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Just to introduce myself.
I am a retired electrical and aeromodelling engineer, my wife and I live in west Wales as from 1987, I have worked for most of that time as a self employed electrical engineer working in a variety of industrial settings in a very rural area.

I have been encouraged by others in this forum to share my ideas and findings so that others with cranky thoughts and ideas might benefit, also that I might gain a nugget or two of useful know how.

Back in 2000, I wound down my electrical engineering due to the enormity of red tape that went with it. My wife and I then deviated into model aircraft kit manufacturing, that had the blessing of no red tape which is rare these days. Anyhow, we did model air trade shows which meant being out in an open field for a good few days totally off grid. 

This is where I began to use the knowledge gained over the years to facilitate this. I decided to install wet NiCad cells in the caravan rather than use lead acid batteries. I did this because they have a very long guarantee (25 years then) that has now been reduced to 20, but nontheless I "personally" feel that they are a very good option for long term projects of this sort. I built a wind turbine from a very "Very" old washing machine motor and bits of left over alluminium sheet and odds and ends from other projects, mounted that on a mast atached to the tow hitch and roof of the caravan. Also fitted a very small solar panel on the roof of the van and this meant we could comfortably live off grid for a week or more depending on wind/sun. When we sold our model kit buisiness, my wife asked me what I was going to do with those NiCad cells, as they are still good. My Avatar is that wind turbine!!

 

After some umming and arring, we decided to re-install them in the house and start a new system to offset some of our costs (being that we had the NiCads and windmill). While what we subsequently added cost a few bob, it became very absorbing and with a few nice little rewards.

Here below is a circuit diagram of what I have done, I will answer as many questions as possible about it, that way I don't just boringly describe things if not needed.

 

Hi @Rocksteady , nice info piece. 
I'm sure you will have a few interested readers .. can I ask how you manage the battery performance given NiCad’s and the presumed charge and discharge cycles?

Ahh, battery performance, to be fair I don’t concern myself too much with eeking out every scravelin of efficiency from any of this, as I know that burying your head too deep into the facts and figures can be quite disuasive in doing the job. As you can see from the drawing, I had it initially set up to to charge the battery at 15.8v but I have since increased that to 16.8v as in reality they could go to something like 17.4v but my Victron inverter will only go to 17v so I go as close as I can. The solar will get them up there very easily in good sun, and what I do is occasionally let the sun give them a substantial run of charging, then another time we give them a good draining down to their low end. I know that what I’m doing is not by the manufacturers book, but in reality, who can achieve that anyway. Cell manufacturers have to offer their recommended charge/discharge rates and times, but from my experience, it’s all very flexible. What I have found though is that these cells are far more durable in service than lead acid, and require less maintenance.

Very good - another point on the wind vs solar feeds .. can you determine how much is being generated from each individually (I can see an ammeter but presume that is for instantaneous readings) ?

I have an off grid system on our summerhouse but rarely get much more than 10’s of watts from the turbine compared to 100’s from the (small) solar pv.

Hi Yes, I don’t monitor the PVs and the windy separately, I just monitor the 230v output from the inverter through a small din rail KWH meter. As a rough guide, when we go away on caring duties for my daughter a few times a year, we regularly check our daily OVO consumption readings online. We always leave just the freezer on, there may have been the odd tv or amp been left on as well, but they take next to nothing less a bit. When we have been away, we have noticed that the freezer and other bits left on by mistake will only need about 0.8 - 0.9 units a day. When we’ve been home and had a few days of wind and no sun, the turbine has managed to put in enough to give us a similar output. While this is not an exact science, it has inspired me to build a new, more efficient turbine that hopefully will be more effective. I have trolled youtube, and there are all manner of very interesting home made device clips on there. I decided for my next one to use a modern direct drive permenant magnet washing machine motor. It is a 3 phase motor driven from an inverter, the same sort of thing as for model aircraft and now some full size ones. Anyhow, being permenant magnet, it will work as a generator. I have to re-configure the coil connections to reduce its voltage output to what I need, but in a strong enough wind it might well achieve 200+ watts. It keeps me out of mischief in my workshop, but I have to confess that without the kind of general workshop equipment that I have collected over the years, it would be very difficult to just do the things I am doing. The maximum I am having from the current turbine is about 100w.

Just an update. Being that I was installing this system during the first few months of last year, I was unable to really see any form of accuracy of readings in order to gain a reasonable understanding of what this system is giving us. I have looked at the calculations from 1st of Jan to now (27th June) and it has produced just over 1/3rd of our total consumption for this first 6 months. Obviously the most accurate figure will be on 1st July, but I is very encouraging for a first real effort.

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