Landracing Forum
Misc Forums => NON LSR Posting => Topic started by: Clay Pitkin on August 21, 2013, 12:10:06 AM
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Greetings:
I have a question. On my racer I have a 12 Volt battery. I want to in-expensivly have a amp meter put on to monitor how many amps I used, or have left.
I have a volt meter on the car, but it will read 12 volts becuase I have a 12 volt battery.
Is there an in-expensive way of doing this?
Also, I do not run a alternator as I run a snowmobile engine for power. I am trying to figure out a rectifier as we speak, just looking for something fast and easy, as WOS is in a couple of weeks.
TIA
Clay
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Clay, I really doubt it will be an issue. If you're running so many circuits that you're drawing your battery down to 0 amps, you're voltage would have long been below what you would need to drive whatever it is you're running on electricity.
I was getting 4 runs per recharge, and it only took 30 minutes on the charger to be back to full force. You can do that in line while you're waiting.
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We use this monitor on dragbikes, small, easy to install. this, or something similar might be worth looking into. Granted it is not a gauge, just three LED's, but will give you a battery status at a glance.
http://www.dynaonline.com/skins/products/accessories/Dyna_Monitors/
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Greetings:
I have a question. On my racer I have a 12 Volt battery. I want to in-expensivly have a amp meter put on to monitor how many amps I used, or have left.
I have a volt meter on the car, but it will read 12 volts becuase I have a 12 volt battery.
Is there an in-expensive way of doing this?
Also, I do not run a alternator as I run a snowmobile engine for power. I am trying to figure out a rectifier as we speak, just looking for something fast and easy, as WOS is in a couple of weeks.
TIA
Clay
Clay;
A voltmeter will show you a crude estimate of the charge left in the battery but an ammeter will only show how many amps that you are pulling out of the battery.
Batteries are rated in amp-hours so you would need to know how long you have pulled that current out of the battery. Two things complicate this-- the amp-hour rating is specified under certain amp load conditions (higher amp loads reduce the amp-hour rating of a battery) and the rating is not constant over temperature or over the life of the battery. A "12V" battery is only nominally 12 volts. Under charge it is around 13.8V depending on temperature and after charging the voltage drifts down to a little over 12V. As the battery supplies current to a load, its voltage gradually decreases and as it nears exhaustion, its voltage drops more rapidly.
I'd suggest buying a little digital volt-ohmmeter from Harbor Freight ($4.99 on sale, sometimes $2.99) and using it to determine the battery's state of charge. Whatever you do, don't discharge the battery completely; that will eventually kill it. A deep-cycle battery is more resistant to this but it is still something to avoid.
Voltage curves depend on many things, including the battery chemistry, but if the voltage is below 11.5V or so it will need to be charged.
I don't understand why you need a rectifier.
Regards, Neil Tucson, AZ
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Neil has it right -- there's no true way to measure how many amps are left in a battery. You can get an indication of what is likely to remain by measuring the voltage, but since that doesn't decrease linearly as the battery discharges - it'll only give you a rough indication of remaining charge.
I do not know how "remaining battery charge" is measured in things like our laptop. It's got a small icon that show percent of remaining charge. I've never tried to figure out if it is accurate. And even if it is -- the battery in the computer is probably way different than one in your race vehicle, so it wouldn't necessarily give comparable results.
You could come up with some kind of a good number, though, by measuring two things separately and using some math to get your figure for remaining capacity. First - measure the current draw while operating, and second, measure how long it's drawing that amount. If the engine has an electric starter it'll draw quite a big amount for the seconds that the starter is running (maybe 10 seconds? Maybe 4 tries at 15 seconds each? Whatever. . .). And the amount the engine draws while running will likely be a relatively small amount for a longer time (3 minutes or so for a bit of warmup and a 3-mile run down the short course plus a bit of time for your turn-out.
I have plugged in some W A Guesstimate numbers. Yours may be wildly different.
Battery states 300 amp-hour reserve.
20 seconds of 100 amp* draw = .55 amp hours
4 minutes of 10 amp* draw = 6.66 amp-hours
Result: You've used about 6 1/4 amp-hours, or about 1/16 of your battery's stated reserve. Allowing for dropping voltage as the 100 amp hours is/are used up -- I'd hazard to guess that instead of the implied 16 start/run events -- you might get eight of 'em before the battery is too tapped-out to crank the engine.
In other words, it ain't gonna be easy to figure out how much you've got remaining -- no matter how you do it. Best of luck. C U at WoS.
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Hey Clay
Don't do it
Don't put an Amp Meter on your bike
For them to work, you have to run all the current thru them
I work with English and Italian bikes, and the guys with the English bikes always want an amp meter, and I always say no
I could wire up a regulator for you but I am on the other side of the planet.
They are usually pretty basic with between four and six wires and I should be able to help you with it, even from here
G
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Clay, there are some things an ammeter will show you better than anything else. The one I use for trouble shooting is + or - 60 amps and is made by VDO. I got it from a Volkswagen specialist. Not a VW dealer, but one of those guys that is a real enthusiast and has a little shop. They are hard to find. The needle should stay around the zero in almost all circumstances with most modern charging systems unless there is a problem or you wired something up the wrong way.
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What about the use of a hydrometer?
THR
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Or what about a pentameter.......?
that is the question..... :roll:
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Or what about a pentameter.......?
that is the question..... :roll:
It's OK if it is iambic :-D
Regards, Neil Tucson, AZ
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Thanks, Neil. My fresh, hot cup of tea is now partially coating the keyboard....... :-D
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This is intended for the RC folks but it appears to be able to be configured to show either watt-hours or amp-hours.
http://www.rc-electronics-usa.com/docs/wu100v2_user_manual.pdf
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In the 1930s at least some Fords had voltmeters instead of ammeters .
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Thanks, Neil. My fresh, hot cup of tea is now partially coating the keyboard....... :-D
boo tea? or not boo tea?
:wink:
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Most, if not all, large diesel trucks use volt meters instead of amp meters. If you turn on everything that's on when running, voltage will show the condition of the battery. If voltage is way low, so is battery. Batteries will show 12 volts at rest without a load, even if they're down.
Ron
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Our 2009 GMC pickup is equipped with a Duramax diesel - and a voltmeter on the dash. So was our '04. And in both trucks the "normal" voltage showed about 14 - 14.3 (as close as I can interpolate the hashlines in the display). I've never put a more calibrated meter on the system to see if it really is running at 14+V, but - our truck doesn't have an ammeter, just a voltmeter.