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voltage gauge accuracy?

Old 03-19-2019, 03:59 PM
  #21  
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Originally Posted by Jus Teasin View Post
Where do you think that voltage comes from?
It starts at either the battery or the generator/alternator.

But due to voltage drop there may be (probably will be) a variance between the voltage at the battery or the generator/alternator and the voltage at the power source to the MFD. Or within the MFD itself.

If the battery voltage is 12.7 and the voltage being displayed on the MFD is 12.0, is the MFD displaying battery voltage?

Once the motor is running and the voltage being displayed on the MFD is 14.7 volts, is the MFD displaying battery voltage?
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Old 03-19-2019, 04:25 PM
  #22  
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If you own a boat with more than 2 batteries and venture offshore or overnight at anchor invest in a good battery monitoring system. If you own a basic single or twin engine CC or day cruiser with 1 or 2 batteries inexpensive lcd/led voltmeters show system voltage with 0.1 volts resolution and +or-1% accuracy which is perfectly suitable to monitor both charging system and state of battery charge if you understand how the boat’s electrical systems work. If you don’t understand how the electrical system charges and why system voltage fluctuates while underway and at rest then a voltmeter will most likely create more anxiety than peace of mind.
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Old 03-19-2019, 07:17 PM
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Originally Posted by Jus Teasin View Post
Where do you think that voltage comes from?
A mini universe in a box of course.
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Old 03-19-2019, 08:30 PM
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Originally Posted by mystery View Post
Why have it? Because the builder put it there. and they likely used undersized wiring and there is a voltage drop just from the battery to the gauge.
Only if there's something else drawing current on the same wire.
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Old 03-20-2019, 03:32 AM
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Originally Posted by LeakinLena View Post
If you own a boat with more than 2 batteries and venture offshore or overnight at anchor invest in a good battery monitoring system. If you own a basic single or twin engine CC or day cruiser with 1 or 2 batteries inexpensive lcd/led voltmeters show system voltage with 0.1 volts resolution and +or-1% accuracy which is perfectly suitable to monitor both charging system and state of battery charge if you understand how the boat’s electrical systems work. If you don’t understand how the electrical system charges and why system voltage fluctuates while underway and at rest then a voltmeter will most likely create more anxiety than peace of mind.
Any suggestions on which brands/models to use?
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Old 03-20-2019, 03:58 AM
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Originally Posted by Chimpo View Post
Any suggestions on which brands/models to use?
Hello, have installed a couple of Mastervolt Battman Lite series, very easy, you´ll have to install a shunt in the main negative, I think Blue Seas also now has a battery monitoring system. Hope this helps.
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Old 03-20-2019, 01:57 PM
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Originally Posted by Chimpo View Post
Any suggestions on which brands/models to use?
Check out eBay and buy whichever fits your budget and the application (https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1311.R1.TR 12.TRC2.A0.H0.X12v+digit.TRS0&_nkw=12v+digital+vol t+meter&_sacat=0). Even “cheap” digital voltmeters are accurate, durable and reliable enough for this application. Install and monitor the range of voltages displayed with engine off and running at idle and cruise with various accessories off and on and voltage patterns will emerge that you can use as baselines to track condition of your battery and charging systems.

I use an inexpensive combination LED meter ($12?) with 12v charging socket on my center console that reliably shows the electrical system voltage to 0.1 volts for the last 10+ years and prompted me to perform inspections that revealed both a corroded battery cable and resulting dead battery when it indicated inadequate charging voltage underway. The only drawback to my meter is it needs to be shaded with a hand to be read in direct sunlight (LCD might be better).

Last edited by LeakinLena; 03-20-2019 at 02:03 PM.
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Old 03-20-2019, 02:37 PM
  #28  
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I think the biggest value of any gauge is seeing if it is different than before. In the case of volts, you have a number with the engine off and a higher one with it running. As long as they stay somewhat consistent you should be OK. When things are starting to look different is when you should be investigating.
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Old 03-20-2019, 02:54 PM
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Originally Posted by alloyboy View Post
It starts at either the battery or the generator/alternator.

But due to voltage drop there may be (probably will be) a variance between the voltage at the battery or the generator/alternator and the voltage at the power source to the MFD. Or within the MFD itself.

If the battery voltage is 12.7 and the voltage being displayed on the MFD is 12.0, is the MFD displaying battery voltage?

Once the motor is running and the voltage being displayed on the MFD is 14.7 volts, is the MFD displaying battery voltage?
Huh - OTOH, which came first, the chicken or the egg?
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Old 03-20-2019, 05:12 PM
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Originally Posted by THT Mod 11 View Post
Huh - OTOH, which came first, the chicken or the egg?
The real question is why did the egg roll across the road?
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Old 03-20-2019, 05:48 PM
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I'm looking for one to monitor my 24v trolling motor batteries. I'm happy with the 6YC for the starting battery.

Do the Garmin MFD's or the 6YC have the capability to monitor the TM batteries? That would be the cleanest and most streamlined option.
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Old 03-20-2019, 07:14 PM
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Originally Posted by Chimpo View Post
I'm looking for one to monitor my 24v trolling motor batteries...

Do the Garmin MFD's or the 6YC have the capability to monitor the TM batteries? .
Neither has any innate ability to monitor batteries.

A current Garmin MFD can display data that it receives from a NMEA 2000 battery power monitoring device -
such as "DC voltage", "DC current", "state of charge", "time remaining"
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Old 03-20-2019, 07:33 PM
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I agree. My Garmin and volt gauge don’t agree but as long as they are both moving up with the engine running, I’m happy!
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Old 03-20-2019, 07:34 PM
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Originally Posted by alloyboy View Post
Customer to service advisor: "My voltmeter was reading 14.6 volts yesterday. Today it is reading only 14.5. I want a new charging system installed under warranty."

Actually, I installed a digital voltmeter in the power port of my 2016 Ford. With a "smart" charging system I suppose. The voltage is all over the place. From over 15 volts to down below 13 volts. Changes all of the time. Turn on the head lamps and it jumps up to about 15 volts no matter what it was before. Disconcerting to an old school guy until I got resigned to the fact that is the way that it is.
charging systems have always been inconsistent and react to electrical loads and battery state of charge as that is what excites the charging system....as long as the charging system is providing a higher voltage than battery it is charging the battery...your 2016 vehicle has computer controlled voltage regulation which can change according to necessity in order to keep the battery at a regulated temperature and optimize fuel economy...

the problem with thinking youre doing yourself a favor putting an accurate voltmeter on a vehicle is that most dont have a clue what the vehicle is supposed to be doing at any given time...unless you are monitoring the engine control systems streaming data you are wasting your time...but if it makes you feel better about yourself feel free to continue to question the factory and create your own problems and worry unnecessarily...not you personally...but anyone who is expressing more concern over it than it is worth...


Last edited by bladenbullet; 03-20-2019 at 09:56 PM.
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Old 03-20-2019, 08:00 PM
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I find the gauges helpful in determining that the acr has combined the 2 batteries.
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Old 03-20-2019, 10:09 PM
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Originally Posted by Fwpratt View Post
Neither has any innate ability to monitor batteries.

A current Garmin MFD can display data that it receives from a NMEA 2000 battery power monitoring device -
such as "DC voltage", "DC current", "state of charge", "time remaining"
Does that mean there is a device that can be hooked up to the batteries, then networked to the Garmin?
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