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One charge controller, or two? For opposite facing panels.
Ok, I'm a little bit stuck and could really do with some advice.

I have four 300W panels.  Two of them face east, and two of them face west. That is the way the roof faces and they can't be arranged any other way.
I'll be running a 24V battery system.

Now, my original logic was to use two charge controllers (one for the east facing panels, and one for the west facing panels) and have essentially two strings of series panels. This was to try and deal with the issue of shading between the east and west facing panels.

However, I want to use an MPPT charge controller which works with lithium cells. This feature doesn't seem to be included with any of the controllers at the cheaper end of the range. But, this feature is included with many of the £300+ controllers. 

Now, not wanting to buy two £300+ charge controllers (due to budget), also spending nearly £700 on charge controllers for a 1kW array seems a little excessive... Is there a way of wiring all four panels into one charge controller, even with them facing opposite directions?

I'm thinking maybe the PCM60X like everyone seems to be using, or one of the morningstar Tristar MPPT controllers would have the capacity to handle 4 panels.

I've been reading about bypass diodes being used for shading issues but not specifically for whole strings facing opposing directions, but I'm thinking the same rules apply.

Does anyone else have panels facing different directions? 

I don't know if I'm over thinking this, or if I've missed something obvious.  For me this solar project is just a bit of fun, doing something I find interesting.  So spending vast sums on kit which I am not 100% sure will do what I need it too, is mildly troubling for me.

I've included a quick sketch of what I think may work for my setup.

Any help or advice would be greatly appreciated.

Thanks. Alex


Sorry mate, if you want to use the most out of your panels, the way your setup is laid, only 2 MPPT SCs can achieve this.
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You need 2 chargers to get full power out of it. Otherwise you only get power from 1 side or the other.

Either you get 1 charger with 2 MPPT or you get 2 MPPT chargers or you go the simple route and go 2 PWM chargers or lastly but least effective 1 MPPT and hook them up in paralell.

Thats my 5 cents.

Note that on cloudy days the 2 sides will generate same amount so its only when its sunny you need 2 controllers
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silverse2m6 and daromer are right, since your panels are faced opposite and we only have one sun, only one side will give you max. power. so, in order to get the maximum out your panels, you'll need two strings and seperate charge controllers.
But as far as I can see from your drawing, you have the two panels on one side connected in series and the panels on both sides connected in paralell. This setup should also work ok and I would try it. I also have panels facing in different directions connected to the same string (althoughI have 3 charge controllers for 3 strings, my panels are faced from south-east all the way to north-west). And I also connected panels facing in different directions in parallel and it works fine. The panels in the shadow don't bring down the whole string (as it would be with series connections). So I would give it a try.

Btw, I'm using 3 EPsolar Tracer 3215RN MPPT charge controlers, each costs around 130$.

Have sun!
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permanently on battery from:
- 2017/05/20 - 2017/07/01
- 2017/07/02 - 2017/07/25
- 2017/07/26 - 2017/08/16
-  2017/08/17 . ?
What's left:
my current grid consumption
Yeah it works to have each side in series and then paralell. As I said in shade this will produce equal amount but in sun only kind of 1 side will produce... So it depends on the money you want to spend. But on the other hand look at for instance the cheap 7210 charger that is on ebay.. If it fits your voltage range. Its rather crappy but could be a start....

Preferable is better controllers though.

I run 5 actually.

2x pcm60 for 1 roof. Wasnt enough with one...
1x pip4048 för south for one angle
2xMPPT on the MPI charger. East and south on that one. All to cover it all.
Al's Shed likes this post
Follow me! >> YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcomming: 14S 18650~30kWh | Automatic trip breakers, and alot more
Thank you all for the advice. I've been slowly convincing myself to get going with something cheap, that way I can get some real world numbers (I like having numbers for things).
I think I need to accept that I will inevitably be purchasing several different charge controllers in the search for my ideal balance between price and efficiency.

It's good to know that all of the above setups will work, albeit with varying degrees of efficiency.

I'm very tempted to go with some cheap controllers, then play around with the wiring and the setup and see how much difference different configurations actually make.

It is quite daunting, with so many different bits of kit on the market, all with their own advantages and disadvantages for every individual application. There really is no 'one size fits all' for solar.

I think my longer term plan will be 2 MPPT controllers. I was initially looking at the 30A Tracer actually, as a cheaper option to the PCM60X. I like the way the software interface looks on the PCM though.

I'll have a look at that 7210 while i debate which way to go with the more expensive controllers.
On things like these, I "buy once, cry once". Even with cheaper equipment you will likely only get a portion of what a good charger would deliver (look at efficiencies and idle consumptions)
Watch this... look at just 6 panels how much you can draw from the sun only on one facing direction...
Slightly off question but can you have 2 or more chargers for one battery pack or do you need a pack for each?
More chargers on a pack is no problem, i have 4 in use.
Must be the same voltage of course.

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