Temporary amp guage

super99 · May 19, 2020

Just wondering if you could rig up a temporary amp guage to check a lawn tractor engine to make sure it's charging? A couple alligator clips to fasten it on to check that it's charging. Where would you hook to ??? Thanks, Chris

teddy52food · May 19, 2020

If it is negative ground, hook it to the negative battery cable & ground. Then start the engine. Then take the ground cable off on the chassis end.

Janicholson · May 19, 2020

Teddy's hookup is perfect. The real story is voltage. Tast across the bat terminals while shut off, and while running near wide open. If 12v system, it should read 12.5 to 12.65 when stopped. and about 14+ to maybe 14.5 when running. The reason amps are not as important when testing is that the amount changes with the state of charge of the battery.

Jim

john in la · May 19, 2020

My personal opinion is amp gauges are useless on lawn mowers or tractors.
They do not have enough electrical draw to make the needle move enough you can see it.
I much rather a volt gauge.

buickanddeere · May 19, 2020

Instead of breaking open circuits to measure current. We just use a clamp-on AC or DC ammeter . https://www.amazon.com/clamp-dc-amp-meter/s?k=clamp+on+dc+amp+meter&page=2

Bob M · May 19, 2020

I agree with the others...measuring voltage at the battery will tell you whether the battery is being charged.

You will need to use an "old school" analog VOM or an industrial quality digital DMM (like a Fluke) to take running voltage reading. Cheap Harbor Freight, Radio Shack, etc DMM's give erratic - and often erroneous - readings when measuring automotive charging systems.

David G · May 19, 2020

As the others stated, measure voltage.

To quote my late father, take care of the voltage and the amps will take care of themselves.

Olliejunkie · May 20, 2020

I use to have one similar to this. Dont recall if it worked. Use to be some small engines had them..any body else have one.
https://www.jbtools.com/sg-tool-aid...RTd6_WNnVH9blpg3UEJJJftdgdo-CpJRoC5fAQAvD_BwE

MarkB_MI · May 20, 2020

I have an inductive pickup ammeter from the sixties similar to the one in the link below. Simple to use, just hold it up to the battery cable. I never use it; a voltmeter tells me what I need to know.
Inductive ammeter

Russ from MN · May 20, 2020

Like others have said, just use a voltmeter, much easier.

John T · May 20, 2020

Super 99, Its possible to use an accurate volt meter on the battery which can provide an indication if its under charge or not. A full charged 12 Volt lead acid battery at rest and stabilized is around 12.6 volts. If its under a good working charging system, subject to battery size and condition and the charging system capacity, voltage should rise to around 13 (at least RISE above 12.6) even up to 14 volts. If it never causes the battery voltage to rise whatsoever ITS LIKELY NOT WORKING unless the battery is bad.

Many typical old car or tractor or even lawn tractors may have two terminal ammeters with a range of say 10 or 20 or 30 amps. For a lawn tractor Id use a small rated one like 10 or 20 amps max and simply place it in series with the battery to see how many amps are flowing in or out. That would be cheap, simple and easy peasey to wire in place.

I have no idea where I got it or its accuracy or brand but I have an induction ammeter you simply place up against the wire to measure current flow.

John T

guido · May 21, 2020

Hello super99,

An amp meter displays rate of charge, a volt meter displays a state of charge.
Voltage then is a better indicator of battery state of charge-potential.
If you hook up a volt meter on a lawn tractor battery, it may read more then the nominal 14 volts.

Some of the lower capacity units, 1 1/2 amp or so are not regulated, that is the reason for the higher then normal voltage.

Charging voltage only verifies that the battery is receiving a charge. It I then important to check battery voltage with the engine off.
Which should be 12.6 volts @ 80 degrees F*

You can buy an induction amp meter that will work for what you want to do. You just lay it on a battery cable, at least 2 inches from the battery clamp, and will display amps charging.
p>Search on amazon and you will see what I mean. I can post a picture if you want also,

Guido.

Temporary amp guage

super99

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teddy52food

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Janicholson

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john in la

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buickanddeere

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Bob M

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David G

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Olliejunkie

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MarkB_MI

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Russ from MN

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John T

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guido

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