Victron Shunt settings. Help please.

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mvweebles

mvweebles

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Mar 21, 2019
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United States
Vessel Name
Weebles
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1970 Willard 36 Trawler
Right now, I'm pulling drywall at our house and the only power we have is a simple 100w panel driving a 100ah LFP battery via a Victron 75/15 MPPT. I also installed a Victron Smartshunt. All this to run a small fridge and recharge my cordless tools which has been invaluable.

I cannot get the monitor to read properly.

First. It's bright sun here today. Gorgeous day to pull Sheetrock

#1. At 11:30 this morning, shunt showed showed system voltage of 12.83v and consumed AH of 60.6ah.
Screenshot_20241013_124057_Photos.jpg

#2. One hour later (12:41) voltage has increased to 12.97v so clearly it's receiving a charge from the MPPT, but the AH consumed continues to increase negative (as does the SoC).
Screenshot_20241013_124125_Photos.jpg

#3 for reference, here are my battery settings on the shunt.
Screenshot_20241013_123508.jpg

#4. And the settings on the MPPT
Screenshot_20241013_125442.jpg

Screenshot_20241013_125457.jpg


So the system is charging fine but the readings are not correct - AH consumed are not adjusted for solar charge from MPPT. What am I doing wrong?

Thanks in advance

Peter
 

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  • Screenshot_20241013_125457.jpg
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first set mppt charger on lifepo4 not used defined.
second on 12,83v battery is on 5-10%

set charging 14,4
 
Is the ground for the MPPT going through the shunt? If anything is grounded directly to the battery and not through the shunt then it won't be measured.
 
First, I don't own any Victron gear.

From your displayed values, I would at least do these things to improve accuracy.

Set Peukert Exponent to 1.0 or whatever your battery manuf. says it is. 1.25 is a typical lead acid value.

Set Charge Efficiency to 98% or whatever the battery manuf. says.

If possible, set Auto Equalize to never, or get an understanding of what it is and set it correctly.

Then I think you need to get the battery to fully charged and manually set the current state of charge to 100%.

Read to find out what the actions mean for Sych SOC to 100% and Battery SOC on Reset and chose if you want to implement these actions.

Set all other parameters to whatever the battery manuf. recommends.

RTM.

Hope this helps.
 
First...double check Shunt wiring. Is it backwards? Coming off the batt negative terminal? And all grounds only coming off the shunt?

[battery neg]----[batt side-SHUNT- load side]---all negatives

no other terminals on the batt negative except the shunt as above.


Charge settings:

* Disable equalization
* Set absorption a bit higher to 14.2 IMO to take advantage of limited solar. This will result in faster charge times for the last 5-10% as compared to your current settings
* Float 13.5 (slightly above resting voltage) so if it hits the 14.2 and gets full absorb time it will automatically drop to 13.5 and not be held at higher voltage excessively. 13.5 after absorption is still 100%

Shunt setting to change:

* Charged voltage is .2 volts below absorption or 14.0v
* Puekert 1.04
* Charge efficiency 98 or 99%
 
Last edited:
I'm not seeing those two snapshots in time as inconsistent. In the first one, you are drawing near 5A from the battery, a significant load (from a static voltage point of view) on a 100AH battery. In the second, only 0.5A, so static voltage could easily be more because the load is less. You've consumed 4AH in between, probably due to the ~5A draw.

The one of the panel shows 5 amps output, without knowing the load on the battery, hard to know what's going in or out.
 
Barking Sands said:
First...double check Shunt wiring. Is it backwards? Coming off the batt negative terminal? And all grounds only coming off the shunt?

[battery neg]----[batt side-SHUNT- load side]---all negatives

no other terminals on the batt negative except the shunt as above.


Charge settings:

* Disable equalization
* Set absorption a bit higher to 14.2 IMO to take advantage of limited solar. This will result in faster charge times for the last 5-10% as compared to your current settings
* Float 13.5 (slightly above resting voltage) so if it hits the 14.2 and gets full absorb time it will automatically drop to 13.5 and not be held at higher voltage excessively. 13.5 after absorption is still 100%

Shunt setting to change:

* Charged voltage is .2 volts below absorption or 14.0v
* Puekert 1.04
* Charge efficiency 98 or 99%
Click to expand...
This is the first thing I would check. It is so easy to accidentally get the shunt turned backwards. Add to that most don’t realize the shunt has a specific direction.
 
Thanks all. I'll check in the morning when I return for more storm cleanup. Ugg....

Peter
 
DDW said:
I'm not seeing those two snapshots in time as inconsistent. In the first one, you are drawing near 5A from the battery, a significant load (from a static voltage point of view) on a 100AH battery. In the second, only 0.5A, so static voltage could easily be more because the load is less. You've consumed 4AH in between, probably due to the ~5A draw.

The one of the panel shows 5 amps output, without knowing the load on the battery, hard to know what's going in or out.
Click to expand...

I'm no expert (explains why I posted to tmTFs bigger brain), but the the voltage is increasing over time yet the Consumer AH also increases. The battery is getting charged which should reverse the Consumer AH.

First thing I'll check is where the MPPT is grounded. It's been several months since I installed and this is the first time I've used it with vigor. I would have thought the VE Networking would see the usage information and account for it, but maybe not.

Peter
 
The voltage is only really significant if you have a fixed (or no) load. The state of charge between 60AH and 65AH down is not all that significant if you were measuring resting voltage, but the difference between 5A draw and 0.5A draw is. Could easily acount for 0.17V difference in voltage.
 
DDW said:
The voltage is only really significant if you have a fixed (or no) load. The state of charge between 60AH and 65AH down is not all that significant if you were measuring resting voltage, but the difference between 5A draw and 0.5A draw is. Could easily acount for 0.17V difference in voltage.
Click to expand...

I see what your saying. There is a 4.68A load on the first screenshot, and only 0.5A in the second. Voltage sag with higher load in this small system (100ah LFP battery) could explain it but I think there is something more. Even with 5 amps of solar in bright sun and no load (inverter off), the power/current will not go positive (it stalls at 0) or the accumulated AH to reduce. I thought it was a setting of some sort but I think the suggestion to check the ground is a good place to start - I should have thought of it but didn't. Power seems to be getting to the battery but bypassing the shunt.

More to follow tomorrow......in the meantime, gotta say that having even a tiny system when there's an extended power outage makes a huge difference. Finding ice is impossible so a fridge is great. There are long lines still at gas stations so even a small generator would be challenging.

Peter
 
Last edited:
Peter...if you need a generator, I have a Westinghouse 7500/9000 unit. You are more than welcome to use it. Gas should be available in the next day or two. I also have gas cans as well as a 25 gallon gas caddy.
 
Thanks but we are fine. The weather has been exceptional so no AC needed at our house, and power was restored to our condo today.

I had a 2000w generator that I sold last year and I don't miss it a bit. Only thing I'd use a big generator for right now is to run out coffee maker in the morning.

But many thanks - so many people have offered help. It's the silver lining of catastrophes. We're in good shape - so many others aren't.

Peter
 
I've been watching voltage vs SoC on my system for a while, and under even moderate use they're not well correlated in the 20-90% charge state. I wouldn't sweat it yet :)

Glad to hear you weren't hit too hard.
 
PROBLEM SOLVED.

MPPT negative was indeed run to the battery negative thereby bypassing the shunt. Problem appears to be solved.

Thanks to all who contributed.

Peter
 
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