question

manny-martinez avatar image

SmartShunt battery capacity drifting showing incorrect percentage

c8b1e79a-cee0-48bd-ab99-9130624b2f0a.jpegeea5c00b-2436-4da1-b225-5fedf8b4fb9c.jpegMy voltage on Cerbo GX and VictronConnect is correct but the percentage is incorrect. The SmartShunt is setup to be the provider for the voltage. My shunt is hooked up properly via battery minus/load minus but I do have the power cable from the shunt hooked up to a small fuse block instead of the batteries directly. Could that cause the drift? I’ve also never done a Zero Calibration.


Batteries are 500AH LifePo4 Battleborn Batteries

One thing that is interesting is that if I reboot the system by turning off and on the master disconnect switch, the percentage will correct itself.

Anyone ever deal with this percentage drift?

voltagesmartshuntbattery system voltage
4 comments
2 |3000 characters needed characters left characters exceeded

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

The lower (battery?) isolator is off, and the upper (load/charge?) isolator in on?


the lower isolator is strictly for the Multiplus at the moment. The battery isolator is the top one

Can you make some screenshots of the setting of the SmartShunt in VictronConnect?

What do you mean by "...if I restart the system, the percentage will correct itself." ?
It jumps back to 100% ? This is a setting of the SmartShunt.

And what exactly is your problem?
On the first picture you have a current of 3.3A out of the battery so the SOC will drop after some time.

manny-martinez avatar image manny-martinez Matthias Lange - DE ♦ ·

Hi @Matthias Lange - DE I’m attaching the screenshots below.


what I mean by “restart” is if I power off the main disconnect switch and turn it back on, it’ll show the correct voltage percentage.


The main problem I’m having is that I’m showing 13.7v which should be 100%, yet at times it shows the percentage less than that. I’ve seen the system show 90% at 13.5v. After rebooting the system, it showed 100%.


4 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Ok, I think I know what your "problem" is.

Your system is working like it should but you have a false understanding of how it works.

A fully charged LiFePo4 battery completely disconnected from everything normally have a idle voltage of about 13.3V (+/- 0.1V).

Absorption voltage during charging should be 14.2-14.4V.
In the moment you stop charging and with no loads connected the voltage will drop slowly to the idle voltage but it has still 100% SOC.
With loads connected the BMV will start counting the current out of the battery and lower the SOC.

LiFePo4 have a very stable voltage from 100% to about 20% SOC (depending on the load).
Below 20% the voltage starts to drop faster.

What happens if you "reset" the system is the setting "Battery starts synchronized".
With this setting enabled the BMV will always jump to 100% after a reset even if the battery voltage is 12V or the real SOC is 0%.

1 comment
2 |3000 characters needed characters left characters exceeded

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 this makes sense, thank you for the detailed explanation! This led me to finding this:

1619643256207.png

1619643256207.png (106.8 KiB)
dgnevans avatar image
dgnevans answered ·

You have 2 battery isolators or switches in your photo where do these feed, you have 2 large negative wires entering your victron lynx where are these from. you also have a large negtive connected to the top of your shunt where does this go?

2 comments
2 |3000 characters needed characters left characters exceeded

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

Hi @dgnevans thanks for responding. Below are responses to your questions


Q: You have 2 battery isolators or switches in your photo where do these feed?

A: Using the photo as a reference, the top isolator (the one next to the Orion) is Batteries -> 400A ANL Fuse -> Switch -> POS Bus Bar of the Lynx. The bottom switch is: POS Lynx -> 400A T-Fuse -> Switch -> Multiplus.


Q: You have 2 large negative wires entering your victron lynx where are these from?

A: The 2 large wires are the Multiplus case ground and the chassis ground


Q: you also have a large negtive connected to the top of your shunt where does this go?

A: I've made a diagram for you to see the details:
1619590501550.png



Hope this helps! Thanks again

1619590501550.png (832.5 KiB)

Here's the entire system diagram in case it helps

vanbuild-electrical-system-2-14-21.png

manny-martinez avatar image
manny-martinez answered ·

Here is a diagram of my system if it helps anyone:


vanbuild-electrical-system-2-14-21.png


2 |3000 characters needed characters left characters exceeded

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

dgnevans avatar image
dgnevans answered ·

There are a few things i would check. Starting with the Smartshunt. battle born is pretty good with their documentation. have a look at this https://battlebornbatteries.com/faq-all-about-bmvs/ Check your settings match what they suggest for their lithium batteries.
Second thing I would check is in the cerbo gx that the battery monitor is set to the Smartshunt.
I would then start the van and make sure you seeing the battery charge through the smart shunt. Also confirm that the solar is showin as charging the battery.
If you can put screen shots of your Smart shunt config that would be good.

1 comment
2 |3000 characters needed characters left characters exceeded

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

Hi @dgnevans,


I’ve gone through that documentation a few times now and things seems to match up. Below is a screenshot of my settings