Opinions - 2 banks, one solar array

[Simen]

Currently i have one 12V bank with 4 Rolls S-530 and 4 130W solar panels, with 2x 30 meters of 16mm² (2x 2-cord 16mm²) from the panels to the battery bank.

Now, i've just finished building a pottery workshop for my mum, and it's situated at the same distance from the panels as the current location of the bank.

I want to spilt up my current bank in two, since i do not need 1060Ah here at my house, used for led-lighting mainly. (avg. 350Wh/day)

The pottery workshop's needs would be led-lighting and a 1000W inverter for a pottery turntable, grinder etc.; maybe 500Wh/day on busy days (rare), average 200Wh/day.

Now, what's the easiest (read: cheapest) way to let those two banks share the same solar array?

I do have several controllers available, so i'm thinking about taking one of the two 16mm² wires and drag it over to the pottery, and connect it to the battery there via it's own controller.

Any comments?

[SparWeb]

Can you split the set of 4 solar panels into two separate arrays of 2 panels each?
Then make a similar split of the 4 batteries, into two separate pairs, too.
You say you already have the extra charge controllers and inverter, so, all you need to buy is wire.
Your daily consumption in house and shop will drain each battery to 1/10 capacity, on busy days, so there is capacity for many days without sun to fully recharge.
You end up with the same re-charging rate (about C/24) if all arrays charge all batteries, or if half the array charges half the bank.

[Simen]

Yes, i could split the array in two. (I had not considered that; thanks. )

One point though;
The S-4000 series from Rolls likes a hard charge, and in my current configuration, they doesn't get that. (they like an even harder equalize according to spec; 30% of C/6...)
Since the house uses power mainly in the evening, and the shop during daytime, i was hoping to get closer to a C/10 charge on each bank by just splitting the bank in two and use the full array on both...

Edit:
Another point;
In dec/jan there's just 2 hours of sun hitting the panels, if at all... (I'm at 58deg. N...)

[SparWeb]

Well you can still do it, but you'll need a LOT more wire, and then there's the switching from bank A to bank B question.
Answering that one will drive us in many many directions.

Throwing out a first guess...  Put a junction box under the array of panels.  Inside is a Big relay.  Its contacts will switch the array from supplying Controller A to Controller B.  Controller A regulates only bank A in the house (and of course Controller B regulates only bank B in the shop).  Now you need a control circuit that will monitor the status on Controller and bank A.  Once battery bank A is full, and hence Controller A regulates the PWM of the charge current to essentially zero, then the control circuit observes the fact, and *switches* the solar panel output from Controller A to Controller B.
Essentially, the relay connects to only one controller at a time.
There's probably a reason for this to not work.

[Bruce S]

How far is the shed from the banks?
Maybe since your winter months the sun is so low in the sky it might be better to keep everything where it is and have the inverter located right there and drop a good AC cable from the inverter over to the shed?
Control box in the shed would allow for plugins?
The AC will travel much better with less line loss than DC. Of course there may be things like a road or other factors that could keep this from working.
Bruce S

[Simen]

Sparweb;
I'm actually looking for an electronic battery switch, which i can just send a pulse to make the switch... It seems so wasteful to use an ordinary relay... 

Bruce;
The distance to the shed are around 20 meters from the current bank location... Now, why didn't i thought of that?! Probably because i was so set on splitting up the bank...
There's only lawn between the house and the shed, so no problem burying a cable...

[SparWeb]

... There also exist battery isolators.  Instead of switching, a diode on each branch prevents one battery from interacting with another.  This is unlikely to be compatible with your goal, however.  The charge controller is interactive with the battery voltage and already capable if isolating the battery from the array's supply - meaning conflict.  Searching for electronic battery switching will bring up a lot of passive battery isolators and that will be a dead-end, I fear.

Of course, choosing the right relay is also tricky.  It's switching DC so the contacts must make a clean break before making the other circuit.  Depending on how the circuit it set up, though, you could be switching the voltage difference between battery banks, which will only be a few volts (good) instead of switching all of one battery voltage to another.  Long relay life and less difficult selection.

Enough now on the direction I was headed...

I like Bruce's suggestion too.
Since, no matter what you do, you have the prospect of buring electrical wires from the array to the shop, and already have them going to the house, it seems like the only "additional" cost to the buried AC choice is the junctions you must make at the inverter, and relocating the inverter itself.
Definitely worth considering.

[Bruce S]

SparWeb;
 The one though a bit pricy I used in my wife's cake carrying truck, was the "Split Diode Rectifier".
I get  them from a friend that has a boat repair shop. They're for doing just this type of thing.
I have aux batteries in the back for keeping things chilled.
The SDR keeps the aux batteries (2 series 24 marine batteries) topped off while she drives while not allowing the started battery to be drained.
by pricy I mean $125.00USD for a 140A 12v unit.
Bruce S

[Simen]

I think i'll go with the councils recommendations by installing the inverter where the bank currently resides, and bury an AC cable over to the shed...

I've also looked into those 'diode splitter' things, but i think they prioritize the main bank and only charges the secondary bank when the main bank are full.

Over time, i probably buy some more panels, and then decide to split the bank and panels both...

Thanks for your inputs guys.

[SparWeb]

...by pricy I mean $125.00USD for a 140A 12v unit.
Bruce S

Yeah, about the same price for one at NAPA auto parts, here, too.
They're just big barrier diodes, inside aren't they?  Scaled-up versions of the 3-legged TO-220 units found in every other DC power supply, right?