Rincón de la Victoria: 23 km · ~23 min
• Fuengirola: 31 km · ~28 min
• Camping Cabopino: 45 km · ~37 min
• Camping Laguna Playa, Torre del Mar: 46 km · ~42 min
• Camping Nerja: 69 km · ~55 min

We take your old battery away and recycle it free of charge. One thing to note: we don't fit it in the vehicle, but we'll explain how to connect it. Opening hours: Monday to Friday, 08:30-14:00 and 16:00-18:30. Phone: +34 952 31 01 18.

A note on where to stay

In Spain, sleeping in a properly parked motorhome is generally allowed wherever parking is allowed. "Camping" is not: awning out, levelling ramps, tables or chairs outside. Each town also has its own by-laws, so check locally and, for long stays, use motorhome aires and campsites, which also give you hook-up.