Thank you for your diligence. On this occasion the battery was able to be saved but they have given a route to hopefully arrange a repair from the manufacturer.
David Bateman · Jun 2026 Google
Problem diagnosis · Off-Grid · All brands
Low voltage disconnect — loads cutting off
Your off-grid system is cutting power to loads — lights, fridges, sockets — because the battery voltage has dropped below the LVD threshold. It may recover shortly after, only to trip again under load.
The cause is usually one of four things: the LVD threshold is set too high, high-current loads are causing voltage sag, cold weather has reduced battery capacity, or the battery bank is undersized for the daily load.
The cause is usually one of four things: the LVD threshold is set too high, high-current loads are causing voltage sag, cold weather has reduced battery capacity, or the battery bank is undersized for the daily load.
Free remote diagnostic · pay only if we fix it — from £75 if remediable remotely
- LiFePO4 and lead-acid covered
- Voltage sag is often the cause
- No fix, no fee
Loads keep cutting off in your off-grid system?
We diagnose LVD trips remotely — checking your threshold settings, voltage sag under load, battery temperature, and daily energy balance to find the root cause and recommend the fix.
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Excellent service from Solar Tech Support. Extremely quick to respond, easy to deal with and clearly very talented engineers. They were persistent throughout a complex GivEnergy battery issue and resolved everything completely. Highly knowledgeable, professional and reassuring support from start to finish. Highly recommended.
David Harris · May 2026
I can’t praise this firm enough. After hearing my solar panels rattling in very windy conditions, I contacted Solar Tech (as my installers no longer trade). Ronald was fantastic at explaining what he thought the issue was likely to be. Communication was great throughout keeping me fully updated. The team worked really hard on the day to carry out the necessary work. I can now sleep soundly at night without worrying about the solar panels on my roof. I would thoroughly recommend this firm. Thank you for sorting the problem out.
Carolyn Addison · Jun 2026 Google
Brilliant support to get my solar battery working again. I didn’t expect help on a Saturday but Ron answered the phone, listened and sent me the information I needed to get it going, answered questions etc. A brilliant service I’d happily recommend.
Alison F. Cockerill · Jun 2026 Google
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David · May 2026
Solar Tech Support is an absolute lifesaver. My solar and battery system stopped working completely, but after one quick phone call, they fixed the problem straight away. The original provider, GivEnergy, has gone into administration, leaving me entirely without support from the original installers. It was a terrible situation on GivEnergy’s part, but thankfully, Solar Tech Support came to the rescue!
sohaib maroof · Jul 2026 Google
Why LVD trips are more common in winter
LVD is a protection mechanism, not a fault
The low voltage disconnect exists to prevent battery over-discharge. The problem is either that it is triggering when it shouldn't (wrong threshold or voltage sag), or that it is triggering correctly because the battery genuinely doesn't have enough capacity for the load. Diagnosing which of these applies determines the fix.
UK peak sun hours drop from 4–5 per day in summer to 1.5–2.5 per day in December and January — and low sun angles mean the first and last hours of generation are marginal.
Batteries in unheated outbuildings or sheds can drop to 5–10°C, reducing usable capacity by 15–20% and increasing internal resistance so that voltage sag is worse under the same load.
A 10 kWh battery bank delivering 8 kWh usable in summer may only deliver 6.5 kWh in winter — and sag under load will trip the LVD sooner. If your system triggers LVD in winter but never in summer, the sizing and temperature combination is the diagnosis: the fix is insulation, additional capacity, load reduction, or a generator backup charge source.
Step 1 — settings
Most common fix
Check the LVD threshold setting on the MPPT controller or inverter
Compare your LVD setting against the correct value for your battery chemistry:
RECOMMENDED LVD VOLTAGES BY CHEMISTRY
Reference values
12V LiFePO4: LVD 11.5–12.0V · Reconnect 12.5–13.0V
24V LiFePO4: LVD 23.0–24.0V · Reconnect 25.0–26.0V
48V LiFePO4: LVD 46.0–48.0V · Reconnect 50.0–52.0V
12V AGM/GEL: LVD 11.5–11.8V · Reconnect 12.5–12.8V
12V Flooded: LVD 11.8–12.0V · Reconnect 12.8–13.0V
If the controller is set to a sealed lead-acid profile but you have lithium, the LVD will be set to the SLA value — which may be too high for LiFePO4. Switch to a custom profile and set LVD manually from the battery manufacturer's specification sheet.
Step 2 — measurement
Measure actual battery voltage under load to check for voltage sag
Voltage sag is the most misdiagnosed cause of LVD trips. The battery has capacity remaining, but the terminal voltage drops below LVD under load:
How to test
Use the MPPT monitoring app, VRM (Victron), or a multimeter to read battery voltage during a load event. Note the voltage at the moment of disconnection.
Confirming sag
If the voltage immediately recovers to a healthy level (e.g. jumps from 47V back to 51V the moment loads disconnect), the battery had capacity — the sag triggered LVD, not genuine depletion.
Sag magnitude
A well-sized battery bank should sag less than 2V under normal load. Sag of 3–5V under a 3kW load on a small 5kWh bank is common and means the bank is too small for that load.
Victron-specific
VRM shows a detailed battery voltage graph — look for sharp dips at the time of LVD events in the advanced history section.
Step 3 — loads
Identify loads drawing excessive current and causing voltage sag
Identify which load is active when LVD trips occur. High-current loads cause the most pronounced sag:
HIGH-DRAW LOADS TO CHECK
Reference draws
Kettle: 2–3 kW · 42–62A at 48V DC equivalent
Immersion / water heater: 2–3 kW · constant draw
Workshop tools (angle grinder, circular saw): 1.5–3 kW · surge on startup
Washing machine (heating cycle): 1.5–2.5 kW
Induction hob: 1–3 kW per zone
Fridge: 0.1–0.3 kW · compressor surge 3–5× running draw
Running a kettle and washing machine simultaneously on a small battery bank is a common LVD trigger. Stagger high-draw appliances or run them only during solar hours when the MPPT is also contributing current.
Step 4 — temperature
Often the missing piece
Check for cold-weather capacity loss reducing effective battery size
LiFePO4 capacity and internal resistance are both affected by temperature. A battery in an unheated space in winter is effectively smaller than its nameplate rating:
Capacity by temperature
Capacity at 25°C: 100% (rated capacity)
Capacity at 10°C: ~88–92% of rated
Capacity at 0°C: ~72–80% of rated
Capacity at −10°C: ~55–65% of rated — BMS will likely block charging entirely
Increased internal resistance: Means greater voltage sag per amp drawn at low temperatures — so LVD threshold is hit sooner even with the same load.
If LVD trips are concentrated in winter or at night, check the battery temperature. Insulating the battery enclosure or moving it to a heated space can recover 15–20% of winter capacity loss. See our cold weather battery guide for more detail.
Step 5 — system sizing
Resize the battery bank or adjust load schedule if the system is fundamentally undersized
If LVD trips frequently regardless of season or threshold setting, the battery bank is too small for the daily load. Use this sizing check:
BATTERY BANK SIZING FORMULA
Calculation
1. Total daily load (Wh) ÷ usable DoD (0.8 for LiFePO4, 0.5 for lead-acid)
2. Add 25% for inverter & cable losses
3. Divide by days of autonomy (1–3 typical for off-grid with generator backup)
= Minimum battery bank capacity (Wh)
Add battery capacity
Most lithium systems allow stacking additional modules — check battery compatibility list for parallel limits.
Reduce load
Swap resistance heating for heat pump alternatives. Replace incandescent or halogen with LED. Move washing to solar peak hours.
Add a generator
A generator backup charge input allows the battery to be topped up during sustained low-solar periods rather than relying on the battery alone.
Low voltage disconnect — common questions
The most likely cause is voltage sag — the battery voltage drops below the LVD threshold under load even though the SoC is reasonable. Check what the voltage reads at the moment of disconnection: if it recovers immediately after loads disconnect, voltage sag is the cause. Fix: lower the LVD threshold slightly, reduce peak load current, or increase battery capacity to reduce sag per amp drawn.
For 12V LiFePO4: LVD 11.5–12.0V. For 24V: 23.0–24.0V. For 48V: 46.0–48.0V. These correspond to approximately 10–15% SoC. Setting LVD too high wastes usable capacity and causes trips at healthy SoC levels. Setting it too low risks the BMS triggering deep discharge protection instead. Check your battery manufacturer's specification for the exact recommended value.
Winter LVD trips combine reduced solar input and cold-weather capacity loss. Most effective fixes in order of cost: (1) insulate the battery enclosure to keep temperature above 10°C, (2) reduce high-draw loads during low-generation periods, (3) add a generator as a backup charge source for poor-weather days, (4) add more battery capacity, (5) add more solar panels to improve winter generation.
Yes — most MPPT controllers allow manual LVD configuration. For Victron SmartSolar, it's in VictronConnect under load output settings. For EPsolar/Tracer, it's via the front panel or PC software. For Renogy Rover, it's in the LCD menu. If the controller is set to a preset battery type (e.g. sealed lead-acid), the LVD will use default values that may not match your lithium battery. Switch to a custom profile and enter the LVD voltage from your battery spec sheet.
This is voltage sag under load. Terminal voltage under high current is lower than open-circuit voltage — if the controller reads 48V during a high-current event and your LVD is 48V, it disconnects loads even though true SoC is 20%. Once loads disconnect, voltage recovers to 51–52V, confirming there was capacity remaining. Solution: lower the LVD threshold by 1–2V so it only trips on actual low SoC, or reduce peak load current to reduce the sag magnitude.
The remote diagnostic is free and you only pay if we fix it. Most LVD trips turn out to be settings or sizing issues we can sort remotely, from £75. If the fix needs hardware work, such as adding battery capacity, an on-site visit starts from £245 and we quote before anything is booked. Diagnosis is usually same-day: use the form below to tell us the voltage it disconnects at, your LVD setting and what loads were on, and we will come back with the cause and the fix.
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Loads keep cutting off in your system?
Tell us your battery voltage at the point of disconnection, your LVD threshold setting, and what loads were running. We'll identify whether it's a settings issue, voltage sag, or a sizing problem.
- No fix, no fee
- LVD settings, sag & sizing all covered
- All MPPT controller brands supported
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