Battery gauge


#1

I am looking for a battery gauge. This would indicate battery strength at a glance to prevent those awful times when you come back from the picnic, out of the movies, etc.-- and find the car won’t start. Would mount on the dash like the oil pressure and fuel gauges. J.C. Whitney, Eastwood, local parts shops never heard of such. Please advise. Thanks!!!


#2

What you want is a voltmeter. You can tell how well the battery is being charged while the car is running by looking at the voltage. There isn’t much use for a gauge that tells you the battery is discharged after the fact. What you need then is a charger.


#3

There are two types of gauges, voltmeter and ammeter.

The voltmeter will tell you the voltage of the battery when the engine is not running, it should be 12.6 volts. If its lower, it can mean a partial discharge or a battery going bad. It should read 13.8 to 14.2 volts with the engine running, that indicates the alternator is putting out. You can buy a digital voltmeter that plugs into the power adapter (cigarette lighter).

The ammeter only measures the current being put out by the alternator. Under normal circumstances, the current should be around 1-4 amps. Immediately after starting, the current will be 10 to 30 amps as the alternator recharges the battery. This lasts for a minute or two. As the battery ages and begins to deteriorate, the normal running current begins to go up. When the normal running current gets up to around 10 amps, you battery is about shot, it could leave you stranded at anytime.

I personally use the plugin digital voltmeter for troubleshooting purposes only. I don’t see a need to have one permanently installed in the dash. I don’t see much need for an ammeter either, but it would be my choice if I wanted to fill an extra hole in the dash. My first choice would be a water temperature and an oil pressure gauge. A dead battery is a lot cheaper to deal with than a dead engine.


#4

Thanks! How would you hook up the ammeter?


#5

A ammeter needs to placed in series with the alternator lead. This means all the charging current has to flow through the gauge unless there is a shunt installed. This means installing fairly heavy gauge wiring to keep wire losses down. I recommend you install a voltmeter instead. Most vehicles today use a voltmeter to monitor the charging system.


#6

I installed an ammeter in my Fiat many moons ago. If you purchase one it should come with instructions. If not, check with us again. Understand you must use heavy wire for all circuitry. Use 10-gauge, no less.

I haven’t had an ammeter in any of my cars for years. I especially don’t need a voltmeter. The red idiot light is all anyone really needs. It warns of a malfunction before your battery goes dead.

If your battery runs down overnight because you didn’t slam the car door and left the dome light on, no meter can help you. Buy a portable jump starter rather than a meter.


#7

A voltmeter tells you if your battery is charged or not. If it is not charged then it is obvious that the alternator is not putting out the needed amps. I prefer a voltmeter as an ammeter will not indicate overcharging or battery voltage condition. Radio Shack may still have a simple LED voltmeter that plugs into your cigar lighter. You can plug it in when you suspect a problem. If RS does not have one then check with a car parts store or Whitney. Charging systems are very reliable on modern cars, much better than the bad old days with generators instead of alternators so there is normally no need to be concerned with the charging system. Keep your towing insurance current.