victron shunt not keeping up with the shore charger

simonfraser

simonfraser

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victron shunt on the house batteries
2x 110 Ah gel batteries
shore charger

the shore charger keeps the voltage at 13.8, irrespective of what i use on the boat

the victron shunts shows a gradual decrease in % battery capacity left, always showing it is going to run out of charge after 10 days
with a steady 13.8 V showing on the victron app ??!!

disconnect the shore power and connect it again, virtually instantly the victron shows a 100% charged battery again
Voltage graph shows a 0.5 drop of a few secs when disconnected, then to 14.4 for a few sec, then back to a steady 13.8

any way i can reset the victron software to show a true reading of the battery state ?
 
What does your multimeter tell you about the voltage of the batteries AT REST, by that I mean turn off the shore power and leave everything switched off for at least an hour ideally overnight?

My shore charger holds the batteries on a float charge of 13.2 volts when the batteries are fully charged no matter what systems I have switched on. There will be a slight change in the amps when I turn the fridge on as it draws the greatest amount of power, but the charger soon catches up.

The hours/days used figure is based on a mathematical sum that is there for guidance rather than a scientific fact. 10 days would indicate to me that your batteries are fully charged, this might be a limit on the display. Try running all your systems overnight and see what the Victron is telling you in the morning.
 
The battery must be fully charged at 13.8v, because that's the float stage of the charging cycle.

When you reboot the charger the 14.4v indicates it's entering bulk / acceptance stages, then it drops back down to float because it realises that the battery is already fully charged.

Therefore I assume that "10 days" is the equivalent of ∞ on this model of Victron - it's probably the max number of days the unit can display.

Xa0UQkn.jpg
 
Sandy said:
What does your multimeter tell you about the voltage of the batteries AT REST, by that I mean turn off the shore power and leave everything switched off for at least an hour ideally overnight?

My shore charger holds the batteries on a float charge of 13.2 volts when the batteries are fully charged no matter what systems I have switched on. There will be a slight change in the amps when I turn the fridge on as it draws the greatest amount of power, but the charger soon catches up.

The hours/days used figure is based on a mathematical sum that is there for guidance rather than a scientific fact. 10 days would indicate to me that your batteries are fully charged, this might be a limit on the display. Try running all your systems overnight and see what the Victron is telling you in the morning.
Click to expand...

running the systems afloat / overnight with no charging shows a usage of about 30A per 24 hrs on the Victron
the voltage drops to 12.6 whilst in use, so batteries look ok to as you pointed out

just odd how the victron indicates a 'loss of amps' even though that is not the case
 
simonfraser said:
disconnect the shore power and connect it again, virtually instantly the victron shows a 100% charged battery again
Voltage graph shows a 0.5 drop of a few secs when disconnected, then to 14.4 for a few sec, then back to a steady 13.8

any way i can reset the victron software to show a true reading of the battery state ?
Click to expand...

I have the same 'problem'.
The smartshunt does not reflect true SOC when connected to shore power.
It does show the electric draw though and tells me I will run out of power in ....
Disconnect shore power and the shunt shows SOC 100% almost instantly.

It's not a huge problem as the boat lives on a swinging mooring, but I'll follow this thread with interest.
 
simonfraser said:
yes, ALL negative loads
other than engine start

there is an SMS switch connected to the 12V house battery, 24/7 and that is causing the 'loss'
but as said the charger keeps up with it
Click to expand...

Where is the engine battery negative connected ?

What mains charger do you have ?
 
Have you calibrated the shunt? Ie turn off everything chargers and loads let the battery rest a bit.

Then connect using the app, vixtron connect and then zero the shunt. Should sort you out
 
My Victron BMV712 gets out of kilter with the batteries SOC over a couple of months. I charge them to the point where I know they are at 100%SOC, then set them at 100%in the app.
 
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PaulRainbow said:
Where is the engine battery negative connected ?

What mains charger do you have ?
Click to expand...

just realised the starting battery is connected to the system minus of the shunt at the mo
that is likely to be the issue, victron specify ALL the bateries -ve cables are connected to the batery minus of the shunt
i will change it when back with the boat

this issue arrises as the shunt has a max current which can be below the requirement of the starter

i have emailed victron regarding the rating of the shunt and the starter requirement
 
simonfraser said:
just realised the starting battery is connected to the system minus of the shunt at the mo
that is likely to be the issue, victron specify ALL the bateries -ve cables are connected to the batery minus of the shunt
i will change it when back with the boat

this issue arrises as the shunt has a max current which can be below the requirement of the starter

i have emailed victron regarding the rating of the shunt and the starter requirement
Click to expand...


I think how you have it is correct

1639482517209.png
 
simonfraser said:
k, victron has no problem with a current draw from the starter that is higher than the rating on the shunt, no damage is going to result

Paul, if my engine battery charge is low / in poor condition, will the resistance in the shunt make any significant difference with respect to starting my engine ?
Click to expand...

Won't make any difference to starting.

VicS is correct in post #13 though, the engine battery negative should be connected to the load/system side of the shunt, as per the diagram he posted.

I usually connect the load/system terminal to a negative busbar, then connect all loads, the engine negative and the engine battery negative to the busbar.

When Victron "specify ALL the batteries -ve cables are connected to the battery minus of the shunt" they mean all of the domestic battery negatives.
 
'When Victron "specify ALL the batteries -ve cables are connected to the battery minus of the shunt" they mean all of the domestic battery negatives'

yep, but i have a further battery in the bow, as far as i can tell there is no massive -ve cable back to the aft area where all the other batteries are
guess that shows a slight voltage difference (and its not the same type of battery as all the others) which the victron somehow picks up:

if i include the starter battery with the house battery -ve, no problem starting
but the victron still shows a slight -ve draw, 0.0A to 0.2A, when on the charger
as a result the victron needs resetting to 100% charge before going afloat
all no big deal ofcourse
 
simonfraser said:
'When Victron "specify ALL the batteries -ve cables are connected to the battery minus of the shunt" they mean all of the domestic battery negatives'

yep, but i have a further battery in the bow, as far as i can tell there is no massive -ve cable back to the aft area where all the other batteries are
guess that shows a slight voltage difference (and its not the same type of battery as all the others) which the victron somehow picks up:

if i include the starter battery with the house battery -ve, no problem starting
but the victron still shows a slight -ve draw, 0.0A to 0.2A, when on the charger
as a result the victron needs resetting to 100% charge before going afloat
all no big deal ofcourse
Click to expand...

Where does the negative from the bow battery go to ? (apart from the windlass/thruster, or whatever it's connected to).
 
indeed not, that would take some tracing, the connections are not easy to see
the forward battery is obviously somehow grounded to the other three aft ones, at least a 7m cable run with various connectors
there is going to be some minor voltage difference between the front and aft setup, perhaps the shunt sees that ?
anyway, its not important to me, the battery 'usage' shown on the victron when on charge is around minus 0.15A that in turn adds up over the days and ? reduces the 'aparent capacity' shown
i just reset the total capacity to be available to 100% when i disconnect the shore charger
the battery voltage is def 13.80 when on charge, new batteries
 
simonfraser said:
indeed not, that would take some tracing, the connections are not easy to see
the forward battery is obviously somehow grounded to the other three aft ones, at least a 7m cable run with various connectors
there is going to be some minor voltage difference between the front and aft setup, perhaps the shunt sees that ?
anyway, its not important to me, the battery 'usage' shown on the victron when on charge is around minus 0.15A that in turn adds up over the days and ? reduces the 'aparent capacity' shown
i just reset the total capacity to be available to 100% when i disconnect the shore charger
the battery voltage is def 13.80 when on charge, new batteries
Click to expand...

That's why i asked the question. It could be the connections to the bow battery that are causing the issue. But if you're happy with how it is, no problem.
 
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