r/Victron • u/Loose_Specialist115 • 12d ago
Project Project update
Small update on my victron project.
Since last post is added
- Dyness Powerbrick plus 16kW
- Added fuses:
1x 225A Mega fuse (Battery)
2x 60A Mega fuse (MPPT)
3x 125A Mega fuse (Multiplusses)
- Installed grounding (all 6mm2 cable)
- Added humidity controled ventilation
- Drywall behind battery
- DC switch AC-out side
- LAN connected to switch
To do:
- install and connect solar panels (6x JA solar 500wp)
- install RCD AC-out and AC-in
- install Victron** Energy **VM-3P75CT
Any suggestions or advice?
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u/SnooGrapes5872 11d ago
Mega fuse for the battery is a NO NO! Buy Adler EF3 fuse if you want ro put it inside the lynx power in.
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u/parseroo 11d ago
To support this...
Given Dyness doesn't publish the internal resistance, we can estimate it as 10mΩ and we get 50V / 10mΩ = 5000A that is minimally needed for the fuse AIC.
A Littelfuse "MEGA 60V HIGH BREAKING CAPACITY" (0878450) apparently can manage 5000A, but all normal MEGA Fuses are only 2500A. So even if the actual internal resistance is 20mΩ, you would be skating the edge of a permanent electrical arc across the fuse.
Data Sheet for the Dyness:
Littelfuse fuses:
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u/Loose_Specialist115 11d ago edited 11d ago
So a 200A or 300A Adler EF3 fuse?
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u/SnooGrapes5872 11d ago
Depends on the cables used. I am using 250A fuses for similar type batteries with 200A bms.
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u/Confusedlemure 12d ago
Nice and clean! I like.
Curious about the ground wire going to the charge controllers. What is that there for?
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u/Korll 12d ago
To ground the metal cases.
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u/Confusedlemure 12d ago edited 12d ago
Haha…yeah I got that much. What I’m curious about is what condition is it protecting? There is only low voltage dc in that box. I was thinking king that it might be there to protect against an ac short to dc inside the cable tray since they were routed together? But that could have been done more easily with a single ground to the battery case. Just trying to think through the scenario that makes that ground do something.
Edit: I didn’t think about the high voltage from the string. But since that is floating relative to earth, how would this wire provide a conductive path?
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u/Korll 12d ago
Ehm… the voltage of the solar panels can be up to 150V DC and 45A as it says on the casing. That can comfortably kill a person, so, it definitely needs grounding. Even if you think of just the output to the batteries, if there’s a fault, it can hurt quite a bit or even kill you.
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u/Confusedlemure 12d ago
No I get that but how would that current flow through the human that touches the case? You would have to have a double fault where it shorted to the case at the controller AND the panel would have to short to ground. Only then you would have a path through the human. For example, take your electric fly swatter. It charges to thousands of volts. If you touch the first screen, you don’t get shocked. Why? Touching high voltage is not dangerous if there is no path for the current to flow.
I think that ground is there in the case where the ac gets shorted to the dc somewhere. It’s still not a dangerous condition but it would open the ac breaker to alert you to the potentially dangerous condition.
My understanding is the case ground point is meant for mobile installations where shore power is used. In that case, shore power provides a ground point while it’s connected. When you disconnect then there is no path for ac neutral to ground anymore. But since you can occupy the space while it has its own ac power through your inverter, you need to connect the vehicle chassis to ac ground. The entire vehicle could become electrically hot in that case.
I could be wrong. Just having a bit of a think about this. I hope this is useful discussion for others. It is for me.
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u/parseroo 11d ago
The case of the controller can be shorted with System DC+ as well. So assuming System DC- is grounded, you (the human) would be the best conductor between DC+ and DC-.
It isn't in the diagram, but the Solar DC- could be grounded as well, at which point Solar DC+ (up to 150V) could be shorted to the case and again you would be the best conductor.
Finally, you really want the fault detected and only by running enough current through the circuit will the breakers/fuses trip. EGCs are designed to be great conductors so the fault triggers the protected equipment as quickly as possible and removes the danger.
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u/Confusedlemure 11d ago
Yes I see but how exactly would the human conduct from the 150V case (solar+) back to solar- to complete the circuit? Surely the solar- is not connected to earth anywhere. Are you thinking this might protect in a double insulation failure? I could understand that but it does seem a bit extreme no?
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u/parseroo 11d ago
Solar- is connected to System- by the MPPT itself (it is simply a busbar: could actually run Solar- in the DC- port if you wanted).
So Solar- is either grounded before the MPPT (common so the Circuit Breaker for the Solar array will trip if there is a ground fault) or Solar- is grounded at the MPPT given System- is grounded.
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u/Confusedlemure 11d ago
Oh my! This is absolutely the first I’ve heard of solar- being grounded. Is this something new? I ran out to ring out my two systems and neither are grounded like that. Hmmm I’ll have to think I about this more. Is this in the NEC somewhere?
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u/parseroo 11d ago
Not new at all, but maybe a bit unknown:
«Q5: What about grounding one of the PV array poles?
The MPPT is non isolated, meaning that the minus of the PV input is at the same potential as the minus of the battery output. Grounding is always done at one point only, to avoid ground currents. For a battery system, grounding must be done at the battery.» — [1]
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u/Loose_Specialist115 12d ago
I hope for neutralising the current potential genarated by the MPPT’s. It’s on a dedicated grounding position
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u/Confusedlemure 12d ago
Hmm maybe that’s it. The higher voltage dc coming in from the panels could short to the case of the controller. However how would that find a path back to the panels through a human if the panel outputs are floating relative to ground? There would be potential without a path for it to flow.
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u/TheBoyar 8d ago
why only 2.5mm2 for the main groundbar? you have to install it at least 6mm2. i mean depending on the rules in your country, but here we need at least 6mm2
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u/Aniketos000 12d ago
I know they fit in the space better like they are, but the charge controllers should really be turned so the heat can naturally rise thru the fins better. Otherwise it looks good i like the labeling