How to Store Your Mars Caravan So the Batteries Don’t Discharge

If your Mars caravan is parked for weeks or months at a time, it’s normal for the batteries to slowly discharge. All batteries self-discharge, and modern caravans often have small “always on” devices that draw power in the background.

The good news is that with a few simple steps, you can store your van in a way that protects the batteries and helps them last longer.

This guide covers:

• How caravan batteries lose charge in storage
• Storage tips for short, medium and long-term
• How to use isolators, solar and trickle chargers safely
• Signs your battery needs attention or replacement

1. Why Batteries Go Flat in Storage

Even when you’re not using the van, batteries can discharge because of:

• Self-discharge: All batteries slowly lose charge over time, even when disconnected.
• Parasitic loads: Small devices like trackers, control boards, monitors and USB outlets may draw power in the background.
• No charging source: No solar, no mains power and no vehicle charging while the van is parked.

If a battery is left flat for a long time, it can be permanently damaged. Preventing deep discharge in storage is one of the best ways to extend battery life.

2. Know Your Battery Type (AGM vs Lithium)

Storage recommendations can vary slightly depending on battery type. Older Mars Campers may have AGM batteries whereas new models have Lithium:

• AGM / Lead-acid batteries: Prefer not to be left deeply discharged. They like to stay topped up and may be kept on a suitable smart charger when stored.
• Lithium (LiFePO4) batteries: Generally more tolerant of deeper discharge and have lower self-discharge, but they can still be damaged by being left flat or overcharged. Many manufacturers recommend storing lithium around a partial state of charge rather than 100% for very long-term storage.

Tip: If available, check the battery manufacturer’s recommendations for optimal storage state of charge and temperature.

3. Short-Term Storage (Up to 2–4 Weeks)

For short periods between trips:

• Fully charge the batteries using 240V mains or a good drive combined with solar.
• Turn off unnecessary loads:
  • Lights, fans and pumps off
  • Fridge turned off and doors propped open to prevent mould
  • Inverters switched off if fitted
• If your van is in a sunny spot and has solar, leave the solar system active so it can maintain the batteries.

In most cases, a healthy battery will be fine for a few weeks without extra intervention, especially if solar is helping top it up.

4. Medium-Term Storage (1–3 Months)

For periods of a month or more, take a few extra steps:

• Start with the batteries fully charged.
• Decide how you will keep them topped up:
  • Option 1 – Solar maintenance: Park the van where panels receive sunlight and ensure the solar regulator is active.
  • Option 2 – Smart/maintenance charger: If the van is stored at home or near power, connect a suitable charger designed for long-term maintenance (often called a “trickle” or “float” charger).
• Turn off as many loads as practicable:
  • Main lights, fans and pumps
  • Fridge off
  • Inverter off

Isolator use: If your van is fitted with a main battery isolator, you may choose to turn it off to disconnect most loads. Be aware that some devices (e.g. trackers, alarms, certain chargers) may bypass the isolator depending on how your van is wired.

5. Long-Term Storage (3+ Months or Over an Off-Season)

For long-term or seasonal storage, battery care becomes even more important:

5.1 Charge Before Storage

• Charge the batteries fully on 240V mains and allow them to rest.
• For lithium, you may choose to store at a slightly reduced state of charge if the manufacturer recommends it (for example, 50–80%).

5.2 Decide on a Maintenance Strategy

Common options include:

• Solar maintenance:
  • Park where the panels are in regular sun.
  • Ensure the solar regulator is working and configured for your battery type.
  • This can keep batteries topped up with minimal intervention.
• Smart/maintenance charger:
  • Use a quality charger designed for long-term connection.
  • Confirm it has modes suitable for AGM or lithium, as applicable.
  • Follow manufacturer instructions and do not use cheap, unregulated chargers.
• Isolator only:
  • Turn the main battery isolator off to minimise parasitic draws.
  • Understand that the battery will still slowly self-discharge over time.
  • For storage longer than a few months, you should still periodically recharge.

5.3 Periodic Checks

Even in storage, plan to:

• Check battery voltage every 4–8 weeks if possible.
• If voltage has dropped significantly, recharge fully using mains or solar.
• Visually inspect cables, terminals and the battery area for corrosion or damage.

6. Using a Trickle or Maintenance Charger

A good quality smart charger can be an excellent way to maintain batteries in storage. Some general tips:

• Use a charger that is compatible with your battery type (AGM / gel / lithium).
• Aim for a charger with a maintenance or float mode that automatically adjusts once the battery is full.
• Follow the manufacturer’s instructions for long-term use.
• Ensure the charger is in a dry, ventilated area and cords are safely routed.

Note: Not all chargers are suitable for permanent connection. Always check the specifications.

7. Extra Tips to Reduce Battery Drain in Storage

• Turn the fridge off and leave the doors slightly open to prevent mould (this also stops the fridge drawing power).
• Switch off or unplug any 12V accessories added after purchase (extra lights, USB hubs, etc.).
• If your van has added accessories like alarm systems, trackers or aftermarket gear, confirm how they are wired and what they draw in standby.
• Consider labelling the main 12V switch and isolators so it’s clear what each one does.

8. Signs Your Battery May Need Replacement

Even with good storage practices, batteries eventually wear out. Your battery may need testing or replacement if:

• It goes flat very quickly even after a full charge and light use.
• Voltage drops rapidly under small loads.
• It has been left flat for a long time (weeks or months).
• There are visible signs of damage, swelling, or leaking (for lead-acid types).

A load test performed by a qualified technician or auto-electrician can confirm the battery’s health.

9. When to Contact Mars Support

If you are unsure about your setup or notice unusual behaviour, it’s a good idea to contact Mars Campers support. When lodging a ticket, include:

• Your full name and contact details
• Van model and VIN
• Battery type (AGM, lithium, etc.) and approximate age
• How long the van has been in storage and whether it was on solar, mains, or isolator only
• Battery voltage readings (if available) and any photos of the battery area and chargers

Summary

Storing your Mars caravan correctly is one of the simplest ways to protect your batteries and avoid nasty surprises before a trip.

By:

• Starting with fully charged batteries
• Minimising parasitic loads using isolators and switches
• Using solar or a suitable maintenance charger where possible
• Checking voltage periodically during long-term storage

…you’ll greatly reduce the risk of your batteries going flat in storage and extend their overall life.