Solar panels & MPPT charge controllers FAQ
If you’re building a campervan, a solar power setup is one of the best upgrades you can make.
When you start spending real time in a campervan, one thing becomes very clear: power management is freedom. Your leisure battery and solar setup determine whether you can stay off-grid comfortably for days or weeks at a time.
What is a leisure battery?
A leisure battery is your campervan’s “off-grid fuel tank” for electricity. Unlike a starter battery, it is designed to be slowly discharged and recharged over time.
It typically powers:
- LED lights and interior lighting
- Water pumps
- Fridges (12V compressor or absorption systems)
- Charging phones, laptops, and cameras
- Fans and other low-power appliances
- Small heating systems (where applicable)
Most modern campervans use 12V deep-cycle AGM, Gel, or Lithium (LiFePO₄) batteries.
Keeping your leisure battery charged up can be achieved in various ways, here we will cover charging via a solar panel(s) and charge controller.
What is a solar panel system in a van?
A van solar system typically includes:
- Solar panels (on the roof or portable)
- A charge controller (usually MPPT but PWM controllers exist)
- A 12V leisure battery
- Optional inverter (to run 230V appliances)
The solar panels generate electricity, and the MPPT charge controller manages how that power is safely stored in your battery.
What is an MPPT charge controller?
An MPPT (Maximum Power Point Tracking) charge controller is a smart device that sits between your solar panels and your battery.
Its job is to extract the maximum possible power from your solar panels at any given time.
Solar panels don’t produce a fixed output, their voltage and current change depending on:
- Sunlight strength
- Temperature
- Angle of the panels
- Cloud cover
An MPPT controller constantly adjusts to these changes to keep your system working at peak efficiency.
Why is MPPT better than PWM?
There are two main types of solar charge controllers:
PWM (Pulse Width Modulation)
- Simple and cheaper
- Works best for small, basic setups
- Less efficient with modern high-voltage panels
MPPT
- Up to ~20–30% more efficient in real-world conditions
- Works especially well in UK weather (clouds, low sun angles)
- Can convert extra panel voltage into usable battery charging current
We only stock and use MPPT controllers as they are far better than PWM controllers in pretty much every situation.
What size MPPT controller do I need?
This depends on:
- Total solar panel wattage (e.g. 200W, 400W, 800W)
- Battery system voltage (12V or 24V)
- Maximum charging current rating (amps)
Simple rule of thumb:
- 200W–400W system → 20A MPPT
- 400W–600W system → 30A MPPT
- 600W–1000W system → 50A–60A MPPT
Always size slightly above your expected output for safety and future expansion.
Can I use solar panels without an MPPT controller?
We do not recommend running a solar panel without some form of controller.
Without a proper charge controller:
- Your battery can be damaged
- You lose efficiency
- No voltage regulation can create unsafe conditions
MPPT ensures safe, controlled charging.
Do solar panels still work in cloudy UK weather?
Yes, but output is reduced.
The good news is:
- Solar panels still generate power in overcast conditions
- MPPT helps maximise low-light performance
- Larger panel arrays help compensate for winter months
Even in the UK, a properly sized system can significantly reduce or eliminate the need for mains hook up charging.
What is the best battery setup for solar in a van?
Most campervan builds use:
- AGM or Gel batteries (older systems)
- Lithium (LiFePO₄) batteries (modern, more efficient option)
Lithium batteries:
- Charge faster
- Allow deeper discharge
- Work extremely well with MPPT systems
How much battery capacity do you need?
This depends on your daily energy use.
Here’s a rough example of a typical campervan day:
- Lights: 30Wh
- Water pump: 20Wh
- Phone/laptop charging: 150Wh
- Compressor fridge: 400–800Wh
- Miscellaneous: 100Wh
Total: ~700–1100Wh per day
So you might size your system like this:
- Light use (weekends): 100Ah battery
- Medium use (occasional off-grid): 150–200Ah
- Full-time van life: 200–400Ah (often lithium)
Matching solar to battery size
A good rule of thumb:
Solar should be able to replace your daily usage.
Example:
If you use ~800Wh per day:
- 200W solar panel may just about cope in summer
- 300–400W gives reliability and buffer
A typical balanced setup:
- 200Ah lithium battery
- 300–400W solar panel
- MPPT charge controller (important for efficiency)
Final thoughts
A campervan electrical system doesn’t need to be complicated. The key is balance. Matching your battery capacity with realistic daily usage, and ensuring your solar setup can reliably replace what you consume.
Get that right, and you stop thinking about power altogether and that’s when van life really starts to work.