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Panel configuration.
#1
I have 2 strings of 3 panels. 1 string is mounted facing east and the other is facing west. I realize this is suboptimal but it's the only mounting option I have right now.

Will anything bad happen when I connect both strings together in parallel? In the morning and late evening the opposite string will be slightly shaded. Do I need any blocking diodes? I'm not in the position to buy another charge controller.

Thanks!
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#2
Yes and Yes.

If you can't buy a second charge controller, I would recommend manually switching from one set of panels to another. Otherwise you will "always" loose power production from the non-producing panels. Even in parallel with diodes, as the diodes cause voltage drop, and you don't have enough panels in series to make this not an issue.

Charger controllers aren't that expensive. You can buy a decent one for <$50. Or you could always make one from some FETs, diodes, arduino, inductor and some code. Julian Ilett made the MUPPET which is exactly that and explains the process of construction through several videos.
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#3
The voltage drop due to the diodes is not an issue and it does not help with more panels in series...

Even a cheap Charge controller Will be better than parallel Them. You Will save that money within a small time frame.

You need to decide if wasting that energy in parallel is cheaper than another Charger is.
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#4
(05-23-2019, 12:48 AM)srk Wrote: Will anything bad happen when I connect both strings together in parallel? In the morning and late evening the opposite string will be slightly shaded. Do I need any blocking diodes? 

No and no.

Assuming the panels you are using are all identical and that bypass diodes have been fitted within the terminal box at the rear of the panel (by the manufacturer)

This topic has been debated on this forum previously, at length.
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#5
I agree with Sean but as he says it is important that all panels are the same. Besides that the 3 panels of each string must be in the same direction, so same tilt and direction. Both strings don't have to be in the same direction (learned that from the thread and the links in it Sean is referring to).
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#6
(05-23-2019, 09:58 AM)RikH Wrote: .....  the 3 panels of each string must be in the same direction, so same tilt and direction.

...... both strings don't have to be in the same direction.

exactly this ...
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#7
You can basically have as many directions as you want as Sean state. Its just a matter of that the power tracking point differs due to the sun and you therefore will loose some energy from the panels not directly towards the light.
How much depends on angles and orientation.
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#8
Ok, I hooked them up in parallel. I'll monitor power output tomorrow and see how much gets wasted.
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#9
You can only theoretically calculate how much you loose unless you change between face 1, face 2 and then the combination. This only under full direct sunligt under set of angles. Smile
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#10
Realistically, with this setup of one string facing east + one string facing west, the difference between
a) having the stings in parallel feeding one MPPT
and b) having each string feeding it's own MPPT is going to be minimal.
the change power caused by the drop in voltage MPP as sun light level drops vs full sun MPP typically only makes about maybe 15-20 % difference in power output & for part of a day only (approx 1/3 day).
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