Why have a genny to drive a motor?
Why not run the milking machine off a methane engine?
I was imagining the AD plant & genny would be quite large & static.
shadiya
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Can you explain? I thought that as long as you didn't drain the battery below fifty percent min, it'd be alright but you are suggesting no more than about ten percent?
Is that simply best practice or for a good reason that I haven't picked up on yet? The batteries will be charged using a combination of wind and solar, but primarily solar. I have a mostly south facing roof that I'm thinking of covering in panels, assuming I go ahead with the micro dairy, which is not a given at this stage. I'm just trying to get all the figures together to make an informed decision.
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vegplot
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It depends on the battery type. Automotive batteries, as you are probably aware aren't suitable as they shouldn't be discharged to more than 10%. Deep discharge batteries can be discharged to about 80% (depending on type) but maximum economy is achieved with a daily 50% discharge/recharge but again this depends on type. Battery manufacturers will have the relevant data.
As you have a mixed system with various inputs and outputs things get complicated. If you monitor your loads carefully for while you can get a good idea of your peak and mean loads and therefore judge more accurately the battery capacity you need to maximise your investment.
When planning a new install or updating an existing systems a diagram of all the parts really can help in making decisions as you can show the entire system to someone.
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shadiya
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I do have a rather mongrel system at the moment but for this, I was planning on buying a whole new set of batteries....
Well, by new, I possibly mean new to me....
Those two volt ones are quite heavy though so not sure if they are the best to go for, though of course they do make changing broken ones less expense. It's all a bit unknown at the moment as my current system works well for me but then I have low standards 
However, if I do decide to go down the micro dairy route, I will need considerably more power than I do now and so would be looking at funding and spending lots of money on installing a slightly less heath robinson system, as can't have my yogurt going off before I get to market.
The problem with data is that to the uninitiated eye, it look like gobbledegook. My current thinking is to have a mobile battery bank with solar panels attached, after all, it's bound to be sunny sometimes when I'm milking, that I can park and plug in near the dairy. However, It may make more sense to simply have a mobile battery bank that charges when it's docked. What do you think?
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vegplot
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Really difficult to say TBH as I've no idea what your layout is there. My preference would be for dedicated PV array and single battery feeding an inverter (could be more than one to feed different circuits) that could handle all your requirements but that might not be appropriate for you.
By single battery I mean a series of cells/batteries connected to form a single unit.
2V cells are a good way to go and as you say are easy to change if broken but require well designed connections so you don't have an cell imbalance (one or more cells being charged/discharged at a different rate to the others in the bank).
The problem with a portable PV array to power a single application is that they are very nickable, easily damaged, not very economically efficient, and take up a lot of room.
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RichardW
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You have misunderstood why I am suggesting that size.
Its not to do with energy used but power drawn.
Power & energy are not the same.
You will be using 50ah worth of energy in total but consuming power at 50amps as you will be using all that 50ah in one hour. Had you been using it over say 10 hours then the power draw would fall to 5amps but the total energy would stay the same.
If you have a large power draw compared to the size of the battery then the amount of energy that the battery can give falls. A 100ah battery will only give 100ah of energy if the rate of power draw is at the same rate the battery is rated for (normally c20, thats all the power in 20 hours). If you draw the power at 50amps then it wont last 2 hours. It prob wont even last 1 hour. Pulling power at more than 10% of the bats size will cause it to heat up & you will be shortening its life lots as well as getting less energy out.
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Ty Gwyn
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Would nt a little Lister engine to drive a compressor for the air line be a lot simpler?
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shadiya
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Thanks for the explanation Richard. I'm afraid that electrickery is not one of my special skills, despite having lived off grid for the last five years. So I either have to have a large mobile battery bank or a very long extension cable! I wonder how feasible running power to the fields would actually be? I def don't want the expense and trouble of a milking parlour.
Ty Gwyn : I daresay a small Lister might well work but I'm trying to get off fossil fuels and it seems crazy to start a business which requires me to be dependent on something that I have absolutely no control of, ie fuel, and that is clearly only going to keep galloping up in price. Maybe a gasifier might be a better bet?
I can see a lot more head scratching is on the cards followed by more idiot questions I don't doubt! Thanks for your help so far, I'll be back! 
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shadiya
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Given that people have mains electric fencing, I was wondering whether there was any reason why you couldn't have sockets as part of a fence system that you could then simply plug the milking machine into, so that it drew power from the main battery bank? I appreciate there are power loss implications but my limited understanding is that with 240 that's not such an issue?
Sorry if this is a numpty question 
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RichardW
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The actual electric that goes along the electric fence it not at main voltage. You have a mains transformer & pulser that sends jolts of elec drown the line at about 10,000v plus.
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shadiya
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So, does that mean you can do it through an off grid set up or not? 
I only speak English I'm afraid 
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RichardW
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You cant use the electric fence to do anything apart from be an electric fence unless you count giving a mate a shock.
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shadiya
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Oh no, I didn't mean off the electric fence, I meant, could I run cable and have outside sockets without having ridiculous power losses? I suppose I didn't make much sense, plus ca change....
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RichardW
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The electric fence charger unit is normally sited within a building using leadout cable to take the power to the field & not pluged in at the field. Battery ones are normally sited in the field & wired direct to the fence.
Long runs of mains cable do have issues with voltage drop unless the cable used is very thick (IE costly).
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shadiya
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Oh well, I guess it's back to some kind of mobile energy source then. On the bright side, I spoke to the milking machine people yesterday and they reckon it takes about ten minutes to milk a cow so I'd probably only be running the machine for half an hour which will make things a bit easier than having to run it for an entire hour. Still a fair bit of head scratching to do though I reckon.
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RichardW
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Why swim against the tide?
Just do the same as everyone else & bring the cows to the machine & not the other way round.
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shadiya
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It's because of the cost of installing a parlour and dealing with the waste, vast amounts of water for washing down etc etc. Dairying as it happens 'normally' uses a lot water and produces a lot of slurry. Milking with bails in the field was quite popular in the thirties and was shown to be very efficient.
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RichardW
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You wont need much of a "parlour" for 3 cows.
In fact IF the EHO will accept in field milking (which I cant see happening) then virtually no parlour is needed as standing in the yard has got to be better than that.
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shadiya
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The EHO are ok with milking in the field, I know someone doing it and there are a couple of blokes down in the south west that are running a large dairy herd, milking in the field, think Rob put a link up a while ago. I don't have a yard anyway so can't use what you haven't got
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RichardW
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I'm betting that their in field milking is highly industrialised.
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sean
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The link's in this thread.
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