wiring 3 horns in series

[newb123]

I have a fully charged 42 volt 8P10S Li ion 18650 pack, and I want to add a 12V scooter horn, to my bike.

Problem is, the pack is @ 42 V fully charged so putting that much V into one 12V rated horn is problematic. I know they make 36 V+ horns but I dont have one.

So, I was thinking about putting (3) 12 V horns in series ( I have allot of these scooter horns, from trashed scooters etc)

The ground on these horns is on the case, or chassis level. So, can I come in with the 42 V battery pack + lead, after the switch, to the 1st horn +, then its - to the next horns +, and its - to the next horns + then last horns (#3) - to the pack negative? Of course there is a momentary switch on the handle bars

I will check the amp draw with the multimeter in series, then fuse accordingly.

 

[HK12K]

Can you? Yes. Should you? Maybe not.

Sending full pack voltage to a button on the bars could end badly. At best a stuck horn button, at worst

Whether a 12v automotive fuse would have the desired effect is anyone's guess when operated at 4x it's rating. Might be fine, might arc and let your your finger continue to smolder.

Maybe grab a dc-dc converter and just go 12v for lights and horns and such.

 

[newb123]

yes I have a DC DC converter but I read horns can pull allot of amps. I guess I will go with the converter; Im using it for my lights

I was thinking 12V dropped across 3 horns would divide up the V but yeah, 42 V is still across the button with whatever amps that would be at

 

[HK12K]

True that the amperage could be a concern, especially if the momentary switch isn't rated for the load (and perhaps even if it is). Using a relay for switching would likely be a good practice. Cheap, easy to deploy, and shouldn't take up much space.

If you're into overkill you could still drive the 3 with pack voltage and switch the relay with 12v through the button.

 

[newb123]

:thumb:

 

[MJSfoto1956]

I wired two PIAA horns via relay to one of these 10A DC-DC converters:

https://www.ebay.com/itm/Pro-Chaser...ulator-Step-Down-to-12V-180W-15A/223130946668

In fact I have three of these on my 72V bike. One for the horns, one for the lights, and one for everything else.

M

 

[newb123]

when I connect my 42 V Li ion battery to the buck converter, I get a nasty spark, until its caps charge. How can I prevent the spark?

 

[john61ct]

https://www.rcgroups.com/forums/showthread.php?3441731-Anti-spark-or-SAFE-START-SYSTEM