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css145hs asked

HE battery post-installation performance

I’ve got 3 of the 24v 200ah HE batteries, 2 of the Multiplus 24/230/5000 paralleled and 2 SmartSolar 150/70 units. There’s a Venus GX and Lynx BMS. The system is working well overall but there are a couple issues and things that could be improved. My Lynx firmware is 1.2

(1) The deepest discharge I’ve been able to do is 400ah. I’m doing another test right now but it looks like it will be the same. I expected to be able to pull out closer to 600ah or at least 480ah for the 80% DoD on the spec sheet. Is this expected? It would give me 20% more usable capacity which is non-trivial. They have been charged up to 28.4v. It was a low drain test, about 0.1C.

(2) With the SmartSolar being managed by the BMS via DVCC, it stops charging as soon as the SOC is at 100, it drops the charge voltage to 27v. The problem is if I disable DVCC I can sometimes put another 20% of capacity in, so the SOC is wildly off. Sometimes it’s 10%. The synchronization count increments most days, but it’s rare it actually is fully full, so maybe that’s the problem? I’m currently running with DVCC off the past week and now it gets up to 28.2 or 28.3 most days, and I wake up at 50% SOC rather than 35%. Much better but I’m effectively overriding the BMS even tho it’s the charge voltages on the spec sheet. It also means the solar can power things directly since when it drops to 27v it’s often lower than the battery. Good or bad?

(3) The fans on the batteries run 24/7 even when the temperature is 31C and they are cool to the touch. However they also get damn warm, my max cell temp was 48C on one particular day. It wasn’t more than 33C in the boat. The electrical cabinet is ventilated, triggered by the multiplus fans going on, however the battery can get hot while the multiplus doesn’t so I’m adding a temperature relay on the batteries as well so either can trigger the ventilation fan. Still it be nice if the internal fans didn’t run all the time, it doesn’t seem necessary at night.

(4) I’d really like to reduce my idle draw on the paralleled multiplus. If I turn the inverters off at night, I save over 10% of the battery, but I have a couple very small draw items that I’d prefer to keep them on for. I’m almost considering a separate small AC circuit and a micro inverter. However, I’d be happy if I could somehow have the 2nd inverter in a proper standby mode unless it was needed, which is almost never (electric kitchen, dive compressor and AC drove the sizing, but they rarely run together or near max).

(5) I’ve got a small 3kw Fischer panda inverter genset that feeds into the multiplus AC input. The current limit is set to 15a but it does a very odd thing where it sometimes only pulls in 7-8 and sometimes does 15. It seems random, but is usually stable at whatever it decides for a particular charge cycle. It sometimes changes after an hour. If it’s running low at half the input setting i can increase the input setting and it continues to do half, but then I have to watch it closely since if it flips back to full draw then it would overload the genset. Given that it’s literally half, it seems related to the parallel setup somehow.

I’m considering adding a 4th HE battery but would like these resolved first.

Lithium Battery
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Finished the discharge test. Got a low cell voltage warning at slightly under 3.3v 22.8v battery. 420ah total down to 5.5% SOC started full at 28.2v (so might have have left a little on the table, but it was also reporting 100% for 90 mins). Should be getting more right? Definitely can’t discharge down to 21V without ignoring alarms (could turn the audible alarm off on Venus I suppose). Taking it down to 21V from 22.8V may indeed have given another 100-150ah, maybe should try that next.

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css145hs answered ·

Most recently, just the last few days. The multiplus isn’t even accepting the genset input. I can hear the transfer switch cutting in and out rapidly. It’s got all the recommended settings for an inverter genset. I also have a skylla universal charger for shore power input, I may put that on a switch and move the genset input to that. It’s probably less finicky then the multiplus with the parallel setup. I’ll lose the genset as an AC boost but I have plenty of inverter capacity as is.

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