Is there a such thing that actually measures how much batter life you have left?

I found something kinda like it on ebay but i'm not sure if its for cars:


http://cgi.ebay.com/ebaymotors/12V-L...QQcmdZViewItem


http://lechi.com/discE.htm

 

Not that I'm aware of.

That device tells you the state of charge left not the life of the battery. All that really tells you is you will need to get this battery charged up soon.

 

Those are fancy voltmeters. They measure the output voltage from the battery. It should show around 14 when the engine is running, and then will go to around 12-13 with it shut off. It helps when running your accessories with the engine off, since you can tell when the battery is getting low. The one in the dash also works, but has no markers. You could also get an amp gauge (ammeter) to measure how good the charging system is working.

 

thats what im looking for. I want to know when I need to turn my truck back on or turn it off so the battery doesnt run empty. Where do i get that? does it have a name?

 

It's called a Voltmeter, and all the gauge manuafacturers make them. Look for ones from VDO or Autometer. They are a pretty simple install, since it just needs a good feed from the truck's battery. Try to find a circuit that's not used, or just run a direct one from the battery.

http://store.summitracing.com/egnsea...=KeywordSearch

 

It'd be a lot easier to throw a jumper cable in under the seat and not worry about it. I've left my truck "On" in accessory mode for a few hours while meticulously detailing it and my battery only got "low". As long as you start the truck and let it run for a minute or two once every 30 minutes or so, you'll be fine.

 

after a while of looking around for exactly what I want I found this:

http://www.helmarparts.com/product_p/906d12hg.htm




the reason I want something thats pretty precise like this is that I'll be running an amp, flipout screen, ipod, and a ps2 off of my battery and I really have no clue how fast those things will drain it.

 

I'm pretty sure the one you selected is probably the least precise when compared to sweeping dial meters. There are only a few LED segments, and no markers. How can you tell the volts when there are 10 LED segments and the gauge is marked 0 to 1? You get the same info from the stock gauge and at least it has more steps.

Things to read:
http://hp.autometer.com/techtips/faq...erammeter.html

http://www.oldholden.com/possible/in...ter_vs_ammeter

http://en.wikipedia.org/wiki/Voltmeter

http://engineering.wikia.com/wiki/Voltage

 

but this is like a sweeping dial in a sense, its always shows you how much left. Cause where ever the gauge is it basically says that there is either 90 or 80% left and it moves down with the battery life. I think it's alot better for easily knowing how much is left.


this is the best way to check how much is actually in the battery, not necessarily the volts. They refer to them as battery "fuel" gages because they are used for things that run off of primarily battery such as certain fork lifts of that type. I dont think it really matters how many volts just as long as there is more then 10-20% of the battery life "fuel" left.

 

I'm not sure how to respond here, other than suggesting you read up on how batteries work. They aren't like fuel tanks in that you can have a gauge that tells their remaining capacity.

An automotive battery will do it's best to hold "charge", and keep it's output constant at 12 volts. As it reaches the end of it's "charge", that output voltage will drop quickly. Batteries are tested on their ability to hold a constant voltage output over a certain period of time. They are also tested on their ability to hold this charge while not producing output. When a battery cannot hold a steady output voltage, or cannot store a "charge"; then it's time to replace it. Using a voltmeter gives you the ability to see the current output voltage of a battery, and how long it can hold that steady voltage. My meter shows around 14 volts as the engine charges the battery; then it's around 13-12 volts when running just off the battery. After a period of time, that will drop to around 10 volts, and it's time to start the engine. The amount of time that my battery can produce 12-13 volts determines the "health" of my battery. After a few years, that time will decrease as the battery ages. If I notice that my output voltage drops quickly to around 10-11 after I turn the engine off, then it's time for a new one.

I use a graduated sweeping gauge because I want a good visualization of my battery's output voltage. I want to know if it's producing 13 volts or 12.5 volts. You can't get this kind granularity on a 10 segment LED display. I'm not saying the LED display isn't a good gauge, but it's just not accurate enough if you want something to replace the stock voltmeter in your gauge cluster. There are some computerized LED displays that will actually monitor the battery over time, and can give good indications of it's projected capacity, but you won't find those in the $30-$40 price range. Most are for aviation or commercial applications, and they aren't cheap.