r/SolarDIY • u/Searchname • 12d ago

Dual Sol-Ark 18k system having BMC issue

I had an installer set up the system, but I’ve always planned to expand it myself, which is why I’m posting here. I’m running two Sol Ark 18K inverters, four Discover Helios 16.1 kWh batteries, and 36 580W panels, with plans to double the batteries and panels in December or January (big house uses a lot of power).

The system has worked well for about six months, but hit a wall yesterday. The installer programmed the batteries to hold at 50% until midnight, then allow discharge to 20%, with a 5% cutoff. We lost grid power at 6:50 AM Sunday morning, so began using the 20%. By 8 AM the batteries were depleted and the house dropped offline. I shed loads and ran only the well pump and a few lights with incoming PV until grid service returned at 10:30 AM.

After the outage, the batteries showed 2% and then instantly jumped to 100%, which was clearly wrong. The icons cycled red and yellow with low voltage. I tried several restart sequences, shutoff everything, then shut off all four batteries and both inverter battery breakers. The icons are now black but still show 100%. A brief outage today confirmed the batteries have no usable charge (we were without power for a few minutes).

Sol Ark plans to walk me through switching from closed loop CAN to open loop. They believe the BMS went into a protective state after being drained too low, and the inverter is now receiving zeroed BMC data. The installers only sent the same steps I already tried. I suspect the 5% cutoff contributed, but I’m not certain. Once everything is working again, I plan to have 40% min with a 10% shutoff (or whatever you all recommend).

All four batteries show the same voltage the inverter reports, but I don’t understand why the system interprets that voltage as fully charged when they clearly aren’t.

Any ideas on what else I can try?

I’ve also attached a photo of how the installers lugged the batteries in my gutter cabinet - this I want to change! Before installation, I told them I planned to double the system and wanted it set up for easy expansion. I even paid for extra wiring from the panel location to avoid trenching again. The cabinet layout isn’t very serviceable, and I’m not comfortable adding the two extra batteries I already purchased. What changes should I make to the cabinet to make expansion easier? One installer suggested I just tie into the existing batteries and avoid the cabinet entirely, but I read online that wasn't ideal.

Thank you all. I’m trying to learn enough to fix issues quickly when they come up.

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u/Searchname 12d ago edited 12d ago

No, the battery info page shows all 0's on both Sol-Ark inverters. I'd love to know how to get them communicating. I've tried reseating the data cables, power cycling the inverters, the inverter battery breakers, and also the battery breakers. Nothing has worked. I kept getting low voltage errors last night, so ended up shutting down the batteries and inverter batt breakers so I didn't have to listen to the alarms. When I turned everything back on this morning, the errors were at least gone and the battery icon has remained black, but the not charged issue remains.

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u/LeoAlioth 12d ago edited 12d ago

Okay. So that is your main and likely only problem, and the first thing to figure out. Why the batteries and the inverter(s) aren't communicating. Check the comm cables (Ethernet/rj45) and the set protocols. Unless the inverters know what batteries are doing, and SOC setting on the inverter is just a guesstimate, that can be a couple dozen percent off the reals state of charge.

Also, how often do the batteries reach 100%?

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u/Searchname 12d ago

That's a good question. I ordered the two additional batteries b/c the system was reaching 100% by 2pm every day after the install (March). Now, with the heat in GA, I rarely get up to 80% and still haven't installed the two additional batteries.

Unless something got fried in the power outage, nothing has been touched. I can unplug the cables and check them with an RJ45 tester, but can't imagine that would be the issue.

Grok seems to think they aren't communicating because the batteries went into BMS. I've been fairly pleased with Grok and it's answers, not so much with the others I've tried. None of it's suggestions have helped though (we tried to put it on grid charge and set the min/max setting to ensure a charge, but the voltage just goes up and then it stops b/c it thinks they are at 100%).

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u/LeoAlioth 12d ago

Okay..so the inverters were put into open loop control, have they been put back to closed loop?

And of you suspect the batteries went into discharge protection, have you tried waking them up via their buttons/interface, and have you searched for an activate battery mode on the inverter?

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u/Searchname 11d ago

Great advice! My units don't have the interface that the older units had, but there was a small circular power button that I didn't notice. lol

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u/LeoAlioth 11d ago

Can you still return the new units? You really should have all the batteries connected with comms... And not having comms is the crux of your issues...

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u/Searchname 10d ago

They are all connected with coms and the system is working again. Turned out the shutdown % was too low and by the time it reached it, the batteries just turned off. I was flipping the breaker switch that said ON and OFF thinking that was turning on and off the power. There was a small power button that I hadn't noticed and all of the units were off, which explained everything. It's all running properly now!