Battery appears dead after a power cut

Why is my battery not turning on after a power cut?

If your solar battery has no lights, won't turn on, and the inverter is showing a “Battery Not Connected” fault (code 1055 on Solis inverters), this is a known situation and normally not a hardware fault.

During a power cut, your inverter can continue running by drawing power from your battery. If the power cut lasts long enough, the battery can become fully drained. When a battery's voltage drops too low, the Battery Management System (BMS) shuts everything down to protect the cells from permanent damage — just like a car battery that has been left with the lights on overnight.

The good news: this is usually recoverable. The battery needs a controlled recharge to bring its voltage back to a level where the BMS will wake up again. That process requires trained hands, but we can walk you through getting it sorted.

Good to know

Why does a power cut drain the battery?

When the grid goes down, your solar panels stop generating. They are required by regulation to shut down during a power cut to prevent feeding electricity back onto the grid.

However, your inverter can stay powered on by drawing from your battery while it waits for the grid to return. As it does this, the battery slowly drains. Once it reaches a critical point, the Battery Management System (BMS) triggers safety measures to protect the battery itself.

How to tell if this is your issue

Check for these three signs:

You recently had a power cut — even a few hours without grid power can fully drain a battery that is powering the inverter, if the battery had a low charge.
The battery has no lights at all — press the power/on button on the battery. If no indicator lights turn on, the BMS has shut down due to low cell voltage.
Your inverter shows a battery fault — on Solis inverters, you will see fault code “1055 — Battery Not Connected”. On other systems, you may see “CAN Fail”, “No Battery”, or similar.

If all three apply, your battery has entered deep-discharge protection mode and needs to be recovered by a trained engineer.

If you are unsure, please do contact us and we can help you confirm. We would much rather you check with us than try anything that could damage your equipment.

What to do

What to do next

Do not attempt to open the battery enclosure or connect any external chargers yourself. Battery recovery involves working with live DC voltages and should only be carried out by a qualified engineer with the right equipment and PPE.

Here is what will happen once we are involved:

We will confirm the issue — over the phone or remotely, we can check your inverter logs and confirm the battery has entered deep-discharge protection.
We will schedule a site visit — one of our engineers will attend to recover the battery. The recovery itself is normally quick (30–60 minutes) once we are on site.
We will apply a controlled charge — depending on your battery brand, our engineer will either use the inverter's built-in battery wake-up function (for Solis systems) or connect a low-current DC charger to raise the cell voltage enough for the BMS to reactivate.
Your system will be back to normal — once the BMS is awake, the battery will begin charging normally from your solar panels or from the grid.

How long does it take?

If we can recover the battery remotely using the inverter menu (Solis systems), we can talk you through it right away.

If a site visit is needed, we can typically arrange one within a few working days, depending on our schedule. On-site recovery takes about 30–60 minutes.

For Solis inverter owners: checking the wake-up option

If your system uses a Solis Series 5 or Series 6 hybrid inverter, there is a built-in Battery Wake-Up menu that may allow us to recover the battery remotely without a site visit. This uses the inverter to send a controlled trickle charge from the grid to wake the battery up.

This is the first thing we will try if you have a Solis inverter — and it often works. To see if this is an option for your system, get in touch with us and let us know you have a Solis inverter with a battery that went flat during a power cut. We can talk you through the steps or, in some cases, access the inverter remotely to do it ourselves.

If the inverter menu does not work (which can happen if the battery is too deeply discharged), we will arrange a site visit for the full recovery procedure.

Fault code 1055 on your Solis inverter?

We have a dedicated guide explaining all Solis fault codes, including what code 1055 means and the first things to check before calling us. If the battery has no lights at all, skip straight to contacting us — the checks on that page assume the BMS is still active.