A real conundrum for you experts (26 Viewers)

[Purrfecttune]

Here’s something that I have ‘googled’ to death and still don’t know the answer. I have also passed the problem back to Offgrid Power Solutions who are still investigating and I await their response, but in the meantime, it’s driving me mad not understanding.

Four days ago, I had fitted:
One solar panel, 185w to add to existing 100w
Victron MPPT controller
Fogstar Drift 280a
B2B
12/1200 Inverter

Drove home and battery 98%

Since then, the battery has slowly diminished despite a good amount of sunshine (although that is irrelevant because the new panel is soooo efficient and is providing reasonable power even with no sun and some rain).

Currently showing 61% on the app, although the Sargent control panel in the motorhome indicates that both batteries are 100%

The only draw is the newly installed inverter, only 0.8a per day (turned it off this morning, now there is no draw registering).

The solar charger has gone though Bulk, Absorption and Float each day (see attached picture).

BUT, it is going into Absorption too early and then Float when it is far from fully charged.

I have researched this so much I now have a much greater understanding on how the system works/is supposed to work, which is a good thing but I have always hated not knowing or understanding anything in complete detail.

So why is it doing this? With so many self builders out there like Lenny etc, someone must know

 

[Rjcamper]

No idea, but thought I would bump it for you

Lenny HB

 

[AdrianChen]

Here’s something that I have ‘googled’ to death and still don’t know the answer. I have also passed the problem back to Offgrid Power Solutions who are still investigating and I await their response, but in the meantime, it’s driving me mad not understanding.

Four days ago, I had fitted:
One solar panel, 185w to add to existing 100w
Victron MPPT controller
Fogstar Drift 280a
B2B
12/1200 Inverter

Drove home and battery 98%

Since then, the battery has slowly diminished despite a good amount of sunshine (although that is irrelevant because the new panel is soooo efficient and is providing reasonable power even with no sun and some rain).

Currently showing 61% on the app, although the Sargent control panel in the motorhome indicates that both batteries are 100%

The only draw is the newly installed inverter, only 0.8a per day (turned it off this morning, now there is no draw registering).

The solar charger has gone though Bulk, Absorption and Float each day (see attached picture).

BUT, it is going into Absorption too early and then Float when it is far from fully charged.

I have researched this so much I now have a much greater understanding on how the system works/is supposed to work, which is a good thing but I have always hated not knowing or understanding anything in complete detail.

So why is it doing this? With so many self builders out there like Lenny etc, someone must know
View attachment 959405

Could you post up the solar controller battery settings, (inc expert page)...

 

[Speve]

Have you checked the status of your battery on the Fogstar app and also check that your voltage settings are set correctly on you solar regulator.
I have upgraded our system with extra solar,300ah Fogstar Pro with 2000a victron multi smart inverter charger and victron 30a battery to battery dc-dc charger all works well I will try and find settings for devices.

 

[Speve]

Thinking about your usage since you have stopped any drain on battery could it have dropped into storage mode which is a lower voltage for when not in use

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[fishplug]

Too many variables to really try to make sense of it.

Drove home and batteries at 98% - what were they at before you drove home? How long a drive was it? What amps does the new B2B put out? Where was this reading taken from?

Batteries showing 61% on the app. Which app? The Victron one? The Fogstar one? Do you have a shunt on the system? Is it a smart shunt and if so what does that say?

I don't know much about the Sargent systems but from what I understand you can plumb a solar panel into them and they'll charge your batteries. If the old solar panel has now been removed from the Sargent and run through the Victron alongside the new panel then maybe the Sargent doesn't have any way of monitoring the batteries and is somehow defaulting to saying 100%?

As for the MPPT controller - has this definitely been configured to the right charging profile for your Fogstar battery chemistry?

Again, inverters are outside of my field of expertise but I know they'll have some level of parasitic drain unless you isolate them (which it sounds like you have now). Where were you getting the 0.8A / day reading from?

With the inverter off, are the batteries continuing to deplete lower than the 61% on whatever you measured that from?

You say that's the only draw, so in theory with that completely isolated I'd expect the batteries to at least stabilise but actually I'd expect them to increase in capacity through the solar charging. If not then either your method of measuring is incorrect somehow, or there's something else draining the system that has perhaps not been properly connected to the shunt (assuming there is one) and therefore not registering...

Storage mode sounds unlikely to me as it's usually 70-80% so 61% sounds low. I also didn't think that Fogstars had this (but that could be old information or even just me plain old misremembering it!)

Like I say, lots of questions but I can't even hazard a guess at what's causing that much of a drop - assuming it's an actual drop and not an error in measurement.

 

[Speve]

Here’s a link to Fogstar 280 drift recommendations they are saying store at 30 to 50%.

https://cdn.shopify.com/s/files/1/1347/0997/files/NEW250A_280_Spec.pdf?v=1711983516

 

[Purrfecttune]

Too many variables to really try to make sense of it.

Drove home and batteries at 98% - what were they at before you drove home? How long a drive was it? What amps does the new B2B put out? Where was this reading taken from?

Batteries showing 61% on the app. Which app? The Victron one? The Fogstar one? Do you have a shunt on the system? Is it a smart shunt and if so what does that say?

I don't know much about the Sargent systems but from what I understand you can plumb a solar panel into them and they'll charge your batteries. If the old solar panel has now been removed from the Sargent and run through the Victron alongside the new panel then maybe the Sargent doesn't have any way of monitoring the batteries and is somehow defaulting to saying 100%?

As for the MPPT controller - has this definitely been configured to the right charging profile for your Fogstar battery chemistry?

Again, inverters are outside of my field of expertise but I know they'll have some level of parasitic drain unless you isolate them (which it sounds like you have now). Where were you getting the 0.8A / day reading from?

With the inverter off, are the batteries continuing to deplete lower than the 61% on whatever you measured that from?

You say that's the only draw, so in theory with that completely isolated I'd expect the batteries to at least stabilise but actually I'd expect them to increase in capacity through the solar charging. If not then either your method of measuring is incorrect somehow, or there's something else draining the system that has perhaps not been properly connected to the shunt (assuming there is one) and therefore not registering...

Storage mode sounds unlikely to me as it's usually 70-80% so 61% sounds low. I also didn't think that Fogstars had this (but that could be old information or even just me plain old misremembering it!)

Like I say, lots of questions but I can't even hazard a guess at what's causing that much of a drop - assuming it's an actual drop and not an error in measurement.

Being a new battery it was 33% when installed (apparently new batteries shouldn’t be transported fully charged).
The drive home was just under 3 hours.
The Fogstar app is what is showing the 61% charged reading.
MPPT set to lithium correctly.
I only turned the inverter off today and will see tomorrow if the voltage has decreased again. Before turning it off, the battery was decreasing by 0.8a per day with no other draw (as in the picture below).
Tonight the app is showing exactly the same as below except for the amps on the right are now zero (instead of 0.8) with the inverter switched off.
The reason the battery is down to 61% since Saturday is because after getting home, I tested all my electrical items on the inverter which obviously decreased the battery further.
So the bottom line is that the battery does not appear to be dropping as such, but that the solar is only keeping it static, with no increase.
The screenshot below of the Fogstar app was taken close to the same time as the screenshot of the MPPT controller app above.

 

[Purrfecttune]

Screenshot taken tonight that shows the settings.
Before today, they were all set to default which included the Tail Current set to zero and the absorption set to 2 hours.
I custom set it this afternoon to what it is now using Fogstars recommended settings on their user manual.

 

[pappajohn]

Ignore all the gizmos and gadgets and stick a proper multimeter on the battery to check voltage.
Plenty of online voltage charts to choose from.
You'll probably find the Sargent reading is correct.

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[barryd]

Can't help but watching as I have a Sargent system and I am close to getting an almost identical system fitted by Off grid solutions. Good luck getting it sorted.

 

[Purrfecttune]

Ignore all the gizmos and gadgets and stick a proper multimeter on the battery to check voltage.
Plenty of online voltage charts to choose from.
You'll probably find the Sargent reading is correct.

That was my next step, although research tells me that a battery can be fully charged (voltage) but have low amps and this is where my confusion lies.

So the 280ah drift could be fully charged at 13.6v but still only be (apparently) only 61% charged because of the amps My head hurts!

 

[barryd]

That was my next step, although research tells me that a battery can be fully charged (voltage) but have low amps and this is where my confusion lies.

So the 280ah drift could be fully charged at 13.6v but still only be (apparently) only 61% charged because of the amps My head hurts!

Thats how I understand Lithium works. They dont really decrease in Voltage much so at 61% it will likely show 13.6 on a meter same as it would at 100%. I stand to be corrected as its all new to me as well. Just learning off here.

 

[AdrianChen]

Screenshot taken tonight that shows the settings.
Before today, they were all set to default which included the Tail Current set to zero and the absorption set to 2 hours.
I custom set it this afternoon to what it is now using Fogstars recommended settings on their user manual.View attachment 959650

The tail current setting on my chargers is set to disabled (use it on my shunt but not any of the chargers).

Those settings would mean that when the battery hits 14.2v it will switch to absorption (Mine are set a little higher to 14.25 to suit my BMS/cell balancing). Then when the current is less than 11.2a it will drop into float. My bats at 14.2v would probably be below 11.2amps (especialy if the sun is weak/cloudy) so I think it is better disabled. The rest looks fine though

Given the battery is in float (set at 13.5v) on your first screenshot, and the battery voltage is shown as 13.49 which lines up with the settings, I think the fogstar app/bms is out of sync for some reason.

I would guess it needs to be cycled a few times awith good recharges (best done through ehu) till the BMS resets to 100%. Just for a few cycles I would be tempted to go up to 14.4v, and idealy down below 60% SOC but only because I don't know the parameters the Fogstar BMS regards as a cycle, my battery isn't fogstar.

 

[Purrfecttune]

The tail current setting on my chargers is set to disabled (use it on my shunt but not any of the chargers).

Those settings would mean that when the battery hits 14.2v it will switch to absorption (Mine are set a little higher to 14.25 to suit my BMS/cell balancing). Then when the current is less than 11.2a it will drop into float. My bats at 14.2v would probably be below 11.2amps (especialy if the sun is weak/cloudy) so I think it is better disabled. The rest looks fine though

Given the battery is in float (set at 13.5v) on your first screenshot, and the battery voltage is shown as 13.49 which lines up with the settings, I think the fogstar app/bms is out of sync for some reason.

I would guess it needs to be cycled a few times awith good recharges (best done through ehu) till the BMS resets to 100%. Just for a few cycles I would be tempted to go up to 14.4v, and idealy down below 60% SOC but only because I don't know the parameters the Fogstar BMS regards as a cycle, my battery isn't fogstar.

That’s very helpful and informative, thank you.

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[Wanders from Glos]

Can't help but watching as I have a Sargent system and I am close to getting an almost identical system fitted by Off grid solutions. Good luck getting it sorted.

Yes me too.

 

[fishplug]

I think AdrianChen has hit the nail squarely on the head.

The battery's BMS doesn't know exactly what the state of charge is until it has hit 100% for the first time. Once it has it should give you accurate readings.

The good news is that your B2B is clearly working!

 

[Lenny HB]

Ignore all the gizmos and gadgets and stick a proper multimeter on the battery to check voltage.
Plenty of online voltage charts to choose from.
You'll probably find the Sargent reading is correct.

Voltage readings on Lithium won't help to establish the state of charge the voltage on Lithium remains almost constant until there are nearly flat.

 

[Lenny HB]

First ruled with Lithium is ignore what your control panel says 2nd rule take the BMS reading with a pinch of salt.

The BMS will not read small discharges so it will gradually drift out of sync with the state of charge settings.
As Adrian says to get it back in sync you need a few decent charge/discharge cycles.

Best to fit a Shunt they can read much lower currents and once set up properly give good results.

 

[Wanders from Glos]

I get very lost in all this, I am fitting a Victron Energy Battery Monitor BMV-712 Smart, is that a shunt or is it a separate piece of kit? Sorry to hijack the thread.

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[AdrianChen]

I get very lost in all this, I am fitting a Victron Energy Battery Monitor BMV-712 Smart, is that a shunt or is it a separate piece of kit? Sorry to hijack the thread.

It is a shunt with a gauge/screen. I think the shunt part is the same piece of kit as the Smart Shunt, but has the advantage of the screen and and other useful stuff like a relay etc.

 

[Wanders from Glos]

Thanks I thought it was, my other trusted advisor is on holiday and I didn’t want to bother him with a message.

 

[Jabstatt]

Going back, your inverter seems to be drawing 0.8 amps. If it is on, that is 24 times 0.8 amp hours per day.
Or 20 amp hours per day which in this weather is a lot.

Leave it off unless you are using it! Why waste 20 amp hours each day! That will run the coffee machine for fifteen minutes!


Tony

 

[Lenny HB]

I get very lost in all this, I am fitting a Victron Energy Battery Monitor BMV-712 Smart, is that a shunt or is it a separate piece of kit? Sorry to hijack the thread.

As Adrian says but the display is not very useful, easier see on your phone.
I bought a BMV 712 for the programable relay that the Smart Shunt doesn't have.

 

[Lenny HB]

Going back, your inverter seems to be drawing 0.8 amps. If it is on, that is 24 times 0.8 amp hours per day.
Or 20 amp hours per day which in this weather is a lot.

Leave it off unless you are using it! Why waste 20 amp hours each day! That will run the coffee machine for fifteen minutes!


Tony

Always turn ours off between use as on standby it uses 30ah over 24 hours even set to AES it still gets through nearly 20ah.

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[Purrfecttune]

Voltage readings on Lithium won't help to establish the state of charge the voltage on Lithium remains almost constant until there are nearly flat.

Thanks for confirming that Lenny, I was reaching that conclusion myself.
So this suggests that the 100% readings on the Sargent controller are likely based on voltage not amps.

 

[Purrfecttune]

Going back, your inverter seems to be drawing 0.8 amps. If it is on, that is 24 times 0.8 amp hours per day.
Or 20 amp hours per day which in this weather is a lot.

Leave it off unless you are using it! Why waste 20 amp hours each day! That will run the coffee machine for fifteen minutes!


Tony

Thanks Tony. There was me thinking it was 0.8amps per day, (d’oh!)

 

[Purrfecttune]

Always turn ours off between use as on standby it uses 30ah over 24 hours even set to AES it still gets through nearly 20ah.

Thanks Lenny, all becoming clearer now.

 

[Purrfecttune]

Today’s readings at 10.45am. It’s been a sunny morning.
The MPPT shows les and less charge per day, suggesting that as the motorhome is parked on the drive/not being used, the battery doesn’t need any more.
The battery % is the same as yesterday with the draw showing 0.0a, now that I have switched the inverter off.
So it all suggests that the Fogstar app is not giving me a true reading?
See pictures below, and thanks everyone for your input.