12 Volt Battery Monitor

bogeybob513 · 11-21-2006, 04:46 PM

After reading all the posts regarding the 12 volt battery problems I remembered I had a 12V voltage indicator from my Bonneville that could be used to monitor that battery. Mine is a Whistler, has a digital readout and three indicator lights (red/yellow/green). It plugs into one of the power outlets and gives a constant reading. When the car is not running it will give you the battery voltage. When running, it gives you the charging voltage. I wouldn't keep it in when not running as it will drain the battery a little.

I went to whistlergroup.com but could not find the voltage indicator there. I'm sure you can pick it up in any auto parts store.

hobbit · 11-21-2006, 06:20 PM

I'd rather have a real voltmeter. Well, so I do. It lets me watch
small deltas as things turn on and off, giving me a rough idea of
how much power they draw..
.
_H*

FireEngineer · 11-22-2006, 09:51 AM

Your device won't work very well in a Prius. The power outlets are not powered when the car is off. When the car is powered the inverter gives a very nice constant voltage to the 12 volt system. You need something more direct like Hobbit mentioned.

Wayne

DanMan32 · 11-22-2006, 10:04 AM

The MFD diagnostic screen provides a digital voltmeter.

bogeybob513 · 11-22-2006, 10:23 AM

<div class='quotetop'>QUOTE(FireEngineer @ Nov 22 2006, 09:51 AM) [snapback]352976[/snapback]</div>

Quote:

Your device won't work very well in a Prius. The power outlets are not powered when the car is off. When the car is powered the inverter gives a very nice constant voltage to the 12 volt system. You need something more direct like Hobbit mentioned.

Wayne
[/b]

It works very well when the the car is on. I just suggested this device for those who are concerned about the status of their batteries as they grow older. Obviously, any voltage under 12 would be an indication of a battery going bad.

DanMan32 · 11-22-2006, 11:02 AM

<div class='quotetop'>QUOTE(bb513 @ Nov 22 2006, 10:23 AM) [snapback]352991[/snapback]</div>

Quote:

Obviously, any voltage under 12 would be an indication of a battery going bad.
[/b]

Not when off. 10-11V is not uncommon for a battery voltage.

c4 · 11-22-2006, 11:37 AM

In the 11V range I'd agree would be non-indicative of any kind of fault, but if the battery voltage drops down to 10V while the vehicle is off, this means that the battery is either bad/going bad or is very low in charge, and you'd better keep an eye on it..

Remember, because the converter puts out a fixed voltage, this means that the charge rate to the 12V battery is effectively current limited and it can take *much* longer for the vehicle systems to recharge a dead/low 12V battery than a conventional vehicle.. If your vehicle required a boost, do *NOT* count on a 20 minute drive being able to recharge the 12V battery to a healthy state- you should connect the battery to a 115V mains-powered charger as soon as possible, otherwise you may walk out to another dead battery the next day..

DanMan32 · 11-22-2006, 12:49 PM

The DC-DC converter actually has 2 voltage outputs, very close to each other. 13.8 versus 14 I think, based on the sensed state of charge on the 12V battery.

bogeybob513 · 11-22-2006, 12:55 PM

<div class='quotetop'>QUOTE(DanMan32 @ Nov 22 2006, 10:04 AM) [snapback]352983[/snapback]</div>

Quote:

The MFD diagnostic screen provides a digital voltmeter.
[/b]

How does one obtain a MFD diagnostic screen?

DanMan32 · 11-22-2006, 01:11 PM

Excellent question.
One way is to hold down the Info button on the bezel and flash the taillights 3 times.
The other way is to press the 'display' button, then touch the left half of the screen, first under the top banner, then above the lower banner, doing this three times. Much like the speed override.

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11-21-2006, 04:46 PM	#1
bogeybob513 rtc513 Join Date: Oct 2006 Location: Myrtle Beach, SC Posts: 68 My Car: 2006 Prius Package: #6 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	After reading all the posts regarding the 12 volt battery problems I remembered I had a 12V voltage indicator from my Bonneville that could be used to monitor that battery. Mine is a Whistler, has a digital readout and three indicator lights (red/yellow/green). It plugs into one of the power outlets and gives a constant reading. When the car is not running it will give you the battery voltage. When running, it gives you the charging voltage. I wouldn't keep it in when not running as it will drain the battery a little. I went to whistlergroup.com but could not find the voltage indicator there. I'm sure you can pick it up in any auto parts store.

11-21-2006, 06:20 PM	#2
hobbit Senior Member Join Date: Mar 2005 Location: Bahstahn Posts: 2,989 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	I'd rather have a real voltmeter. Well, so I do. It lets me watch small deltas as things turn on and off, giving me a rough idea of how much power they draw.. . _H*

11-22-2006, 09:51 AM	#3
FireEngineer Senior Member Join Date: Oct 2004 Location: SW-Side of Chicago, IL Posts: 792 My Car: 2005 Prius Package: #6 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 4	Your device won't work very well in a Prius. The power outlets are not powered when the car is off. When the car is powered the inverter gives a very nice constant voltage to the 12 volt system. You need something more direct like Hobbit mentioned. Wayne

11-22-2006, 10:04 AM	#4
DanMan32 Join Date: Aug 2004 Location: Tampa Bay, FL Posts: 3,775 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	The MFD diagnostic screen provides a digital voltmeter.

11-22-2006, 11:37 AM	#7
c4 Join Date: Mar 2005 Posts: 523 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	In the 11V range I'd agree would be non-indicative of any kind of fault, but if the battery voltage drops down to 10V while the vehicle is off, this means that the battery is either bad/going bad or is very low in charge, and you'd better keep an eye on it.. Remember, because the converter puts out a fixed voltage, this means that the charge rate to the 12V battery is effectively current limited and it can take much longer for the vehicle systems to recharge a dead/low 12V battery than a conventional vehicle.. If your vehicle required a boost, do NOT count on a 20 minute drive being able to recharge the 12V battery to a healthy state- you should connect the battery to a 115V mains-powered charger as soon as possible, otherwise you may walk out to another dead battery the next day..

11-22-2006, 12:49 PM	#8
DanMan32 Join Date: Aug 2004 Location: Tampa Bay, FL Posts: 3,775 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	The DC-DC converter actually has 2 voltage outputs, very close to each other. 13.8 versus 14 I think, based on the sensed state of charge on the 12V battery.

11-22-2006, 01:11 PM	#10
DanMan32 Join Date: Aug 2004 Location: Tampa Bay, FL Posts: 3,775 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Excellent question. One way is to hold down the Info button on the bezel and flash the taillights 3 times. The other way is to press the 'display' button, then touch the left half of the screen, first under the top banner, then above the lower banner, doing this three times. Much like the speed override.