Author Topic: Tidying up (a tale of 4 trackers)  (Read 898 times)

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Offline rossw

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Tidying up (a tale of 4 trackers)
« on: April 15, 2016, 08:01:41 pm »
So ages and ages ago I built a bunch of trackers (described elsewhere), and as a "temporary" thing, I just ran a length of figure-8 flex from the battery/control room up top, over and to the first tracker, then daisy-chained from there to the next, and the next, and the last...

Well, as time has gone on, and the actuators have stiffened up, and the trackers have stiffened up a bit I guess, and the temporary connections have oxidised, and one thing and another... the far end trackers have slowly been getting further and further behind by the end of each day.

It's been a "round tuit" job for quite some time.

And then the other half got a dozen sheep. And they started getting tangled up in the cable just lying in the long grass... and the kangaroos would get caught in it from time to time, and about once every month or two I'd find an array that stopped tracking and would have to go find and fix the break.

The final straw came the other day when two of the old AGM cells decided they'd had enough, and wanted to die... which meant my centre-tapped 48V supply for the actuators (+24/-24) became more like +20/-24 and likely to get worse real soon.

So I've rebuilt my power controller for the trackers, so I can send out a single 24V supply, but completely reverse the polarity to drive the trackers home.

Of course, that only works while the actuators are isolated... and while I ran 3-conductor cable out to the panels, I need 4 conductors for power + isolated actuators. So I hatched a cunning plan, to kill several birds with one stone.

I bought a couple of inexpensive, 24V/5A switched-mode supplies. (One for now, one as a spare).
These are fully isolated.... an essential part of the equation!

The reversing output to the actuators has one side connected to the system negative (common of PV-, battery-, ground), with the other side connected to the (previously spare) 3rd wire to each tracker assembly.

Next was to go to each tracker, disconnect the actuator and connect it between ground and the 3rd wire.

I've now removed about 150m of flex, tidied the whole thing up, removed all reliance on the old AGM cells and reduced the voltage drop to the far actuators, meaning things seem to be tracking much better again.

Been a long time coming, but a job well done I say!