Good day,pls who can help with a simple circuit of a 12v 14ah lead acid battery charger using a 12v transformers and also a 24v 7ah lead acid battery charger using the same 12v or 15v transformer

 

Everything will depend on the Specifications of Your Transformer.
Have You already purchased a new Transformer ?
Are You trying to make a salvaged Transformer work ?

2-basically identical MOTs (Microwave Oven Transformers) are an excellent place to start.
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Most of the old battery chargers used a 15V AC transformer and bridge rectifier, for the 12V batteries, so for 24V you need a 26-28V transformer.