I've returned to this (new) forum after a gap due to moving house. I've built 2 SSGs, both on 26" bicycle wheels. I've also built 4 different coils, all slightly different, mainly as my first one kept shorting due to either poor insulation or over twisting. I've made many mistakes but have learned a great deal.

I'm now starting again, changing everything which did not quite match the spec on the forum. I'm now using 4Ah FLA batteries instead of 3.2Ah SLA and they do behave very differently. I'm only on run 3, but have already seen a big improvement in the charging rate. The COP figure is less than one but does seem to be improving with each run.

What I really want to do is tune my machine so that I can charge a 4Ah FLA battery using one charge on a similar sized battery which I believe from the moderator replies should be readily achievable. My first run needed 6 charges, which is not even close. I recharged before getting down to 12v as I couldn't monitor it all the time, so less would have been needed if I'd used the full charge; it would probably have needed 4 though. I'm now using a 85Ah FLA primary, but it's only a stop gap until I find out what I'm doing wrong.

I do have several sweet spots and I do think I'm on the one with the best magnets per min per ma draw current.

The figures are:-
rpm 105, draw 130ma, charge 40ma. I can it run much faster at 135 rpm but it takes a 250ma draw then.

I'm looking for advice to tune my machine better. I don't currently have an oscilloscope but am beginning to think that I need one.

Does anyone have tuning advice to achieve my current goal?