Author Topic: Maxing out my small off-grid system  (Read 13619 times)

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mab

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Re: Maxing out my small off-grid system
« Reply #27 on: July 22, 2016, 04:03:27 PM »
For drilling ally I'd use a regular HSS drill bit for metal, rather than masonry, though I daresay a masonry bit would go through; when I drilled mine I held a piece of wood behind the ally to stop the drill going into the back of the panel. I'd take it slow & steady, and use a sharp bit so you don't have to press it in to make it cut.

Mary B

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Re: Maxing out my small off-grid system
« Reply #28 on: July 22, 2016, 06:20:14 PM »
I had to enlarge the holes in my panels ro accept a 1/4" bolt. I used a scrap of aluminum slid in behind as a drill bit stop to keep from hitting the panel.

DamonHD

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Re: Maxing out my small off-grid system
« Reply #29 on: July 23, 2016, 02:00:57 AM »
Both useful tips that I can understand, thank you.

Rgds

Damon

Bruce S

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Re: Maxing out my small off-grid system
« Reply #30 on: July 25, 2016, 07:04:57 AM »
Damon;
Being that I am too cheap to buy drill collars  :o, I use cheap paper tape on the drill bit to tell me when I'm getting close.
I used a piece of wood  to stop the drill from hitting the back of the panel. As has already been said, use a metal drill bit, nice sharp one and easy does it as it gets close to getting through each hole. There have been times when the bit grabs the metal your drilling. Things can get "dicey" real fast. The Al bits hurt and can slice through a finger in 0.00001 sec.

Have fun!
A kind word often goes unsaid BUT never goes unheard

DamonHD

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Re: Maxing out my small off-grid system
« Reply #31 on: July 25, 2016, 11:40:59 AM »
Ah!  I am a huge coward!

OK, thanks for the advice.

And even as a cheapskate I have tape...  B^>

Rgds

Damon

Harold in CR

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Re: Maxing out my small off-grid system
« Reply #32 on: July 27, 2016, 03:15:11 PM »

 Yeah, I'm cheap too. That's why I suggested drill collars. You can also drill through a piece of wood that will slide over the bit and prevent going too deep.

 I try to not take chances around 100's of dollars of items that cab ruined in a split second,    anymore.  ;D

 "the bit grabs the metal your drilling."

DamonHD

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Re: Maxing out my small off-grid system
« Reply #33 on: July 30, 2016, 09:36:24 AM »
I shall have a go at the new holes in the frame today or tomorrow.

I shall put tape on the bit and a ceramic tile and maybe cardboard behind the part of the frame I am drilling to protect the panel itself.

Rgds

Damon

DamonHD

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Re: Maxing out my small off-grid system
« Reply #34 on: July 30, 2016, 12:03:09 PM »
OK, did a first test hole.  Rather slowly, but without drama.  Thanks for the advice!

Wasn't sure the best way to clean the swarf/nasties on the rear of the drilled hole, so for now flattened them with pliers to literally take the edge off them and allow the nut to sit flat.  What would a responsible adult do given that access is tricky...

Rgds

Damon

Mary B

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Re: Maxing out my small off-grid system
« Reply #35 on: July 30, 2016, 03:47:33 PM »
When drilling aluminum you can cut down on the ragged exit hole by drilling slow with very sharp bits. The aluminum should come off in a constant curl and not in chips.

DamonHD

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Re: Maxing out my small off-grid system
« Reply #36 on: July 31, 2016, 09:00:01 AM »
Thanks!

I was going slow, out of cowardice as much as anything else.  I don't have a choice of bit at the moment.

About to do the first real set of 4, and *may* get to mount the first panel today...

Rgds

Damon

DamonHD

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DamonHD

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Re: Maxing out my small off-grid system
« Reply #38 on: August 03, 2016, 01:54:56 PM »
More frame-drilling fun, and removal of older panels today.  Hoping to put second 255W panel up tomorrow!

Rgds

Damon

DamonHD

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Re: Maxing out my small off-grid system
« Reply #39 on: August 04, 2016, 04:07:39 AM »
Yeah!  Second panel up and connected...  B^>

Rgds

Damon

DamonHD

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Re: Maxing out my small off-grid system
« Reply #40 on: August 05, 2016, 03:04:10 PM »
Latest schematic:



with half-decent charge to the batteries today:



Rgds

Damon

SparWeb

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Re: Maxing out my small off-grid system
« Reply #41 on: August 06, 2016, 12:08:41 PM »
Looks good:  I can see Bulk + Float appear in the plot.

You don't have to ground the battery negative to earth... as long as nothing else in the system is earthed either.
No one believes the theory except the one who developed it.  Everyone believes the experiment except the one who ran it.

System spec: 135w BP multicrystalline panels, regulated by Xantrex C40, DIY 8ft diameter wind turbine, regulated by Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024

DamonHD

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Re: Maxing out my small off-grid system
« Reply #42 on: August 06, 2016, 12:43:26 PM »
Yes, more than one real-life electrician has suggested that leaving the entire system to float is probably best.

Rgds

Damon

DamonHD

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Re: Maxing out my small off-grid system
« Reply #43 on: August 10, 2016, 07:59:03 AM »
Next part of my plan for world domination (Mwahahahahaha) involves my shiny new Morningstar PC MeterBus Adapter for my SS-MPPT-15L controller which arrived today.

The aim is to use the controller's measurement of (a) battery voltage and (b) battery charge current and/or SoC wholly or partly in place of values measured (or computed/guessed) at the RPi.

I'm hoping that this improves my ability to handle bigger loads (without being panicked by apparent sag) for example.

Anyway, I get to learn some MODBUS, which should be fun.

Rgds

Damon

PS. Minutes after finally relenting and buying the Meterbus RS232 adaptor that I had been considering for years, and working out how to interface it to USB for my RPi for example, I noticed that there is a USB version of the Meterbus adaptor which would be simpler and probably more power efficient.  Oh well.

DamonHD

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Re: Maxing out my small off-grid system
« Reply #44 on: August 23, 2016, 02:55:22 PM »
Looks good:  I can see Bulk + Float appear in the plot.

Even clearer here:

http://www.earth.org.uk/MODBUS-and-Raspberry-Pi.html#20160823

Rgds

Damon

DamonHD

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Re: Maxing out my small off-grid system
« Reply #45 on: September 11, 2016, 02:53:15 AM »
Update:

1) I've seen the controller hitting its max 15A into the batteries, at slightly over 200W power from the array.

2) Currently the ratio of power from the roof to power from the off-grid array is about 30:1 even though the array size is about 10:1.  If my over-build experiment is to 'work' this ratio had better improve in favour of the off-grid system by mid-winter!

3) I've tracked down some of the supply impedance that I was detecting, ~0.1 ohm from battery to input to the RPi 12V-to-5V switch mode supply (Vbus).  I'm taking measurements at the battery and load terminals of the controller, and Vbus, and an output snippet from my program with the system under some load is:

Code: [Select]
Verbose mode ($Id: powermng.cpp 15411 2016-09-11 08:40:19Z dhd $).
SS-MPPT-15L Vb_f slow battery voltage (mV): 12473
SS-MPPT-15L Adc_il_f load current (mA): 1472
Load power (mW): 18361
Input flag DUMPING is unset.
SS-MPPT-15L Adc_ic_f battery charge current (mA): 658
External flag file /var/log/SunnyBeam/LOW.flag is absent.
ADC command 6a 80
ADC (6a 0) response 1307 (5 1b 0)
Battery voltage 1 local (LA) 12262mV, 2 (Li) -1mV.
Supply drop B1 to BV 211mV; implied supply impedance 0.143342ohm.
Adc_vl_f load voltage (mV): 12397
Supply drop controller to BV 135mV; implied wiring impedance 0.091712ohm.

The upshot is that maybe 1/3rd of the voltage drop I see happens between the battery and load terminals of the controller, probably as part of its measuring and short-circuit protection.  The rest is still higher than I'd like (and the lumpiness of the measurement for small voltage drops means that these absolute values are probably only roughly right), but at least its getting closer to my estimates of what it should be.

I took the opportunity to tidy up the wiring yesterday.

4) It was open day at my house yesterday for SuperHomes and again today and I get to show off my little off-grid system to the visitors!

http://www.superhomes.org.uk/superhomes/london-kingston-upon-thames-willingham-way/

Rgds

Damon

DamonHD

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Re: Maxing out my small off-grid system
« Reply #46 on: February 18, 2017, 10:07:08 AM »
That didn't work then:

http://www.earth.org.uk/expanding-off-grid-PV-system.html#20170218-no-500Wh

More like 150Wh/d rather than the target 500Wh/d, mid-winter!



Rgds

Damon