How useful is it to have a voltmeter as an advance warning for battery failure? I'm talking about a digital/numeric gauge and not an analog/needle-style gauge.

 

Not very.

When a battery gets old and sulfation begins to occur, it will show a good voltage yet drop rapidly and provide much less current than when it was new.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PupaScoopa &raquo;</TD></TR><TR><TD CLASS="quote">Not very.

When a battery gets old and sulfation begins to occur, it will show a good voltage yet drop rapidly and provide much less current than when it was new.</TD></TR></TABLE>

It may be useful if you run your stereo with your radio off though. Besides that I cannot think of a reason for it.

 

actually it is a good idea. A perfect condition 12 volt auto battery will actually read 12.6V. If after cruising you turn your car off, and the voltage only reads around 11.8, you know either A&gt; your chargine system is taking a ****, B&gt; you're pulling more load than your alternator can replenish, C&gt; your battery is getting low and/or needs maintence if it's a non-sealed battery, or D&gt; your terminals are getting corroded which means you won't get the full power of the battery, and if allowed to corrode too much can leave you stranded with a car that won't start.

 

That's sounds good, assuming the turn off threshold for the meter is low enough, that it will still be working, to tell you your battery is cooked when it is actually happening.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rjr162 &raquo;</TD></TR><TR><TD CLASS="quote">actually it is a good idea. A perfect condition 12 volt auto battery will actually read 12.6V. If after cruising you turn your car off, and the voltage only reads around 11.8, you know...</TD></TR></TABLE>

My plan was to hook the voltmeter up to my primary (and only) battery. Wouldn't the gauge just turn off once the car is off?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nOOber &raquo;</TD></TR><TR><TD CLASS="quote">That's sounds good, assuming the turn off threshold for the meter is low enough, that it will still be working, to tell you your battery is cooked when it is actually happening.</TD></TR></TABLE>

The gauge I'm considering has a range of 8-17 volts. Search says that Dakota Digital is pretty good...

http://www.dakotadigital.com/D...-05-3

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ITRJunkie &raquo;</TD></TR><TR><TD CLASS="quote">
The gauge I'm considering has a range of 8-17 volts. Search says that Dakota Digital is pretty good...

http://www.dakotadigital.com/D...-05-3 </TD></TR></TABLE>

Looks good. $90 though

 

if you hooked it up to your battery of course it wouldn't turn off with the car. Now if you hooked it up to your ignition or accessory line, then yes, it wouldn't read anything unless the key was "on"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ITRJunkie &raquo;</TD></TR><TR><TD CLASS="quote">How useful is it to have a voltmeter as an advance warning for battery failure? I'm talking about a digital/numeric gauge and not an analog/needle-style gauge.</TD></TR></TABLE>

Its actually very useful.

With the meter attached, watch the voltage as you start your car. If shouldnt drop lower than 11.5 volts. If it does it means your battery is weak.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rjr162 &raquo;</TD></TR><TR><TD CLASS="quote">if you hooked it up to your battery of course it wouldn't turn off with the car. Now if you hooked it up to your ignition or accessory line, then yes, it wouldn't read anything unless the key was "on"</TD></TR></TABLE>

So if it's hooked to the battery and would NOT turn off with the car, then what prevents the gauge from just sitting there draining away?

 

like i said it depends on how you connect it. Most meters wont' pull a whole lot either... sorta like the clock in a car, or the memory for the radio + ecu, alarm, etc. But your best bet is to put it on the ignition line or something of that nature

 

putting it on the ignition line wont change how it would read from the battery?

 

no, or not by enough to do make it really off. It's all being fed from the same place

 

I made a voltmeter from the circuitry off of a capacitor monitor-top. Cost: $0.