Your little transformer does not have enough voltage and does not have enough current. 1) The "36V" battery will need an input of 41.4VDC to be fully charged. But your 24VAC transformer will produce only about 32VDC. 2) The 24VAC 500mA transformer makes peak DC of 33.9VDC at 0.354A. It will take 12Ah/0.354= 34 hours to fully charged the battery if the voltage was higher.
Now have two 12-0-12v transformers with 5A secondaries. This would give me about 50Vdc if I use the full secondary on one and series it with 12v winding on second trafo. Methinks this voltage is to high to use a regular voltage regulator on, but what if I connect the latter as a constant current source, and rig a max voltage cutout to switch off when the batteries reach 42V?
The 50v is too high for an ordinary voltage (current) regulator IC when the battery is dead and is nearly 0V. Also then the voltage(current)regulator will smoke and be extremely hot.
Most of us do not make a charger for a high voltage battery. The last charger I made was for one Li-Ion cell with a max charged voltage of 4.2V.
36v battery charger
Posted - Mar 23 2011 : 4:25:24 PM
