enhancement request: DVCC

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nickdb asked Jul 25, '20

enhancement request: DVCC

I have noticed that DVCC responds immediately to changes, particularly temperature changes.

Where equipment is in a warmer environment and then gets exposed to cooler air this results in rapid temperature drops and larger, sudden increases in charge voltage. This sets off midpoint voltage alarms on shunts and these transients aren't great for battery life.

Could DVCC logic not be improved, to normalise these changes (temp/voltage) over a few minutes, say 5 to 10 minutes so that changes are smoother and more gradual, eliminating transients?

Multiplus-II BMV Battery Monitor Venus OS DVCC mppt charging

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Modifications Space

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Answer 1 · 2020-07-25T08:03:18Z

mvader (Victron Energy) answered · Jul 25, 2020 at 08:03 AM

Hi Nick, the (only) temperature involved with charging is battery temperature - how can that go up and down so quickly? The mass of the battery will make for such changes to be slow always.

are you sure the sensor is properly thermally connected to the battery and/or that the right sensor is chosen in the system?

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

nickdb ♦♦ commented · Jul 25, 2020 at 08:53 AM

Looking at it in more detail the temp changes are more gradual but contribute to the broader issue. I will attach a chart. Whether it is the mppt/ESS contributing, I do see transients which ultimately set off midpoint voltage alarms.

Sensors are all correct and genuine victron parts. I have adjusted the VRM collection interval to be more granular.

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screenshot-2020-07-25-at-105031.png (417.6 KiB)

mvader (Victron Energy) ♦♦ nickdb ♦♦ commented · Jul 25, 2020 at 09:49 AM

Hi, looks to me like your batteries are out of balance. 1.4V difference is a lot - no?

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nickdb ♦♦ mvader (Victron Energy) ♦♦ commented · Jul 25, 2020 at 11:09 AM

No install will be perfect. These are quite new Victron batteries. The differential increases with increasing charge which is a direct result of cooler temperatures. As it warms up, voltage drops, so does the difference between them. Alarms are only triggered at transient times during cool weather and clear after a few minutes.

I could set the float voltage down a bit which would also affect the difference.

The setup and interaction of the various devices isn't intuitive so adjusting them to be optimal in a given environment is more art than science.

The distributors answer is always to buy more stuff, which is rarely the right answer.

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nickdb ♦♦ nickdb ♦♦ commented · Jul 25, 2020 at 11:17 AM

Just to add. Difference is about 1V for normal ops (~0.5V per battery), alarm triggers at 1.2V.

Will see if it changes at the next discharge cycle.

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