question

Peter Hanslope avatar image
Peter Hanslope asked

Understanding Smart Shunt readout

I have x2 100 Ah Leisure Plus sealed lead acid batteries wired in parallel and have just installed a 500 A smart shunt to monitor battery usage. From the product description it suggests the best way to do this is through the State of Charge SOC readout. Following a installation I used the van for two night stop and had a reading 94% SOC but a battery voltage falling to 12.4V at which point I was minimising usage to protect the batteries.

From the above the SOC indicates I should be good to go for a significant amount of time but the this is not reflected in the actual battery voltage which clearly points to needing to put them on charge.

Apologies for my lack of understanding but hopefully someone can point me in the right direction

SmartShunt
3 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
Please add some screenshots from VictronConnect (Main screen and settings).

What other components do you have in the system?
Did you do a full charge cycle after the installation to synchronize the SOC?

0 Likes 0 ·
pwfarnell avatar image pwfarnell commented ·
How do you charge your batteries, do you have solar
0 Likes 0 ·
Peter Hanslope avatar image Peter Hanslope pwfarnell commented ·
Fully charged initially on hook up at home and then yes solar panel on top of van
0 Likes 0 ·
8 Answers
Peter Hanslope avatar image
Peter Hanslope answered ·

Yes did a full charge cycle on hook up overnight.

No other components victron-image.png


victron-image.png (174.7 KiB)
1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

cybermaus avatar image cybermaus commented ·
I suspect Mathias would like the settings also, specifically the battery settings. They are hiding behind the settings cogwheel top-right.
0 Likes 0 ·
Peter Hanslope avatar image
Peter Hanslope answered ·

The requested settings page

img-6841.png


img-6841.png (188.2 KiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Kevin Windrem avatar image
Kevin Windrem answered ·

If you shut down the battery (specifically the shunt) the SOC will be reset to 100% the next time you power up. Battery SOC on reset should be turned off unless you can guarantee that the battery is fully charged any time you power up the shunt. This is hard to guarantee.


This does not explain what you are seeing necessarily.

2 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Peter Hanslope avatar image Peter Hanslope commented ·
Ok I can change that setting
0 Likes 0 ·
kevgermany avatar image kevgermany ♦♦ commented ·

I did this some time ago. It caused low battery alarms. I don't know if this was changed in later firmware.

0 Likes 0 ·
delf67 avatar image
delf67 answered ·

18.6Ah is approx 9% of your capacity, so the SOC should be reading 90/91%. That voltage looks pretty low for that amount of power drawn. How old are the batteries?

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kevgermany avatar image kevgermany ♦♦ commented ·
Battery capacity varies according to load. Usual manufacturer statement is at the 20 hour to discharge rate (C20).
There's a very low current draw here, so the calcs in the shunt will compensate and reflect a higher SOC than you calculate.
0 Likes 0 ·
Peter Hanslope avatar image
Peter Hanslope answered ·

Unfortunately I don’t know the age of the batteries as I’ve only had the van they are installed in for 12mths. One has the indicator disc that is still coloured green ie ok but I guessing this is a pretty crude indicator.


I’m leaning towards it’s the batteries but was trying to understand what the readings were before jumping in and changing them

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

delf67 avatar image
delf67 answered ·

You're sure all of your loads are wired through the shunt? You haven't got anything else that is draining the batteries that the shunt is not measuring? 12.4V for a sealed lead acid battery should correspond to a SOC of about 60%.

I have a 48V system using SLA batteries that are a few years old and definitely below original capacity, and they read 50.6V @ 93%, so 12.63V/ battery.

2 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Peter Hanslope avatar image Peter Hanslope commented ·
Hi can you just provide info on how you relate the measured voltage to a SOC. eg you say that 12.4 should correspond to around 60% - that would be a big help in understanding the relationship between them thsnks
0 Likes 0 ·
Show more comments
Peter Hanslope avatar image
Peter Hanslope answered ·

Single cable coming off the battery through the shunt so can’t see missing anything but will check.

Your point made about SOC should be around 60% is exactly why I’m scratching my head. Battery voltage clearly doesn’t align with the SOC. Would I be right in thinking the SOC is a calculated figure while the voltage is measured. Just trying to understand how the unit works - are the batteries at fault or something else

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

pwfarnell avatar image
pwfarnell answered ·

As you have said that you charge with solar once out on your journey you should change the settings in the SmartShunt because the default ones can confuse low solar power with a fully charged battery and synchronise the SOC to 100% before the batteries are full so you think you have more capacity than you really do. With the default settings, a limited amount of solar can get the battery above 13.2V with a low current which resets the SOC to 100%

Set the charged voltage to 0.2V or so below the absorption voltage, so if the battery charges at 14.4V set the charged voltage to 14.2V. Set the tail current to 2%. This means that the solar has to get the battery up to full charge voltage before synchronisation to 100%.

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Peter Hanslope avatar image Peter Hanslope commented ·
Thanks I will setup as you suggest
1 Like 1 ·