SmartShunt funny?

[dogz]

I have a basic one AGM battery + one solar + one Victron SmartShunt setup. After a night on EHU and a long motorway run yesterday I’ll accept the battery was at 100% SOC.

Off grid last night tV, charging phones and then some heating this morning the shunt reported 93% SOC, no surprise. You can see the (blue) SOC stepping down in the image

What I don’t understand Is that as soon as the solar was active and the battery current went (minimally) positive reported SOC stepped instantly to 100% … you can just see the blue SOC trace level out on the top right.

Any thoughts appreciated. Faulty shunt?

 

[Lenny HB]

A shunt is only as good as the setting, post your battery setting and we can have a look.

 

[dogz]

Settings attached ….

A shunt is only as good as the setting, post your battery setting and we can have a look.

 

[dogz]

Settings attached ….

And thanks.

Battery is 100Ah AGM. 110W solar panel giving 10 to 20W this grey morning.

 

[Hoovie]

No Settings attached

A jump to 100% is common (but erroneous) when the settings are not correct.
A battery is considered by the Shunt to be fully charged if the current is below a certain amount for a certain time while the voltage is at a certain level. Using the word "certain" as it depends how it is configured, but from memory, typically the values are Current below 3% (so 3A per 100AH of battery) for 3 minutes when the voltage is at 13.8V.
It is VERY easy when there is a solar charging a battery to get a jump to 100% when there is a cloudy day as the current from the solar is quite low and the default voltage is set to just above float. This is why Victron have different recommendations for settings with a setup that has Solar compared to one that does not. If you have a search on YouTube for Victron BMV or Smartshunt, you can find a couple of videos from Victron that explains how they should be configured for different setups.
Personally I will sometimes set the voltage higher than will ever be achieved in some setups to avoid a jump to 100% ever being possible (it means you may only ever get to a 99.9% SOC reported, but is better then a jump to 100% incorrectly.

Note that things like voltage settings on a Smartshunt has NO bearing on how the battery is charged - the Shunt is just a monitor so setting a higher voltage will just affect the reported SOC and not the charge to the battery.

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[Hoovie]

And thanks.

Battery is 100Ah AGM. 110W solar panel giving 10 to 20W this grey morning.



View attachment 1039059

Voltage setting way too low.

 

[dogz]

Voltage setting way too low.

No Settings attached

A jump to 100% is common (but erroneous) when the settings are not correct.
A battery is considered by the Shunt to be fully charged if the current is below a certain amount for a certain time while the voltage is at a certain level. Using the word "certain" as it depends how it is configured, but from memory, typically the values are Current below 3% (so 3A per 100AH of battery) for 3 minutes when the voltage is at 13.8V.
It is VERY easy when there is a solar charging a battery to get a jump to 100% when there is a cloudy day as the current from the solar is quite low and the default voltage is set to just above float. This is why Victron have different recommendations for settings with a setup that has Solar compared to one that does not. If you have a search on YouTube for Victron BMV or Smartshunt, you can find a couple of videos from Victron that explains how they should be configured for different setups.
Personally I will sometimes set the voltage higher than will ever be achieved in some setups to avoid a jump to 100% ever being possible (it means you may only ever get to a 99.9% SOC reported, but is better then a jump to 100% incorrectly.

Note that things like voltage settings on a Smartshunt has NO bearing on how the battery is charged - the Shunt is just a monitor so setting a higher voltage will just affect the reported SOC and not the charge to the battery.

Thank you for the very helpfull explanation, clears this up for me nicely.

 

[AdrianChen]

I have a basic one AGM battery + one solar + one Victron SmartShunt setup. After a night on EHU and a long motorway run yesterday I’ll accept the battery was at 100% SOC.

Off grid last night tV, charging phones and then some heating this morning the shunt reported 93% SOC, no surprise. You can see the (blue) SOC stepping down in the image

What I don’t understand Is that as soon as the solar was active and the battery current went (minimally) positive reported SOC stepped instantly to 100% … you can just see the blue SOC trace level out on the top right.

Any thoughts appreciated. Faulty shunt?



View attachment 1038983

What absorption voltage setting do you have set on the charger? Normally I would use 0.2v lower than absorption for the Charged Voltage setting on the shunt.

Once you have hit 13.2v as set on yours the shunt will use the tail current of 4% of the AH setting so in the case of a 100AH battery 4amps to determine the battery is full, this condition must be met for 3mins (Charge detection time). So with Solar that can mean that as the sun rises the solar puts out a small current, enough to raise the battery voltage to 13.2v, if the current stays at 4amps or less for three minutes, the shunt sets to 100%.

If the charged voltage is set to 0.2v below absorbtion, say 14.5v for agm with 14.7v absorption, the shunt is less likely to got to 100% early, especially on an EHU type charger - with solar there is always a risk of low output I guess. Mine (Lithium) is set for 2% currently, on a 430ah bank.

 

[Lenny HB]

Charged voltage needs to be around 14.5v and charge efficency 75/80%.
Your settings explane your odd readings.

With lead batteries you need to tweak the settings and until the SOC reads correctly.

On my last van with Gel batteries I spent a couple of weeks discharging and recharging the batteries between tweaks to get it reasonably accurate. You will never get it much more accurate than 5% with lead.

Also for each year of battery age you need to reduce the battery capacity by 2.5%.

 

[dogz]

What absorption voltage setting do you have set on the charger? Normally I would use 0.2v lower than absorption for the Charged Voltage setting on the shunt.

Once you have hit 13.2v as set on yours the shunt will use the tail current of 4% of the AH setting so in the case of a 100AH battery 4amps to determine the battery is full, this condition must be met for 3mins (Charge detection time). So with Solar that can mean that as the sun rises the solar puts out a small current, enough to raise the battery voltage to 13.2v, if the current stays at 4amps or less for three minutes, the shunt sets to 100%.

If the charged voltage is set to 0.2v below absorbtion, say 14.5v for agm with 14.7v absorption, the shunt is less likely to got to 100% early, especially on an EHU type charger - with solar there is always a risk of low output I guess. Mine (Lithium) is set for 2% currently, on a 430ah bank.

On the solar controller absorbtion 14.7V, float 13.8V. (from the Victron AGM profile example)

What absorption voltage setting do you have set on the charger? Normally I would use 0.2v lower than absorption for the Charged Voltage setting on the shunt.

Once you have hit 13.2v as set on yours the shunt will use the tail current of 4% of the AH setting so in the case of a 100AH battery 4amps to determine the battery is full, this condition must be met for 3mins (Charge detection time). So with Solar that can mean that as the sun rises the solar puts out a small current, enough to raise the battery voltage to 13.2v, if the current stays at 4amps or less for three minutes, the shunt sets to 100%.

If the charged voltage is set to 0.2v below absorbtion, say 14.5v for agm with 14.7v absorption, the shunt is less likely to got to 100% early, especially on an EHU type charger - with solar there is always a risk of low output I guess. Mine (Lithium) is set for 2% currently, on a 430ah bank.

absorbtion = 14.7V, float = 13.8V (adopted from the Victron AGM profile.

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[dogz]

Thanks all, that really helps. It was obvious from the current profile that the SOC reporting was off. I haven’t put too much effort into tweaking the AGM settings as I’ve not had this van that long and have been planning a change to Lithium (in the next couple of months now ).

 

[headlight]

Thanks all, that really helps. It was obvious from the current profile that the SOC reporting was off. I haven’t put too much effort into tweaking the AGM settings as I’ve not had this van that long and have been planning a change to Lithium (in the next couple of months now ).

Game changer going to LifePo4.
I went from 2 x 100AH lead acids at 58kgs, 100 amps usable power and 40 amps total continuous discharge to a 230AH LifePo4 at 23kgs, 200 amps usable power and 200 amps continuous discharge.
Cue 2,000 watt inverter, air fryer, panini maker etc .