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Victron Smart Shunt and Battery Monitors

ICT

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Apr 9, 2020
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Super long story of Victron being of no help and extremely rude and disrespectful. Here is my bottom line. My Victron Smart Shunt is not accurate on the discharge or recharge side. Victron got a distributor involved and this person was helpful. After many emails and a few screen shots he determined that because I never drop below 65% state of charge the Victron smart shunt will not work. He said that at least once every two weeks the shunt must see below 65% discharge and above 90% recharge for my AGM batteries. Sounds like it is true but my question to the group is does anyone else with AGM batteries have a smart shunt issue? Does anyone else have a battery monitor that is working correctly with AGM batteries?
 
I don't know what the 65% has to do with anything but if you never go above 90% it is a difficult situation. Coulomb counting is imperfect so error is always trying to drift in. (this is not a Victron issue, it is an electricity issue.) This is mitigated by the Battery Monitor re-synchronizing with the battery. It can do this only when the batteries are fully charged as this is the condition where we know (by voltage and charge current) what the state of charge is (100%) and therefore an out-of-synch monitor can re-synch.

Do you have any opportunity to fully charge your batteries periodically with generator or grid? Your batteries will last longer too if they get a good, aggressive and complete charge cycle once in a while.

Or if you are ALWAYS cycling between 65% and 90% than your battery bank is too big. Reduce battery bank to something that cycles between 50% and 100% :cool:
 
Thank you for the reply. I am fully recharged every day. I have synchronized at least a dozen times after fully charged. I agree that 65% seems strange but that must be part of there programming. I have two 100 amp hour agm so hard to reduce to fit their criteria and I shouldn't have to.
 
I had the same issue during my Summer holiday with the camper. Since the battery where never fully charged the SOC started to drift and getting towards 50%. But after a short charge from shore power (which I never use normally) and charging too full voltage the SOC was correct again.
 
I had the same issue during my Summer holiday with the camper. Since the battery where never fully charged the SOC started to drift and getting towards 50%. But after a short charge from shore power (which I never use normally) and charging too full voltage the SOC was correct again.
Thanks for the reply. I do get back to 100 percent every night. Interesting that yours works correctly. What SOC do you normally get down to everynight?
 
Just to clarify, Victron does NOT offer direct customer support, they instead train distributers to handle customer queries, so whoever you buy the equipment off should be able to help. They also have a very useful forum to ask questions.
 
Thanks for your reply. I did go to the dealer first and they couldn't fix it. Very nice people though. I then reached out to Victron and the battle was on after they insulted me with there first reply. In hind site I guess maybe the dealer couldn't fix it because there is no fix.
 
You charge fully every NIGHT and it won't synch and work properly? I'm sure we can figure this out but will need much more information. Please provide detailed photos of your batteries and SmartShunt from several angles. Please describe your system in as much detail as possible. And please send screeenshots of every setting in the Smartshunt.

Also please describe in as much detail as possible what is the problem. How is the unit "not accurate on charge or discharge."
 
Thanks for the help!!

2 100 amp hour AGM batteries with 630 watts of solar using a Victron 100/50 MPPT. Also have a Victron on board charger when using my generator. My batteries are a little hard to get to but last week I did look at them. I have one ground wire going to the shunt and one ground wire going from the shunt to a buss bar where all grounds including the chassis ground are connected. I also verified I do not have the shunt wired backwards.

Here is the issue--At night when it is discharging the amp hours used does not equal SOC. As an example when it shows 90% SOC I will have used roughly 23 amp hours. This discrepancy grows and continues as it discharges. Before solar kicks in when the sun comes up I am usually somewhere around 75% SOC and 59 amp hours used.

When charging I could never get back to 100% even though I would go into float mode around 2 in the afternoon. I also had 12.9 volts. I reached out to this forum and Rocketman said my charge voltage which was set at 14.7 was too high. He suggested 14.5 and then it seem to hit 100% SOC maybe a little early so I then went to 14.6. Victron distributor had me change this setting to 14.2 and then I would check SOC and it would say 92% and five minutes later it would jump to 100% even though I was still charging in absorption mode so that number sure seems wrong to me. They also had me change charge efficiency factor from 95% to 80%. Screenshot_shunt.jpg
 
TI have one ground wire going to the shunt and one ground wire going from the shunt to a buss bar where all grounds including the chassis ground are connected. I also verified I do not have the shunt wired backwards.

Wait.... I'm not even reading the rest of that until we clarify this. Are you saying you have a cable from one of the battery negative terminals to a buss bar where other cables are connected? Please clarify or provide pictures.
 
Sorry I wasn't clear. I have one ground cable 2/0 if I remember correctly to the shunt from the batteries. I then have the same size cable from the other end of the shunt to the ground buss bar. I also verified I have the shunt wired correctly and not reversed. Batteries are wired in parallel.
 
Also if the MPPT is primary charging source we would need to see all settings of the MPPT.
 
It takes some time to get to but my understanding if I had the shunt wired backwards readings would be all screwed up or not work at all. If you need a picture to move forward I can get one in the morning.
 
Windy Nation but do not know the model. Just looked online and they only show one model. If you need the model I can also get that in the morning.
 
Hi, the dealer talk about discharging below 65% is rubbish. There are a number of facts you must consider with your batteries and shunt settings. You may be expecting too much from the shunt, its readings with AGM batteries are a 'best guess'. Fine tuning may help.

Battery capacity.
You are assuming the batteries each have 100 Ah capacity. This is true when the average 100 Ah battery is in good health, correctly fully charged, at 25deg C and with a load of 5 amps. If conditions vary then the capacity under those conditions will be different . Thus in real life conditions the SOC readings may differ from your expectations because the effective battery capacity has changed.
Variables also occur on charging, expecially with solar , where conditions vary. Thus an early sync to 100% may occur, or no sync at all.

The net result of variables is that the SOC may not be fully accurate especially when charging, with AGM batteries charge efficiency can vary significantly.

Battery charging voltages.

Windy nation offer 3 types of AGM battery, each type has slightly different charging voltages. These are printed on the battery case. And discussed in the data manual sheet, available on the site,

Assuming your battery is type NSAP12, the manual suggests, absorbtion volts 14.1 to 14.7 and long term float 13.5. The printing on the battery suggests 14.4 to 15 volts charge and 13.5 to 13.8 float. I suggest 14.5 volts absorbtion and 13.7 float for a solar charger. Long term on a AC charger drop the float to 13.5.

On the Victron charger set up these user values in expert mode with adaptive absorbtion period or absorbtion period set to 3 hours.
You may need to vary the absorbtion period to ensure the batteries are fully charged.

Smart Shunt Settings

The shunt syncs to 100% when the following is true,

Charge voltage exceeds 14.2 volts, (0.2 or 0.3 below charge setting on solar controller),
And the current into the battery has fallen below tail curent, set to 1%, ( 2 amps for 200 Ah battery).
And the above conditions have existed for charge detection time set to 3 minutes.
Tail current can effect sync especially with variable solar conditions or aged batteries.

Charge efficiency is not easy to set as it varies depending on depth of discharge, battery state of health, charge current, charge voltage.
For AGM start with 90% and Increase or decrease with experience. This has most effect on SOC under charge conditions.

Peukert value, for AGM set to 1.10 for a starting point. Increase or decrease in steps of 0.05. This has most effect under discharge conditions.

Knowing the battery is full so as to manually set 100% SOC.

With AGM batteries you can consider the battery 100% charged when the current under absorbtion volts, falls to less than 1% of capacity, 1 amp per 100Ah, ( or for aged batteries where the current falls to a low value and stops decreasing).
Note this current is under the absorbtion voltage applied to the battery, and where the possible available current is greater.


Summary.

Monitoring AGM batteries in a cyclic application with a modest solar charge source with variable loading, will never be completly accurate.
With fine tuning of the shunt and charger it's possible to get within a few%, however long term drift may occur and ocasional manual sync to 100% will be needed when you are absolutely sure the batteries are fully charged.

Mike
 
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