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duswami avatar image
duswami asked

Stuck on Float Voltage in ESS

After monitoring VRM since installing ESS I've noticed that my Bat and Charging voltage never reaches absorption voltages. My absorption volage is 57.6v, Float is 54.4v (AGM) as configured on the Multi. In ESS, SOC is 85% (Min and actual.) I also have two scheduled charges. One charge begins at the tail-end of usable PV late in the day, overlapping the last bit of sun (to capture some PV so as to limit some of the draw from the grid when charging.) This charge ends roughly 6 hrs later around 1:00 AM EST at which point I am inverting for 6 hrs, until the sun comes up. Both scheduled charges have SOC limit reached unchecked so that it stays in the charging cycle, intentionally, to keep the Multi from slipping back into inverting.

Other ESS settings that might be pertinent, Optimized Mode with Battery Life, DC-Coupled Feed-in with Limit 0W.

Even during the scheduled charges, mostly grid supplied, I never see more than the float voltage. Any thoughts as to what or why this is? @Alexandra perhaps you can comment as you are very knowledgeable on this area? :)

Multiplus-IIbattery chargingESS
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4 Answers
Alexandra avatar image
Alexandra answered ·

@Duswami

The simplest way to see if it needs charging... or not (not is indicated by the float state). If there is a problem anyway....

Set it to keep batteries charged. If it does not start charging from grid, then they don't need a charge.

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Alexandra avatar image
Alexandra answered ·

@Duswami

Have you set the same voltages on your PV?

The system should go into a bulk state everyday when PV is available. Do you have enough PV to cover your loads during the day?

On the charger tab, do you have an absorption time set?

It may be best to keep batteries charged for a few days to check on things.

With AGM and ESS a BMV is a necessary thing to have.

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duswami avatar image duswami commented ·

@Alexandra I do not have a BMV. Just the SmartShunt 500A between Bats and loads. Must I acquire one?

As for the PV, do you mean the charge controller, if so, yes, they match the Multi. But I thought in ESS the CC was ignored anyway as the Multi takes precedent? Incidentally, the system was going into Bulk and I saw proper voltage readings before ESS installed. When scheduled charges begin I am near the set SOC of 85% (usually around 87-89%.)

Absorption time is set, see image

screenshot-2022-06-25-182310.jpg

Sometimes I have enough to cover my loads, sometimes I do not. When there is a surplus and my loads are light, the MPPT will start charging, usually back to 100% before I reach the part of the day PV is insufficient and I begin inverting.

screenshot-2022-06-25-181503.jpg

This is a pretty typical day, as the PV drop off is due to a shading event that is present for 6 months a year.

So a bit of an update from when I posted this, I see absorption voltage in the Realtime System Summary, but in the Advanced tab widget it shows Float, weird, thoughts??

screenshot-2022-06-25-193130.jpgscreenshot-2022-06-25-193224.jpg

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Alexandra avatar image Alexandra ♦ duswami commented ·
@Duswami

I thought i had seen one of your posts about a smart shint but could not find it. The smart shunt it the battery monitor.

In an ESS system the GX has control. Check of the system is using the sbunt as the battery monitor.

C an you post some of your ESS settings?

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duswami avatar image
duswami answered ·

@Alexandra Shunt is selected as main battery monitor in control panel. Settings below, no external meters (yet), no pv inverters.

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seb71 avatar image seb71 commented ·

Not related to your main question:

Disable "Has DC system".

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duswami avatar image duswami seb71 commented ·
@Seb71 thanks for this, I was going to do this, my dealer suggested I turn this on for a more granular view of the DC side of things. Aside from bat loads, I don't have DC appliances, consumers except GX device, it made no sense to me to have this on.
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Leslieanne avatar image Leslieanne duswami commented ·
Hi, I think your problem could be as simple as voltage not dropping below the ESS rebulk level (which for your Pb batts is float minus 1.3x4= 49.2 volts.)

Test by running a big load or skipping scheduled charge for a bit??

Cheers, Leslie

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duswami avatar image duswami Leslieanne commented ·
@Leslieanne Interesting...min Bat Voltage History for the SmartShuntshows 47.88v in VRM, so that'd cross the threshold, I did get an absorption cycle with the proper voltage later on buring a sched charge from Grid, however, VRM DC Voltage reading shows a consistent float Voltage recorded, it's bizzare
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Leslieanne avatar image Leslieanne duswami commented ·
That history is a "lifetime" history unless you actively reset it. So it likely indicates a low voltage from before you switched to ESS.
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duswami avatar image duswami Leslieanne commented ·
@Leslieanne thank you
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seb71 avatar image
seb71 answered ·
I don't think there is any actual issue.


You are comparing voltages indicated by different devices. They will be different.

That's one reason for using a SmartShunt/BMV - so that the system can know and use the actual battery voltage.

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duswami avatar image duswami commented ·
@Seb71 thank you
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