question

Hi @Allswell

Nice system. But you underestimate it. I run twice your usage on a bigger inverter with less batts (fla too). I've more solar but aren't immune to foul days. And my SOC 'emergency level' is 75%, so I don't flog em.

11 hr genset runtime is crazy though. I usually don't run mine above 95% SOC because I find no value in less than 1500W output (of 6kVA). Nice to get the batts back to 100% every few days, so then Ill run it in the morn and let the solar dribble finish it. And why I don't bother with auto start. 1.5hr of genset is a bad day.

Ignore your SOC until you tune it. Your little anecdote of the solar reaching 100% quickly is symptomatic of a possible false sync (the default settings need fixing).

You can get a good idea of your SOC from how much A the batts will accept at Absorb V. A bit of a guess, but for your 705Ah, when they can't accept 20A, then they're ~99% done. Regardless of what the SOC says, it ain't worth running the genset.

Make sure your Multi is set to allow a sufficient ac input, both passthrough and charge level. But you wanted settings, these are my Smartshunt's (48V)..

Enough for now. Kick me for more, I love yarning true offgrid. :)

Hey John,

Very kind of you to reply, thank you so much. Lots of support and encouragement there, and great information. When you said a false sync with the charge controller/solar, what are your settings on yours? I don't really know what I'm looking for there to resolve that.

Here's what I have setup right now.

Getting this system fine tuned and operating optimally is so important to me. I invested $10k in Magna and new batteries 4 years ago but they were installed incorrectly by a neighbour and the batteries were not managed properly, hence new batteries. I moved away from Magna because there was such primitive reporting. Love the tech and communication in VE.

What do you suggest I change:

@Allswell

The false sync (that's in the shunt) I surmised won't be happening with your shunt settings. The Charged V is too high. It should be called Sync V, and mine is set just below Float level as I don't want it to sync while still in Absorb phase. It still can, but the low Tail only happens in Float. Your Tail is too low for that CV, and it will likely never sync anyway. See my shunt settings.

Your 50A Genset limit is at 120V and is fine. As an aside, if it's a diesel genset and you run it often at at low load, it will eventually become a smoky monster.

Be concerned about your charge settings. Fine for the Rolls boffins to test for performance on a single battery and recommend a highish Abs V. Then you set up 12 in 3 parallel strings. I don't like paralleled Pb's because imbalance comes into play, and high V worsens it. And it can kill. Ease back a little, they'll still charge fine, and last longer. My settings..

Also check your Temp Compensation figure. Rolls should know that for 24V.

Your fixed 6hr Abs will just boil off water. I have that too, but Adaptive and the Tail overrides it. This is not the same as the shunt tail. It will drop to Float when charge drops to less than 7A in my case. (and where the 20A thing in my first post comes from). This is an 'overcharge preventer'. It uses a figure from the charger, but can be set up to use the shunt A with DVCC. That's in the Cerbo manual, and along with shared V and Temp, something you should set up too.

Hit the manuals if you don't follow this stuff, but come back as you need. This is high-end kit, and there's a learning curve to get the best from it.

Thank you so much John for all of your support, though I must admit I struggle to keep up. I'm learning quickly though. Thank you for your contribution.

Charge Controller Discussion: Soooo many questions:

1. Today is a sunny day and right now, this morning, we are getting good sun on the panels. More sun power than the house is using. Can you tell me why it's not putting the extra into the battery bank?

2. In terms of max charge voltage you're saying the 30v is too high. What do you suggest here for my 24v system? I see in your 48v system you have them set at 2.4v per cell for max charge, then 2.26v per cell for float and 2.7 for equalization. You have said you have flooded lead acid like I do. So should I instead go with these values akin to what you have setup? What are your thoughts on each? Your setup on my system: 28.8v charge, 27.12v float, 32.4 equalization or should I go with what a neighbour has suggested: 26.64v charge (2.22v per cell), 27.2v float (2.26v per cell) and he gave no equalization number for some reason. What do you suggest for tail current? I have no information here.

3. My generator is gas, not diesel. Thank you for asking. I'm currently working on how to figure out the auto start/stop connections to the Cerbo GX. You said you have not connected yours so that means you are starting and stopping it manually, which I am doing right now. Can you please tell me at what rates should I turn it on, and when should I turn it off? I know only what the shop said "when it's 50% turn it on. The minute it hits 100%, turn it off." Is that correct? (See Shunt Discussion below #2 because I'm thinking my comments there are more on track than this approach... I'm learning : )

4. Temperature compensation figure: You mentioned to check it. I have no idea where or what to check for or where to put the information, once I figure out what it is supposed to be. Any advice here?

5. Lost on this: "Your fixed 6hr Abs will just boil off water. I have that too, but Adaptive and the Tail overrides it. This is not the same as the shunt tail. It will drop to Float when charge drops to less than 7A in my case. (and where the 20A thing in my first post comes from). This is an 'overcharge preventer'. It uses a figure from the charger, but can be set up to use the shunt A with DVCC. That's in the Cerbo manual, and along with shared V and Temp, something you should set up too."

But I'm happy to hit up manuals instead of taxing you to teach me what this means. I don't want to boil off water, I think? I just have to top water losses off so that seems counter intuitive! Let me take a stab at this: So you're saying in the Charge Controller I should have it at Fixed at 6 hrs (what Tail Current please?) and then in the Shunt I should have it at Adaptive at 6 hrs (what Tail Current please?). Did I botch that?

6. Newbie Alert: What does DVCC mean? Lost on this: "This is an 'overcharge preventer'. It uses a figure from the charger, but can be set up to use the shunt A with DVCC." I like the idea of setting up an "Overcharge Preventer" so please clarify here. This sounds like a smart thing to set up.

7. Lost on this: "That's in the Cerbo manual, and along with shared V and Temp, something you should set up too."

8. I have an external temp sensor connected to the pos (+) on the battery and running to the shunt. For the life of me anywhere on the dashboard I cannot see the temperature of the batteries so I'm guessing I need to buy another one and hook it up to something else because that one's not working or doing it's job??? Kinda frustrated about this very thing since battery temperatures are a necessary thing to know about and have the system aware of?

9. I added a TP-Link UB400 today so I could extend the reach of the Cerbo GX so that I could see everything I need to from further away. I guess I wrongly assumed it would boost the signal so I could see the Shunt, Inverter and Charge Controller as well, but it seems to have only boosted the Cerbo GX. Any advice here about being able to boost the bluetooth capabilities of all of the devices? Right now, I can only access the full device list from the bathroom and my kids tell me I'm spending far too much time in there!

Thank you so much John. I'm so appreciative to have someone to ask these questions to.

All the best,

Kate

@Allswell

1. The Dashboard doesn't really know what the Multi is using itself with standby current and inverting efficiency. For you it might be like 30-40W at that low load, but the figures will flick about a bit. You could try turning on 'Has DC' in the Cerbo, and it might show something to help a balance. But I just suck it up as 'best effort'.

2. The time-honoured Abs is 28.8V for cycling use. Specialty setups might use something else, but if you want your batts to last, don't go higher than that. Float and Storage modes are more flexible, say 27.0V and 26.4V respectively. You may know you neighbour better than me, but I wouldn't touch those. Peeps are divided on whether to Equalize at all. And they may all be right. With daily cyclers I don't think it's necessary, but in a storage situation has merit. Your 30V and 6 hr Abs is doing it every day.

My 7A Tail I derived from experience. It's over 225Ah, so ~3%. Your 705Ah means ~22A at the same 3%. I roughed yours at 20A as a start point. My Smartshunt is tuned to within an inch of it's life, and at 7A (on an uninterrupted solar day) usually happens at 99.0 to 99.2% SOC. Why flog the batts beyond that?

3. Gensets are expensive, noisy, polluting, maintenance needing, and fuel hungry. (& sometimes #%& unreliable.). Your 'shop' man shows poor comprehension (generous assessment). At 50% SOC your batts will be essentially worthless delivering to a decent load. 75% for me is minimum. So when do I run the genset? Surely not when daybreak and a good solar day imminent. So this stuff gets complex to programme an auto-start. Mine never runs when I can't handle decent power from it (loads plus batts).

4. Temp Comp in the mppt is in Expert mode down the bottom..

This is a roughish thing, but essential for consistent charge. It's in the Multi's charge settings too.

5. Yeh, more thought needed. The Tail function in the mppt is a great feature. It terminates Abs when the batt A setting is reached, ie. it can't accept charge because it's near full. But the stock A reading is from the mppt too, so loads on top of the batt charge foul it up. An A reading from the batt shunt is the cure.

6/ DVCC fixes this. Yep, hit the Cerbo manual. Having consistent V, T and I across your system is good. Mini-network stuff.

7/ Same.

8/ More info needed. If it's a shunt accessory then DVCC can share it across the system. And your chargers can actually compensate in real time.

9/ Please don't *network* your kit with bluetooth while you have Cerbo wires. Extend the bathroom. :)

Shunt Discussion: Sooooo many questions:

1. "And my SOC 'emergency level' is 75%, so I don't flog em."

So what you're saying is on the Shunt I should set my Discharge Floor to 75% so that I don't dip the batteries lower than that before charging them? Right now I have it at 50% because I was told I need to train the batteries through a complete cycle (100%>50%>100%>50%...). Please educate me about this and is 75% better protection for my bank? I'm looking to understand and learn here.

2. "11 hr genset runtime is crazy though. I usually don't run mine above 95% SOC because I find no value in less than 1500W output (of 6kVA). Nice to get the batts back to 100% every few days, so then Ill run it in the morn and let the solar dribble finish it. And why I don't bother with auto start. 1.5hr of genset is a bad day."

So what you're saying here is that when I saw that output/amperage drop down on the last couple hours on the chart below from 8pm/20hrs on to 11pm/23hrs is un necessary and to instead do a maintenance charge to get to that 100% on a sunny day if I'm lucky to also be at my 75% DOD threshold (from question 1 above) and get it to 100% in the morning with the genset and then let the sun do the rest of the bulk/float/absorb? But on other times of day or kinds of weather when that isn't possible, to instead do the genset run up to when the output/amperage drops down and ignore the SOC numbers because I can always get them to 100% another day on a maintenance charge?

Is this one of those, "By Jobe! She's got it!" moments? (Please say yes?)

I had it in my head that each and every time I had to do a charge, I had to get it up to that 100%+absorb to ensure the best battery bank longevity and health. Please confirm/correct me. I'm here to learn.

3. Lost on this: "Make sure your Multi is set to allow a sufficient ac input, both passthrough and charge level." So for my Shunt settings, picking up from the settings conversation in the Charge Controller above, should I set it at:

• Bat Capacity: 705ah
• Charged Voltage: 27v (Your setting per cell at 2.25v)
• Discharge Floor: 75%
• Tail Current: .6% (no idea what this means or what to do here)
• Charged Detection Time: 5m (mine is currently at 3m and I have no idea what this means or what this does when it's changed)
• Peukert exponent: 1.10 (I have reached out to the Rolls rep to ask him what it should be for my exact fla's)
• Charge Efficiency Factor: 89% (Huh? What is this and what does it mean?)
• Current Threshold: 0amps (Huh? What is this and what does it mean?"
• Time-to-go Averaging Period: 3m (Huh? What is this and what does it mean?)

Thanks again John, dare I say I'm beginning to feel just a wee bit more capable about this whole thing due to you?

: )

Kate

@Allswell

1/ That Discharge Floor doesn't control anything. It's used only for the shunt to give you an estimate of how long you have left before you reach it. Your choice how far you run them down. I bought my current set back 5.5 years ago when Li's were expensive and I didn't reckon they were quite ready yet. I budgeted 5yrs but exceeded that, and they still act like brand newies. And I've never drawn them below 70%. So follow the google advice as you may, but mine might be different. Daily exercise is good, but overdoing it maybe not. Batts are evil things, but force yourself to treat em like a lover and they respond. Gentle does it.

2/ By Jobe, yes!! Nice to get them back to the full 100% once a week or so. But wasting fuel on a nothing charge isn't needed. Nor economically viable. How you achieve that in your own situation is for you to consider.

3/ Time to hit the manual. I can answer all that, but it gets tedious. Please forgive me for saying that, but you really need to understand what these things are before you ask how to use them.

That's not a brushoff, you've been a joy to help out. But Victron have masses of documentation on the website. They don't mince words, and anything said is there for a reason.

Come back though, hey..

Thanks again John. I will certainly hit the books!

And after all that progress... yesterday, I changed the settings and woke up this morning to lowbatcutout and no power. No problem. It was time anyway... so fearing the cutout was due to the change to 75%, I changed it back to 50%... no inverting, still that red low battery cutout light blinking at me. I gassed up the genset and fired it up. After a few minutes, the system came back online and was inverting and charging. However, I guess due to the change in my settings, the VRM showed me that the style of charging went from bulk for a couple minutes, to absorb to float all in 5 mins but the batteries are still at 61.5%. Not sure what I screwed up here.

Any ideas why it's not bulk charging now? It's just floating. It's been 30 minutes and the inverter is running the house but the battery level hasn't changed a wink.

Update: I disabled the tail current and the generator went into bulk mode at full watts again. Seems I do not understand tail current...

Back to the manuals!

@Allswell

Don't confuse the TWO Tails, one in the mppt, the other in the shunt. Different functionality, but won't matter if turned off for testing. The Multi charger has NO TAIL setting, and disabling either of the others won't affect how it charges with the genset.

Best not to quote your Charge State by 'style of charging' until you become more familiar.

I hope that Dashboard screenshot isn't typical. It shows the genset working, with low batt V and a miserable 9.5A. You want to see those Watts well into 4 figures at that early stage. The charge settings in the mppt are not used for the Multi/genset. They are separate things, and the Multi's not quite so easily adjusted.

The longer time goes on the worse this setup seems to get. My genset that is 9,000w is now not charging the system at anything higher than 300w. I have no idea what to do here anymore and I'm just getting super discouraged to tell you the truth.

The manuals are so technically written, I need another degree to comprehend it all. Are you aware of any service, anywhere who will just tell me the settings to start me off with?

I feel your pain.. To be honest when you get tied up in knots like this it may be time to start again from scratch regarding your system, I don't mean selling it all and buying something else!! But, it seems, from what you have said, it's the Generator > Multiplus charging that is not working as expected? Now, it maybe that you DO need a local engineer that understands the Victron equipment to help you, rather than the community knowledge here firing away different ideas for you to try? To start with we don't really know whether the generator is working as it should or if there is a compatibility issue? It maybe also that you need to configure the Multiplus correctly? It is possible to have just one software switch or tick-box wrong, or one Voltage/Current setting wrong and things will just not behave.

Have you read this https://www.victronenergy.com/live/multiplus_faq there maybe some gem buried in this document that provides a lightbulb moment?
You may need to use VE configure 3 to setup the Multiplus correctly for the generator.

As someone mentioned above this is "high end kit" and the very fact that it has sooo much setup flexibilty makes for a high level of complexity and potentially an overwhelming learning curve. If I were you I would Hassle your dealer who sold you this equipment until they send an engineer out!!

If you really have to continue on your DIY route then, as they say in Apollo 13 "work the problem".... what do we have that DOES work? Sit down with a flask of coffee and read through the Multiplus documentation again for your particular setup. You have an Off-Grid set-up so don't get distracted or waste time on any of the ESS configuration.
I would also re-read all the documentation on the Smart shunt, check the setup regarding SoC calibration. Hassle the Battery manufacturers for definitive Bulk/Absorb Float numbers for your 24V setup.
Finally go through the same process with the MPPT charge controller.

I know you are getting to a point of frustration and just want a quick fix but in all honesty I don't think this is necessarily going to be solved here? Calm, methodical troubleshooting is the way forward which means just starting with Battery and Multiplus to begin with and adding to it piece by piece checking that it is setup correctly and doing what it is supposed to at each stage. (If you feel up to it you could start by updating the Multiplus firmware before this "re-build" process but I don't think that is the problem here, so if you are not comfortable then don't do it). There is I am sure a solution but sometimes you have to go back before you can move forward. Good luck.

Hi just wondering if you sorted out your charging issues, and if so what the problem turned out to be?