Battery not dischargingwhat to check
Before treating it as a fault, check what your tariff is asking. A battery holding charge in the evening is very often following a schedule correctly.
Take care
What this means
A battery that sits full and refuses to discharge in the evening, or sits empty on a sunny afternoon, is one of the most reported problems in home storage and one of the least often a fault. The reason is that a modern battery is not simply a bucket the solar fills and the house empties. It is following a strategy, and that strategy is usually built around a tariff. If you are on a time-of-use tariff, the system may be holding charge deliberately to cover a peak period later, or charging from the grid overnight at a cheap rate and holding it, or reserving a proportion for backup. Tesla publish a Backup Reserve setting that does exactly that: it holds a floor of charge that the house cannot use, so the battery can carry you through a power cut, and a reserve set high looks precisely like a battery that will not discharge. They also publish Storm Watch, which charges the battery in anticipation of bad weather and overrides normal behaviour for the duration. Neither is a fault and neither will announce itself unless you go looking.
GivEnergy’s owner diagnostics guide lists the same family of settings in its own words for their equipment: a battery paused from the app, a reserve set too high, a discharge power limit set too low, Export First selected instead of Load First, a smart-tariff lockout, and a battery that is too cold — below freezing — or too hot, which pauses charging until it recovers. There is a generation point worth knowing too. A battery charges from what is left after the house has taken its share, so on a dull morning a system can show solar production and no battery activity at all with nothing wrong. The only number GivEnergy put on this is a note in their installer commissioning portal — the inverter must be generating a minimum of 180 watts to activate the battery, try again at a time of suitable generation — which is a commissioning step, not an operating threshold, and it should not be read as the point below which a running system stops storing. Enphase list, among their published causes for a battery not charging or discharging, tariff settings that do not match the behaviour expected, insufficient sunlight for the solar to supply the home and charge the battery, meters placed or configured incorrectly, and loss of communication between the gateway and the batteries for more than an hour. Solis publish export limiting as a named state rather than a fault.
Every one of those presents to an owner as a battery doing nothing. The genuine faults in this area are worth naming so you can tell them apart. Communication between the battery and the inverter is the common one, and it usually produces a named event in the app rather than silence; GivEnergy add that if the portal shows home consumption but no grid data, the inverter is not seeing the grid meter and the battery will not charge, which is an installer call. So the sequence is: check the tariff and the schedule, check the reserve setting, check for a named event, and only then treat it as a fault. One warning from GivEnergy applies whatever you conclude: do not update firmware while the battery is in a fault state or not operating correctly, because updating during a fault can leave the firmware stuck and make recovery harder.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| A tariff or schedule holding the charge | The commonest explanation. Time-of-use tariffs make systems charge and hold deliberately, and a schedule set up months ago will not match a tariff that has since changed. GivEnergy publish a separate guide on removing a smart-tariff lockout for exactly this. | Common |
| A backup reserve set high | Tesla publish Backup Reserve as a setting that keeps a floor of charge available for a power cut, and GivEnergy’s owner guide says a reserve set too high stops the battery discharging below that percentage. The house cannot use it, so the battery looks stuck. | Common |
| Not enough generation to activate the battery | A battery charges from the excess after the house load, so a dull morning can show solar production and no storage activity. GivEnergy’s only figure is a commissioning-portal note — at least 180 watts of generation to activate the battery at set-up — not an operating threshold. | Occasional |
| Export limiting, a pause, or a weather-anticipation mode | Solis publish export limiting as a named state. GivEnergy publish a play/pause control for the battery and an Export First priority. Tesla publish Storm Watch, which charges ahead of bad weather and overrides normal behaviour. All look like malfunctions and are settings. | Occasional |
| Temperature outside the battery’s charging range | GivEnergy’s owner guide: if the battery is too cold, below 0 °C, or too hot, charging pauses until it returns to normal conditions. A garage battery on a frosty morning can sit idle for this reason alone. | Occasional |
| A communication fault between the battery and the inverter | The genuine fault case. It normally produces a named event in the app rather than silence, which is what distinguishes it from the settings above. Enphase put the threshold at more than an hour without communication between gateway and batteries. | Occasional |
What to try yourself
Look at your tariff first and what the system has been told to do with it. A battery holding charge for a peak period is following instructions rather than failing.
Check the backup reserve setting. If it is set to a high percentage, the battery will sit at that level and the house will not be able to draw below it.
Check whether the battery is paused, limited or set to prioritise export, and whether any weather or storm mode is active. GivEnergy’s owner guide walks through the pause control, the discharge power limit and Export First versus Load First; Tesla’s Storm Watch overrides normal behaviour while it runs.
On a dull day, check whether there is any excess generation for the battery to take. It charges from what is left after the house has drawn its share, so low generation and a running kettle can leave it nothing, with nothing wrong. On a very cold morning, remember GivEnergy pause charging below freezing.
Look in the event history for a named alert. A settings explanation leaves no event; a genuine communication or battery management fault usually does.
If there is a named fault, or the portal shows house consumption but no grid reading, contact your installer rather than trying to clear it yourself.
Do not update firmware to try to fix it. GivEnergy publish the instruction directly: do not update firmware while the battery is in a fault state or not operating correctly, because updating during a fault can leave the firmware stuck.
Get a registered electrician to look at your solar or battery system
We do not pass enquiries to a repair firm, so there is no form here. When you book a registered electrician, tell them the make, the model and the exact code or message on the display, and ask whether they carry parts for this make — that is what turns one visit into a repair rather than a quote.
What it costs to fix
Typical repair cost
£0–£300
Time on site
40 minutes
Nothing if it is a schedule, a reserve or a tariff mismatch, which covers most cases. An installer visit for a communication or battery management fault, which on a system in warranty should be at no cost.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Own this appliance and had this code? . Nothing is published until a person has read it.
Related solar or battery system fault codes
- Inverter shutting down in the middle of the dayUsually simple to fixUsually the grid rather than your system. Inverters must disconnect when mains voltage goes outside the G98 protection settings, and exporting solar is what pushes it there.Related: same brand
- Generating less than expectedUsually simple to fixThe rated figure is a laboratory number a British afternoon rarely supplies. Two published non-faults explain most of the rest: darkness and export limits.Related: same brand
- Panels are still liveStop — call an engineerThere is no switch that stops a panel generating. Turning the inverter off makes it safe to stand next to and leaves the roof wiring live at hundreds of volts.Related: same brand
Related guides
Common questions
Why does my battery stop at 20 per cent?
Almost certainly a backup reserve. Tesla publish it as a floor of charge held so the battery can carry the house through a power cut, and their app shows a Low Backup Reserve indicator once the level is set below 20 per cent, which is why that figure comes up so often. GivEnergy’s owner guide says the same thing in its own words: if the reserve is set too high, the battery will not discharge below that percentage. It looks exactly like a battery that will not discharge fully, and it is a setting you can change.
It charged from the grid overnight. Is that wrong?
Not if you are on a time-of-use tariff, and that is usually why it happens. Charging cheaply overnight and using it during the expensive part of the day is the whole point of pairing storage with that kind of tariff. It only becomes a problem if your tariff has changed and nobody updated the schedule.
The sun is out and the battery is doing nothing.
Check the actual generation figure rather than the weather, and what the house is drawing at the same moment. The battery charges from the excess, and a hazy day can produce a lot less than it looks like. Export limiting is the other common explanation, and that is a setting rather than a fault.
When is it actually a fault?
When there is a named event in the app, when the behaviour does not match any schedule or setting you can find, or when the battery capacity available has visibly dropped over a short period. Communication faults between the battery and the inverter are the common genuine failure, and they generally announce themselves.
My battery is an LG RESU. Is there a recall?
Yes, for a defined batch. LG Energy Solution run a free replacement programme for RESU home batteries containing cells made between April 2017 and September 2018, recorded by the Office for Product Safety and Standards as UK recall 2103-0025 (recall date 26 March 2021; risk of overheating and fire). The UK models listed are RESU3.3, RESU6.5, RESU10, RESU13, RESU7H and RESU10H in Type R and Type C, and the EM048 battery modules. LG say owners are contacted directly, that a remote modification may be applied to reduce the risk until the battery is replaced, and that you can check your serial number on lgessbattery.com. If cables hide the serial label, LG say not to dismantle the battery or cabling to reach it — ask your installer for the number or ask LG to inspect. A RESU of that age behaving oddly is worth checking against the programme before anything else.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer support portal
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.