Guides · Faisalabad, Lahore, Punjab
Solar Battery Not Charging or Draining Too Fast
Short answer
A solar battery that is not charging, or that empties too fast, is usually not a dead battery. The common causes are inverter settings, too little spare solar after your daytime loads, heavier night loads than the battery was sized for, a battery communication (BMS) error, or temperature. Check the app first: battery state of charge (SOC), charge and discharge power, and any alarms. If the battery is swollen, hot, smells or shows a BMS fault, stop and call a technician.
Safety first
Lithium batteries store a lot of energy and can deliver very high currents. This guide covers checks you can make on the inverter screen and app only.
- Do not open the battery case, remove covers or disconnect battery cables.
- Do not move a battery that is hot, swollen, leaking or smells of burning. Keep people away and call for help.
- Never use water on a battery fire.
Our fire safety guide for rooftop solar and lithium batteries covers what to do in an emergency.
Why the battery is not charging
Mode
Inverter priority setting
Communication
Battery and inverter not talking
Solar
Too little PV left after the load
Problem 1: the battery is not charging
Not enough spare solar
Solar power goes to your loads first. The battery only charges from what is left over. On a hot day with two ACs running, there may be little or nothing left for the battery. In foggy winter weeks, the panels may not produce enough to fill it at all.
Check: in the app, compare solar generation with load at midday. If load is close to generation, the battery gets very little. Our guide to why a solar system produces less than expected helps if generation itself looks low.
Charge settings
Hybrid inverters have settings that control when and how the battery charges:
- Output priority (SBU, SUB, utility first) decides whether solar feeds the loads, the battery or the grid first.
- Charger priority decides whether the battery charges from solar only, solar first, or solar and grid together.
- Maximum charge current limits how fast the battery can charge.
- Battery type must match the battery. A lithium battery set as lead-acid, or the wrong lithium profile, can charge badly or stop early.
Our guide to SBU, SUB and utility-first modes explains these in plain language. Settings should be changed by your installer, because the wrong combination can shorten battery life.
The battery breaker or isolator is off
If the battery breaker has tripped or was left off after maintenance, the inverter cannot charge the battery. The app may show the battery as disconnected or at 0%.
Check: look at the battery breaker position. If it has tripped, note it and call service rather than resetting it repeatedly.
BMS communication error
Most lithium batteries talk to the inverter through a communication cable. The battery's battery management system (BMS) tells the inverter how much current it may accept. If that link fails, many inverters stop charging or charge very slowly to stay safe. A battery that does not match the inverter's supported list can cause the same problem.
Check: look for a BMS, battery communication or "battery not connected" alarm. See battery management systems explained.
Temperature limits
The BMS blocks or slows charging when cells are too hot or too cold. In a Punjab summer, a battery in a closed, unventilated room or in afternoon sun can reach its upper limit. On cold winter mornings, a battery in an unheated outbuilding may charge slowly until it warms up.
Check: the battery temperature in the app. Our guide on where to install your inverter and battery covers good locations.
Problem 2: the battery drains too fast
Night load is higher than the battery was sized for
This is the most common cause. A battery is sized for a certain load and number of hours. Add an AC, a water motor, a fridge or an iron at night, and the backup time falls sharply.
Example arithmetic, with round illustrative numbers: suppose a battery has, say, 10 kWh of usable energy. With 1 kW of fans, lights and a fridge, it could in theory last around 10 hours. Add a 1.5 ton inverter AC drawing, for example, about 1.2 kW, and total load becomes about 2.2 kW. Backup falls to roughly 4.5 hours. These numbers are for illustration only; your loads and battery will differ.
Check: the app's load graph at night. Our battery sizing guide and batteries for a full night of backup explain how to match battery size to night use.
Discharge settings
Settings such as the battery cut-off SOC (the level where the inverter stops using the battery) and return-to-grid level change how much of the battery you can use and when. If the battery is set to discharge into the house as soon as solar fades, it may be empty before load-shedding starts. If it is set to hold a reserve, it may look like it is "not being used".
Inverter self-consumption and standby load
An inverter draws some power simply to stay on, and many homes have small loads running all night: Wi-Fi, chargers, CCTV, a fridge. Together they add up over many hours.
Grid charging at night
Some owners set the battery to charge from the grid overnight and then wonder why it is full by morning but empty by evening. Whether grid charging makes sense under your tariff is covered in should you charge your solar battery from the grid at night?
The battery is ageing or a cell is weak
All batteries lose capacity over time. A battery that once lasted the night but now lasts only a few hours, with no change in load, may be wearing out. A sudden drop in SOC (for example from 40% to 10% in minutes) can point to a cell imbalance or BMS calibration problem.
See how long lithium solar batteries last and, if replacement is needed, when and how to replace or expand your solar battery.
Quick diagnosis table
| What you see | Likely cause | What to do |
|---|---|---|
| Battery charges slowly on hot, busy days | Loads using most of the solar | Move heavy loads to times when solar is spare |
| Battery never charges, app shows battery missing | Breaker off or BMS communication lost | Check breaker position; call service |
| BMS or battery communication alarm | Cable, settings or compatibility | Call service; note the exact alarm |
| Charging stops in summer afternoons | Battery too hot | Improve ventilation; ask installer about location |
| Battery empty well before morning | Night load too high or wrong cut-off setting | Check night load; ask installer to review settings |
| SOC jumps suddenly | Calibration or cell imbalance | Call service |
| Backup time has slowly fallen over years | Normal ageing | Check against warranty terms; plan replacement |
Safe owner checklist
- Read the battery SOC, charge or discharge power, and temperature in the app.
- Note any alarm text on the inverter screen.
- Check the battery breaker position by eye.
- Look at what was running when the battery charged poorly or drained fast.
- Reduce heavy night loads for a few days and see whether backup time improves.
- Record screenshots and photos, then contact your installer.
If you are planning to add batteries or upgrade, see our lithium battery price guide. We supply batteries and BESS from Luminey and current Huawei and Sungrow options, matched to a compatible inverter. Our solar load management guide helps you get more from the battery you already have, and our inverter faults guide explains common alarms.
How Solar Works handles battery complaints
For systems we install, our own engineering and technical staff handle after-sales complaints. Once a complaint is registered, we target sending service personnel within 48 hours to begin diagnosis; the time to fix depends on the fault, parts and manufacturer involvement. Our 1-year service warranty applies under the applicable project terms. Battery defects go through the manufacturer's warranty, which.
We can also inspect and diagnose systems installed by other companies, as a chargeable service, across Punjab.
Get today's price or a free site survey
Battery not lasting the night, or planning a bigger one? Send us app screenshots of a full day's battery SOC and load.
- WhatsApp or call: 0336 666 4321
- Email: info@solarworks.pk
- Head office: Main Boulevard, Sargodha Rd, Block F FDA City, Faisalabad
- Lahore branch: 2nd Floor, Jeff Heights, Gulberg, Lahore
- Hours: 9:00 AM to 6:00 PM, daily
We serve customers throughout Punjab. See our Faisalabad and Lahore pages, or contact us.
Frequently asked questions
Why is my lithium battery not charging from solar?
Usually because your loads are using most of the solar, the inverter's charge settings limit it, the battery breaker is off, or the BMS has lost communication with the inverter. Check the app for load, charge power and alarms.
Why does my solar battery drain so fast at night?
Most often because night loads are higher than the battery was sized for, for example an AC or water motor. Wrong cut-off settings, standby loads and battery ageing also shorten backup time.
Can heat stop my battery from charging?
Yes. The BMS slows or blocks charging when cells get too hot, to protect them. Batteries should be kept in a shaded, ventilated place, away from direct sun.
What does a BMS communication error mean?
The battery and inverter have stopped talking to each other, so the inverter cannot safely control charging. It can be a cable, a setting or a compatibility issue. A technician should check it.
Should I change my inverter's battery settings myself?
No. Settings such as battery type, charge current and cut-off levels affect safety and battery life. Ask your installer to review them with you.
Is my battery dead if backup time has dropped?
Not necessarily. Check first whether night loads have grown. If loads are the same and backup has slowly fallen over years, the battery may be ageing; compare with the warranty terms given with your quote.