What your batteries actually power

In most Mars caravans, the 12V battery system powers day-to-day essentials like:

• Lights (internal/external)
• Water pump
• USB ports (often)
• Control panels / monitors
• Diesel heater fan (if fitted)
• Fridge (commonly a 12V compressor fridge)

Bigger loads like air con and microwaves are typically 240V and rely on shore power (or a generator), unless you have an inverter setup designed for that level of demand.

Battery types (common in caravans)

Your Mars may have one of these (or a variant):

• AGM(Older Models): proven and affordable, but doesn’t love being deeply discharged.
• Lithium: lighter, higher usable capacity, quicker charging, and generally better off-grid performance.

If you’re not sure which you have, check your battery label or your handover paperwork. Battery management is slightly different between AGM and lithium, especially around “how low is too low”.

How to monitor your batteries (the right way)

1) Use your battery monitor first

Many vans have a monitor that shows either % or voltage (V). If you have a percentage readout, that’s usually the easiest to follow.

2) Don’t rely on voltage alone (but it can still help)

Voltage readings change depending on load and whether you’re currently charging. For example, batteries can show a higher voltage while charging even if they’re not actually “full” yet.

Battery protection: what “too low” looks like

Deep discharging is one of the quickest ways to shorten battery life (especially AGM). Your system may have low-voltage cut-outs designed to protect your batteries, but it’s better not to rely on them.

Good habits

• Avoid running batteries down to empty whenever possible.
• If you’re staying off-grid for multiple days, keep an eye on your usage (fridge + lights + pump + inverter adds up).
• Recharge early (solar during the day, vehicle charging when moving, or 240V when available).

Tip: If your batteries keep dropping quickly, the issue is usually either high consumption (inverter appliances are a big one) or not enough charging (shade, short drive times, incorrect settings, etc.).

How your Mars batteries charge (and what to expect)

1) Vehicle charging (when driving)

• Great for topping up on travel days.
• Short trips may not replace what you used overnight.
• Best results come from longer drives and healthy charging connections.

2) Solar charging

• Works best in full sun with minimal shade.
• Cloud, trees and heat can reduce output significantly.
• Solar is brilliant for “maintenance charging” across the day, but won’t always outpace heavy usage.

3) 240V charging (shore power)

• Usually the fastest and most reliable way to recharge.
• If you’re plugged into 240V and batteries aren’t rising, check breakers/RCD and the charger status.

The top battery killers (avoid these)

1. Running high-draw 240V appliances off the inverter (kettles, heaters, hair dryers, toasters).
2. Leaving the van in storage with loads still on (fridge, lights, accessories, monitors).
3. Shade on solar panels (even partial shade can drop output massively).
4. Short drives only (not enough time to recharge what you used).
5. Ignoring battery health (old AGM batteries often “look fine” until they drop quickly under load).
6. Not keeping connections clean and tight (loose/dirty terminals can cause charging issues).
7. Storing batteries flat (especially AGM) for long periods.

Storage tips (so your batteries don’t die in the shed)

• Turn off unnecessary loads (inverter off, lights off, accessories off).
• If your system allows it, use the battery isolator for longer storage periods.
• If you have solar, try to store where panels still get some sun, or plug into 240V occasionally to top up.
• Check battery status regularly during long storage (especially in hot conditions).

Important: Hot storage environments accelerate battery aging. If you’re storing your van in a very hot shed, battery care matters even more.

Troubleshooting: quick checks

A) Batteries going flat too fast

• Check what’s running overnight (fridge + lights + inverter standby loads).
• Confirm solar is actually charging during the day (no shade, regulator reading/input visible).
• If towing/vehicle charging, confirm you’re driving long enough to meaningfully recharge.
• Older batteries may have reduced usable capacity.

B) Batteries not charging (solar/vehicle/240V)

• Check 240V RCD/breakers if you’re plugged in.
• Check isolator positions and charger/inverter status.
• Solar: check for shade and confirm regulator shows input.
• Vehicle charging: check connection and whether charging is enabled/active.

C) Weird 12V behaviour (lights dim, pump surges, fridge errors)

• Often a sign of low battery voltage or a poor connection under load.
• Charge batteries, then re-test.
• If it persists, log a support ticket with details (below).

What to include in a support ticket (so we can help fast)

• Your model + year (and VIN/chassis number if available)
• Battery type (AGM/Lithium) if known
• Photo of your battery monitor (voltage/%), plus a photo while charging if possible
• Are you charging via solar, vehicle, or 240V?
• What was running when the issue happened (fridge, inverter, heater, lights, etc.)
• Short video if something is tripping or behaving oddly