What happen to the solar power going in the Mppt, if the fuse/breaker between Mppt to batteries blows ?
I hear Mppt should be connected to battery prior to PV to avoid damage.
Does it mean that, if the breaker at the batteries jump, it will result of the Pv energy having nowhere to go and damage the Mppt ?
One day I disconnected the batteries before disconnecting the PV, and a fire started in a Growatts all-in-one mppt/inverter.
Many MPPT converters rely on the battery voltage to regulate and limit the output voltage. If you remove the battery before removing the PV voltage, it is easily possible that the internal voltage spikes caused by the switching operation of the MPPT will exceed the maximum design voltage for the FET switching devices, or other components like capacitors or internal voltage regulators. This can cause instant and irreversible damage to the unit, and if the PV voltage & current connected is large,then this can easily result in a fire.
Some MPPT units can absorb the spike, and internal processing will then detect the increased output voltage quick enough to prevent this from exceeding damaging levels. This all depends on the amount of energy contained in the first pulse after the battery disconnects.
The charge controller is a Victron mppt 100/50, connected to a 550w solar panel.
So if by using too much power in the camper can, we blow the fuse between the batteries and the mppt. Do you know if this Mppt will get damage or most important, do you think there is any risk than it takes fire ?
Seems like this scenario can happen to anyone, how can we prevent that ?
Your MPPT can only produce 50A so you should have a fuse of about 70A so that you can never blow this from PV production. The only cause of blowing this would be a short circuit in the wiring or MPPT. You should not connect heavy loads to the load terminals on the MPPT and you should fuse these less than the 70A if you do. Heavy loads should be connected to the battery through their own fuse.
You should change the wiring. Having excess consumption should not blow the fuse connecting the mppt.
In my Opinion:
Excess Power requests should never blow fuses, fuses are kinda final escape if something seriously goes wrong.
Excess Power requests better should trip properly sized breakers to stop undesireable high consumption with no physical damage beeing caused.
I would recommend to direct connect the mppt with it’s own fuse, then having a seperate cable from the battery towards your consumers, which is protected / limited by a DC Breaker. (Note that regular AC Breakers are NOT suitable for DC Power, they are to weak, because DC has no 0-pass)
The internal fuse will NOT be blown by anything other than an internal fault in the MPPT OR by a short on the PV side. The fuse is to prevent either of the above drawing too much current from the battery.
However, faulty wiring on the PV side can cause a lot of heat - though from a single 550W module, this is not going to be the same as from a 2kW or larger array.
When installing the MPPT this should be direct to the battery bus bars, using wiring rated for the MPPT current - at 50A this would be a minimum of 10mm^2. The wiring should also be protected at the bus by a suitable fuse - in this case (50A) 63A. Fuse should be appropriate for the voltage. Under these circumstances, the unit is fully protected, and so is the wiring, and except in the case of a fault, the fuse will not blow. If there is a main battery isolator switch, then a notice to disconnect the pv before opening the battery isolator should be posted.
If the wire from the busbar to the MPPT is very short, with absolutely no chance of a short, then the fuse may be omitted, but this is not recommended.
I wired 4 batteries to a bus bar, to have equal charge on each of them. Then to another bus bar which is connected to
inverter / charge controller / fuse box
Pretty sure I used the right size wire and breaker everywhere, (i did not install any fuse, only breakers)
So if the solar charges the batteries, the inverter works hard (2000w) and all the DC loads are on, it most likely be more than this 0ga wire, ( between the two bus bar ) can handle and so the 180a breaker will jump right ?
Will that result of damaging this Victron mppt, or does this model have an internal protection ?
If I absolutely have to rewire the MPPT to the first Bus bar ( that connects the batteries together ) will that still charge all batteries at the same speed or will they go out of balance ? ( meaning charging the closest wire on the bus bar faster than the wire connected further away on the bus bar )
Hope I make sens.
I did this for my ex, but we broke up. I want to make sure it’s safe. But try to stay away at the same time…
I first had commented about this, but deleted because it was not clear you are using an inverter.
So, IF you have an inverter which may cause overload to the system, you could simply set the inverter to a suitable Inverter-Limit that does not overload your DC Breakers and/or wires.
(There’s an Option to limit the max. inverter Power Output - it will not affect pass-through limits, when there is a shore-connection)
Then, the inverter will simply stop inverting, when that power is exceeded, avoiding any overload to the DC System. Fuse / Breaker are still required as backup safety measure.
General note: You have both, the inverter and the bus-bars, connected with a 180A Breaker, assuming it’s the same kind? When putting breakers in series you can choose Models with different characteristics (i.e. milliseconds they allow excess current) to ENSURE that your inverter-breaker is always tripping first - before the overall DC-Breaker disconnects everything including the MPPT. With regular fuses that is “builtin” with the size of the fuse, for Breakers you need to check the Characteristics. A 180A and 250A may just trip in random order if the current out of sudden hits 250A+
I would exchange this one with a breaker with a “more lazy” characteristic to allow any other breaker to trip first (or use a mega fuse there, as last resort - will be way cheaper than a breaker):
Just noted, that you also have DC Loads with an 180A Breaker there. That is a bit of a unfavourable layout, this also kinda could bypass configurative inverter limits, if both, AC + DC Loads just sum up to something that would trip the main breaker, while beeing at < 180A each.
So, ultimately you should move the MPPT connection, making that second busbar a “Consumer-Only” busbar, then it would be fine to have a main-breaker disconnecting the whole bar:
or an additional distribution, another busbar BEHIND that 180A breaker, where the mppt could connect:
Love it, thank you, I learn something knew about breakers, very interesting to know that there is different type, kind of like fuses now that I think of it.
Seems like I got my answer, and will connect my Mppt to the first bus bar instead of second.
You’re welcome. Just another note, but I don’t want to irritate you:
Ultimately the best layout and safety measure would be to ensure that breakers don’t trip.
Even if they could be (apparently) simply be enabled again, that is not quite the truth.
If a breaker disconnects due to excess current, it has to extinguish a strong electric arc. That always leaves “traces” on the chambers responsible to extinguish. So, the more often a breaker trips, the more likely it will become that it will start malfunctioning and not be able to extinguish the arc anymore, which ultimately could lead to a burn.
Especially if breakers trip due to a shortcut current, it is recommended to replace them, german VDE even says it is mandatory after (iirc) 3 trips due to shortcuts.
For a trip due to 185A it might not be that critical, but if you could avoid it ever happening, that would be the overall best solution.
Usually the manufacturer should state in the datasheet how often the breaker can “savely” disconnect a certain current.
