Knox Krypton Fault 03 — Battery Voltage Too High (Battery Over-Charged)

⚠ DANGER — this fault involves lethal voltage. Do not attempt a DIY fix. Call a qualified technician.

What it means: The inverter has measured the battery bank above its permitted voltage ceiling and stopped. Knox Krypton hybrids are rebadged Voltronic Power InfiniSolar units — an identification that comes from retailer listings and an exact specification match, never from Knox itself — and the InfiniSolar V IV fault table gives code 03 as "Battery voltage is too high", with the troubleshooting table describing the condition as "Battery is over-charged" and giving two instructions — return the unit to a repair centre, and check that the specification and quantity of batteries meet requirements. Read that second instruction carefully, because it is telling you the fault may not be in the inverter at all. It may be that the bank wired to it is the wrong voltage, the wrong chemistry setting, or the wrong number of batteries. Code 03 also exists as a warning — flashing, listed as "Battery over charged", with the unit still running. Solid, with the red fault light, it has shut down.

Why does Knox show 03?

The Pakistan factor

This is the code where Pakistan's battery habits become genuinely dangerous. The tubular to lithium upgrade is now routine here, and it is very often done by swapping the bank and leaving the inverter's charge profile untouched — a lead-acid absorption voltage applied to a LiFePO4 pack will drive it over its ceiling every sunny day, and the only thing stopping a fire is a BMS that the installer may never have wired for communication. The second local pattern is arithmetic. Adding one more battery to a string to "get more backup" changes the string voltage, and the InfiniSolar manual's own instruction to check the specification and quantity of batteries exists precisely because that is what people do. The third is the parallel generator charger left connected from the pre-solar days, quietly charging the same bank the inverter is charging. Add the fourth factor, an unventilated store room at 45°C in June, and an over-charge fault stops being a code on a screen. If your bank is flooded or tubular, hydrogen collects at ceiling level in a closed room and there is no smell to warn you of it — the rotten-egg smell is a different gas and its absence proves nothing. Get the room open and get a qualified person in front of it.

How to fix it

  1. Stop and treat this as a hazard, not a nuisance code. An over-charged battery bank is the one fault on this list that can hurt you before the inverter does. A flooded or tubular bank being over-charged gasses hydrogen, which is explosive in an enclosed room. A lithium bank being over-charged is a fire risk. Do not clear the code and walk away.
  2. Safe for a homeowner — ventilate and stay back. Open the door and window of the battery room. No naked flame, no smoking, no switching things on and off near the bank, no torchlight from a switch that sparks. If you can smell rotten eggs, that is hydrogen sulphide from a gassing lead-acid bank and the room needs air before it needs anything else.
  3. Safe for a homeowner — look, from a distance, at the batteries themselves. Bulging cases, a hot terminal, weeping electrolyte or a distorted lithium module are all reasons to stop reading and phone someone now. Do not touch the terminals, do not attempt to disconnect a hot or swollen battery, and do not move it.
  4. Safe for a homeowner — read and photograph the battery voltage shown on the inverter display, and note whether the icon is flashing or solid. That number is the single most useful thing you can hand to the technician, and it is what tells him whether this is a settings problem or a hardware failure.
  5. Safe for a homeowner — if there is a clearly labelled battery isolator or breaker outside the battery enclosure, switching it off stops the charging. That is the limit. Do not open a battery, do not unbolt a lug, do not remove a cell link, do not remove a pack from a live rack, and never attempt to "bleed off" charge. Lithium terminals are live whatever the inverter is doing.
  6. Do not reset the BMS as a way of clearing this. On a lithium bank, an over-voltage protection firing is the protection doing its job — it is the symptom of a real charging fault upstream, not a glitch to be cleared. Resetting it and carrying on removes the last thing standing between a mis-set charger and a fire. A BMS reset is only appropriate once a qualified engineer has found and fixed why the pack went over voltage.
  7. Qualified installer, from here, and before the inverter goes anywhere. Ask him to confirm the three things the manual points at — the nominal DC voltage of your model against the number of batteries actually in the string, the battery-type and charge-voltage settings against the battery manufacturer's data sheet, and whether any second charging source is connected to the same bank. Knox's Krypton 9000 and 9055 are 48 VDC nominal models; other Krypton models are not, so this has to be checked against your unit and not assumed.
  8. Manufacturer service centre if the settings and the bank are both correct. At that point the charge control inside the inverter has failed, which is the condition the InfiniSolar manual returns to a repair centre. Do not keep the system running on it in the meantime.

References