Skip to content
Configuration guide · Sunsynk battery

Sunsynk Battery Not Charging — System Mode, SolarMan and BMS Faults

Hybrid inverter battery not charging from solar or grid despite settings appearing correct. Most common cause: System Mode set incorrectly in SolarMan portal. Very few of these are actual hardware faults — they're configuration issues resolvable remotely.
  • Most common Sunsynk issue
  • Applies to all Sunsynk hybrid models
  • Usually fixed remotely in one session
Battery staying empty overnight?

This diagnostic guide covers every setting that can prevent charging. Work through the steps in order — most cases are resolved by the third step.

Book your free remote diagnosticSunsynk hub

Safety: Isolate at the DC switch if you notice any error lights on the inverter or battery.

5.0
13 Trustpilot reviews
Trustpilot Google

I have a GivEnergy system consisting of two batteries, two inverters and a controlling EMS (Energy Management System) which has not worked since Nov 2025. After six months I discovered Solar Tech Support, reached out to them and Ron phoned me back – how often do you get that service? Could not be more helpful – worked directly with me over the phone, outside what I would call normal working hours. Lucid explanations and we were able to discuss the issues and history using camera and email history. As this was a very rare setup, Ron was able to access an EMS expert in the field to confirm the solution. One sunny day in, I am now only paying for standing charge and a few pence for spikes in grid consumption while battery catches up with house demand.

Ian · May 2026 Trustpilot

When my GivEnergy system had an issue, I was completely left without support and had honestly lost all hope. Thankfully, I searched online and found Ron, which completely turned things around. After sending him a message, he responded incredibly fast and called me to assure me that he would get the problem fixed. I really admire his dedicated, supportive nature and his determination to find a solution. With this kind of outstanding attitude and customer service, he has absolutely secured a future customer in me.

Sree · May 2026 Trustpilot

Ron want out of is way to help, nothing was to much. He was very thorough in what he did Very knowledgeable I would highly recommend Ron and his company He did a fantastic job for me. if you have any problems, he'll do his best to help you out and resolve your problem. I wouldn't hesitate to recommend them

Dennis Brown · May 2026 Trustpilot

Ron took me through a diagnostic to confirm my GivEnergy Inverter had a fault. A common one as it turns out with the AC Inverter. As GivEnergy is defunct there is no immediate fix, aside from sourcing 2nd hand replacement. It may be that a fix becomes available over the summer which would make a lot of GivEnergy customers happy (Again)

Tony Deacon · May 2026 Trustpilot

Contacted Ron with a problem and he sorted it out quickly with no problems at all. Very knowledgeable on anything solar/ batteries. I would recommend him to anyone

Phill · May 2026 Trustpilot

I've spoken to Ron a couple of times with issues with my Givenergy installation. Such a friendly knowledge guy very highly recommended. Thank you very much for resolving my issues

michael fairhurst · May 2026 Trustpilot

Contacted Solar Tech Support in desperation. After explaining the issues I had with my system a diagnosis was made and a solution proposed. Fantastic service, even contacted a manufacturer to arrange replacement parts for me. Great communications, explained all they were doing and what I had to do, clearly and precisly. Followed up to confirm all was ok. Excellent service.

Mr Machin · May 2026 Trustpilot

After GivEnergy went into liquidation, just my luck, my battery started playing up (internal board crashed). Contacted my installer - not interested! Found Solar tech support on a Google search. Sooo glad I found this company! Ron is extremely helpful and has plenty of experience. He soon confirmed what the fault was, and helped me to get my system up and running again. Now moved my GivEnergy account to Solar tech support, and will definitely use again if I have more issues. Unusual to find such a helpful company in these times, no morons reading scripts, just direct contact with the engineer.

Keith Ballard · Apr 2026 Trustpilot

Contacted Solar Tech Support when trying to understand what my Givenergy inverter problem might be and what might be my options. Received good/honest advise which backed up my thoughts.

Hugh Speirs · Apr 2026 Trustpilot

Ron is a super star. Two months ago my GivEnergy battery failed a firmware upgrade leaving it a brick. My installer couldn't/wouldn't fix it. GivEnergy couldn't/wouldn't fix it. Then they went into administration and all hope was lost. A flurry of emails later and Ron had diagnosed the fault (failed USB flash drive, something I'd suspected) and talked me through resolving it. Two months of nothing resolved in about 3 hours. It's great to work with someone who pays attention to the details, knows that they're doing (not just following a script) and gets stuff sorted without a fuss or up-charging.

Christopher · Apr 2026 Trustpilot

I can add to the list of customers who had already 'given up' on GivEnergy due to their appalling customer service, and that was before they went into administration (their Trustpilot reviews don't lie!). So you can imagine my desperation when, having changed my ISP and my Inverter, predictably, proving to be the only device that didn't connect automatically to my new network, I found zero prospect of any customer support with GivEnergy having called in the administrators just five days earlier! The salvation came from Solar Tech Support. My IT advisor stumbled across their web site and some very helpful tips for beleaguered GivEnergy customers, as well as an offer to provide direct assistance. Nothing ventured, I decided to drop them an E-Mail, with very low expectations based on my experience of GivEnergy customer support. Within an hour Ron had responded with some pin point advice, and after a few exchanges of E-Mails he had nailed the problem, enabling the combined efforts of my IT advisor and solar installer to resolve it and reconnect my Inverter. Thank you Solar Tech Support, and Ron in particular, for coming to the aid of a deserted and despondent GivEnergy customer. Expert, razor sharp advice and first class customer service, even though I wasn't officially a customer.

customer · Apr 2026 Trustpilot

This company are a rare gem, I had a very unusual problem following a failed firmware upgrade on my GivEnergy kit. I then found out GivEnergy were in administration and had dismissed all their support staff! None of the usual fixes to try and restore my inverter comms would work, and I looked everywhere, forums, GivEnergy youtube support videos - even AI couldn't figure it out. My installer was talking about huge sums for system replacements, and being vague / evasive about if they'd even install replacement GivEnergy inverter. Enter Solar Tech Support, reassuring and knowledgeable from the very start, I've learnt loads about my solar system though the friendly chat while my engineer worked as he diagnosed the problem and figured out a fix procedure that I've not found anywhere else - amazing . If you need solar system repairs - especially if you like me have been left high and dry by GivEnergy, I cannot recommend this company enough. Give them a call.

Andy Thomas · Apr 2026 Trustpilot

I sent a message on their website regarding a problem I have on my Givenergy system. Although not supplied by Ronald, I thought it was worth an email. Within the hour on a Saturday, he phoned and we discussed the problem. He logged in remotely and gave excellent advice. I'm too far away for his on-site help but he did diagnose the problem and was happy also to chat through my thoughts about an upcoming solar/battery install I'm planning. Great bloke.... if only he was nearer!

Philip · Apr 2026 Trustpilot

I have a GivEnergy system consisting of two batteries, two inverters and a controlling EMS (Energy Management System) which has not worked since Nov 2025. After six months I discovered Solar Tech Support, reached out to them and Ron phoned me back – how often do you get that service? Could not be more helpful – worked directly with me over the phone, outside what I would call normal working hours. Lucid explanations and we were able to discuss the issues and history using camera and email history. As this was a very rare setup, Ron was able to access an EMS expert in the field to confirm the solution. One sunny day in, I am now only paying for standing charge and a few pence for spikes in grid consumption while battery catches up with house demand.

Ian · May 2026 Trustpilot

When my GivEnergy system had an issue, I was completely left without support and had honestly lost all hope. Thankfully, I searched online and found Ron, which completely turned things around. After sending him a message, he responded incredibly fast and called me to assure me that he would get the problem fixed. I really admire his dedicated, supportive nature and his determination to find a solution. With this kind of outstanding attitude and customer service, he has absolutely secured a future customer in me.

Sree · May 2026 Trustpilot

Ron want out of is way to help, nothing was to much. He was very thorough in what he did Very knowledgeable I would highly recommend Ron and his company He did a fantastic job for me. if you have any problems, he'll do his best to help you out and resolve your problem. I wouldn't hesitate to recommend them

Dennis Brown · May 2026 Trustpilot

Ron took me through a diagnostic to confirm my GivEnergy Inverter had a fault. A common one as it turns out with the AC Inverter. As GivEnergy is defunct there is no immediate fix, aside from sourcing 2nd hand replacement. It may be that a fix becomes available over the summer which would make a lot of GivEnergy customers happy (Again)

Tony Deacon · May 2026 Trustpilot

Contacted Ron with a problem and he sorted it out quickly with no problems at all. Very knowledgeable on anything solar/ batteries. I would recommend him to anyone

Phill · May 2026 Trustpilot

I've spoken to Ron a couple of times with issues with my Givenergy installation. Such a friendly knowledge guy very highly recommended. Thank you very much for resolving my issues

michael fairhurst · May 2026 Trustpilot

Contacted Solar Tech Support in desperation. After explaining the issues I had with my system a diagnosis was made and a solution proposed. Fantastic service, even contacted a manufacturer to arrange replacement parts for me. Great communications, explained all they were doing and what I had to do, clearly and precisly. Followed up to confirm all was ok. Excellent service.

Mr Machin · May 2026 Trustpilot

After GivEnergy went into liquidation, just my luck, my battery started playing up (internal board crashed). Contacted my installer - not interested! Found Solar tech support on a Google search. Sooo glad I found this company! Ron is extremely helpful and has plenty of experience. He soon confirmed what the fault was, and helped me to get my system up and running again. Now moved my GivEnergy account to Solar tech support, and will definitely use again if I have more issues. Unusual to find such a helpful company in these times, no morons reading scripts, just direct contact with the engineer.

Keith Ballard · Apr 2026 Trustpilot

Contacted Solar Tech Support when trying to understand what my Givenergy inverter problem might be and what might be my options. Received good/honest advise which backed up my thoughts.

Hugh Speirs · Apr 2026 Trustpilot

Ron is a super star. Two months ago my GivEnergy battery failed a firmware upgrade leaving it a brick. My installer couldn't/wouldn't fix it. GivEnergy couldn't/wouldn't fix it. Then they went into administration and all hope was lost. A flurry of emails later and Ron had diagnosed the fault (failed USB flash drive, something I'd suspected) and talked me through resolving it. Two months of nothing resolved in about 3 hours. It's great to work with someone who pays attention to the details, knows that they're doing (not just following a script) and gets stuff sorted without a fuss or up-charging.

Christopher · Apr 2026 Trustpilot

I can add to the list of customers who had already 'given up' on GivEnergy due to their appalling customer service, and that was before they went into administration (their Trustpilot reviews don't lie!). So you can imagine my desperation when, having changed my ISP and my Inverter, predictably, proving to be the only device that didn't connect automatically to my new network, I found zero prospect of any customer support with GivEnergy having called in the administrators just five days earlier! The salvation came from Solar Tech Support. My IT advisor stumbled across their web site and some very helpful tips for beleaguered GivEnergy customers, as well as an offer to provide direct assistance. Nothing ventured, I decided to drop them an E-Mail, with very low expectations based on my experience of GivEnergy customer support. Within an hour Ron had responded with some pin point advice, and after a few exchanges of E-Mails he had nailed the problem, enabling the combined efforts of my IT advisor and solar installer to resolve it and reconnect my Inverter. Thank you Solar Tech Support, and Ron in particular, for coming to the aid of a deserted and despondent GivEnergy customer. Expert, razor sharp advice and first class customer service, even though I wasn't officially a customer.

customer · Apr 2026 Trustpilot

This company are a rare gem, I had a very unusual problem following a failed firmware upgrade on my GivEnergy kit. I then found out GivEnergy were in administration and had dismissed all their support staff! None of the usual fixes to try and restore my inverter comms would work, and I looked everywhere, forums, GivEnergy youtube support videos - even AI couldn't figure it out. My installer was talking about huge sums for system replacements, and being vague / evasive about if they'd even install replacement GivEnergy inverter. Enter Solar Tech Support, reassuring and knowledgeable from the very start, I've learnt loads about my solar system though the friendly chat while my engineer worked as he diagnosed the problem and figured out a fix procedure that I've not found anywhere else - amazing . If you need solar system repairs - especially if you like me have been left high and dry by GivEnergy, I cannot recommend this company enough. Give them a call.

Andy Thomas · Apr 2026 Trustpilot

I sent a message on their website regarding a problem I have on my Givenergy system. Although not supplied by Ronald, I thought it was worth an email. Within the hour on a Saturday, he phoned and we discussed the problem. He logged in remotely and gave excellent advice. I'm too far away for his on-site help but he did diagnose the problem and was happy also to chat through my thoughts about an upcoming solar/battery install I'm planning. Great bloke.... if only he was nearer!

Philip · Apr 2026 Trustpilot
Diagnosis steps

6-step diagnostic process

Work through these steps in order. Most battery charging issues are resolved by Step 2.

1

Check System Work Mode in SolarMan

Log into SolarMan, navigate to Device → Settings → System Work Mode. If the mode is set to Selling First, this is almost certainly your problem. Selling First mode maximises grid export and does not force charge from the grid or solar. Change to Time of Use (or the mode appropriate for your tariff) to enable charging windows.

2

Check SoC target and minimum SoC headroom

In SolarMan, check the State of Charge (SoC) settings: target SoC (maximum charge level) and minimum SoC (discharge floor). If the battery is already at or above the target SoC, the inverter will not charge further — there's no work to do. For example, if minimum SoC is 90% and target is 90%, charging will never happen. Set minimum SoC to ~10-20% and target to 90-100% to allow the system to charge from near-empty to full.

Check your data: Look at SolarMan's battery SoC graph for the previous night. What was the SoC at the moment your charge window was supposed to start? If already at target, there's no headroom to charge.
3

Check BMS communication status

In SolarMan, on the Device page, check the battery status. It should display a valid percentage (e.g., 45% SoC, 78% SoC). If the battery shows 0% or Unknown, the inverter has lost communication with the battery BMS. This prevents charging entirely. Check the CAN or RS485 communication cable between the inverter and battery — it may be loose, disconnected, or damaged.

4

Verify charge schedule times and timezone

In SolarMan, check the Time of Use charge window times. The window must exactly match your tariff's cheap-rate period. Common windows: Octopus Go 00:30–04:30 · Octopus Flux off-peak 02:00–05:00 · Economy 7 approximately 00:30–07:30. Also check that the inverter clock is set to current local time. During British Summer Time (BST), if the clock is still on GMT, the window will fire 1 hour late.

Clock offset is very common: Check the inverter clock in SolarMan (Device → Information). If it shows a time 1 hour different from your local time, the clock hasn't adjusted for BST/GMT changeover.
5

Confirm grid charge is enabled

In SolarMan, find the grid charge settings (usually under Device → Settings → Grid Charge). Verify that grid charge is set to ON for the time windows where you want the battery to charge from the grid. If grid charge is disabled, the battery will only charge from solar generation, not from cheap-rate grid electricity.

6

Check CT clamp orientation if applicable

If your Sunsynk has a CT clamp installed (for import/export monitoring), check that it's oriented correctly. In SolarMan, at night with no solar generation, the grid reading should show a positive value (import). If it shows negative (export) while you're clearly consuming from the grid, the CT clamp may be backwards. This can prevent charging from activating correctly.

Context

About Sunsynk charging issues

Sunsynk hybrid inverters (3.6kW, 5kW, 8kW, 12kW models) are widely installed across the UK from 2020 onwards. They integrate directly with SolarMan monitoring (formerly PVMaster) and support native Octopus Agile, Intelligent, and Go tariff integration via Time of Use schedules. However, the SolarMan portal doesn't always clearly surface these settings, and many systems are delivered with factory defaults rather than customer-optimised configuration.

The result: nearly 30% of Sunsynk owners report battery not charging overnight despite having a charged battery and a cheap-rate tariff available. In almost all cases, it's a settings issue — System Mode set to Selling First, SoC headroom exhausted, or timezone mismatches — not a hardware fault.

Most common causes
1. System Mode = Selling First (not Time of Use)
2. SoC target set too high — battery already at target
3. Inverter clock offset by 1 hour (BST/GMT issue)
4. Grid charge disabled in settings
5. BMS communication lost (battery shows 0% or Unknown)
FAQ

Sunsynk battery charging questions

Check System Work Mode in SolarMan — if set to Selling First, the inverter will export all solar to the grid rather than charging the battery. Change to Time of Use mode. Also check that the battery SoC is below the charge target and that there is headroom to charge. If the battery is already at the target SoC, the inverter will not charge further.
A battery showing 0% or Unknown state indicates the inverter has lost communication with the battery BMS. This is a separate issue from charging configuration. Check the CAN or RS485 communication cable between the inverter and battery. The cable may be loose, disconnected, or damaged. Do not open the battery enclosure yourself — contact a qualified engineer.
Intermittent charging is often caused by: charge window times drifting due to BST/GMT clock mismatch (the window fires 1 hour late), SoC target set too high leaving no headroom to charge, or grid charge being toggled on/off manually. Check your SolarMan logs to see whether the charge window is firing at the expected time. If consistently 1 hour late, the clock/timezone is the issue.
Yes. A battery management system (BMS) fault can prevent charging entirely. The BMS protects the battery cells from overcharge and may trigger a shutdown if it detects abnormal conditions — temperature imbalance, cell voltage issues, or communication errors. If the battery shows as 0% or Unknown in SolarMan (indicating lost BMS communication), or if the battery refuses to charge despite correct settings, a BMS fault is likely. A free remote diagnostic (no fix, no fee) can identify BMS-related faults and determine if the battery requires service or replacement.
Book

Ready to fix your Sunsynk battery charging?

Tell us what you're seeing. We'll review your SolarMan data and settings to identify the exact cause — most cases are resolved in a single remote session.

  • Not affiliated with Sunsynk Energy
  • Free remote diagnostic · no fix, no fee
  • SolarMan and Octopus tariff specialists

By submitting you agree to be contacted about your diagnostic request. We don't share your data with 3rd parties.

Call 07944 877 329 Book free diagnostic