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Posted: Fri, 08 May 2015, 03:48
The Rpi is very internet capable Dave. I'm from more of a microcontroller (pics/arduinos) background but I have to say an OS based micro is a dream for the higher level stuff (we're using python).
The down side, as celectric says, is no analog in on card & just a single uart. There are USB ports but I hate the complexity of USB drivers so we've just used a little ebay TTL to RS232 to chat to the PIPs. There are some nice cheap analog add on cards for the Pi, but not so much in the way of affordable RS232 multiplexors.
2 PIPs in parallel is not a whole lot of fun. In theory you can chat to either PIP from the one you are jacked into with cmds like QPGS0/QPGS1 to selectively address them but in practice the bloody things are inclined to reset themselves to factory default (single mode) so you have to then move the RS232 plug to the one that has the sulks to get it back into parallel mode.
The only good thing about MPP gear is the price, don't get me started on the veracity of some of the values it reports (solar + mains + battery power in < inverter power out)!!
Posted: Fri, 08 May 2015, 04:09
Thanks celectric and Plan B. I found the Wikipedia comparison article.
http://en.wikipedia.org/wiki/Comparison ... _and_ports
So it looks like the slightly more expensive BeagleBone Black
(BBB) might be a better option since it has ADC and more UARTs. And its CAN bus might be handy if I was forced to switch to say a Schneider XW+ inverter. It will still need a USB WiFi dongle.
I see neither RPi or BBB have a battery-backed-up real-time-clock, but rely on getting the time from an NTP server. But an I2C RTC can be added.
Do you know any reasons why a BBB might be a bad
Posted: Fri, 08 May 2015, 04:36
We mainly went Rpi 'cause you can get almost anything on it, including Fortran! But the BBB looks good too & the extra I/O for just twenty bucks seems like a good deal. The BBB seems to come out best here http://makezine.com/magazine/how-to-cho ... one-black/
Posted: Fri, 08 May 2015, 14:02
+1 for BBB - I was about to suggest it based on Weber's first post last night. My friend builds electronics prototypes for a living - started with Arduino, then went to Rpi, now uses mostly BBB.
If there are specific questions/issues with BBB let me know - I can ask him.
Posted: Fri, 08 May 2015, 15:34
weber wrote:I'm working up to building Black Monolith #2, for a client. It will have double the storage capacity and double the power of Black Monolith #1. It will be an on-grid peak-load shifter, which may or may not have PV input itself, but will certainly maximise the client's export from his existing Solar Bonus Scheme PV system (50c/kWh).
I realise that I'm in Victoria and the rules are probably different but when I got the 66c feed-in tarrif I signed a contract that said I would not change the system in any way other than repairs. If I do, I lose the tarrif. Just a gotcha to look for.
Posted: Fri, 08 May 2015, 17:02
Johny wrote:I realise that I'm in Victoria and the rules are probably different but when I got the 66c feed-in tarrif I signed a contract that said I would not change the system in any way other than repairs. If I do, I lose the tarrif. Just a gotcha to look for.
A good point. And I should have mentioned that I will be building an equivalent system for myself at the same time (but with only one PIP and using an existing 8 kWh SkyEnergy battery).
My household is also one of those who are, quite deservedly, on the 50c/kWh feed-in tariff, because a decade ago we paid 10 times what people pay today for a PV system, to help prime the very pipeline that people today benefit from.
We will not be touching the existing grid-feed systems at all. The rule in QLD is that you cannot increase the total rated AC output power of all grid-feed inverters at the address. These Monoliths will not have any grid-feed capability. From the network's point of view they will purely be shifting the household load to off-peak, and possibly reducing it (by using an additional PV array).
Posted: Fri, 08 May 2015, 18:54
weber wrote:We will not be touching the existing grid-feed systems at all. The rule in QLD is that you cannot increase the total rated AC output power of all grid-feed inverters at the address. These Monoliths will not have any grid-feed capability. From the network's point of view they will purely be shifting the household load to off-peak, and possibly reducing it (by using an additional PV array).
Gotcha! I'll be watching (reading) with interest. I'm currently conducting a year-long sunshine audit on our property with that in mind.
It's where I thought I'd retire the Vogue batteries to if ever something outstandingly better (for the car) comes along (and I can afford it).
Posted: Fri, 08 May 2015, 18:58
I am also on the 60c/kwh scheme. I also have a grid feed solar which cannot be changed. However I also built a separate Stand Alone Solar Power System using a PIP which supplies power to a distribution board (or a UPS Switchboard which has no public access) located on the other side of the house opposite side to the main switchboard. It reduced my power usage from the grid from about 1000kwh a quarter to about 20kwh. Someone from Endevour Energy came to check my Main Switchboard because they thought I was stealing electricity. He opened up my main switchboard and checked that I had not bridged out the council meter which is illegal. I just happenned to be home and I explained to him that I am using a energy storage system. It was all fine with him.
After 2017 the 60c/kwh infeed tariff reverts to 6c/kwh. I will consider going off-grid and have my Electicity account closed. Use a NG generator set to replace the grid.
Posted: Fri, 08 May 2015, 21:17
the problem with more and more people doing that sort of thing is power prices will go up rapidly to make up for the loss of profits (notice i didnt say income because they dont care about that just profit)
Posted: Fri, 08 May 2015, 21:55
I disagree, increasing of electricity prices will give users more incentive to do what I have done. Yin and yang.
Posted: Fri, 08 May 2015, 22:49
i am not even going to bother fighting on this one it has already happened about 6 years ago when the solar rebate started in QLD prices jumped 28% in 3 months and again 3 months later
Posted: Fri, 08 May 2015, 23:06
Though Perhaps people can load shift for now (If it's economically viable)Then if and when the price comes up for grid supply power. They can make a 2nd economic decision to just add more batterys and disconnect from it all together.
For most people it's a pure financial decision. They just want there power and to pay as little as they can for it.
Posted: Fri, 08 May 2015, 23:39
Watch the topic drift please guys. Feel free to start another thread on the reasons for electricity price rises.
Posted: Fri, 08 May 2015, 23:54
Good article here on different battery sizes and energy management algorithms.
http://www.businessspectator.com.au/art ... ly&modapt=
I particularly like the idea of having the EMU pull tomorrow's weather forecast off the net and use it to decide how full to charge the batteries with off-peak grid power that night versus how much room to leave for solar power the next day.
Posted: Mon, 11 May 2015, 15:11
Hi all, first post hope it relevant.
We live in a van full time as we travel Aus. I recently installed 1000w worth of panels along with a mppt reg and am about to purchase a 2400w inverter. Batteries are 24v 200ah lithium. The inverter im looking at is the pip2424 so that it will revert to mains when the battery is depleted.
The van has 3 main circuits, one for the power points, one for the 3 way fridge and one for the HWS/stove and Aircon.
The plan was to connect the inverter to the circuit that runs the power points only as it can be fed via an already wired inverter feed in under the lounge. All the other appliances draw too much power to be run simultaneously off the inverter.
My concern is that the inverter having a mains feed from one of the other circuits for backup may interfere with the rest of the circuits, tripping the board or worse.
Posted: Wed, 13 May 2015, 04:53
Hi BeauJewel. It sounds relevant to me. However I think you should get an electrician to have a look at it. I don't think it's something we could safely advise you on over the net.
I went out to the bush to visit Black Monolith #1 again today. I updated its software and I made it so the customer can (just barely) read the display on the PIP, and push the buttons to change what is displayed.
I made the display readable in a way that preserved the featureless look of the monolith. Over a 75 x 75 mm area in front of the display, I used a cutting disc on a dremel to cut away the _inside_ layer of polycarbonate, and the flutes or ribs. I left the outer layer of polycarbonate intact, except for four 8 mm holes in front of the four buttons. The customer can poke a biro through to push the buttons.
It was a very fiddly job. I'm not sure I'd bother in future.
I also updated the software to eliminate two cases where the State-of-Charge meter would jump to 100% prematurely, and to eliminate some spurious low voltage alarms now that the weather is getting colder.
One case of premature meter reset occurred when the monolith was shutdown and restarted. The coulomb counter in the IMU (the BMS master) is in RAM and is lost when powered down. The CMUs are never powered down since they are on cells, so I made the IMU send the coulomb counter value to CMU-1 every 2 minutes for safe-keeping, then ask for it back again on reset.
The other case of premature jocularity occurred when there was a high charge current from either the genset or the PV array. Coulomb helped me solve that one on the weekend, by reading the code and figuring out where I'd gone wrong.
The cold-weather spurious low-voltage alarms were eliminated by adjusting the estimated internal resistance based on temperature. I looked up the internal resistance versus temp relationship in that great set of slides that Johny found.
http://www.cse.anl.gov/us-china-worksho ... %20BMS.pdf
See page 16.
The cubic equation they give would have been very slow to run with no hardware multiplier. But it turns out it can be modeled quite well as the sum of a fixed component and an Arrhenius component -- a temperature-dependent component that doubles for every 10 K drop in temperature. And at 10 degC, the temp-dependent component is approximately equal to the fixed component.
Posted: Wed, 13 May 2015, 15:36
I'd be worried chitters are gonna crawl in through those button access holes & not be able to find their way out again Dave. Can you not put some rubber bungs in or maybe fit a little clear, hinged access hatch?
Posted: Wed, 13 May 2015, 16:02
I would say the vents in the enclosure would already give a access point for tiny bugs. Unless they were covered with a ultra fine mesh at the rear?
I have found the screen attracts tiny flying bugs unless you turn it to auto sleep mode. Ants can be a issue with inverters. I have been told some horror story's about ant's setting up nests. I regularly keep tabs on that. Though the most attracted critter to my inverters has been snakes. They love seeking warmth and using the inverter as a electric blanket. Typically I have to pull one snake a month from my power room and find them a new home (Often different snakes). Frightens you when you pull on what you think is 95mm2 cable at the back of a cabinet in the dark. Then it moves in your hand by its self.
Posted: Wed, 13 May 2015, 16:31
Take care if adding any kind of mesh. When I was preparing the Lenze inverter for my car I wanted to stop droplets of water entering the vents so did quite a lot of mucking around measuring what various kinds of mesh did to low-velocity airflow. All of the ones I tried had quite a detrimental effect on airflow.
I settled on dress taffeta glued to the inside of the vents. It was just small enough (holes) to cause water to ball but not constrict airflow by very much. I use the same stuff glued under the garage chest freezer to try to stop insects finding nice warm homes in the compressor.
Love the snakes story Kurt.
Posted: Wed, 13 May 2015, 21:16
That's a good point Kris. So I have just emailed the customer and asked him to put some clear tape over the holes.
Yes Kurt, the louvred vents are screened on the inside (holes 1 mm x 2 mm).
The only insect problem so far is small black ants eating the neutral-cure silicone. Anyone know of a brand that doesn't contain ant-food?
Posted: Wed, 13 May 2015, 21:26
If this stuff can stop termites I'd expect it would also stop ants...
CSIRO tested too
Posted: Fri, 15 May 2015, 05:22
I've emailed AltTerm as follows:
Where can I buy it in Brisbane, or over the net? What is the RRP for a single cartridge?
Does it contain metal powder? I'm thinking of using it in an application where it would need to be electrically insulating.
I'm having trouble with ants eating the neutral cure silicone I'm using now. I know ants aren't termites and vice versa but is there reason to think ants would not eat your silicone? I'm guessing its the methylethylketoxime curing product (oxime cure) that the ants are after. I notice from the MSDS that your silicone seems to have a combination of oxime cure and alkoxy cure. So why wouldn't ants still go for it after the methanol cure product evaporates leaving the methylethylketoxime?
Just to explain the above terminology: I have spent hours researching on the web, just what the ants might be after. All I could find was a bunch of people asking the same question, with no answers. Certainly no admission from any silicone manufacturer that it's even a problem.
The non-neutral cure is called "acetoxy cure" and produces acetic acid. I learned there are two main neutral cure chemistries "oxime cure" which produces methylethylketoxime or MEKO and "alkoxy cure" which produces one or more alcohols such as methanol, ethanol or isopropanol. Usually, the only way you can find out is to look up the Material Safety Data Sheet (MSDS) and look for the presence of the word-parts "acetoxy" versus "oxime" versus "methoxy","ethoxy" or "propoxy".
The kind the ants are eating is an oxime curing type. Why would they go for that? It's toxic to humans. The only clue I found was when I happened across the fact that a different oxime is used as an artificial sweetener, and apparently many oximes taste sweet, at least to humans. It's the only hypothesis I can come up with. I have no evidence that's why the ants are "eating" the silicone. When I say "eating", they don't actually seem to swallow it, or even carry any of it away. They just turn it to white powder, as if they are just removing a liquid from it.
I'd like to try an alkoxy cure silicone, assuming the ants wouldn't be interested in methanol, but the only place I can find to buy it is on Element 14 at nearly 10 times the price of typical oxime cure silicones. $70 a cartridge!
http://au.element14.com/acc-silicones/a ... dp/2400713
Posted: Fri, 15 May 2015, 06:23
The problem with having an anty monolith, is that one must make very sure it never comes into contact with a monolith, or there would be mutual annihilation and a massive release of energy according to E = mc^2.
And it's funny that they're called sealants, when in fact they don't.
Posted: Fri, 15 May 2015, 12:42
Are you sue you didn't accidentally use a bathroom silicon that was ( (Anti-Mould)
Are they the little black (house ants) Like the ones that were invading your lab and my house - garage in Brisbane over summer? I found that if I clean a surface with a citrus based cleaner they leave that area alone for some time.
Posted: Fri, 15 May 2015, 19:52
Yes, those ants. Black, about 2 mm long and 1 mm wide. I first saw them chewing their way into freshly cured neutral-cure silicone on circuit boards maybe a decade ago.
I tried spraying an insecticide onto the silicone in the monolith, but it only kept them away for at most two weeks.
I have had no response to my query to ALTERM
about the Termite-proof silicone (which appears to have a hybrid oxime/alkoxy cure).
But I finally found a source of some lower-cost alkoxy-cure silicones. Interestingly they are described as "electrical sealant" and they are only available in white. They are AU$32.20 from Blackwoods and they are Dow Corning 738 which produces isopropanol on cure and Dow Corning 748 which produces methanol on cure. As far as I can discover, ants don't like either of those substances.
https://www.blackwoods.com.au/search/73 ... /302026846
https://www.blackwoods.com.au/search/74 ... /302026848
I ordered one cartridge of the 738. Delivery was free. The 748 is out of stock.
I have a new hypothesis as to why these ants are attracted to oxime-cured silicone. The particular oxime produced on curing is methyl ethyl ketone oxime (MEKO). This is described as having a stale musty smell (i.e the smell of mould, which are fungi). Methyl ethyl ketone (MEK) (but not necessarily the oxime) is produced naturally by certain fungi including some that ripen cheese. Perhaps the ants think they are going to get a meal of mould or fungus protein and just keep gnawing away at the silicone hoping to find it. Or maybe they really can metabolise the MEKO for energy.