Lights are on, the inverter display shows mains power present, and yet the battery percentage is not moving, or is slowly draining even though grid electricity is clearly available. This is a different fault from a battery that will not charge from solar panels, and a different one again from an inverter that will not transfer load to the battery. Here, the grid is present and working, but the inverter is choosing not to use it to charge the battery, almost always because of a setting rather than a hardware failure.
This guide covers why you would want grid charging at all, the seven most common reasons it stops working, and a safe order to check them in.
Why grid charging matters in the first place
Not every system relies on it daily. A fully solar-charged setup may rarely need grid charging except during a stretch of cloudy weather. But grid charging matters in a few common situations: a run of weak solar days leaves the battery too low heading into an expected evening outage, a system has panels installed but they are not yet commissioned, or a household deliberately tops up the battery from cheaper off-peak grid power before a daytime period of load shedding. When grid charging stops working in any of these situations, the battery simply never recovers, no matter how much mains power is available.
Cause 1: Charger source priority is set to solar-only
Most hybrid inverters let you choose where charging current comes from, commonly a menu named charger source priority, charge source, or similar, with options along the lines of solar only, solar first, or solar and utility. If this is set to solar-only, the inverter will not touch grid power to charge the battery even while mains is present and perfectly healthy, by design.
This setting is sometimes changed deliberately, for instance to avoid pulling grid power during peak tariff hours, and then forgotten. Confirm what the menu is currently set to and what the installer originally configured it to, since a setting changed during a service visit and never reverted is a common and completely silent cause.
Cause 2: The AC charging current limit is set to zero or very low
Separately from the source priority setting, many inverters have their own numeric limit for how much current can be drawn from the grid specifically for charging. If this value has been set to zero, whether by mistake, by an installer being cautious about load on a shared circuit, or through a reset to factory defaults that did not restore your original configuration, the inverter will show grid power as available for the house while charging the battery not at all.
Check this setting specifically, separately from the source priority setting above. The two are easy to confuse, and a technician who corrects one while assuming the other is also fine can leave this cause undiagnosed.
Cause 3: Grid voltage or frequency is outside the inverter’s acceptable charging range
An inverter can be perfectly happy running your lights and fans from a grid supply that is still outside the narrower window it requires before it will use that same supply to charge the battery. Voltage sag during a brownout, or frequency drift on a weak local grid, can trigger this even though the house appears to have normal power.
This is more likely during periods of heavy local demand or on weaker feeders, and it often resolves on its own once grid quality improves. If brownouts are a regular feature in your area, ask your installer whether the inverter’s acceptable charging voltage window can be widened slightly, understanding that widening it too far risks charging from power that is genuinely unstable.
Cause 4: A time-based charging schedule is excluding the current hours
Many hybrid inverters let you program specific hours during which grid charging is permitted, often used to take advantage of off-peak electricity or to avoid drawing grid power during the day when solar should be doing the work instead. If you are checking the system outside its programmed charging window, it will correctly show no grid charging happening, not because anything is wrong, but because it is not supposed to charge right now.
Check the time-based charging schedule menu and confirm the current time falls inside a permitted window. If the schedule no longer matches your actual needs, for instance because your outage pattern has changed, this is a straightforward adjustment rather than a fault.
Cause 5: The battery’s BMS is reporting full or is in a balancing state
If the lithium battery’s own management system believes it is already at or near full charge, it will refuse additional current regardless of what the inverter is prepared to send. This is correct, protective behaviour, not a fault, though it can look identical to a charging failure from the inverter’s side if you are only watching the inverter display rather than the battery’s own indicator or app.
Lithium packs also periodically enter a cell-balancing state near full charge, during which charging current tapers or pauses briefly even though the battery is healthy. If the percentage shown is already high, this may simply be normal behaviour rather than something to fix. How lithium’s voltage and charge behaviour differs from lead-acid is covered in our lithium battery guide.
Cause 6: A wiring or breaker fault on the AC input specific to charging
If the inverter takes grid power for the house load but seemingly not for charging, and the settings above all check out correctly, a wiring issue specific to the charging circuit inside the inverter becomes more likely. This is less common than a settings problem but does happen, particularly after a service visit where a connector was not fully reseated.
This is not usually a safe do-it-yourself repair. If settings are confirmed correct and the fault persists, note exactly what you have already checked and arrange a technician visit rather than opening the unit yourself.
Cause 7: The inverter firmware or display is simply not reporting it correctly
Occasionally the inverter is charging the battery from grid power perfectly normally, and the issue is that the display, app or a particular screen is not reflecting it accurately, especially after a firmware update or a factory reset that changed which values are shown by default. Before assuming a genuine fault, measure the battery’s actual voltage or percentage at two points an hour apart with the same load running, and see whether it has in fact risen, rather than relying on a single display reading.
How to tell this apart from similar-looking faults
This fault specifically means grid power is present and the house load is running from it, but the battery is not charging. It is different from a battery that will not charge from solar panels, which is a daytime, sunny-weather problem covered in our solar panel not charging battery guide, and different again from an inverter that will not switch the house load over to the battery during an outage, covered in our inverter not switching to battery guide. If what you are actually seeing is a low-voltage warning rather than a charging failure, our inverter showing low battery voltage guide covers how to read that reading correctly first.
A worked example
A household in Karachi notices their battery has stayed at around 40 percent for two days despite the grid being on for most of that time, with no loadshedding and no unusual weather. They first check the charger source priority setting and find it correctly allows both solar and utility charging, ruling out cause one.
Next, they check the AC charging current limit and find it set to 0A, left that way after a technician visited the week before to investigate an unrelated overload warning and reset several settings without mentioning it. Correcting the limit back to the installer’s original recommended value resolves the issue immediately, and the battery begins climbing within the hour. This is a textbook case of cause two, where a setting changed during an unrelated service visit went unnoticed because nothing else about the system’s behaviour looked wrong until the battery level stopped recovering.
A diagnostic order that saves time
- Confirm grid power is genuinely present and stable at the inverter, not just at a light switch elsewhere in the house.
- Check the charger source priority setting and confirm it is not set to solar-only.
- Check the AC charging current limit separately, confirming it is not set to zero.
- Check any time-based charging schedule and confirm the current time falls inside a permitted charging window.
- Check the battery’s own indicator or app for its reported state of charge and whether it shows a balancing or full status.
- Measure the battery voltage or percentage twice, an hour apart, under a steady load, to confirm whether charging is genuinely absent or just under-reported.
- If every setting is correct and the battery still is not charging, call a technician and report exactly which of the above you have already ruled out.
Preventing this from happening again
Photograph every settings screen after commissioning, including charger source priority, AC charging current limit and any time-based schedule, so you have a reference if something drifts or a service visit changes a setting without telling you.
Review the time-based schedule seasonally. A schedule that made sense for last winter’s outage pattern may not fit this season’s, and an outdated schedule is one of the quieter causes of a battery that seems to charge inconsistently.
Ask any technician who services the inverter to confirm these settings are unchanged before they leave, rather than discovering weeks later that something shifted during the visit.
Don’t rely on a single display reading. A quick before-and-after voltage check removes most of the ambiguity about whether charging is genuinely happening.
Getting help through BuySolars
Send us your inverter brand and model, what the charger source priority and AC charging current limit are currently set to, and whether the battery’s own app or indicator agrees with the inverter’s display. That combination usually narrows the cause quickly. We supply hybrid inverters and documented batteries with nationwide delivery, and current stock is on our products page.
WhatsApp 03192070022 with your inverter settings for a quick diagnosis.
Most often a charger source priority set to solar-only, an AC charging current limit set too low, or a time-based schedule excluding the current hours.
Yes, a lithium battery’s BMS can taper or pause charging briefly during cell balancing near full, which is normal behaviour.
This fault is about grid charging specifically, with mains power present. Solar charging failures happen in daylight and relate to the panel-to-battery charging chain instead.
Yes. An inverter’s acceptable voltage window for charging can be narrower than what it tolerates for simply powering the house.
You can check it, but confirm any change with your installer first, since setting it too high on an undersized circuit can cause other problems.