Just a few more comments. Firstly you said the resistance has increased, this shouldn't have happened and may have been the reason for failure. Any burnt or shorted coils should have dropped in resistance.
I would look very carefully at any soldered joints as this is the only real place for resistance to increase.
Now perhaps a few comments about changing the winding as it is not the normal approach.
In very low wind areas people go for the slowest cut in so that they can get something when the winds are very light ( 6 - 7 mph). This approach is excellent for low wind areas as long as you don't go too low in the cut in speed. If you attempt to cut in below 7mph you will reach stall near 12 mph and the power you get in the more useful 10 - 15 mph will be significantly reduced. By the time you get to 20 mph this approach will be having significant effect on the performance, the blades will be significantly stalled and the alternator efficiency will be dropping to below 50%. half the power will be heating the stator.
If the normal winds are not generally much over 20 mph then this is likely to be a good compromise. Beyond much over 20mph you will have to furl and if you can do this reliably in such a way as to keep the stator temperature within safe limits then fine, your batteries will probably be charged in these sort of wind anyway.
A better and safer compromise is to keep the cut in as high as reasonable for the wind area then use a very efficient alternator, which will stall badly from about 12 mph upwards. You can add the inefficiency required for blade matching in the line as extra resistance and not have the heat in the stator. This does require significantly more magnet and copper and results in a costly machine. Not justified for very low wind sites but safer on windier sites.
For the type of machine you are looking at, there is not really enough magnet or copper to use this approach for a very windy area, the machine efficiency is already too low to benefit from much added line resistance. You could raise the cut in speed and change the blades for 8ft and use this approach. It would be safer in high winds for the same power out but you will raise the windspeed band upwards for the same power out.
To stay at 10 ft you could keep the same winding and make absolutely sure that it furls to keep the maximum current below 25A under all conditions. Should be possible but much of the information I see here suggests that it doesn't happen with the present set up.
The next approach is to do something about the efficiency of the alternator and that leaves you little option but to reduce turns and use thicker wire. Just playing with it doesn't have much effect, you need to be drastic enough to be able to significantly increase wire size. Reducing turns from 70 to 50 would let you increase the copper section by 50% or more and that would let you raise the maximum current in high winds to something more manageable.
Yes it does increase cut in speed and that will probably kill all chance of output below 8 mph wind speed. It will make the output in the 10 mph region a bit choppy but the peaks will be higher and the average will not be significantly worse. Beyond 10 mph you will gain all the way, you will not get near stall and the higher alternator efficiency will help the output. It will start to load very rapidly beyond 15 mph and will track the steeper part of the prop curve much better. Although you start with higher speeds the speed in the 20 mph region may be no greater because of the better loading ( depends how well the original winding could hold it in stall).
The one serious problem here is line resistance. You have lowered the alternator resistance significantly and the line resistance is going to have a big effect. To use this approach to best effect you will need to keep the line resistance very low or you will not be able to use the extra loading capability in the higher winds and speed rise will be excessive.
What it eventually comes down to is whether the loss of a few watts on the days when winds are below 10 mph are more than compensated by a better performance on days with winds above 10 mph. My guess is that on the west coast of Ireland you will win hands down with the higher cut in speed.
My experience in poor wind area is that there is not a lot of power available on the low wind days, we only get a few hours and the total Ah is small. In other low wind areas with long periods of steady low wind things would be different.
I have a 10 ft machine ( very different construction) that cuts in on the main winding at 220 rpm, it uses a boost converter below 220 rpm. Even without the converter it works well enough from 10 mph upwards and is producing something like 1500W by about 25 mph. I have the best of both worlds and if I had to compromise with no converter I certainly wouldn't take the cut in below 200 rpm for the sort of thing we get in low winds. ( If you live in the trade wind belt or something it could be different with many hours of steady low winds).
I must stress that you shouldn't do this if you can't keep the line resistance very low ( ideally below .1 ohm for 24v).
Flux
