geomz avatar image
geomz asked

Why is MPPT charge voltage 30V in a 24V ESS system?

I have 2 100/30 Smartsolar MPPTs integrates with a Quattro 5000 into an ESS, running on 24V lithium batteries.

I understand that with ESS the inverter takes control of the charging profile from the MPPTs.

However, I was looking under “Networked Operation” section of my MPPTs and noticed the following screenshot

Why/how is charge voltage 30V?!?

Nothing anywhere is set to that voltage

Not the MPPTs locally

Not the bmv’s battery settings

Not the inverter veconfig settings

So I’m confused as to where this is coming from and how/why.

I doesn’t appear to be causing any issues as charging appear normal, but...

Should I be concerned about this?

Thanks in advance

MPPT ControllersESSvoltage
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1 Answer
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

The voltage of the MPPT must be set with a margin above the Multi/System Voltage so that it will produce and push (so the PV is the priority charge/power source), and/or allows for PV export.

This offset voltage value is set by the DVCC/External control system, and is not user adjustable. Which is why it is not shown to you.

I understand that it could lead to some confusion, and will pass it along to see if this can be made clearer/less scary/removed from the user interface.

As you have seen the actual battery voltage is controlled by the External Control system so that it will not overcharge the batteries.

For now, it is normal, and you should not be concerned.

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geomz avatar image geomz commented ·

Thank you @Guy! That makes perfect sense and I appreciate your explaining it to me :)

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thanar avatar image thanar commented ·
This is definitely perplexing. I am also getting a bit scared by seeing this reading. Why not report the target charging voltage instead? And -while we're at it- is there any way on an ESS system to get the target charging voltage? Apart from using VE remote to download the configuration file from the inverter and run it through VEconfigure?
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Jay Kote avatar image Jay Kote commented ·
It appears that Victron uses "nominal" numbers and not actual voltages in its documentation and ratings. For example, the 100/20 @ 12V claims a 290W max. But if you do the math, at 12V*20A = 240W. What Victron seems to use is 14.5V. Likewise, instead of 24V, Victron document again assumes 29V (not 24V) as a nominal value for a 24V system. In particular, the same controller is said to operate at 580W. But if we take 24V*20, again it's well shy. The nominal value is 29V. So 29V * 20A = 580W. This is the basic specification.

But here is the problem. It appears that even if you choose 24V in a 100/20 MPPT, unless it sense voltage around 29V, it will not give you 20A. It will limit system to 290W output even if the battery is around 24V.

How can this be fixed?

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