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surely you can use in5408(reverse voltage peak=1000v) in place of in5400(reverse voltage peak 50v) to make bridge rectifier.mbr1545 is a schottky diode . These diodes have high reverse current and low dropout voltage. So I guess author used the above one to protect and as it has low drop out voltage so it wont affect output voltage from IC. the below one in circuit diagram has probably been used to discharge capacitor.So if you don't have these use in5408 to protect from reverse polarity. (the above one).But your charging speed will decrease. After removing other one mbr1545 beware of capacitor so don't touch leads even it is off.
hmmm.....simple solution would be to get a chinese made led light. they have a buck regulator and according to box specs it works anywhere between 6-25 volts dc. So if you suspect some noise you may add a bridge rectifier prior to it. Otherwise install it simply.Following is a 9-30volts led lighthttp://www.ebay.com/itm/5-Dia-18W-Motorcycle-LED-High-Low-Beam-Light-Headlight-Lamp-Bulb-Suzuki-GN125-/361246135007?hash=item541bf292df:g:YBsAAOSwpDdVCnum&vxp=mtr
Are you willing to make it? I can give simple instructions
You can read my other instructable about motorcycle headlight.From standard you mean 12volt ones? Then you need some boost circuit to raise voltage and then apply same circuit. Lm317 can be adjusted. Just google for its calculator.Another dangerous option will be to take current directly from alternator and manage it.But you need to tell me input voltages prior to making any decision.Remember if there is less power production then dont imagine for a big light ;)
Fun with transistors
Restoring a damaged table edge