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Author Topic: Grid Hopping  (Read 90958 times)
Scruff
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« on: July 07, 2015, 02:37:19 AM »

« Last Edit: June 22, 2020, 11:15:57 PM by Scruff » Logged
biff
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« Reply #1 on: July 07, 2015, 08:55:46 AM »

Oh,Scruff,!
        Looking at those pics and reading that prose, I got all wobbly at the knees.
 You my friend, are obviously in a land of much happiness and contentment, Your smile widens and your step gets jaunty every time the sun shines and the wind blows.
  Long may it be so.!
                       Biff
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roys
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« Reply #2 on: July 07, 2015, 10:59:36 AM »

Think I am going to like this thread. Grin
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« Reply #3 on: July 07, 2015, 11:38:38 AM »

Please take that black battery out of the electronics-box! They have bad breath and will eventually spoil the party atmosphere in the box.
Put a fuse in every thin wire that is connected to the big battery as near to the battery as possible. (sense-wires?) Those wires will vapourise in the event of an accidental short, giving an orange glow to the horizon as your installation goes up in flames.
Use the thickest cable physically possible to all battery connections. If you pass 60A continuously through any of the cables in the pics, they will get hot to the touch, plastic will soften, and at the places where the wires cross/touch will get thinner and flow. BZZZT!  Bus-bars look good though.

Can I get some of those batteries pleeeze!

N
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1.140kW mono south-facing at 49*
EpEver 4210A at 24v
New (Old) 8S7P LiFe battery, 105Ah @ 26.4V
EpEver STI1000-24-230 pure sine inverter
Of course it'll work. (It hasn't caught fire yet).
jonesy
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« Reply #4 on: July 07, 2015, 11:54:41 AM »

Looking at this Swiss inverter it's 2.3VA, 1.3 times rating for 15 mins. Where did you get this 6A figure from and how do you find an inverter Isc the easy way?
The 6a figure came from the SMA SI3.0M manual, which is a 2.3kW unit, for which they recommend B6.  Basically it's limited by the output impedance, which rises a tad as the inverter warms up.  Is it in the manual?
You'll have a loop impedance tester. Had odd results trying that on a large diesel genny, and IIRC the PWM output of an inverter ain't going to help.  Or try a 10A mcb and a 6kw load.  If it doesnt trip, drop the breaker. It's a really tricky subject, particularly on large island generation, as fault levels change depending on source.  Protection engineers earn their money.
Hopefully another member will have a good answer.

Ok...so hypothetically if my inverter has a live-earth or neutral-earth fault and the inverter RCD(s) sticks closed, and the fault goes to the grid neutralising point backfeeding the Grid RCD, no smoke?
A N/E fault doesnt always trip an RCD (in PME), and the fault current will be minimal and won't exceed the touch voltage. The live fault would go inverter L, (RCD) MCB, RCBO, load, load case/E, earth point, inverter E = inverter N, so the MCD should trip in 0.4s. On a socket circuit.
If the breaker didnt go, then the inverter would probably shut down on over current. So other than sharing the earth point, there is no connection to the grid. If you're still in doubt, drop an earth rod and use that for the inverter.  Your protection will be worse due to rod impedance/touch voltage. Hmm. Wouldnt recommend that as you'd then have different earth potentials in one room, and that will be outside the regs.
For info, note that you have the potential for 380V at your inverter only sockets WRT grid, as the two aren't synchronised.  Many years ago there was a 'rule' that you couldn't have socket outlets on different phases in the same room, but I can't remember reading that anywhere that mattered.
Just noticed you're using DP MCB.  You could go single pole safely, as inverter N & E are linked.

With a 12 year life on those batteries, if you limit the continuous current to c/10 = 125/10 = 12.5A, twice for each string, = 25A x 48V = 1.2kva, they will probably go on longer.
I got a similar set up to you (10 year Yuasa 100Ah), in similar circumstances. All 8 lasted ok for 12 years, 2 died at 13 years, but I didnt notice as they were in series on a 24V setup. Now at year 15, they are not in great shape and have around 25Ah capacity.  Time to scrap them.

Calculations for cables assume an operating temperature of at least 60C, and a lot higher depending on insulation.  I have to admit not liking feeling incomers at that temperature in factories, etc. Good tip on the sense cables. I have used bolt on fuses in the past, covered in heatshrink.

No more pictures of your solar po*n.  We'll need to call a nurse for Biff.

« Last Edit: July 07, 2015, 12:05:27 PM by jonesy » Logged

1.1kWp PV & SB1700. 7kW log burner.
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« Reply #5 on: July 08, 2015, 08:20:11 AM »

 faint faint
                    Biff
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« Reply #6 on: July 08, 2015, 06:04:49 PM »

Looks like it's all got a bit too much for Biff.  BIFF. 

I've worked with some cables that are rated to 150C.  Just got good insulation.  Volt drop still spanners you.
24V was easy.  12V was too low.  I also had 48V for a while. And 96V.  I like 96V best, as you could wire up with 4mm and go 3kW in a beat. I also had about 200V DC to run standard CFLs, so I didn't need to run an inverter at night.
Nice fuse holder with the bullet connectors.
My batteries were standby type. The life is lengthened hugely if you keep the continuous discharge rate down.  I did read recently that partial discharge/charges don't count toward a whole cycle, which helps.  IIRC Biff is an advocate of low discharge.
I think it was a 2m 'rule' as you say, not room.
And don't try kidding us the 12V battery and clips are for 'testing'   Grin
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« Reply #7 on: July 12, 2015, 08:30:55 PM »

 genuflect  genuflect  genuflect
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Kidwelly South Wales
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« Reply #8 on: July 12, 2015, 08:59:32 PM »

Im Ere,!
      Just having a little lie down Jonsey, faint,
    Interesting set up Scruff,
                                Simple and efficient. I have had different systems, 12v, 24v, 48v,and our present household of 120vdc,which in my mind is the best of all. I am off the opinion that the batts gets a better deal, can deliver quicker and charge quicker and more evenly. We have 60 forklift cells,36flouride 600ah and 24 ordinary Powersafe,850ah, (Ithink) L.A,s. They get on quite well apart from the 36 flourides drinking a little more booze than the other half. And yes,! I believe in the minimum discharge,very very seldom dropping under 124volt under load.
  Our immersions are dump loads 138vdc and work very well. We run most things an ordinary house runs,,washing machine, vacuum cleaner, Microwave and Iron. no problem, I also power the shed now with the house supply, angle grinders,drills etc. The stove installation tools were all powers by renewable energy,drills,grinders and mixer,The system hardly felt it.
                                                                                        Biff
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« Reply #9 on: July 12, 2015, 10:39:10 PM »

Hi Scruff,
        Never thought of putting toothpaste in our cells,, H,mmmm. I know that it fizzes and burbles but ....in the cells,?
  I did have a 1000ah 24 pack that was lazy and daringly one day decided to add some acid, so I measured out a half cupfull onto each cell. They were off the charge then. Then after a while i put the volt meter on the cells and got the shock of my life, They were all complaining and going mad with the pack voltage going through the floor, at one point the entire pack was registering 9 volts.
  So I packed everything away and went and had a cuppa. I did not go near the pack till late the following day and lo and behold they were sitting up at 26.5volts. I connected up the the pv directly into them and let them frazzle for a few days in good sunlight. I think I was just lucky but the pack has much improved.
                                                                                                                 Biff
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« Reply #10 on: July 13, 2015, 10:19:50 PM »

Where do you get concentrated H2SO4
35% strong enough?  Any hardware store in France, along with acetone, hydrochloric, ammonia.  Can't get IPA easily.
Iirc 2/litre
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« Reply #11 on: July 14, 2015, 10:55:43 AM »

Ready for dilution for batteries.
UN1830-Sulphuric acid with more than 51 per cent acid. Delivery guy wanted to throw it off the lorry as he didn't have a tail lift and my forklift was broken help.


* acid.jpg (554.92 KB, 920x1632 - viewed 2022 times.)
« Last Edit: July 14, 2015, 10:58:22 AM by Tinbum » Logged

85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
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« Reply #12 on: July 14, 2015, 05:48:02 PM »

Ah Ha,, Tinbum,
               That stuff would shift the soot,,if not the bricks themselves.. whistlie
                                                             Biff
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« Reply #13 on: July 14, 2015, 06:21:34 PM »

If I recall its pretty well 100% acid. horror
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« Reply #14 on: July 14, 2015, 07:11:34 PM »



One shot drain cleaner from b&q is 91% sulphuric.  Add acid to water to dilute, and I always wear safety glasses and gloves.  I used it for anodising a home made bike light some time back, worked well, bike now nicked though😩
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