Would I be able to gain a reference (Link) of one of those bicycle generators.
Your best bet would be to get a dynohub from a scrap bicycle front wheel. In the populous areas of the UK many bicycles are chucked out. But I will get a link for you for a new Dynohub. You would need a bridge rectifier to get DC and would only get around 5W as a guess. On reflection, I now think that a bicycle bottle dynamo will also work and have the same kind of power.
Concerning the 12 V battery, it is a lead acid battery from a car (I think, though it says it's a 'calcium battery' on the battery itself. Not sure what you mean by capacity. All it says is 38Ah?
That sounds like a normal car battery. Calcium is added to many lead acid batteries theses days to increase the strength of the plates, but it does not alter the basic characteristics of the battery.
Batteries are specified by chemistry: lead acid, nickel cadmium (NiCad), Nickel Metal Hydride (NMH), Lithium Ion (LiIon). Then their voltage: Lead Acid= 2.1V (6 cells in series in a car battery=12.6V), NiCad= 1.2V, NMH=1.2V, LiIon=3.6V.
(lead acid information corrected 2016_06_07)
Batteries are also rated by their current capacity which is the number of amps they will produce for one hour. Your battery, when fully charged, will produce 38 amps for 1 hour or 3.8A for 10 hours or 380 mA for a 100 hours. Unlike the other batteries though, you can normally only use around two thirds of the capacity of a lead acid battery.
The charging efficiency of a lead acid battery is also low at around 50%, which means, in the case of your battery, to charge it fully you would need to put in 76 Ahs, ie 72A for 1 hour, or 7.2A for 10hrs etc.
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