Sudden Voltage Drop when I turn the inverter on (2 Viewers)

[Huffum]

Hi everyone!

Hoping someone could help please.

Electrical setup has been working fine for the past year.
But this morning it decided to act up.

Using the following:
2000w Renogy Inverter
300ah Fogstar Drift Lithium
100/50 Victron MPPT

When the inverter is turned on I'm getting a loud beeping noise indicating a voltage drop.
Victron Connect app is showing it dropping down as low as 7v.
I tested the input terminals on the inverter and it's also reading 7v.

The battery is currently at 13.3v.
The fogstar app doesn't seem to be updating or offering any realtime information.
Also doesn't show any signs of issues in the Protect History.

Does this sound like a BMS issue on the battery causing this problem?

Any ideas?

Thank you in advance!

 

[Jev88]

As you have a Fogstar I would start with calling them for advice on working out what is wrong. Loose connection seems too obvious?

 

[Gromett]

Loose connection seems too obvious?

That would have been my guess as well.
I would also measure voltage at battery end.

 

[Huffum]

Yeah I've looked for loose connections and everything seems totally fine.
I've also checked voltage at battery end and its reading 13.35v.

Just seems to have gone haywire from one day, to the next.

I'll see if Fogstar can advise as it's looking like a battery issue if anything!

Thanks Jev88 Gromett

 

[Guigsy]

It sounds to me like the BMS is not allowing discharge. At low current, your solar supplies everything required. Hence you can see a healthy voltage at the battery. But when the inverter kicks in, it pulls more than the solar can provide, so the voltage sags to 7v.

I confused myself for about an hour in a similar situation. It was late afternoon. Lights were on. But everything would die when I ran the pump... My monkeying with the electrics had disconnected the battery. But I was getting just enough to keep the lights on from the solar.

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[Huffum]

It sounds to me like the BMS is not allowing discharge. At low current, your solar supplies everything required. Hence you can see a healthy voltage at the battery. But when the inverter kicks in, it pulls more than the solar can provide, so the voltage sags to 7v.

I confused myself for about an hour in a similar situation. It was late afternoon. Lights were on. But everything would die when I ran the pump... My monkeying with the electrics had disconnected the battery. But I was getting just enough to keep the lights on from the solar.

Thanks for the detailed response.
Still trying to get to grips with the electrics.
Really appreciate it!

 

[Millcourt]

Could be several different things, but I would initially suspect the App and/or Bluetooth-BMS, meaning that the App was falsely under reporting a higher state of charge whilst the state of charge was progressively falling (perhaps over several weeks) until you observed the problem when you switched on your inverter. A simple first check may be to simply put the battery on EHU charge for 24 hours, check the App is then reporting 100% charge and try out the inverter. Failing this, as others have suggested, ask Fogstar.

 

[ChrisL]

Can we see your solar settings? 14.62v is a bit high, mine is set at 14.25 for absorption and 13.61 for float.

 

[Ian_H]

OP: A screenshot of the fogstar app might be helpful too. You haven't accidentally turned discharge off by any chance?

 

[DandG5515]

With a meter, check voltage at battery terminal when inverter on and solar controller reads 7 volts should all read the same unless a connection has gone.

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[suavecarve]

OP: A screenshot of the fogstar app might be helpful too. You haven't accidentally turned discharge off by any chance?

I was guilty of that on ours last week !

 

[ChrisL]

You haven't mentioned if there was a load connected to the inverter when it was turned on, there was another thread on here earlier this year regarding over discharge protection, symptoms similar to the ones you're experiencing.

Thread 'Fogstar Drift Battery Overload.' https://www.motorhomefun.co.uk/forum/threads/fogstar-drift-battery-overload.299402/

 

[Derbyshire wanderer]

If the inverter has no output load then I suspect it is the problem. If under load, then the battery has probably lost connection to at least one module as the remaining cannot supply enough current.

 

[Huffum]

Can we see your solar settings? 14.62v is a bit high, mine is set at 14.25 for absorption and 13.61 for float.

Hi Chris,

The below was the original setting 14.4v for absorption and 13.6 for float.
As this was recommended on the Fogstar website.

I reduced the absorption to 14.2 this morning after experiencing this issue.

 

[Huffum]

OP: A screenshot of the fogstar app might be helpful too. You haven't accidentally turned discharge off by any chance?

Hi Ian, thanks for responding.

I did double check that, as I read about this happening.
But that is on.

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[Huffum]

You haven't mentioned if there was a load connected to the inverter when it was turned on, there was another thread on here earlier this year regarding over discharge protection, symptoms similar to the ones you're experiencing.

Thread 'Fogstar Drift Battery Overload.' https://www.motorhomefun.co.uk/forum/threads/fogstar-drift-battery-overload.299402/

The Mrs was making a coffee and we had two laptops plugged in.
The inverter usually manages that.
Think the coffee machine is 1400w.

I'll take a look at this thread - thank you for sending it over!

 

[ChrisL]

Do you have the Fogstar app? If so go to the dashboard (bottom right) then protect history and see if you have any occurrences of a protection event having being triggered, they should all be zero if no protection events have occurred.

 

[Huffum]

I've checked the battery with a multimeter and it's still reading 13.35v across the terminals.
My MPPT has now shutdown, my 12v powered items no longer work.
Fridge, lights, water pump etc.

I've spoken with Fogstar and they gave me a password to access the advanced settings to try to change two settings and then immediately charge via electric hookup.
My charger now wont recognise the battery, so that doesnt work either.

So waiting on a further response from them.

Our ferry back to the UK is the 5th September - so we'll have to survive on eating out until then

Thanks for the troubleshooting everyone, really appreciate your input and time.

 

[ChrisL]

I've checked the battery with a multimeter and it's still reading 13.35v across the terminals.
My MPPT has now shutdown, my 12v powered items no longer work.
Fridge, lights, water pump etc.

I've spoken with Fogstar and they gave me a password to access the advanced settings to try to change two settings and then immediately charge via electric hookup.
My charger now wont recognise the battery, so that doesnt work either.

So waiting on a further response from them.

Our ferry back to the UK is the 5th September - so we'll have to survive on eating out until then

Thanks for the troubleshooting everyone, really appreciate your input and time.

You might try using jump leads from another battery to the leisure battery to fool the charger into working.

 

[Guigsy]

I've checked the battery with a multimeter and it's still reading 13.35v across the terminals.
My MPPT has now shutdown, my 12v powered items no longer work.
Fridge, lights, water pump etc.

I've spoken with Fogstar and they gave me a password to access the advanced settings to try to change two settings and then immediately charge via electric hookup.
My charger now wont recognise the battery, so that doesnt work either.

So waiting on a further response from them.

Our ferry back to the UK is the 5th September - so we'll have to survive on eating out until then

Thanks for the troubleshooting everyone, really appreciate your input and time.

I sounds like the battery thinks it's fine. But it's either not outputting any current. It's just not connected at all. Fuse? Loose cable or terminal? It maybe something has failed inside the battery?

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[Ian_H]

Just a thought
Does the battery have a single fused positive wire running to a distribution block? If it has, check the fuse in it, should be at the battery end. If you measure less than 13.x volts at the distribution block it must be a cable issue if you are still getting 13V on the battery terminal.

 

[DandG5515]

If you're seeing 13v at battery and mppt is shut down. ie mppt port to battery seeing 0v then it's a connection problem between battery and mppt and probably the rest of the 12volt. Then nothing to do with battery. This is possible if the inverter was trying to work off the solar only would give low voltage fault.

 

[royw]

just to add the fogstar bms is not that great for capturing true soc due to its threshold of .7 aamp. using a victron shunt with .1 amp trigger will give a far more accurate soc.

 

[headlight]

just to add the fogstar bms is not that great for capturing true soc due to its threshold of .7 aamp. using a victron shunt with .1 amp trigger will give a far more accurate soc.

I have found that with my 230Ah Fogstar the BMS doesn't register any drains less than 1.5 amps so the app SOC can be wildly out compared to the true SOC as shown by my shunt.

 

[royw]

I have found that with my 230Ah Fogstar the BMS doesn't register any drains less than 1.5 amps so the app SOC can be wildly out compared to the true SOC as shown by my shunt.

yup par for the course fogstar are open about the app being a very rough guide, lots of foggy fanboys try and say otherwise . roamer battery/bms far more accurate.

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[MisterB]

I have occasionally had the 'scream of terror' from my Renogy inverter (Fogstar battery as source) and powering off the inverter turning off appliances then powering inverter back on has resolved the issue, albeit by not plugging in as many appliances afterwards.

Our inverter also feeds the Truma so I suspect that leaving it on has sometimes been the problem!

 

[headlight]

yup par for the course fogstar are open about the app being a very rough guide, lots of foggy fanboys try and say otherwise . roamer battery/bms far more accurate.

Yes my Fogstar doesn't detect any drain until I hit 1.6 amps so if you are using low drain items like led lighting, even charging a phone the app SOC can Drift quite a bit out.
The Victron shunt on the other hand registers drains of 0.1 amp so is far more accurate.

 

[Cush]

App I use (xiaoxiang) registers / shows as low as 0.65 amp discharge

 

[Guigsy]

The FogStar BMS doesn't show smaller currents. Which is a pain when the app says the battery is full, but it's been in storage for a couple of months and it is in fact half dead.

But when you're actually in the van and using far more of the battery capacity on a daily basis, the low sensitivity doesn't matter. It doesn't get enough time to Drift (pun intended).

 

[Ian_H]

The FogStar BMS doesn't show smaller currents. Which is a pain when the app says the battery is full, but it's been in storage for a couple of months and it is in fact half dead.

But when you're actually in the van and using far more of the battery capacity on a daily basis, the low sensitivity doesn't matter. It doesn't get enough time to Drift (pun intended).

.For me its easy enough to look at the voltage on the fogstar when the van has stood for a few weeks. If it reads 13.2 or 13.3V its well charged, if 13.1 or less it wants the solar charger turning back on for a couple of days. Before a trip (solar) or on the first day travelling (b2b) I charge it fully so it resets to 100%

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