Charging Explained: Vehicle, 240V & Solar — What Charges What in Your Mars Caravan
One of the most common questions we get is: “Why aren’t my batteries charging?” The answer usually comes down to understanding the three charging sources in your Mars caravan: vehicle charging, 240V shore power charging, and solar charging.
This guide explains how each charging method works, what to expect in real life, and the quick checks you can do before lodging a ticket. (Exact hardware varies by model and year.)
The big picture (simple version)
Your Mars caravan’s 12V batteries can be charged by:
- Vehicle charging while you’re driving/towing
- 240V battery charger when you’re plugged into shore power
- Solar (roof panels and/or portable solar if fitted)
These sources don’t always produce the same results. It’s completely normal for charging performance to vary with weather, driving time, battery type, and what loads you’re running.
1) 240V charging (shore power): the most reliable top-up
When you plug your van into 240V at home or a caravan park, your 240V battery charger should switch on and begin charging the batteries.
What to expect
- Generally the fastest and most consistent way to recharge.
- While plugged in, your 240V outlets should work (assuming RCD/breakers are on).
- Many 12V items still run from the battery system, but the charger keeps it topped up.
Common reasons 240V charging isn’t happening
- RCD/safety switch tripped
- Breaker OFF (either at the pedestal or inside the van)
- Faulty/loose power lead or outlet
- Charger switched off (or not receiving 240V)
Quick check
- Confirm the caravan park pedestal/home outlet is ON and working.
- Confirm your internal RCD and 240V breakers are ON.
- Check your battery monitor: do you see the battery % rising, or voltage increasing while plugged in?
2) Vehicle charging (while driving): great, but depends on drive time
Vehicle charging typically tops up your batteries while you’re towing/driving. Most modern setups use a DC-DC charger to charge safely and efficiently from the vehicle.
What to expect
- Perfect for travel days and keeping batteries healthy between stops.
- Short drives often won’t fully replace what you used overnight.
- Results vary depending on battery type, charger capacity, wiring, and vehicle setup.
Common reasons vehicle charging feels “weak”
- Trips are too short (not enough time to recover overnight usage)
- High loads running while driving (fridge + inverter loads can reduce net gain)
- Connection/plug issue (poor contact can reduce charge)
- Vehicle alternator behaviour (modern alternators can be different to older vehicles)
Quick check
- Confirm the caravan plug is connected properly and seated firmly.
- After 20–30 minutes driving, check your monitor: does it show charging / increasing voltage?
- If you stop for the night, check if the battery level is higher than when you started driving.
3) Solar charging: brilliant… but it’s not magic
Solar is the best “set and forget” charging option when you’re camped — but output changes constantly. Even partial shade can reduce performance significantly.
What to expect
- Best performance in full sun (minimal shade), especially mid-morning to mid-afternoon.
- Output drops with cloud, shade, panel angle, and high heat.
- Solar often keeps you stable off-grid, but heavy loads can still drain batteries.
Common reasons solar isn’t performing
- Shade from trees, awnings, roof racks, antennas
- Dirty panels (dust + road grime adds up)
- Hot roof surface (heat reduces efficiency)
- Loose/poor connections (less common, but possible)
- Battery is near full (charging tapers off as batteries fill)
Quick check
- Move into full sun if possible and re-check in 10–15 minutes.
- Check the solar regulator/monitor: does it show input?
- Clean panels if they look dusty or dirty.
Why your batteries still go flat even though you have “charging”
A key concept is net power: if your usage is higher than your charging input, the batteries will still drop.
Common examples
- Running an inverter for 240V appliances off-grid (high draw)
- Multiple devices charging + fridge running hard in hot weather
- Camping under trees (solar reduced) while still using normal loads
- Short drives between camps (vehicle charging doesn’t have time to recover losses)
Fast diagnosis: which charging source should be working right now?
- Plugged into 240V? → 240V charger should be charging batteries.
- Driving/towing? → vehicle/DC-DC charging should be topping up.
- Parked in sun? → solar should be contributing (unless shaded or batteries full).
Helpful clue: If none of these are increasing battery levels, it’s time to run the checks below.
Quick troubleshooting checklist (before lodging a ticket)
A) If you’re plugged into 240V and not charging
- Check pedestal/home outlet works
- Check internal RCD/breakers are ON
- Check charger is ON (if there’s a switch)
- Check battery monitor for rising % or voltage
B) If you’re driving and not charging
- Check plug connection is fully seated
- After 20–30 minutes, check monitor for charging behaviour
- Confirm no unusual heat or loose wiring at plug points
C) If solar isn’t charging
- Move into full sun and re-check
- Confirm regulator shows solar input
- Clean panels and remove shading objects
What to include in a support ticket (so we can help fast)
If charging still isn’t happening, include the following:
- Your model + year (and VIN/chassis number if available)
- Battery type (AGM/Lithium) if known
- A photo of your battery monitor showing voltage/%
- Tell us which charging method you’re using: solar, vehicle, or 240V
- A photo of your 240V switchboard (RCD + breakers) if on shore power
- A photo of the solar regulator/monitor reading if solar is the concern
- Anything unusual: tripping, burning smell, hot plug, error codes