Portable Horn Testing Battery?

[leo]

Another question from the electrically challenged. Will a small 12 volt battery say like a lantern type have enough juice to test a horn when something like a battery charger or full size battery is not available?

[Tom Wesenberg]

Yes, it should work. The horn uses about 5 amps.

Of course the final adjustment will need to be made on the car and with the engine running to charge the battery.

[leo]

Batteries list their voltage but how do you determine the amperage?

[MikeK]

Originally Posted by leo

Batteries list their voltage but how do you determine the amperage?

With a load tester. A carbon pile variable load with two meters: amps, and voltage across the load. The open circuit voltage drops gradually as load is increasingly applied. At some amperage load point the voltage nose dives.

Some batteries list both maximum intermittent and continuous load (amps) in their published specs. Vehicle batteries generally only list cold crank amps which is measured at a rather severe voltage fall-off. Amp-hours ratings do not tell you how much total load capability you have.

A typical "D" alkaline flashlight battery reads ~1.62V @ zero load. They are capable of 8+ amps intermittently, but the voltage falls off to ~1.45V. Most 6V 'lantern' batteries are simply four D's and a plastic spacer. That will give you 6.5V open circuit and ~5.8V @ 8 amps. With a 5 or 6 amp load you're probably right at 6V, good for horn testing. The little AAA's are also 1.62V but fall off to 1.35V at a 1 amp load.

[SeaSlugs]

what about those portable jumpstart packs? ive used one many times to power a car at a junkyard to test a radio...

[leo]

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Looking at 6 volt emergency light batteries which are rechargeable (4.5 Ah). Can they be recharged with any 6 volt battery charger? How long do they last if not used regularly.

[Tom Wesenberg]

Originally Posted by leo

Looking at 6 volt emergency light batteries which are rechargeable (4.5 Ah). Can they be recharged with any 6 volt battery charger? How long do they last if not used regularly.

You shouldn't charge a lead/acid battery at more than 10% of it's amp rating. So a car battery with a 100 amp rating should not be charged at over 10 amps and preferably less. Those small 4.5 Ah batteries should use a very small charger measured in milliamps, like 400 ma or less.

Those jumper packs that you can easily carry around basically have a small 12 volt motorcycle battery, and if you leave them plugged in to recharge, as my neighbor does, then the water boils off and they last less than a year.

[leo]

Hey guys, referring back to this post I had a knowledgeable person tell me that a battery charger should not be used to test Hutchins horn because:
You need a regulated power supply or a car battery and a Relay. battery charger will burn the brushes and ruin the armature.
Now a previous post said that a 6 volt lantern type battery would not work because it does not put out enough Amps to start the horn motor turning. Could this be fixed using a condenser?

[marc hildebrant]

MikeK,

Per old Heathkit info, the open circuit voltage for a new carbon zinc cell is 1.55 volts.
The VTVM meters used a small red dot at 1.55 volts for a calibration point during assembly.

Where did you get the 1.62 volts value ?

Marc

[MikeK]

Originally Posted by marc hildebrant

MikeK,

Per old Heathkit info, the open circuit voltage for a new carbon zinc cell is 1.55 volts.
The VTVM meters used a small red dot at 1.55 volts for a calibration point during assembly.

Where did you get the 1.62 volts value ?

Marc

Alkaline battery, not the old carbon zinc!

[marc hildebrant]

MikeK,

Thanks...I'll check that out.

Marc

[Bob C]

A friend has one of these and said it is amazing http://www.amazon.com/Astro-Pneumati.../dp/B00KD5VU6U

Bob

[Mike V. Florida]

Originally Posted by Bob C

A friend has one of these and said it is amazing http://www.amazon.com/Astro-Pneumati.../dp/B00KD5VU6U

Bob

Along with the resistor one uses when converting a car from 6 to 12 volt, and you have what you need.

I have seen similar at home depot for $44.00.

[40 Deluxe]

If you use a 12 v. battery on a six volt horn, it will sound different, plus. the horn may not even work on your car's six volt system. Likewise if you test the horn with a battery that's too small or weak, you may pass up a good horn.
Do a search for "6 volt lead acid battery". There are a lot to choose from. Offhand, I don't know what amp/hr. rating is needed for a horn.