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scoraigwind avatar image
scoraigwind asked

Correct sequence to power up MPPT controllers

I am wondering how important is it to always connect the battery first when powering up/down an MPPT controller? Seems more important than I had first thought. The manual does say (in the installation section) to connect the battery first, which I understood was so that it can automatically detect 12/24/48V battery, and set its set-points accordingly. I understood that this was needed during the first power up only, and I assumed that after that it would not matter whether you disconnect the battery before the solar, or reconnect it after the solar is connected. This is not made fully clear, as the manual does not specify the correct sequence for normal operation explicitly.

A customer of mine disconnected the battery while the solar was working. Later he reconnected it, (solar still on) and the controller was damaged. Victron did not cover this damage under their 5 year warranty. They said it was clear from the manual that you should not do this. I will need to read the manual again but I wonder how many people know this? I wonder how many people take care to always check that the solar is not connected when they connect the battery after some temporary down time. Seems like people need to know this.

MPPT Controllers
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3 Answers
nickdb avatar image
nickdb answered ·

It is a good idea for initial setup, though you can set it manually easily enough.

After that, it doesn't matter.

On a system restart after a complete poweroff, powering mppts first, before the battery, is an easy way to precharge the inverters, then powering the battery second.


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Fideri avatar image Fideri commented ·
That's my understanding, so I'm surprised at @scoraigwind outcome.

F.

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nickdb avatar image nickdb ♦♦ Fideri commented ·

The issue here is disconnecting the charger while it is generating power.

The subsequent spike could damage the charger, not to mention the nice spark when the fuses are pulled out.

Always drop PV first on shutdown, and power PV last.

For Precharging, the charger is connected to the DC bus. While batteries may be off, there are still "loads" and PV won't ramp more than is required.

This has nothing to do with the initial detection of the battery voltage, but more to do with abusing the poor charger.


6.5. Shutdown and restart procedure

The solar charger is always active when the PV and/or the battery terminals are powered. The solar charger does not have an on/off switch.

To shut down the solar charger, perform these steps in the prescribed order:

  1. Disconnect the PV supply to the solar charger by switching the PV supply off or by removing the external fuse(s) or circuit breaker(s).

  2. Disconnect the battery supply to the solar charger by switching the battery supply off or by removing the exterenal fuse(s) or circuit breaker(s).

To restart the solar charger after it was shutdown, perform these steps in the prescribed order:

  1. Connect the battery supply to the solar charger by switching the battery supply on or by inserting the external fuse(s) or circuit breaker(s).

  2. Reconnect the PV supply to the solar charger by switching the PV supply on or by inserting the external fuse(s) or circuit breakers(s).


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Fideri avatar image Fideri nickdb ♦♦ commented ·
That makes sense.
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scoraigwind avatar image scoraigwind nickdb ♦♦ commented ·
Where can I find this 6.5 that you are quoting above? I have not seen this text before. It makes sense to me, and this is the way I would personally go about it but I have never seen it in a Victron manual stated in this way. So I cannot blame my customer for not following this procedure.


It is interesting that the manual of a Solis grid tied inverter says you must always have the grid connected before the solar, but you must disconnect the grid before you disconnect the solar. I wonder how many people follow these rules. They are different (on shut down sequence) from the Victron/battery ones.

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Alexandra avatar image Alexandra ♦ scoraigwind commented ·

@scoraigwind

There is no grid input on a Victron MPPT. It is purely DC.

Source of @nickdb comment...

6.5 in the manual.

Solis is totally different as it is an all in one with both AC and DC sources. I would expect the shutdown procedure to be different.

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scoraigwind avatar image scoraigwind Alexandra ♦ commented ·

Hi thanks, Alexandra, Obviously I know that it is different (with grid instead of battery!) but I would really like to understand the technical reasons for all these various rules, and I also wonder how many users are even aware of them.

Thanks for the link to the online manual. Up to now I have relied on the PDF manuals, and I have not see this stated in there yet, but maybe that is coming.

It is interesting that the online manual states there is no on/off switch, but in fact it would be possible to use the remote switch option to turn the unit off, and I wonder if this would be a better or worse way to go about shutting it down. I would worry a little bit about switching off the PV breaker when it is charging full power.

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regman54 avatar image regman54 scoraigwind commented ·

I suspect there are some (many?) who never read the owner manuals from start to end. I'm somewhat guilty of that myself. The PDF that I downloaded last year, Rev 04 - 02/2023, when I purchased my 75/15 in August 2023 does indeed label section 6.5 as a "Shutdown and restart procedure".

I suspect it would be good practice to tell customers to seek the online version of the owners manual to get the most up-to-date information available.

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onrbikes avatar image
onrbikes answered ·

Surely it matters after the initial set-up.

What if the unit is removed and sold to someone with a different battery voltage?

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nickdb avatar image nickdb ♦♦ commented ·

I's non-volatile config remains in place unless changed. It won't auto-configure the second time.

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scoraigwind avatar image scoraigwind commented ·
It will be necessary to change the battery voltage settings, if the voltage is different. This can be easily done by reading the manual.
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klim8skeptic avatar image
klim8skeptic answered ·

@scoraigwind Battery BMS's will disconnect if they are unhappy.

Victron SuperPack will disconnect upon " over discharge, over charge or high temperature."

Mppt's seem to be able to handle that ^.


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