Why the power-on order matters at all
A hybrid inverter is not an ordinary power supply you can "just switch on". Inside it has a DC bus with large capacitors, and on the input there are the battery, the solar panels and the grid. If you apply voltage to these inputs in the wrong order, an inrush of current appears on the bus, and the capacitors may not survive it.
In support practice there is a telling case the team calls the "bang": a customer's capacitors blew when switching from grid to battery. Let us look at why this happens and how to avoid it in a few simple steps.
What happens during the "bang"
When the changeover relay operates — especially in winter, when the house has a lot of reactive load (fridges, pumps) — an extra current appears. If at that moment the DC bus had not been pre-charged, or there is a phase imbalance in the system, the capacitors take an inrush they are not rated for. The result is their failure, sometimes with the characteristic sound that gave the case its name.
The key idea: the problem is not that the battery is "bad" or the inverter "weak". The problem is the uncharged DC bus at the moment of switching. And it charges correctly when the battery is the first thing brought into operation.
Why does reactive load make the situation so much worse? Fridges, pumps, air conditioners are motors, and at start-up they draw a current many times the rated value. If the source switches over at exactly that moment, the inverter takes a double hit: the inrush from switching and the load's starting current. In summer, when fewer such consumers run at once, the system often "forgives" this. In winter, when everything comes on together, the uncharged DC bus becomes the weak link. That is why the correct start-up order is not a theoretical recommendation but protection for the most expensive part of the inverter.
The correct order: DC → initialisation → AC
The golden rule for powering on a hybrid system looks like this:
- Step 1. Switch on the battery (DC breaker). DC from the battery comes in first. It smoothly charges the DC bus and "wakes" the inverter from its proper source.
- Step 2. Wait for inverter initialisation — 5–10 seconds. Let the inverter finish start-up: bring the DC bus up to the working level and initialise the control board and the BMS link. Do not rush the next step.
- Step 3. Switch on the solar panels and the grid (AC). Only after the inverter has fully initialised do we apply the input from the panels and the grid.
This order guarantees that by the time the grid and the sun appear, the DC bus is already charged and stable — and no dangerous current inrush occurs during switching.
The 5–10-second pause between steps is not a whim but a technical necessity. In that time the inverter manages to raise the DC bus voltage to the working level and finish starting the control board. If you apply AC sooner, you are effectively back to the uncharged-bus scenario. So do not try to "save" those seconds by flipping every breaker in a row — the system will not start any faster for it, while the risk of damage rises.
The main warning: never energise the panels into a "bare" inverter
A separate rule that saves equipment: never energise the solar panels into a "bare" inverter with no battery, unless the model explicitly supports it (Battery-less mode). With no battery, the DC bus has nothing to stabilise it, and the input from the panels can cause the same voltage-inrush problem. If your model officially supports operation without a battery, follow its instructions; if not, the battery always comes into operation first.
Power-off order
For a routine shutdown the logic is mirrored: first remove the AC input (panels and grid), let the inverter finish its work correctly, and only then switch off the battery's DC breaker. That way the DC bus stays under the inverter's control to the last and discharges in an orderly way, not with a "jerk".
The same order applies when you need to shut the system down for maintenance — for example, to clean the panels or check the terminals. Do not start by disconnecting the battery: an inverter left without its reference DC source under load is the same risk again. Calmly remove the AC, wait until the inverter has finished, and only then break the DC. It sounds like excessive caution, but it is exactly this habit that separates systems running for years from those that "somehow keep going back for repair".
Quick checklist before the first start-up
- The battery is connected, DC polarity verified.
- The BMS link is configured (battery type LIB, correct Protocol ID) — details in the article on the Veichi SV to Felicity link.
- There is no phase imbalance on the input.
- The order is observed: battery → 5–10 s pause → panels and grid.
If you are still choosing equipment for the system, see the models in the hybrid inverters section, and practical notes on the range in the article on Veichi hybrid systems.
A separate tip for those starting a system for the first time: do not do it alone and in a hurry. Write the sequence down on paper — which breaker goes after which — and walk through it calmly, with pauses. Most "rookie" failures of hybrid inverters happen in the very first minutes of start-up, when a person is nervous and flips everything at once. A few extra seconds of attention at the start cost far less than replacing a power module or a board. And the habit of always following the "DC → pause → AC" order becomes automatic over time and saves equipment for years.
Frequently asked questions
What do I switch on first — the battery or the panels?
The battery (DC breaker) is always switched on first. Then a 5–10-second pause for inverter initialisation. And only after that the panels and the grid (AC) come on.
Why do the capacitors blow when switching to the battery?
Because of a current inrush during relay switching — especially in winter with a large reactive load — when the DC bus had not been pre-charged or there is a phase imbalance. The correct power-on order removes that inrush.
How long should I wait after switching on the battery?
5–10 seconds — until the inverter finishes initialisation and brings up the DC bus.
Can I start the inverter without the battery, from the panels alone?
No, unless the model supports Battery-less mode. With no battery the DC bus does not stabilise, and the input from the panels can damage the inverter.
In what order should I shut the system down?
In reverse: first remove the AC (panels and grid), let the inverter finish its work, then switch off the battery's DC breaker.
Why does the problem get worse specifically in winter?
In winter more reactive load runs at once (fridges, pumps, heating), and the motors' starting currents add to the inrush from switching. The uncharged DC bus becomes the weak link at that moment — which is why the correct start-up order is critical in the cold season.
