Multiple solar panels to a common bus bar?

[tamicatana]

Originally Posted by ozsailer

If in doubt,

that's a good one. As if the ignorant have any doubt... therein lies the problem: often wrong, never in doubt

[emilecantin]

Regarding fusing: Yes, the wires leaving the panel are sized to the panel's Isc so no need to fuse them, but when you parallel panels that doesn't hold anymore unless you also up-size the wires after the parallel connection.

[Hoohaa]

Originally Posted by smac999

How does connecting all the panels to the same bus bar isolate them?…. .

If some panels are getting shaded. You would be better off having each panel go to it’s own controller. The way you had it.

I started that way initially. And come to the realisation that it is probably not necessary hence the reason for this post.
The goal is to effectively separate the panels so that if one gets shaded it doesn't affect the panel next to it.
So if you connect both the panels or all of the panels to a bus bar near the panels and then run your cable from the bus bar to your suitably sized MPPT controller it effectively does the same thing but with half the wiring runs and MPPT controllers.

[goboatingnow]

Well it doesn’t because the Vmp point is very temperature dependant , irradiance dependant and panel specific.

Multiple mppt is better overall

[coopec43]

After reading this thread I am now a bit confused.

• I don't have a fuse between the controller and the panels.
• I have recommended value fuses between the controller and battery.
• I have switches between the panels and controller (my panels are installed in series)
• Is 24V 150A dangerous to a human?

Does that sound OK?

[Wotname]

Originally Posted by coopec43

After reading this thread I am now a bit confused.

• 1. I don't have a fuse between the controller and the panels.
• 2. I have recommended value fuses between the controller and battery.
• 3. I have switches between the panels and controller (my panels are installed in series)
• 4. Is 24V 150A dangerous to a human?

Does that sound OK?

1 - OK providing wire gauge can handle the rated short circuit current of the panels.
2 - OK providing the fuse is located near the battery rather than the near the controller - assuming the controller has built in short circuit protection. What is make and model of controller?
3 - OK although nor needed.
4 - No, 24V is safe. 150A is a lot of current and if in the wrong place, will cause heat and fire. Perfectly safe if the current is contained within suitably sized conductors and load.

[coopec43]

Originally Posted by Wotname

1 - OK providing wire gauge can handle the rated short circuit current of the panels.
2 - OK providing the fuse is located near the battery rather than the near the controller - assuming the controller has built in short circuit protection. What is make and model of controller?
3 - OK although nor needed.
4 - No, 24V is safe. 150A is a lot of current and if in the wrong place, will cause heat and fire. Perfectly safe if the current is contained within suitably sized conductors and load.

Thanks Wotname

2 - OK providing the fuse is located near the battery rather than the near the controller - assuming the controller has built in short circuit protection. What is make and model of controller?

It is a Victron Smart Solar 100/20 (from memory). I don't follow the logic regarding fuse location. Please explain!

Thanks

[Wotname]

Originally Posted by coopec43

Thanks Wotname

2 - OK providing the fuse is located near the battery rather than the near the controller - assuming the controller has built in short circuit protection. What is make and model of controller?

It is a Victron Smart Solar 100/20 (from memory). I don't follow the logic regarding fuse location. Please explain!

Thanks

AFAIK, the Victron Smart Solar 100/20 has short circuit overload protection - which is good thing. It will shut down it detects a short on it's output side (i.e. battery side).

Fuse (or circuit breaker) location - should be must be located as close as practicable to the power source. It can't protect the section of wiring between the power source and the fuse, it can only protect the wiring 'downstream' of the fuse.

It the case of wiring between a battery and a solar controller, both items are power sources so where is the proper location for the fuse? Regardless of any other consideration, there must be a fuse near the battery (because it is a power source with a practicability unlimited current output). As for the solar controller, it has limited current output and if that is exceeded (e.g. by a short on it's output wiring), the solar controller with built in overload protection will either a. shut down or b. cut back; both will protect the wiring. However a solar controller without built in overload protection will burn out (i.e. let the smoke out ). So a solar controller without built in overload protection needs fusing as close as practicable to its output terminals. In all cases, the battery end needs fusing.

Thus if using a controller without built in overload protection, you need two fuses - one near the battery and one near the controller. If you elect not to fuse, then you must provide additional measures to protect the wiring e.g. double insulation, chaff protection, well secured looms, oversized wire gauge, physically separated +ve and -ve conductors.

[Adelie]

Originally Posted by Hoohaa

Ten years ago I set up 2 panel's on my davits and on the advice of the guy that supplied the panel's, I installed 2 completely separate mppt controllers to isolate the panel's from each other inorder to minimise the effects of shadowing.

Apart from doubling up on wiring, it's worked fine.

I've since rewired the boat and upgraded the battery system, got rid of the second mppt controller and simply ran both panels to a small busbar mounted under the panel's and then onto a larger single mppt controller.

I can't see any disadvantages in doing it this way. Less wiring and very simple to add additional panels if require and it effectively isolates each panel from the effects of one of the panel's coping some shadowing.

Can anyone explain to me what the disadvantages are of doing it this way?

If one panel is shaded it will reduce output of both panels. How much is a function of how much is shaded.

[coopec43]

Originally Posted by Wotname

AFAIK, the Victron Smart Solar 100/20 has short circuit overload protection - which is good thing. It will shut down it detects a short on it's output side (i.e. battery side).

Fuse (or circuit breaker) location - should be must be located as close as practicable to the power source. It can't protect the section of wiring between the power source and the fuse, it can only protect the wiring 'downstream' of the fuse.

It the case of wiring between a battery and a solar controller, both items are power sources so where is the proper location for the fuse? Regardless o

Thanks for that.

Another question (I won't start a new thread) I'm busy fusing the switchboard. What capacity fuses should I use?

For example the Shurflow water pump "Requires 7.5A fuse". I can't use a 5A fuse as it would blow. If the electrical cable can carry (say) 12A would a 10A fuse be appropriate?

The reason I am asking is that when I ordered I had a bewildering number of choices. Would an 8A fuse be more appropriate?

[Wotname]

Originally Posted by coopec43

.........

For example the Shurflow water pump "Requires 7.5A fuse". I can't use a 5A fuse as it would blow. If the electrical cable can carry (say) 12A would a 10A fuse be appropriate?

.........

Yes. The underlying principle is the fuse is fitted to protect the wiring rather than the load.
The manufacturer in this instance gives guidance as to what size fuse is required to deal with input rush currents and worse case steady load currents for the item in question.

If you already had (say) an 8A fuse, then it would be OK in this instance but if the cable is good for greater than 10A, then 10A is just as good.

[Hoohaa]

Originally Posted by goboatingnow

Well it doesn’t because the Vmp point is very temperature dependant , irradiance dependant and panel specific.

Multiple mppt is better overall

I know you're right!
One of the reasons for this thread is for me to determine if there are insignificant or significant differences.
I am certain there are small differences but currently I'm pretty sure they can be overcome by cleaning the seagull crap off the panels ( it's that time of the year).
Do you know what the real effects or differences are?

[goboatingnow]

Originally Posted by Hoohaa

I know you're right!

One of the reasons for this thread is for me to determine if there are insignificant or significant differences.

I am certain there are small differences but currently I'm pretty sure they can be overcome by cleaning the seagull crap off the panels ( it's that time of the year).

Do you know what the real effects or differences are?

No I’ve not bothered instrumenting the system to determine the exact differences. I mean mppt scc is relatively cheap so why accept less then optimum. For me only two panels per mppt.

[Hoohaa]

Originally Posted by goboatingnow

No I’ve not bothered instrumenting the system to determine the exact differences. I mean mppt scc is relatively cheap so why accept less then optimum. For me only two panels per mppt.

For me, it's the duplication of the wiring. Trying to fit two seperate sets of wires through the pipes on my davits was not fun.
Also, I'm only running two panels & wind gen.

[goboatingnow]

Originally Posted by Hoohaa

For me, it's the duplication of the wiring. Trying to fit two seperate sets of wires through the pipes on my davits was not fun.

Also, I'm only running two panels & wind gen.

I have 4 panels now. One set of wires through the starboard arch piping , the other through the port side

No biggie really

I’m adding a wind gen