Smart Shunt not reading correctly?

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vtecvfr asked Dec 19, '21

Smart Shunt not reading correctly?

Hello:

I installed a smart shunt on my system a few months ago. I synchronized the smart shunt with the batteries at full charge.

I have 8- 6 volt(370ah) FLA batteries connected in series and parallel to create a 12 V 1480 ah battery bank. The discharge floor is set to 50%.

Attached are images of the status and history tabs for one time:

Can someone have a look at let me know if it looks correct...... and if not what might be going wrong....

1. The state of charge doesn't look accurate.... I think it should be lower.....

2. The time remaining doesn't look accurate....again should be lower....

3. In the history tab there is no average discharge calculated....

If anyone has any ideas as to what might be going wrong, can you please let me know.

Thanks

SmartShunt

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Answer 1 · 2021-12-19T18:25:39Z

Al answered · Dec 19, 2021 at 06:25 PM

@Vtecvfr

As Stefanie says your batteries are getting dangerously low if left uncharged for long!

I think your charge is out of sync because with 4% tail current and 3 mins detection time clouds (assuming solar charge) will trick the charger into thinking the batteries are full, so at some point when they were only 90% charged for example they've synced, this can compound over time. It's also why I have a Smartguage battery monitor as well as Victron.

*edit (if your charger is under sized, the BMV/Smartshunt etc can also assume the charge current when below the tail current means the batteries are full when in fact it's the charger size that's limiting the current.)

I have 2v Flooded lead acid cells I have set:

Tail current: 2%

Charge detection time: 6m

Charge efficiency factor 84%

I would try figures closer to these and keep an eye on voltages or even better Specific Gravity of the acid.

First off charge your batteries ASAP!

battery-voltage-chart.jpg (38.4 KiB)

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vtecvfr commented · Dec 19, 2021 at 09:32 PM

Thanks for the reply Al. Yeah....something doesn't look right. I have been supplementing with generator charging so hopefully I will get it figured out soon......

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Al vtecvfr commented · Dec 19, 2021 at 09:55 PM

@Vtecvfr Cool, I would manually set state of charge to correspond to the battery voltage as it is now, so 40%? and then put the genny on in the morning if possible and run until either the sun can finish off charging from 85% to 90% up, or leave the genny on for longer. Ideally you want to get it back to 100% but that's ideally an 8-12h charge for FLA's.

Play with the settings to minimise it syncing early again, and as you have this time.. keep an eye on voltage to see if it roughly corresponds with SOC. The Victron BMV/Smartshunts are good at counting Ah in and out and normally the tail current etc works well but it's not got a clever algorithm in it to just double check against voltage if the SOC is way off, so we still have to check every so often, it's not a perfect system but still works well when you know what to keep an eye on.

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Answer 2 · 2021-12-19T20:27:02Z

snoobler answered · Dec 19, 2021 at 08:27 PM

How are you charging your batteries (solar, AC charger)?

If you are charging from solar, your shunt is not configured correctly. Victron recommends the charged voltage to be 0.2-0.3V under the ABSORPTION voltage, not float. Inconsistent charging from solar can trip float-based charged criteria prematurely.

How is the charger configured?

Once you return to the cabin, you should make it a priority to get the batteries fully charged via generator or other means. Additionally, you should check all cells' specific gravity and likely conduct an equalization cycle via the generator.

Very good chance your batteries are being damaged.

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vtecvfr commented · Dec 19, 2021 at 09:37 PM

Thanks snoobler. I have both solar and generator charging.

I have been charging with the generator when I am at the cabin.....

I bought the system pre-configured and I am just getting familiar with all the components and settings.....its only a few months old.....

Something doesn't seem right.....

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snoobler vtecvfr commented · Dec 20, 2021 at 01:12 AM

Your shunt settings are not correct for solar charging. Since that's likely what's happening while your absent, you need to set your charged criteria for that.

Due to inconsistencies in solar charging, it can often result in false 100% sync when you have your charged voltage set at 13.2V.

Set charged voltage to 0.2V below the absorption voltage of your charge controller.

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