If you are putting solar on the roof for the first time, this is almost certainly the controller you want. The SmartSolar MPPT 100/20 handles up to 100V of panel input and 20 amps of charge current, which covers roughly 260W of panel on a 12V system — one large roof panel or two smaller ones.

MPPT, and why it is worth paying for

A cheap PWM controller simply connects the panel to the battery and throws away the difference in voltage. An MPPT controller converts it instead, which typically recovers 20 to 30% more energy from the same panel — more in cold weather, more when the panel is partially shaded, and much more when the battery is low. On a roof where you only have room for so many panels, that difference is the whole point.

Set up from your phone

Bluetooth is built in. Open VictronConnect, pick your battery type, and you are done. From then on you can see live solar input, charge current and battery state from your phone, plus daily and 30-day history — which is genuinely useful for working out whether your panel is actually keeping up with your fridge.

Specifications

• Maximum PV input: 100V
• Charge current: 20A
• Battery voltage: 12V, 24V or 48V (auto-detect on 12/24V)
• Bluetooth built in — VictronConnect app
• Weight: 1.62 lb
• Manufacturer part number: SCC110020160R

Sizing it right

The rule of thumb on a 12V system is that 20A of charge current suits about 260W of panel. Going over that is not dangerous — the controller simply limits output — but you have paid for panel you cannot use. Tell us what panels you are running and we will confirm whether this is the right size or whether you want the 150/35.