Fault-finding
The inverter beeps and shuts down in the evening
Almost always the battery hitting its low-voltage cut-off. Three causes account for nearly all of it: something is on the backed-up circuit that should not be, the bank is undersized for the evening load, or the bank has aged. The fault code on the display distinguishes them.
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Read the code, do not guess from the beep
Inverters use distinct codes for low battery, overload, over-temperature and grid-out-of-range, and they beep similarly for all of them. Reading the code takes seconds and separates a battery problem from an overload problem, which have completely different fixes. Note the code before resetting anything, because the reset clears it.
Audit what is actually on the backed-up circuit
The commonest cause is load creep: an air conditioner, a water pump or a second fridge added to the essential circuit after installation. Any one of those transforms the bank's runtime from an evening to minutes. Walk the board and confirm what is genuinely on the backed-up side against what was agreed at installation.
Distinguish overload from depletion
An overload trip happens under load and typically immediately; a depletion cut-off happens at a predictable point in the evening as the bank runs down. If it always fails at roughly the same time regardless of what is switched on, that is depletion. If it fails when a specific appliance starts, that is overload, and the fix is the load rather than the battery.
Measure the bank against its baseline
If the circuit is right and the load is within spec, run a full charge and discharge and compare against commissioning. A bank that has lost a large share of its original capacity will cut out early no matter how the system is configured, and no setting change fixes it.
Why does my solar inverter beep and cut out at night?
Is a beeping inverter dangerous?
It is protective rather than dangerous — the inverter is refusing to continue rather than failing. What it does indicate is that something is wrong with the sizing or the load, and repeatedly running a bank to its cut-off shortens its life measurably. Treat it as a warning to act rather than a noise to tolerate.
Can I raise the low-voltage cut-off to stop it tripping?
You can, and you should not. That setting exists to protect the cells; lowering the threshold to squeeze out more runtime damages the bank and shortens its life sharply. If you need more evening runtime, the honest answers are a smaller backed-up load or a bigger bank, not a changed protection setting.
Why does it happen more in winter?
Because short days mean the bank starts the evening less fully charged, while evenings are longer and lights run more hours. A system that comfortably covers a June evening can cut out in December on the identical load. That is a sizing observation, not a fault, and it is why banks should be sized against the worst season.
Rather have it done?
When a solar system stops producing, the fault is usually the inverter, a string connector or a tripped protection device rather than the panels themselves. Diagnosis in Islamabad or Rawalpindi starts at PKR 5,000, taken off the bill if you go ahead with the repair.
Solar inverter and panel repair in Islamabad — prices and scope