question

blieve avatar image
blieve asked

Overvoltage when keep batteries charged is on

Hi,

I noticed since a few days that the charge logic is not being followed sometimes when the systems is in "Keep batteries charged" mode. See below charts

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DVCC is on and the bms is sending the correct charge voltages.

The pack itself is perfectly balanced within a few millivolts.

It happens when there is a peak in solar production, altough everything is connected on the AC side. (No DC MPPT's and DC system is turned off). I would expect that the grid feed-in would just increase instead of overcharging the batteries.

Is there any explanation or setting that I missed?


Thanx,

Bjorn

Multiplus-IIESS
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blieve avatar image blieve commented ·
@Guy Stewart (Victron Community Manager) someone from Victron able to shine a light on this?
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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ blieve commented ·

Hi @blieve,

As a work around, could you please set the ESS mode to optimised and then set the minimum SOC to 100% (or 99%) and then report back with the behaviour?

Another thing do you have allow AC PV export enabled?

And yet another thing, on the Venus GUI, could you please set the reporting interval to 1 minute - from the current default 15 minutes. That would help in this case to see better if the Victron is following the batteries orders.

Ideally the Charge Voltage Limit is reduced before the battery reaches 100%, at 98% or less.

You don't say which battery or BMS you are using - do they have Victron support and compatibility documentation?

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blieve avatar image blieve Guy Stewart (Victron Community Manager) ♦♦ commented ·

Hi Guy,


I updated the reporting interval to 1 minute.

As a workaround I indeed changed to ESS mode to optimized with minimum SOC to 95%, the problem doesn't seem to happen in this case. (altough not very sunny here in the netherlands the last 2 weeks...)

I've seen another post here with a similar issue that said this as a workaround. (https://community.victronenergy.com/questions/132633/dvcc-max-charge-voltage-not-considered-when-ess-in.html)


AC PV export is enabled (without limits)


The batterypack itself has an JKBMS built-in and supports the Victron protocol, connected via the BMS.Can port. It's currently programmed to request a CVL of 55.2V for 1 hrs and then lower to the float voltage for 6hrs.


Kind regards,
Bjorn


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Alexandra avatar image Alexandra ♦ blieve commented ·
@blieve

Weird how the battery voltage rises like that with no current going to the battery? Something else is afoot. Possibly something like a disconnect is happening.

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blieve avatar image blieve Alexandra ♦ commented ·
It's hard to see on the chart but the charge current drops to about 1.4A so voltage keeps rising very slowly
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1 Answer
pf-1 avatar image
pf-1 answered ·

The maximum charging voltage is also exceeded in my installation when "keep batteries chared" is activated.
However, I do not use the DVCC value "Maximum charging voltage", but the internal settings of the Multis/Quattro.
I use the SmartShunt as the battery monitor and no controlling BMS.
If the "Optimized for battery life" setting is selected, everything works perfectly.
I have the feeling that it somehow has to do with the SVS, which I have activated so that the Multi/Quattro regulates to the actual battery voltage.

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