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VOLTMETER - The Importance Of Having An On-Board Voltmeter

globalrider

globalrider

Alps Adventurer
Some of the more recent vehicles have voltmeters as standard equipment, others do not, so you install one.

Why do you need one? This coming from someone that never seems to have battery issues, so you install a voltmeter so that can tell if the charging system is working correctly, partially or not at all.

Vehicles that come with a voltmeter as standard equipment (part of your dash display):

2016 R1200 GS Adventure LC. Engine off, vehicle system and fog lights are ON therefore there is a current draw and the voltage is low (11.8V) which is normal. With the engine running, it is above 14V as it should be. Factory battery: AGM.
2016 BNW R1200 GSA LC - SM.jpg

2015 Porsche 991.1 Carrera 4 GTS. Engine is idling and 14.8V may sound high, but notice the ambient temperature of 6C (43F) and that voltage is spot on at that temperature. Factory battery: AGM.
2015 Porsche 991.1 GTS - SM1.jpg


Vehicles that did not come with a voltmeter, so you make a voltmeter or buy one:

1995 Porsche 993. Engine is idling and 14.2V is perfectly normal. Factory battery: conventional flooded lead acid. Homemade voltmeter draws less than 2mA and is hardwired to the battery for an "always-on" display.
1995 Porsche 993 - SM.jpg

2003 BMW R1150 GS Adventure. Engine is off, battery maintainer in float mode so 13.3V is perfectly normal. Factory battery: GEL. Homemade voltmeter draws less than 2mA and is hardwired to the battery for an "always-on" display.
2003 BMW R1150 GSA - SM.jpg

2017 Acura RDX. Engine is off, vehicle system and lights are ON therefore there is a current draw and the voltage is low (11.7V) which is normal. Factory battery: Conventional or enhanced flooded lead acid. A cigarette lighter voltmeter was used. Handy in that it also has 2 USB charge ports. Less than $20 off Amazon.
2017 Acura RDX - SM.jpg
Cigarette Lighter Voltmeter - SM.jpg


My 1990 BMW R100 GS still needs to be outfitted with a voltmeter.

And by the way, voltmeters are the best cheap "non-bling" mod you can install. :D


Here are charge and float voltages for AGM and GEL batteries as supplied by East Penn Battery.
AGM - SM.jpg

GEL - SM.jpg
 
Last edited:
RadioFlyer said:
An alternative to a voltmeter is one of those colour changing LED voltage monitors.
Click to expand...

I have seen various types of those over the years.

I just prefer to see an actual voltage reading. And when they are part of a dash display as they are on my BMW Wethead or Porsche, I like to confirm how accurate they are being that the voltmeter is not connected directly to the battery itself, but to some wiring harness in the vehicle. Usually 0.1V out at the most; no big deal.

On the voltmeters that I made, the meter range is 8-50V so I calibrated it in the 13.5V ± 1V range.

I like your signature line. HEY BMW: No service manual = no new bike
 
I display battery voltage through a setting on my radar detector. Been doing that for years.
I also have a "go, no-go" voltage monitor from Clearwater Lights.
On my K1600 its 14.1 steady.

Joe
 
GlobalRider said:
I have seen various types of those over the years.

I just prefer to see an actual voltage reading. And when they are part of a dash display as they are on my BMW Wethead or Porsche, I like to confirm how accurate they are being that the voltmeter is not connected directly to the battery itself, but to some wiring harness in the vehicle. Usually 0.1V out at the most; no big deal.

On the voltmeters that I made, the meter range is 8-50V so I calibrated it in the 13.5V ± 1V range.

I like your signature line. HEY BMW: No service manual = no new bike
Click to expand...

I ended up going the LED monitor route when my Garmin 276C GPS died as it had the option of displaying the input voltage. I was disappointed that the successor 276Cx did not.

Being able to just glance down and see the healthy green LED is convenient though and it did its job last year when it flagged a failing stator by changing to red at idle.

Thanks for the comment on my sig line. Not everyone here appreciates it as it runs counter to the MOA's mandate.
 
I picked this one up for the 11RT this January. Resides in the Hella receptacle on the dash near the radio buttons.

https://www.amazon.com/dp/B07VPZN3R6?psc=1&ref=ppx_yo2ov_dt_b_product_detailsIt's been plugged in since.
The readings I get are

Ignition on, radio and Denali's 13.2-13.3 [ yet it doesn't change when the Denali lights are on or off ].
chargin 13.3-13.4
Idling 14.1-14.3

Cranking it can read 11.5-.6 or 10.5-.7. I've seen it drop to 9.8 while cranking, but the motor cranks right over and there's no slowness [ for a better term ] in cranking.

OP, thanks for the temp reading chart, I'd never seen that before
 
RadioFlyer said:
Being able to just glance down and see the healthy green LED is convenient though and it did its job last year when it flagged a failing stator by changing to red at idle.
Click to expand...

Yeah well BMW really screwed up with the R1200/R1250 alternators. Nothing like the 50A (700W) car alternator they have on my R1150 GSA which can easily be replaced or repaired. The alternator on my R1200 GSA LC better not fail or BMW won't be selling me a new motorcycle again, service manual or not. Glad I still have my R80 G/S PD and R100 GS to fall back on. ;)
 
PGlaves said:
How easy is it to read the display when the Sun is shining??
Click to expand...

I can glance down and read it in the sun just fine. On the RT it's right there on the left dash, plugged in, it's roughly 15 degrees above horizontal. I've turned it to my left a little so the numbers are easier to read. Straight vertical, I'd sometimes barely see the last digit, so it might be a 1 or a 7. With it turned slightly, I can fully see the last number.
 
brownie0486 said:
I can glance down and read it in the sun just fine. On the RT it's right there on the left dash, plugged in, it's roughly 15 degrees above horizontal. I've turned it to my left a little so the numbers are easier to read. Straight vertical, I'd sometimes barely see the last digit, so it might be a 1 or a 7. With it turned slightly, I can fully see the last number.
Click to expand...

Ordered!!
 
Omega Man said:
This looks pretty good. Seems to have some water resistance factor. On the F800GS, the tank bag would be in the way. :dunno

OM
Click to expand...

The cover has two tabs than insert into the two usb ports, I'd think it's waterproof enough but in a torrential rain for some time, not sure. I'll find out this summer on my 5 state tour. Never fails we catch a good soaking rain in Colorado, South Dakota.
 
Looking at Amazon, I found quite a few of these "plug-in" voltmeters. This one is a panel mount but there are others like it that are a plug-in unit.

Some come with dual USB charge ports, others come with one USB charge port and a C charge port.

I like the fact that these have a power switch to turn them off.

Voltmeter 1.jpg

Voltmeter 2.jpg
 
henzilla said:
That switched unit looks good
Click to expand...

Yeah I like it. Note the wiring bundle in the first pic. Looks like it wires directly to the battery because it has a fuse holder.

The ON-OFF switch cuts power to the LED display and I would assume the USB ports.
 
brownie0486 said:
I picked this one up for the 11RT this January. Resides in the Hella receptacle on the dash near the radio buttons.

https://www.amazon.com/dp/B07VPZN3R6?psc=1&ref=ppx_yo2ov_dt_b_product_detailsIt's been plugged in since.
The readings I get are

Ignition on, radio and Denali's 13.2-13.3 [ yet it doesn't change when the Denali lights are on or off ].
chargin 13.3-13.4
Idling 14.1-14.3

Cranking it can read 11.5-.6 or 10.5-.7. I've seen it drop to 9.8 while cranking, but the motor cranks right over and there's no slowness [ for a better term ] in cranking.

OP, thanks for the temp reading chart, I'd never seen that before
Click to expand...

The one I linked above connected to the Din plug near the radio buttons on the RT shuts off at the same time the radio power goes out. It's 1 minute from key off to killing the radio and Din receptacle. In this manner, there's no parasitic draw on my 11RT.
 
GlobalRider said:
Yeah I like it. Note the wiring bundle in the first pic. Looks like it wires directly to the battery because it has a fuse holder.

The ON-OFF switch cuts power to the LED display and I would assume the USB ports.
Click to expand...

I had a similar unit on my AT, but without the on/off button. I wired it to an Eastern Beaver PC8 so it was switched with the ignition.
 
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