question

ranger-rick avatar image
ranger-rick asked

Is a plate missing on the Neg battery post of my 24v MultiPlus II 2x120v?

The + battery post has a thick base plate but the - battery post dies not have one. Is this correct?

Multiplus-II
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5 Answers
ranger-rick avatar image
ranger-rick answered ·

1668263408056.jpeg

Picture shows no plate for the Negative post


1668263408056.jpeg (523.5 KiB)
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ajmacleod avatar image
ajmacleod answered ·

It does look like there's something missing doesn't it? My 24/3000 is just the same though so I assume it's intentional.

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sharpener avatar image
sharpener answered ·

The 48/5000 is similar. I guess the asymmetry in the connections stems from the B- connection being at or near ground level.

I see also there is a legend "B1" on the left hand pcb only, this is perhaps for the component "Busbar 1".

2 comments
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ranger-rick avatar image ranger-rick commented ·
I thought about a busbar. Thank you for your insight.
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bob-bobson avatar image bob-bobson commented ·

Respectfully, I doubt that the potential of the connector vs ground, as such, is a factor at all. My LiFePO battery seems to have its case connected to a point in the middle of a series-connected bank of cells, for example, and thus the earth is equally close to (or far from) either terminal.


Further to this, the potential difference that matters for this discussion is not so much that between the positive and negative electrodes (or between either and earth, if the latter is in any way connected) but rather that small fraction of the total that appears across the (hopefully small) resistances of the contact points. What we are worrying about here is whether a thing that looks like the inside of a sweetie wrapper can conduct tens of amps with a sufficiently low resistance that the heat it can dissipate will be enough for it not to melt. The potential of the sweetie wrapper vs ground does not matter in itself, except insofar as the total potential difference between the battery electrodes determines the current that will flow.

I think the answer lies rather in the fact that that hunk of flat bar is an appendage of a heat-sink inside the case, which may be connected to the (internally connected) case of a transistor (or a bank of them) inside the big blue box.


Victron are too quiet on this point - it is an obvious question and there should be a note in the manual for the novice Victron owner. One electrode looks like a tombstone and the other like the foil in a cigarette box, and some explanation is required.

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

I don't know why it is like that but this is normal.

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ranger-rick avatar image
ranger-rick answered ·

Thank you all for weighing in. My MP-II works fine, but a quick check it out Q came to peace of mind with you three members weighing in

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