Go Back   iRV2 Forums > iRV2.com COMMUNITY FORUMS > iRV2.com General Discussion
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 11-17-2014, 06:17 PM   #1
Senior Member
 
Join Date: Feb 2010
Posts: 4,493
Beware of your voltmeter with AGM/VRLA batteries.

We were out doing maintenance work on some 48 volt equipment (non power related) and noticed batteries a little fat.

We keep a harbor freight dvm in the tool box for just in case instances like this.

Measured the voltage and it was reading too high by about 2 volts...which the fat batteries were indicating.

Found all dc voltages a bit high so later in the day checked against the fluke and discovered it was off by about 4%.

I never trusted their AC Volts readings as they often indicated 130 or more volts and just considered them a voltage present indicator...the VRMS part usually not that good but most DC measurements are usually real close.

So the warning is if you are checking for presense of voltage or checking general things they are great.

But if you are working where it matters like charging voltage where tenths of a volt matters then use a good quality meter or at least confirm the readings on what you are using to be sure it is good or what good should read (make a conversion factor).
__________________

__________________
Tony & Lori
1989 Country Coach Savannah SE
TQ60 is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 11-17-2014, 06:23 PM   #2
Senior Member
 
Join Date: Sep 2014
Location: Newcastle West, Ireland
Posts: 392
Fluke meters only for me
__________________

__________________
'98 Southwind 34L, too many cameras, old hat, young heart.
May the light be with you.
Mentor is offline   Reply With Quote
Old 11-18-2014, 09:21 AM   #3
Senior Member/RVM #90
 
MSHappyCampers's Avatar


 
Monaco Owners Club
Join Date: Nov 2002
Location: Columbus, MS
Posts: 26,345
You get what you pay for! I have a couple of the Harbor Freight "freebie" meters on hand just in case my Fluke quits at the wrong time, but I sure wouldn't depend on them being correct!
__________________
Joe & Annette

2002 Monaco Windsor 40PBT, 2013 Honda CRV AWD
MSHappyCampers is offline   Reply With Quote
Old 11-19-2014, 11:26 AM   #4
Moderator Emeritus
 
Gary RVRoamer's Avatar


 
Join Date: Jan 2000
Location: Silver Springs, FL. USA
Posts: 18,096
"Correct" or "accurate" aren't very definitive terms, but most cheap meters aren't better than a +/- 0.1 volts in the 12 volt DC range and probably worse than that at 120vac range. If you figured they are within 10% from true you would probably be safe enough, but that means you shouldn't attempt to make any fine tuning decisions using them. Rarely do I need more accuracy than that, though.

I use a tape measure more often than my micrometer, too. Know your tools and use the one that best fits the task at hand.
__________________
Gary Brinck
Former owner of 2004 American Tradition
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
Gary RVRoamer is online now   Reply With Quote
Old 11-19-2014, 08:45 PM   #5
Senior Member
 
Join Date: Feb 2010
Posts: 4,493
For general troubleshooting they are great as you have liitle to loose if you drop it or leave it in amps then check volts or other common mistakes.

As mentioned in the op where it matters they should not be used.

Main function that matters is battery charging.

10% is 1.35 volts at 13.5 and vor troubleshooting way close enough but battery float needs to be 13.5 plus or minus 0.1 10% will not cut it.
__________________
Tony & Lori
1989 Country Coach Savannah SE
TQ60 is offline   Reply With Quote
Old 11-20-2014, 09:29 PM   #6
Senior Member
 
Ray,IN's Avatar
 
Join Date: Aug 2001
Location: North America somewhere
Posts: 13,712
Quote:
Originally Posted by TQ60 View Post
For general troubleshooting they are great as you have liitle to loose if you drop it or leave it in amps then check volts or other common mistakes.

As mentioned in the op where it matters they should not be used.

Main function that matters is battery charging.

10% is 1.35 volts at 13.5 and vor troubleshooting way close enough but battery float needs to be 13.5 plus or minus 0.1 10% will not cut it.
Isn't .1 the same as 10 percent?
__________________
2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member,FMCA."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert the Constitution. "Abraham Lincoln"
Ray,IN is offline   Reply With Quote
Old 11-20-2014, 11:12 PM   #7
Senior Member
 
Join Date: Feb 2010
Posts: 4,493
0.1 is a 10% multiplier, but here the voltage measurment matters to 0.1 volt and a 10% error at 13.5 VDC float is 1.35 VDC.

This is worded poorly but a term of plus or minus 0.1 is not a percent unless it is specified as such, here it was listed as voltage plus or minus 0.1
__________________
Tony & Lori
1989 Country Coach Savannah SE
TQ60 is offline   Reply With Quote
Old 11-21-2014, 09:40 AM   #8
Senior Member
 
Ray,IN's Avatar
 
Join Date: Aug 2001
Location: North America somewhere
Posts: 13,712
Quote:
Originally Posted by TQ60 View Post
0.1 is a 10% multiplier, but here the voltage measurment matters to 0.1 volt and a 10% error at 13.5 VDC float is 1.35 VDC.

This is worded poorly but a term of plus or minus 0.1 is not a percent unless it is specified as such, here it was listed as voltage plus or minus 0.1
0.1 is one tenth of 1. That is a mathematical fact. 10% of one is one tenth of 1, that is a mathematical fact. One dime is .1 of one dollar, 10% of one dollar is 10 cents, that is a mathematical fact.
__________________
2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member,FMCA."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert the Constitution. "Abraham Lincoln"
Ray,IN is offline   Reply With Quote
Old 11-21-2014, 09:50 AM   #9
Senior Member
 
brobox's Avatar


 
Entegra Owners Club
Join Date: Apr 2007
Location: SW FL
Posts: 15,119
Quote:
Originally Posted by TQ60 View Post
We were out doing maintenance work on some 48 volt equipment (non power related) and noticed batteries a little fat.

We keep a harbor freight dvm in the tool box for just in case instances like this.

Measured the voltage and it was reading too high by about 2 volts...which the fat batteries were indicating.

Found all dc voltages a bit high so later in the day checked against the fluke and discovered it was off by about 4%.

I never trusted their AC Volts readings as they often indicated 130 or more volts and just considered them a voltage present indicator...the VRMS part usually not that good but most DC measurements are usually real close.

So the warning is if you are checking for presense of voltage or checking general things they are great.

But if you are working where it matters like charging voltage where tenths of a volt matters then use a good quality meter or at least confirm the readings on what you are using to be sure it is good or what good should read (make a conversion factor).
X2, the Harbor Freight meter is worth just what I paid for it (free), but OK for checking the presents of power or continuity on a light bulb.
__________________
Chuck in SW FL
A "Classic" 2014 Entegra Anthem 42RBQ
2016 Colorado Z71 PU
brobox is offline   Reply With Quote
Old 11-21-2014, 10:16 AM   #10
Senior Member
 
HD4Mark's Avatar
 
Winnebago Owners Club
Coastal Campers
Join Date: Oct 2009
Location: Marathon, Florida
Posts: 2,894
Quote:
Originally Posted by brobox View Post
X2, the Harbor Freight meter is worth just what I paid for it (free), but OK for checking the presents of power or continuity on a light bulb.
X3, for nothing or the huge $4.99 regular price it a good continuity tester and ball park voltage meter. Plus if you lose it or break it, so what.

I have a couple of old analog meters that are about the easiest ones to use.
__________________
Mark & Nancy
2004 Winnebago Vectra 40KD
Shep dog, R.I.P. Kenzie dog Toad 2015 Jeep Wrangler Willys Wheeler
HD4Mark is offline   Reply With Quote
Old 11-21-2014, 02:59 PM   #11
Senior Member
 
Join Date: Jun 2013
Location: Gilbert, AZ
Posts: 237
Funny you should mention the junk Harbor stuff - I was troubleshooting my batteries the other day and found the dvm saying my 2 6v batteries were at 20vdc. I then checked my truck battery and a spare battery I had in the garage - all showed 20vdc. In the garbage it went.
__________________
Nunyadamn is offline   Reply With Quote
Old 11-21-2014, 07:02 PM   #12
Senior Member
 
Join Date: Feb 2010
Posts: 4,493
Quote:
Originally Posted by Ray,IN View Post
0.1 is one tenth of 1. That is a mathematical fact. 10% of one is one tenth of 1, that is a mathematical fact. One dime is .1 of one dollar, 10% of one dollar is 10 cents, that is a mathematical fact.

We are not communicating very well and that is my fault!

The actual meter is in error by 4% which at 1 volt is 0.04 volt, but when measuring 13.5 volts it may indicate anywhere from 12.96 to 14.04 which would indicate undercharge to cooking nicely.

The voltage being measured has an allowance or margin of 0.1 volt at a mean value of 13.5 which is an error of about 0.7%

There may be confusion relating the error in voltage allowed to the error of measurement by the instrument (barely)

Most folks assume the DVM being digital would be accurate enough and most of us have suggested using them for general troubleshooting.

There are many threads regarding voltage levels in charging systems where these meters should not be used unless they can be checked and a correction factor used if need be.

Reason for this tread was to make note of the possibilities of bad measurements, this meter was brand new sealed in the box, it was one of the free for showing up thus was in the tool box related to the work at hand for a just in case something was needed meter.
__________________
Tony & Lori
1989 Country Coach Savannah SE
TQ60 is offline   Reply With Quote
Old 11-22-2014, 08:49 AM   #13
Registered User
 
Join Date: Feb 2013
Posts: 472
My Fluke once had bad readings. - Replacing the batteries brought it back to "accurate".

Check you batteries!
__________________
Fl_Richard is offline   Reply With Quote
Old 11-22-2014, 03:42 PM   #14
Senior Member
 
Ray,IN's Avatar
 
Join Date: Aug 2001
Location: North America somewhere
Posts: 13,712
OK, the fog lifted, 10% is a relative term in this case. Thanks for your patience Tony.
__________________

__________________
2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member,FMCA."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert the Constitution. "Abraham Lincoln"
Ray,IN is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bounder: Adding batteries to 2014 Bounder, where? Bruadair Fleetwood Products Owner's Forum 8 05-17-2015 06:22 AM
Starting Batteries Joedean Class A Motorhome Discussions 6 12-12-2014 02:21 PM
Coach Batteries kketterling Monaco Owner's Forum 11 11-03-2014 06:03 PM
House Batteries cooked on us! RV1597 RV Systems & Appliances 13 07-05-2014 02:26 PM
House batteries making buzzing noise Furniss Class A Motorhome Discussions 10 06-21-2014 11:46 AM

» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 10:46 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.