We received a question from Michael Correale today asking for some help on wiring his 24 volt horn to his 12 volt boat electrical system. Here is what he wrote:
Ok, I am that guy who had to go and buy the 24 volt horn for my boat with a pre-existing 12 volt system. I am unsure how to get 24 volts to the horn switch without sending 24 volts to everything and frying a lot of $$$$ in electronics.
My idea is this: I would take a hot and ground directly from each battery and run it to the horn area. At this point I would connect the positive from one to the negative of the other leaving the other ground to be the 24 volt connections. My main issue is (considering that it will work) can the 24 volts go to the other stuff on my boat when the switch is on both batteries.
Michael, it's a good question. The answer is NO, DON'T DO IT!
If you have two batteries right now with a battery selector switch, such as a Blue Sea Systems 9001E shown in the image above, you cannot do what you're asking. The battery switch is designed so that you can choose to run 12 volts from either battery, or 12 volts from both batteries. In this case the switch connects the batteries together in parallel. The negatives on your batteries will already be connected together.
If you were to take the positive from one and the negative from the other and connect them, while at the same time the negatives from both batteries are connected (or at least both connected to ground) then you will short one of the batteries out. This will very quickly melt your battery, or melt the wires, or... melt something!
A better approach would be to install a transformer to step up the voltage to 24 volts from 12. These can be fairly cheap at an electronics store, but since you are in a marine environment it's worth getting a more expensive one designed to withstand the corrosion.
Alternatively, you could always go buy a 12 volt horn! And Michael, if you are still reading and I've somehow missed your point, clarify it below in the comments and I'll take another stab at it. Thanks for asking!
hi there – basically he is looking for a series parallel switch. see 3 options
1, dont do it
2, relay controls
3, thriple pole double throw knife switch – heavy duty
what im trying to do is connect a 36 volt forklift battery to(3)12v batteries there is a total of 18 (2volt)batteries i have a 500watt wind generator that is currently on line with 12v battery bank i have tried numerous ways of connecting them up but just cant seem to figure this out i also have a bridge rectifier in line