The Victron MPPT load output lets the controller switch DC loads off before the battery is drained, then back on when it recovers. The small SmartSolar charge controllers have a third set of terminals labeled “load” for this. It’s simple, but the settings confuse people. Here’s what each mode does, which models have a physical load output, and what not to connect to it.
Which Models Have a Load Output?
Victron’s datasheet for the SmartSolar MPPT 75/10, 75/15, 100/15 and 100/20 lists a load output on all four:
| Model | Battery voltage | Max continuous load current |
|---|---|---|
| 75/10, 75/15, 100/15 | 12/24V | 15A |
| 100/20-48V | 12/24/48V | 20A (12/24V), 1A (48V) |
Source: Victron SmartSolar MPPT 75/10-100/20 datasheet.
On the 48V model, Victron says the load output is meant to drive a relay. Larger controllers have no physical load output, but the MPPT manual describes a virtual load output using the VE.Direct TX cable to control a BatteryProtect or relay.
Victron MPPT Load Output Modes
From the MPPT manual:
- BatteryLife (default). Self-adapting, aimed at maximizing battery life (see below).
- Conventional algorithm 1. 12V: off below 11.1V, on above 13.1V. 24V: 22.2V and 26.2V.
- Conventional algorithm 2. 12V: off below 11.8V, on above 14.0V. 24V: 23.6V and 28.0V.
- Always off or always on.
- User defined algorithm 1. Off below Vlow, on above Vhigh.
- User defined algorithm 2. Off below Vlow or above Vhigh, on in between.
Always on and always off respond immediately. The other modes wait 2 minutes before changing, so a brief inrush current doesn’t trip the output.
BatteryLife Explained
Victron says that if the controller can’t fully recharge the battery each day, a lead-acid battery cycling between partial charge and empty can be destroyed within weeks or months. BatteryLife fixes that. It raises the load-disconnect voltage a little each day until the solar harvest is enough to nearly fill the battery. After that, it modulates the disconnect level so the battery reaches nearly 100% about once a week.
What to Connect
- Good fits: LED lights, small fans, USB chargers, routers and sensors, within 15A or 20A.
- Avoid: inverters and anything whose current exceeds the rated load current. Connect large loads straight to the battery through a fuse, and use a BatteryProtect controlled by the virtual load output if you want low-voltage cut-off.
The load output is short-circuit proof, according to Victron.
For the complete spec sheet and current manual, see the Victron SmartSolar MPPT 75/15 page.
Worked Example: Lights and a Fan in a Shed
A shed with a 100Ah lead-acid battery, a SmartSolar 75/15 and 150W of solar runs LED lights (10W) and a small fan (20W) from the load output. At 30W total, that’s about 2.5A, well within the 15A rating (estimate). On a long cloudy stretch, BatteryLife raises the disconnect voltage so the battery isn’t cycled deep day after day, then lowers it again when sunny days return.
Worked Example: A Lithium Battery With a User-Defined Algorithm
A 12V LiFePO4 battery in a small trailer, with a SmartSolar 100/20 powering a router and lights through the load output. Many owners choose a user-defined algorithm for lithium, since BatteryLife is designed around lead-acid behaviour. For example, user-defined algorithm 1 with Vlow at 12.0V and Vhigh at 13.2V switches loads off before the battery is deeply discharged and back on once solar has recovered it (example values; follow your battery maker’s recommended cut-off voltages).
Setting the Load Output in VictronConnect
- Open the SmartSolar in VictronConnect and go to Settings → Load output.
- Choose the mode: BatteryLife, conventional, user defined, always on or always off.
- For user-defined modes, enter Vlow and Vhigh.
- Watch the load output state on the main screen to confirm it switches as expected.
The Virtual Load Output for Bigger Loads
Larger SmartSolar models without a physical load output can still control loads through the VE.Direct TX port. With a VE.Direct TX digital output cable connected to a Smart BatteryProtect’s remote input, the controller switches the BatteryProtect on and off using the same load output modes. The BatteryProtect then carries the current, so you can control much larger DC loads.
| Load size | Approach |
|---|---|
| Up to 15A (12/24V) | Physical load output on 75/10, 75/15, 100/15 |
| Up to 20A (12/24V) | Physical load output on 100/20 |
| Larger DC loads | Virtual load output plus a BatteryProtect |
| Inverters | Direct to battery, with their own low-voltage cut-off |
Street Light Mode
Victron’s SmartSolar controllers also include a street light function that can switch the load output on at dusk and off after a set time or at dawn, based on solar panel voltage. It’s useful for path lights, signage and security lights on a solar-only system.
Wiring Tips
- Fuse the battery cable close to the battery.
- Connect the load positive to the load output terminal and the load negative to the battery negative side, as shown in the manual.
- Use cable sized for the load current and run length.
Checking the Load Output History
VictronConnect’s history shows daily solar yield and the battery’s minimum and maximum voltage. If the load output has switched off on a given day, the minimum voltage tells you how close the battery got to the cut-off. Over a few weeks, that shows whether the system has enough solar for its loads.
FAQ
What is the Victron MPPT load output for?
Switching DC loads off at low battery voltage, and on again when it recovers, so you don’t over-discharge the battery.
What’s the default mode?
BatteryLife.
Can I run an inverter from the load output?
Not within the 15A or 20A rating of most inverters’ input current. Wire inverters directly to the battery.
Can I use the load output and the battery terminals at the same time?
Yes. Loads that need low-voltage protection go on the load output, while chargers and larger loads connect to the battery.
Does street light mode need a timer?
No. The controller uses solar panel voltage to detect dusk and dawn, and you set the on-time in VictronConnect.
Sources: Victron SmartSolar MPPT 75/10, 75/15, 100/15, 100/20 datasheet; MPPT solar charger manual (load output, BatteryLife, load output settings), victronenergy.com, accessed Oct 2026.
Related: SunSwift 60A MPPT Solar Charge Controller Review, EcoFlow Delta 3 Max Solar Setup, BougeRV Arch Pro 200W Flexible Solar Panel Review, plus the Victron Energy Guide