What Does a Solar Charge Controller Do, and What Do the Numbers in "100/30" Mean?
Summary
It sits between the panels and the battery and turns the array's output into charging the battery can take. Victron's MPPT controllers lock onto the panels' maximum power point and can charge a battery of lower nominal voltage from a higher-voltage array. In Victron's model names, the first number is the maximum PV open-circuit voltage and the second is the maximum charge current, so a 100/30 accepts up to 100 V from the panels and charges at up to 30 A.
Reading the 100/30 data sheet
| Spec | SmartSolar MPPT 100/30 |
|---|---|
| Battery voltage | 12/24 V auto select |
| Rated charge current | 30 A |
| Nominal PV power | 440 W at 12 V, 880 W at 24 V |
| Maximum PV open-circuit voltage | 100 V |
| Maximum PV short-circuit current | 35 A |
The footnotes treat two kinds of excess differently. Connect more PV power than the nominal figure, and the controller limits input power. Connect an array with a short-circuit current above 35 A, and the controller may be damaged. The same 30 A unit handles twice the panel wattage on a 24 V battery as on a 12 V one.
When charging starts in the morning
Per the manual, charging begins once PV voltage is 5 V above battery voltage and continues as long as it stays at least 1 V above. With a battery sitting at 12.8 V, that means charging kicks in when the array passes 17.8 V and keeps going until late-day output falls below 13.8 V. The manual also says the nominal PV voltage should be at least 5 V higher than the battery voltage.
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Sources
- Victron Energy — SmartSolar charge controller MPPT 100/30 & 100/50 datasheet
- Victron Energy — SmartSolar MPPT 75/10 up to 100/20 manual (Rev 10, 02/2026)
- Victron Energy — Solar charge controllers
We have not tested these products. Specs, prices, stock and terms are as published on these pages on the date above and can change; check the manufacturer or retailer before you buy.