Home Improvement → [Electrical] Small solar system

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here's a circuit from

»highfields-arc.co.uk/veh ··· xchg.htm

that shows the use of the diodes or diode block assembly.

that's for use when the one alternator is charging two batteries. you want electric to flow from the alternator to BOTH or either batteries whenever the motor is running. you want the main starting battery to always be charged. you want a flat secondary battery NOT to pull electric from the main starting battery. the diode blocks electric from flowing out of a charged main battery into a discharged secondary battery.

i.e. you don't need any switches. the diodes do the switching automatically.

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normally the diodes are big and come mounted on a heatsink, which also must be mounted on some heatsinking metal part of the chassis, for even more heat distribution.

regular diodes lose 0.7 volts across themselves. more expensive schottky diodes only lose 0.3 volts across themselves.