Dynamo overcharging?

[jamesheath]

Hi,

I'm getting up & running after a while - and found I needed a new battery.
Looking at the ammeter, and watching the battery voltage, I think that I'm over-charging the battery - it's pushing the battery voltage up to over 8 volts on winter, and summer doesn't charge at all.
The car is a special, electrics are pretty early coil setup (declared reg date is 1927, but it's coil, not magneto) - I think the dynamo is probably a DEL
This is a fairly early dynamo, which I think has a shunt.
I'm pretty confident that all the wiring is correct - when on summer charge,  I can see that the ammeter needle moves up just a fraction when I rev the engine lots - though not enough to charge!
Video explaining issue

I think my choices are: 
1) Try and get the summer charge working and use that
or (probably preferred)
2) move to an electronic charge controller - which I'd be very happy with - it's a special (quite a tatty one!).

If I go for 2) does anyone have experience of one they've used successfully on a DEL Dynamo?

Thanks,

James