Power at the farm

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Broch

Full Member
Jan 18, 2009
5,224
4,565
Mid Wales
It's also worth bearing in mind that the usable capacity of a lead acid battery is only about 50% of its nominal capacity and that to fully recharge the last 20% requires a float charge that takes a very long time. In my installs I tend to use LiFePO4 battery's, very expensive but you can use about 80% of the nominal capacity and you can bang loads of amps into it up to 100%. They're much better suited to leisure systems but maybe prohibitively expensive for some projects.

Whereas I agree that it can be much much lower than the stated battery capacity in Ah for lead-acid batteries, it all depends on the discharge rate. For slow discharge rates, typical of LED lighting and small device charging, the actual figures can be nearer 80 or even 85%. You need to apply Peukert’s Law to your discharge calculations.
 

Robson Valley

Full Member
Nov 24, 2014
9,370
2,139
McBride, BC
You must consider the operating requirements of the inverter should you need one. In my system, the pure sine wave inverter eats some power and requires sufficient voltage to make 117VAC from that. The direct result is that the inverter ceases to function at about 11.5VDC, Full charge to begin with is 13.7VDC,.
 

stevec

Full Member
Oct 30, 2003
489
104
Sheffield
Interesting thread this, I've been looking at one of those Jackery things, but I've got an old ups at work, rated at 1kva, the slab's are only 7 or 10ah, so assuming that the inverter bit works I was tempted to rip it apart, rebox it and grab a couple of 95-110ah batteries and run it from those. Mainly for fridge/freezer/fish tank in event of power cut.
 

Robson Valley

Full Member
Nov 24, 2014
9,370
2,139
McBride, BC
stevec: you have to reverse-engineer this thing.
1. How much power do you need for steady running?
2. Inrush starting motor current will be about 2X that number.
3. How long will the system have to drive your essentials?
No matter how you rig this, the batteries are your power.

I ignore both the fridge and the freezer, as I've needed the juice to
run the wood pellet stove during winter outages at -20C and colder.
Just don't open the appliance doors very often until you know exactly what you plan to grab.
Three or four candles add a note of warmth. Your air bubbler and the tank lights will be very pleasant company.

Long term in the freezer, if I have to be away for 7+ days, is a cup of frozen water. There's a coin sitting on the ice. If there's a major power cut and that ice ever melts, I'll find the coin in the bottom of the cup.

Fortunately, we now have a 5MW (?) biodiesel generator in the village which can start and run up to full power in 15 seconds. The village can cut all power beyond 10km in each direction to leave us sitting in a power "island."
But it's true that grid damage within the 10km and we are screwed like the old days.
 
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stevec

Full Member
Oct 30, 2003
489
104
Sheffield
Reverse engineering should be ok! I'm aware of inrush current issues. I'm just punting ideas about my head really for those just in case scenarios
 

Robson Valley

Full Member
Nov 24, 2014
9,370
2,139
McBride, BC
If the Regional District (in their infinite wisdom) and the village had not installed the biodiesel gen set, I would be buying more and more 6VDC deep cycle batteries. Since plate area is the issue, 2 x 6VDC is much more area than a single 12VDC DC battery.

One power outage for 2-3 hours a couple of times a year? Keep the fish tank going. Ignore everything else except your supply of matches for lighting candles.
Three or four times per month, from 10 seconds to 4 hours? Consider a plan.
We get 1 second drop-outs that screw over every digital clock in the house.
 

BumblingAlong

Member
Jun 20, 2021
16
5
48
Winchester
Considering a budget petrol inverter so I can charge phones off-grid. Seen some around £100 but I'm wondering if it will be worth the trouble. The lesson from this thread is don't go cheap. But £300 just to charge phones and avoid going into town !
 

Decacraft

Full Member
Jul 28, 2021
32
12
35
South Wales
Well I bit the bullet and have committed to a jackery 500- will pick up the solar panel next month and will hopefully have something semi decent.
I did think of buying a cheap petrol generator, kind of glad I didn't now as the current situation, and I wanted to have something that didn't have a high running cost or I would just leave the van running with an inverter.

Watched a YouTube video on a portable solar panel (powertraveller falcon 28e) so picked up one of those to charge my powerbank and phone/radio.
The weather here is horrendous so I think ill have to wait before testing out
 

Robson Valley

Full Member
Nov 24, 2014
9,370
2,139
McBride, BC
Decacraft: get out and set up the solar panel to see how well it can perform under shitty conditions. That's when you really need it. We will all agree that it should work OK in full sun.
 
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Decacraft

Full Member
Jul 28, 2021
32
12
35
South Wales
Some initial use of the solar-

Powertraveller 28e, I have no measuring devices to check inputs/outputs I can only go by the included display.
It shows a reading of 0.0 when there's no device connected but in the light, and once the USB is connected to a device it then shows a reading.

So far I have only charged my phone and radio.
The reading was 0.5 on the display, weather was overcast clouds but light. Charging my phone from 20%- 100% in around 2 and a half hours (samsung note 10+). I havent noticed it saying fast charging so can only assume its a regular charge rate?

The jackery on the other hand is a totally different beast being just a battery. I havent put it through its paces yet, and neither do I have a solar panel to charge it so I'm not going to review until I do so and use it how I originally intended.

I'm still looking at different options for the solar (the jackery 100w is not weather/waterproof so no good in the wet).
I may build a small solar station(like a wood store) to hold the panel at the right angle in the right place on the roof, but having a small enclosure underneath to hold the battery to charge and keep dry, and also put my phone and any other electricals.
If I build it big enough i may just put a smaller frame generator in there in the future and sound proof it also. Sort of a mini power grid then?
 

Robson Valley

Full Member
Nov 24, 2014
9,370
2,139
McBride, BC
My house is at 53N. We get high angle sun in the summers and low angle sun in the winter. A lot of cold, wet stormy weather in the west slope of the Rockies. So, I never had any high hopes of seeing really efficient photovoltaic conversion.
No chance of putting the panels on the roof with the potential of 36" - 48" snow in one night. All rain, snow and wind here is dirty with mountain rock dust. That would block a little light, too.

The panels are just vertical on the south face of the house. Keeps off the dust and snow. Plain old ordinary deep cycle 6VDC batteries hooked up in series pairs to see 12VDC. Plate area gives me big storage capacity. That's the sole source of my electricity when I need it. More solar panels might give me faster charging ( of course they are dead at night). More batteries really gives me more operating potential. That, I really like.

Bottom line was about $1,500.00 some 15+ years ago. More pairs of 6VDC batteries would be $500 per set. I can get custom-length battery cables made up in the city for next to nothing. It did get so bad that the village went on the war-path and government did address the issue with a 5(?)MW biodiesel gen set. We can now isolate a 20km "power island" off the grid in about 20 seconds. If the break is within 10 km, inside the switches, we are screwed again, as usual.

Who knows what the hell goes wrong. Trees on the grid, accidents? So far in October, I've used the system for 2.5 hours. Analog light timers fall behind so it's easy for me to figure out the outages. Needed no more than 400W for LED lights & the satellite radio/TV and ran the propane camp stove for hot food. The psychological effect of having your own isolated electricity will brighten your mood.
 

SaraR

Full Member
Mar 25, 2017
809
502
Ceredigion
Does anyone know of any good options for a solar panel - battery bank combination (or failing that just a battery bank) that's capable of charging a laptop and/or iPad a couple of times? DH is looking for something that's self-contained and luggable, but not necessarily for any great distances.
 

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