Smart Shunt question

[Lyrick]

Can anyone give me advice or thoughts on the following :-

I had my suspicions that my 18 month old 100ah AGM battery was on its way out so thought I'd try the motorhome on battery only for a few hours and check the progress with my Victron Smart Shunt.

The result below has confused me (not difficult) . The attached screenshot shows that after about 18 hours the battery voltage is 12.15volts , which according to a previously posted chart says that the state of charge is around 60%, but the Smart Shunt shows it as 97%. The consumed Ah, hidden behind the low battery warning, is 6ah.

When I switched the lights on in the motorhome the 12v system shut down and the battery voltage fell to 10.5 volts briefly so the battery has had it .

The battery showed as fully charged before I started - Smart Shunt showing 100% and the battery voltage was showing the float voltage as 13.5 volts . It had on a mains charger for the previous 3 days.

Am I misreading the information shown ? I have also attached a screenshot of the settings used . Do they look correct?



I'm assuming I'm missing something.
.

 

[Raul]

Well If the setting of charged voltage is set 13,2 (very low), when the battery is charging and reaches 13,2v the shunt thinks is full; but the battery is possibly 40-60% only full. Set the charged voltage much higher, like 14,2v at least, so the shunt has to wait a bit longer to reset to full. Your shunt is as good as the settings you put in. Also, I suspect that capacity remaining is much less than what you put in the shunt setting value. If you took 6ah and voltage was at 12,15v, then looks a dead one more like a 12-15ah battery.

 

[the1andonly]

If you started with a fully charged battery (3 days on charge) then took out 6ah voltage now 12.15 then as Raul says one dead battery. Forget the SOC calcs on this occasion it is confusing the issue, they may have never been robust.

 

[68c]

I assume you do not have a solar panel connected.

Oh..... I am not usually up at this time of the morning, lying in hospital the day after my second knee replacement thinking of what mods I want to do to my van such as fitting the second solar panel sitting in the garage, which is why I took an interest in your post.

 

[Lyrick]

Well If the setting of charged voltage is set 13,2 (very low), when the battery is charging and reaches 13,2v the shunt thinks is full; but the battery is possibly 40-60% only full. Set the charged voltage much higher, like 14,2v at least, so the shunt has to wait a bit longer to reset to full. Your shunt is as good as the settings you put in. Also, I suspect that capacity remaining is much less than what you put in the shunt setting value. If you took 6ah and voltage was at 12,15v, then looks a dead one more like a 12-15ah battery.

Hi, and thanks for your reply

I agree the charged voltage does look low , but it's the setting recommended by Victron in their video titled " How to optimize the BMV-700 series sync parameters " in which the presenter states that the charged voltage setting should be set at 0.3 v below the end of charge , or float voltage . I know I have a Smart Shunt and not a BMV-700 but the setting parameters follow the same structure and I'm assuming (maybe wrongly) that I can use the same settings. As my float voltage is 13.5 volts I therefore set the charged voltage at 13.2 v.

I'd be interested to hear anyone's thoughts on this and what settings other users of this product use.

The battery , as you say, looks dead .

Thanks again

If you started with a fully charged battery (3 days on charge) then took out 6ah voltage now 12.15 then as Raul says one dead battery. Forget the SOC calcs on this occasion it is confusing the issue, they may have never been robust.

Hi, yes that's the conclusion I've come to. Time for a new battery

I assume you do not have a solar panel connected.

Oh..... I am not usually up at this time of the morning, lying in hospital the day after my second knee replacement thinking of what mods I want to do to my van such as fitting the second solar panel sitting in the garage, which is why I took an interest in your post.

Hi , I do have a solar panel fitted , but I've disabled it in the Smart Solar settings so has no impact in this case.
Hope you recover quickly.

Patrick

^{_{Subscribers  do not see these advertisements}}

 

[Lenny HB]

As Raul says the BMV is only as good as the setting you put in. Mine was reading about 20% out and with Raul's help & further tweaking by me I got it reading very accurately on percentage but it did take over a week of playing around.
Always best to look at ah used since the last charge to work out the SOC.

As Raul says your charge voltage is very low I assume your AGM is type 2 which charge at 14.7v so I would set the charged voltage to 14.4v.

All a bit irrelevant as your battery is knackered, 2 AGM's in my last van only lasted 18 months par for the course with them. Replaced them with Gels & current van has 3 x Gel.
I wouldn't bother playing with the settings until you have a new battery.

These are the settings for my Gels, the capacity takes into account the age of the batteries.

 

[Lenny HB]

Can anyone give me advice or thoughts on the following :-

I had my suspicions that my 18 month old 100ah AGM battery was on its way out so thought I'd try the motorhome on battery only for a few hours and check the progress with my Victron Smart Shunt.

The result below has confused me (not difficult) . The attached screenshot shows that after about 18 hours the battery voltage is 12.15volts , which according to a previously posted chart says that the state of charge is around 60%, but the Smart Shunt shows it as 97%. The consumed Ah, hidden behind the low battery warning, is 6ah.

When I switched the lights on in the motorhome the 12v system shut down and the battery voltage fell to 10.5 volts briefly so the battery has had it .

The battery showed as fully charged before I started - Smart Shunt showing 100% and the battery voltage was showing the float voltage as 13.5 volts . It had on a mains charger for the previous 3 days.

Am I misreading the information shown ? I have also attached a screenshot of the settings used . Do they look correct?



I'm assuming I'm missing something.
.

PhilandMena another one bites the dust.

 

[Lyrick]

Yes , as you say another AGM failure.
In my defence it came already fitted and wasn't expecting it to have a long life , I wasn't dissapointed.

The next step is a new battery , question is which one ?

We are only without EHU a couple of times a year. Usually overnight stops with the occasional 3/4 nighters in the summer.
I have a 120w solar panel feeding the battery through a Victron Smart Solar controller.
I was thinking of getting a 130/140 ah lead acid or an 80ah Gel battery

What do you think ? Lenny HB

 

[Lenny HB]

First thing is what does your charger support?
For your use a standard lead acid will do the job. my preference is for Gels, If you charger only has AGM & Gel setting the Varta LDF range of lead acid can handle the gel setting reasonably well.

 

[Lyrick]

First thing is what does your charger support?
For your use a standard lead acid will do the job. my preference is for Gels, If you charger only has AGM & Gel setting the Varta LDF range of lead acid can handle the gel setting reasonably well.

Hi, thanks Lenny

My charger supports Lead, AGM, Gel and Lithium so spoilt for choice. .

Anyway food for thought.

Thanks again

Patrick

^{_{Subscribers  do not see these advertisements}}

 

[Raul]

Have a look at Trojan and Rolls Surrette as well. I know this are available in UK, but often not mentioned on leisure market. The yanks use them for real off grid for years, with good lifespan.

 

[acropolis22]

As Raul says the BMV is only as good as the setting you put in. Mine was reading about 20% out and with Raul's help & further tweaking by me I got it reading very accurately on percentage but it did take over a week of playing around.
Always best to look at ah used since the last charge to work out the SOC.

As Raul says your charge voltage is very low I assume your AGM is type 2 which charge at 14.7v so I would set the charged voltage to 14.4v.

All a bit irrelevant as your battery is knackered, 2 AGM's in my last van only lasted 18 months par for the course with them. Replaced them with Gels & current van has 3 x Gel.
I wouldn't bother playing with the settings until you have a new battery.

These are the settings for my Gels, the capacity takes into account the age of the batteries.

View attachment 581325

Have you knocked down the charge efficiency? Why so low?

 

[Lenny HB]

Have you knocked down the charge efficiency? Why so low?

Because Gels need a long absorption phase before they are fully charged, well that's my thinking. It's higher than Raul's recommendation. I did a lot of trial and error with a lot of discharging & recharging the batteries before I got the BMV giving accurate results.

 

[autorouter]

When I switched the lights on in the motorhome the 12v system shut down and the battery voltage fell to 10.5 volts briefly so the battery has had it .

10.5V is typical of a battery with a shorted cell (5/6 of 12.6V) so I would agree, it's had it.

 

[Russell's Dad]

Just as a slight aside......
When I was setting up my 2 Yuasa AGM 's charging profile for my solar charger I emailed Yuasa who supplied the charging profile pretty quickly. They were really helpful. I also queried what my AGM 95ah should show when full, as I had seen the charts and was a bit concerned that mine seemed low.
12.7v is what they said. I queried this twice and got the same response. Seems my batteries do not align with the 13v the charts seem to suggest for other AGMs . Nearly 2 years later and they are still 12.7v when full and off load.

^{_{Subscribers  do not see these advertisements}}

 

[Raul]

Have you knocked down the charge efficiency? Why so low?

As Lenny says, because the absorb time. When in bulk, you may charge at 90-95 efficiency. But when you hit absorb can be as low as 60-70 efficiency. It’s not uncommon to consume 1,25kwh to push 1kwh into lead. My house lead battery, takes 1,5kwh to put back for every kwh taken out the battery. That’s round trip efficiency, charge and discharge.

 

[acropolis22]

As Lenny says, because the absorb time. When in bulk, you may charge at 90-95 efficiency. But when you hit absorb can be as low as 60-70 efficiency. It’s not uncommon to consume 1,25kwh to push 1kwh into lead. My house lead battery, takes 1,5kwh to put back for every kwh taken out the battery. That’s round trip efficiency, charge and discharge.

So Victron's default value for charge efficiency, (BMV 712), is 95%. Do you think this is ok for a sealed lead acid battery or still too high?

 

[Lenny HB]

So Victron's default value for charge efficiency, (BMV 712), is 95%. Do you think this is ok for a sealed lead acid battery or still too high?

Probably OK.
Discharge your battery to around 75/80% then compare the SOC by ah used to the percentage reading.

 

[Raul]

…

 

[Raul]

So Victron's default value for charge efficiency, (BMV 712), is 95%. Do you think this is ok for a sealed lead acid battery or still too high?

To high

^{_{Subscribers  do not see these advertisements}}

 

[Lyrick]

So I think I've settled on an Exide ES900 gel battery to replace the dead AGM battery.
I just have one question . I have a smart alternator and a B2b charger installed .
I've read that gels don't like a high charging current will this setup cause any problems ?

Thanks

Patrick

 

[acropolis22]

So, finally got the BMV-712 connected. Feel much better informed now, but not entirely clear on setting up. Can someone shed some light on the accuracy of the various readings? Which are actuals that cannot be doubted and which are calculations that will be affected by wrong values I might enter? I assume SOC is a calculation that depends on other values that I enter? And that current is a true value?

 

[the1andonly]

acropolis22 Measured values are voltage and current. Battery size is an initial constant that depreciates with age (so can normally use the label value for a new battery). There are another constants that depend on the battery type and manufacturer. Once determined these are constant. Initially these may require some playing about with.
SOC is calculated but must be syncronized when fully charged.

Edit hope this isnt to dry.
Getting the correct values could take a number of iterations. I'm still not happy with mine. By the way should be easier with Pb acid as you will want to fully charge and thus syncronize manualy more often.

 

[acropolis22]

acropolis22 Measured values are voltage and current. Battery size is an initial constant that depreciates with age (so can normally use the label value for a new battery). There are another constants that depend on the battery type and manufacturer. Once determined these are constant. Initially these may require some playing about with.
SOC is calculated but must be syncronized when fully charged.

Edit hope this isnt to dry.
Getting the correct values could take a number of iterations. I'm still not happy with mine. By the way should be easier with Pb acid as you will want to fully charge and thus syncronize manualy more often.

Thanks, that's helpful. Presumably the "Consumed Ah" is accurate also since it's derived from a measured value multiplied by time?

 

[Raul]

Thanks, that's helpful. Presumably the "Consumed Ah" is accurate also since it's derived from a measured value multiplied by time?

Yes.

^{_{Subscribers  do not see these advertisements}}

 

[jumar]

Coming in on the back of this thread, can I ask what the Charged Voltage Setting should be on my Victron Smart Shunt using a Lead Acid Battery... I've got it set at 13.2 just now, but where I got that from I do not know...any advice out there..

 

[Lenny HB]

Coming in on the back of this thread, can I ask what the Charged Voltage Setting should be on my Victron Smart Shunt using a Lead Acid Battery... I've got it set at 13.2 just now, but where I got that from I do not know...any advice out there..

I think that is the default setting I would set it to 14.1v at 13.2 it will sync far too early.

 

[jumar]

I think that is the default setting I would set it to 14.1v at 13.2 it will sync far too early.

Having read the thread and your answers to the other points I assumed I needed to ask...thanks Lenny I'll get it changed right now...

 

[autorouter]

So Victron's default value for charge efficiency, (BMV 712), is 95%. Do you think this is ok for a sealed lead acid battery or still too high?

That's the amp-hours the battery can put out, compared to the amp-hours the charger puts in. Lithiums are around 95%, but lead-acids are about 75 to 85% depending on type.

 

[acropolis22]

Now another wrinkle. Clearly I'm clueless here! . Pitched up today at about 12.30 after a 2 hour motorway run. Battery appeared to be fully charged as you would expect. Went off sightseeing, got back 5 hours later and checked battery using the Victron Connect app. One thing I noticed is that it tells me in the history that its 53 minutes since last full charge. That doesn't really stack up. What am I missing?