What is it for?
When a few panels no longer keep a battery fed, a sturdier charging stage is needed. This Wattstunde MPPT controller handles a charge current of 40 A, twice that of an entry-level 20 A model, and manages 12 V or 24 V batteries as required. Maximum power point tracking lets you make use of the modules even when their voltage drifts away from that of the battery.
Where to put it
- A motorhome or van with a roof generously covered in modules.
- A leisure boat with a long list of onboard loads.
- A workshop, garden shelter or mountain hut with no grid connection.
- A farm utility room supplying pumps and lighting.
What changes with the voltage
At 12 V the solar array can reach 520 W nominal; at 24 V it climbs to 1040 W. Moving to 24 V therefore doubles the panel power without replacing the device, and keeps the current in the cables lower.
Construction and dimensions
The housing measures 196 x 136 x 97 mm and weighs 1.3 kg. It stays compact enough to be fixed on a plywood board or inside a technical cabinet, while offering a surface that helps dissipate heat. The IP 32 class signals limited resistance to water and dust, so plan a sheltered location that never sees rain. Its idle consumption, below 8 mA, is deliberately low so the battery is not drained during periods without sun.
Commissioning steps
- Fix the controller on a flat, non-flammable surface close to the battery.
- Connect the battery first, following the diagram in the manufacturer’s manual, then the solar array.
- Check that the open-circuit voltage of the panel string, cold weather included, stays below the 90 V input limit.
- Confirm the automatic voltage detection and watch the first charge.
Cable cross-sections and protection devices depend on your installation; if the system is to be tied to a household network, have a qualified installer do it.
Advantages at a glance
This controller combines a 40 A current, a wide power range reaching 1040 W at 24 V and automatic voltage identification. Its modest dimensions and low self-consumption make it unobtrusive equipment, well suited to systems that grow in stages.
Specification sheet
- Brand: Wattstunde
- Charge current: 40 A
- Battery voltage: 12/24 V, automatic detection
- Nominal PV power: 520 W (12 V) and 1040 W (24 V)
- Input: 90 V
- Output: 12V/520W – 24V/1040W
- Self-consumption: < 8 mA
- Protection rating: IP 32
- Dimensions: 196 x 136 x 97 mm
- Weight: 1.3 kg
Precautions and storage
Do not exceed the stated input and output limits. Undersized cables heat up, so use conductors suited to 40 A and fit suitable protection. Let air circulate around the housing, avoid damp dust build-up and check the terminal tightness now and then. Out of season, disconnect the unit and keep it in a dry place.
