Update to

Story: Update to "How long is a piece of string?"Total Replies: 6
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Oct 20, 2015
2:58 PM EDT
Thanks Ridcully, Very informative and interesting read!

Oct 20, 2015
9:38 PM EDT
Enjoyed the update, Ridcully. You have an impressive setup. Makes me want to get some panels and start capturing photons.

Oct 21, 2015
3:35 AM EDT
Thankyou. I believe it has reached the stage here in Australia where at least some parts of the power grid are now supplying only 30% of what they normally could from the coal fired power-stations. If this goes on much longer (and every indication is that it will, and even more strongly) then we will see at least some coal fired power-stations shut down and either moth-balled or removed completely. And then, in South Australia, there are moves that are getting stronger to start an Australian nuclear industry. Personally, I think coal fired power is now on the way out and our new PM is definitely encouraging alternative power.

Oct 21, 2015
5:16 AM EDT
How windy are your cloudy days? It occurs to me to wonder if perhaps a small windmill of some sort which was added to your setup might 'fine the weather' for its obstruction of your solar array and eliminate that deepest discharge. Something to consider.

Oct 21, 2015
6:06 AM EDT
Nice idea cr, but the answer is simple: the winds are too erratic, uneven, unpredictable, and are poorly consistent. Wind generation here in my area has been tried, but never caught on widely - it simply does not justify the outlay cost. However solar panels are "blossoming" on every second roof or commercial building.

Mind you, there are places in Australia where consistent good velocity winds do allow use of wind power - but not here in Blackbutt Qld.

Oct 21, 2015
11:19 AM EDT
Hey Dr Ridcully, one more question from the Penguinist. It's about batteries. These deep cycle batteries made special for solar are really really expensive, but we can get deep cycle golf cart batteries for about half the price since they are manufactured in high volumes.

For example, the Trojan T-105 deep cycle 6-volt battery retails here in the US for between $105 and 115 each and has a capacity of 1.5 kWh.

What is your take on the use of golf cart batteries for solar storage?

Oct 21, 2015
11:31 PM EDT
Hi Penguinist......briefly, I simply cannot answer your question because I've never explored that possibility. On the face of it, a deep cycle battery is a deep cycle battery........if you see what I mean. But there are some questions you must ask.

A solar stand alone system's deep cycle batteries are designed to supply heavy currents for long periods of time. For instance, when a battery bank (such as ours) is new, I would not hesitate to do an hour's vacuuming using the inverter and battery bank. Now, consider, that is a 1200Watt device (often more), so, looking at the situation from the battery bank's side, you are asking it to supply 1200/24 = 50amps for a solid hour. It's probably about 52amps given the power losses in the inverter itself and elsewhere. That means each side of the parallel banks will be supplying 25-26 amps. Solar system deep cycle batteries are designed to take these heavy loads for long intervals.

Now, I have NO idea as to how a golf buggy battery will perform under those conditions, but from what I have seen, the buggy batteries seem to be more used for short periods of time under intermittent conditions.

I stress this is pure hypothesis on my part, but batteries are built for precisely their intended usage. For instance you absolutely cannot use a car battery as part of a deep cycle system......well in an emergency you could but you'd have to be careful to put minimum load on it, because car batteries are designed to produce very high currents for very short intervals - eg the starter motor.

I think your best solution for that fascinating question out of the left field is to go to the experts......and if you do, I'd be very pleased to hear the answer. It's a solution I'd never even considered. Thanks - it's been an interesting one to meditate over, and I am sorry I cannot give you a straight answer.

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