I am trying to connect a 12-volt car horn to two connected (serial) 6-volt lantern batteries. I was successful in getting a 12-volt light bulb to light brightly, so I know I'm getting 12 volts (or close to it). I must be missing something with regard to the car horn. It clicks but doesn't honk. The car horn has two terminals--one for the power and the other to ground. Do I need some type of a relay? If I can get the horn to honk, the I want to wire a toggle switch between the battery and horn so I can activate the horn that way. However, because of my limited knowledge about this topic/area, I'm not sure it will ever work. In that case, I'll probably have to get a small 12-volt lawnmower battery. Any input will be greatly appreciated.

 

Welcome to the forums.

Yes..... you are absolutely right. A car horn draws a pretty good jolt of current.
Those lantern batteries have the voltage but not the needed amperage.

A basic toggle switch in either of the lines will also work fine.

 

Before you run out & buy a lawnmower battery try the horn with your car battery to make sure it works.

 

Now I am thinking of using a 6- or 12-volt siren rather than a car horn attached to either a 6-volt battery or two 6-volt lantern batteries to make a 12-volt serial battery.

Here is a link to the siren:

702 | Ademco 30 watt Siren | Home Security Store

The specs say it is a 6-12 volt DC combination speaker and siren driver, has a 30-watt power rating, uses 1 AMP, and has 110 dB.

If the two 6-volt interconnected batteries wouldn't work, then the following is a 12-volt battery I would consider:

BD412 | 12 Volt 4AH Battery | Home Security Store

It provides 4 AMPs which should be ample as the siren pulls 1 AMP. The battery is sealed, and it is re-chargeable.

Other questions:

1. Is there a limit as to the length of wire (16 gauge) that I could use to connect the battery unit to the siren?

2. Does the battery present any kind of a health hazard or safety issue?

3. Does the siren have to be grounded? If so, to what would I ground it?

Any information that will help me with this project, assuming it is feasible, will be greatly appreciated. I know very little about this topic as you can tell.

 

Yes, although probably not a practical limit. 16 gauge wire should be good for at least a few hundred feet.

Yes, it is a lead-acid battery with a gelled electrolyte. Do not try to use too large a charger on it or to charge it too fast or it might overheat and explode. Do not short the terminals together or it might explode. Keep it in a reasonable temperature, say between 30 and 100 degrees F.


No.


With a one ampere load and a four ampere-hour battery the siren will theoretically sound for four hours before the battery is 100% discharged. In the real world this will be more like three hours or possibly a little less. Completely discharging the battery WILL severely shorten its life as regards discharge-charge cycles. Ideal not to let the battery voltage drop below about 10.5 volts. You may want to incorporate a circuit that will disconnect the battery before it gets so low as to cause damage. The Seco-larm Part #: ST-BD01Q is one such device and sells for a bit under $15.