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Author Topic: Harbor Freight Volt Meter sparking when contacting opposite pole  (Read 875 times)

garyb1st

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Using a Harbor Freight volt meter to measure the house batteries state of charge.  I think I had it set properly but I was getting sparks while touching the opposite pole.  This never happens with my other volt meter.  It didn't occur to me until later that batteries can explode.  Not sure if the volt meter is defective but it's going in the trash.  However, my real concern is the sparking.  Since my batteries are beneath a step and don't get much ventilation how can I be sure the explosive gas has dissipated so I don't end up in the emergency ward?
Gary B1st

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judway

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #1 on: October 05, 2017, 08:15:44 PM »
Sounds like you have the Voltmeter set to measure current.
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Tom

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #2 on: October 05, 2017, 08:25:07 PM »
I have to agree with Wayne's observation.
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garyb1st

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #3 on: October 05, 2017, 08:33:05 PM »
Guys, I'm volt meter challenged.  About the only thing I know, or at least thought I knew how to do, is check the battery. 
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Arch Hoagland

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #4 on: October 06, 2017, 12:12:33 AM »
There is nothing wrong with the voltmeter. If you are going to throw it away send it to me. I'll pay the shipping.

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #5 on: October 06, 2017, 07:25:21 AM »
When the dial is rotated to a current measuring position (amps or milliamps) it places a dead short across the meter leads, so the meter can be placed into the circuit to measure the current flow. This will cause the sparking you saw.

There's nothing wrong with the meter, you just had the selector knob in the wrong place.  One end of the knob handle has a dot on it but it's easy to get the ends mixed up and wind up on the wrong range.  I took a felt tip pen and painted the end with the dot black to avoid this problem.
« Last Edit: October 06, 2017, 07:29:32 AM by Lou Schneider »

Rene T

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #7 on: October 06, 2017, 07:36:05 AM »
On those HF and similar meters, there is usually a separate plug-in socket for a 10A measurement (as opposed to milliamps). If you plug the Plus lead into the 10A socket, I think you get an amp measurement (and sparks) regardless of the dial setting. See the photo at the link Rene posted.

As for the gases, if the compartment is has some openings, it should be OK. The hydrogen gas dissipates easily and is generally only present during active charging. Most likely only when the charge rate is high, e.g. overcharging or a shorted battery.  I don't want to belittle the concern because hydrogen is very explosive, but it's also not a common problem. If it were, your car would suffer battery explosions regularly!
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garyb1st

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #8 on: October 06, 2017, 10:14:49 AM »
Gary Wizard, thank you for setting my mind at ease.  Explosion is my primary concern.  I'm not comfortable working with wire so the only time I'll be using a meter is to test a battery.

I do appreciate all the replies but honestly, this stuff is like a foreign language to me. 

Thanks for all the replies.     
 

 
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TonyDtorch

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #9 on: October 06, 2017, 08:58:41 PM »
There is nothing wrong with the voltmeter. If you are going to throw it away send it to me. I'll pay the shipping.

it's likely the Harbor Freight volt meter that sells full retail for $4.99.....  the shipping will be more that that.   ???

(Sometimes there is a coupon for a free one with any other purchase.)
« Last Edit: October 06, 2017, 09:06:36 PM by TonyDtorch »

Tom

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #10 on: October 06, 2017, 09:24:29 PM »
The 'shunt' connected to the 10A connector on the Harbor Freight, or almost any other multimeter, has a resistance value very close to zero ohms, and so is an almost short circuit, resulting in the sparks. It's not intended to measure anything but current. If you want to measure voltage, change that lead to plug into the V/ohm/mA socket.
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Gary RV_Wizard

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #11 on: October 07, 2017, 11:30:39 AM »
I've actually witnessed a battery explosion under the hood of a nearby car. It's not going to blow up your vehicle like in the movies, but it does make some noise & smoke, may result in fire, and definitely makes a mess around the battery. Splattering acid around the compartment (or near by people) is as bad as the actual explosion damage and fire risk.

If the battery feels hot to the touch or shows evidence of more than slight bulging at the sides, disconnect it immediately, or at least shut off power to the charger.
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Old Racer

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #12 on: October 07, 2017, 07:42:27 PM »
Find the voltmeter manual and read it! While we are at it, take off rings, watches, etc. while working on batteries, battery amperage can melt a watch or ring in a hurry. Many more safety rules to know before plunging in.

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #13 on: October 08, 2017, 08:36:20 AM »
Sounds like you had it set to check current, not voltage.
Those cheap Harbor Freight Volt Meters are junk. They have no protection circuits and can actually blow up or melt in your hand if set incorrectly.
Never use one to check AC line voltage, your shore power connections, or your house batteries.
Throw it away and get a decent one and read the manual before using it.

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Gary RV_Wizard

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #14 on: October 08, 2017, 08:59:32 AM »
Hmmm, can't say that I share that opinion.   I own several of those junk HF meters and have used them for years. They are so cheap I just leave them around in handy places, e.g. in the car, my desk at home, my portable took kit, and a couple different spots in my workshop, etc. Never encountered a problem other than a display dies once in awhile and I throw the meter away.

And yes, I do own a good quality meter as well, but little that I do ever requires much accuracy. Or "protection".
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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #15 on: October 08, 2017, 06:54:31 PM »
Hmmm, can't say that I share that opinion.   I own several of those junk HF meters and have used them for years. They are so cheap I just leave them around in handy places, e.g. in the car, my desk at home, my portable took kit, and a couple different spots in my workshop, etc. Never encountered a problem other than a display dies once in awhile and I throw the meter away.

And yes, I do own a good quality meter as well, but little that I do ever requires much accuracy. Or "protection".

You've been lucky and you probably know the basics of using a meter.
They are junk and can be dangerous to anyone that is not sure of what they are doing and intends to use them for measuring higher current or voltages, especially where higher current is involved like RV batteries. When a meter is used in the wrong mode or range is where protection circuits come in handy.
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John From Detroit

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #16 on: October 09, 2017, 07:14:35 AM »
I think you had it set to AMPS not VOLTS.. thode meterd are ast leasdt 5,000 Ohm per volt usually 10,000 or more and on the 20 volt scale that means 200,000 ohms.. There id alwayds a spark. but with that kind of resistance you won't see it (Mega tiny).

But on AMPS.. You will
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Mike L

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #17 on: October 09, 2017, 08:14:44 AM »
Hmmm, can't say that I share that opinion.   I own several of those junk HF meters and have used them for years. They are so cheap I just leave them around in handy places, e.g. in the car, my desk at home, my portable took kit, and a couple different spots in my workshop, etc. Never encountered a problem other than a display dies once in awhile and I throw the meter away.

And yes, I do own a good quality meter as well, but little that I do ever requires much accuracy. Or "protection".

X2

Additionally, I also own an oscilloscope although I use it less anymore.

 One habit I have is always checking voltage first, then move on to resistance. Yes the accuracy isn't the best, but for troubleshooting, meter is good enough.

glen54737

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #18 on: October 10, 2017, 08:13:45 AM »
It might also be on resistance.
I had a boss that his last day as a worker destroyed a meter testing 480v with a meter on resistance.
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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #19 on: October 10, 2017, 08:14:58 PM »
Battery sparking is hazardous generally only when the battery has been discharged pretty well and is now in charging process by either engine running the alternator or having a charger on the battery. The charging action causes the release of hydrogen gas (smells kinda like rotten eggs) which in confined spaces, sparks can indeed set of a good bang which can destroy the battery and splatter acid all over the place. But the safest way to check battery levels or performance load test is to hook up the positive post of the battery FIRST to the charger or tester and then hook up the negative clamp to the CHASSIS of the vehicle or to the end of the negative cable where it attaches to the trailer frame. That way any sparks that do occur are a 'reasonable' distance from the vents of the battery, where the gasses would be originating. When done checking or charging the battery, turn off the charger, then disconnect the negative clamp first, then the positive. 
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meternerd

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #20 on: October 16, 2017, 09:40:55 PM »
Battery sparking is hazardous generally only when the battery has been discharged pretty well and is now in charging process by either engine running the alternator or having a charger on the battery. The charging action causes the release of hydrogen gas (smells kinda like rotten eggs) which in confined spaces, sparks can indeed set of a good bang which can destroy the battery and splatter acid all over the place. But the safest way to check battery levels or performance load test is to hook up the positive post of the battery FIRST to the charger or tester and then hook up the negative clamp to the CHASSIS of the vehicle or to the end of the negative cable where it attaches to the trailer frame. That way any sparks that do occur are a 'reasonable' distance from the vents of the battery, where the gasses would be originating. When done checking or charging the battery, turn off the charger, then disconnect the negative clamp first, then the positive. 
ASE Master Auto tech, 15 years experience.

OK....I don't want to preach here, but I have been a power company electrician for over 40 years.  Heard all kinds of horror stories, and have seen a few myself.  So here's my opinion.  First. Hydrogen is an odorless, colorless gas.  The rotten egg smell is just the sulfuric acid vapors.  If you smell nothing, it doesn't mean hydrogen is not present.  Next, when working with low voltage DC, such as 12V or 24V, some think there's little danger.  Wrong.  A 12V short circuit can produce huge amounts of fault current. I=V/R  If the voltage (12V) is present across a short (R) of 0.01 Ohms...typical for a solidly connected fault, that's (I) 1200Amps of current....more than enough to vaporize any adjacent metal and explode a battery.  Meters are essential tools, but like any tool, if they are not up to the task or are of low quality, and are used improperly, they can be deadly.  If you're unfamiliar with basic electrical theory and safety, leave it to the pro's.  OK....I did preach, but like I said, I've lost several close friends who "knew what they were doing".  A spark when measuring 12V volts is not normal, so I'd be VERY careful.  No flaming arrows, please... :)

OLDRACER

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Re: Harbor Freight Volt Meter sparking when contacting opposite pole
« Reply #21 on: October 18, 2017, 06:10:05 PM »
That was not preaching, and someone who manages to get a ring or a watch between the hot post of a 6 or 12 volt battery and ground will be not necessarily praying when they scream, but it will likely sound like it!!!

 

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