It is an old ,constant winding ,commutator with carbon brush ,noncompensated ,type of dynamo working for past few years .
There is no possibility of any adjustments of voltage as there is no regulator with the four pole device.
However , I was planning to use a pulse step up generator to charge the batteries
I created an SMPS step up output without storage filtering .(very hi ripples low avg. values)
This was just pulses of 28V and 20% duty cycle fed to the VRLA battery bank.
The pulses were fed to jitter the plates and give adhesion to the ions for cathode layering.
The ratings were 6-7 amps fed to the 120AH battery .
The battery topped up wonderfully and retained .....
Initially the time taken for charging was > 20Hrs as expected since battery was drained for quite long periods..
not now .