testing battery

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  #1  
Old 01-28-07, 09:35 AM
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testing battery

My car is fine but car engine start slower when temperature go below 0 degree. I want to test the battery and I have a general purpose voltmeters. Can I test the car's battery using a general purpose voltmeters? How to do it properly? What should I watch out for?
 
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Old 01-28-07, 10:48 AM
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Using your multimeter, with car running, you should have between 12-15 volts. If you have less then this, either your battery is to old, or your alternator is going. If your battery is over 4-5 yrs old, then it's probably time for replacement. It takes a lot of amps to start a cold car. Autozone type places will test alternator and battery for free.

Just touch your multimeter leads to each post, it doesn't really matter which color to what.
 
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Old 01-28-07, 11:04 AM
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Most DIY Auto Parts places will test it in the car

I agree if the battery is 4 years old, just replace it
And get a good one, with lots of CCA (cold cranking amps)

The grade of oil can affect how the engines starts when cold also
There should be a chart with the correct grade for the expected temps in the manual
Using "too thick" of an oil can cause hard cold starts
 
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Old 01-28-07, 12:39 PM
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A volt meter will tell you the voltage, but that's only part of the story. You need a load test to see the true condition of the battery. Some parts stores and most garages have a carbon pile load tester. That will give a good indication of the reserve capacity of the battery, which is what you need for cold weather starting.
 
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Old 01-28-07, 01:06 PM
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Cold weather is when hard starting will show up due to 5 things.

1. Battery
If 3 years and older. Batteries loose their peak cranking amps as they get older due to the plates in the battery being ate up. With your voltmeter you can test your battery to see what kind of shape it is in. First make sure it has a full charge. Pull the spark plugs wire off the plugs or disable the ignition system. Be sure that all cable connections on the battery and starter are clean and tight. Hook the meter to the battery and using the key turn to start and hold for 5 seconds while watching the voltmeter. If the volts drop below 11.5 volts replace the battery.

2. Starter
The starter could be dragging. The bushing in the starter are worn causing the starter to draw a huge amount of amps to turn the engine. Even with a new battery with a lot of amps this can be a problem. Unless you have a tester to do this test you will have to take the car or starter to a Auto parts store or re-builder to have the starter tested. Some can test the starter while still in the car. If you replace the starter do the test again and see the deference in the amp draw.

3. Oil
Not as big a problem as it use to be because of the multi grades of of oil. 10W-30W and 10W-40W are the most common. Some require 5W-30W. You hardly ever see a single weight of oil being used in autos anymore such as 30W. In colder temps you can move down in the weight of oil but follow what is suggested in the manual.

4. Engine needs to be in good to top shape for cold weather
Does the car have a lot of mile where as the engine has a lot of wear on it. If the compression is down some what it will not start as easy. Does it need a tune up. Plugs, plugs wires, filters, and injectors needing service. These are just the main points of a tune up but with the cars today there are many other things to check for. Unless you do most of the service work yourself and know your car what it likes and doesn't like (Like your wife ) it can and in most cases very hard to find the problem.

5. Fuel
At least once a winter put gas dry in the gas to get rid of water in the tank. A little water in the injectors/fuel line can stop you dead. To help (I said just help) to keep water out of the tank keep the fuel tank full. Moisture in the air in a low fuel tank will collect on the inside walls of the tank then you have a problem when the temp move below freezing.
 

Last edited by Get RRR Done; 01-28-07 at 01:36 PM.
  #6  
Old 01-28-07, 06:30 PM
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"Just touch your multimeter leads to each post, it doesn't really matter which color to what."

It does matter with most multimeters as this is DC, not AC. Black to ground, red to hot.
 
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Old 01-28-07, 09:05 PM
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you cant really test it with a voltmeter you can do some test with a voltmeter like check charging voltage and battery voltage but on any car that starts and runs fine voltage is ok to begin with so its kinda pointless to be checking voltage when your only complaint is that it cranks a little slower in cold weather.
a load test on the battery is the only sufficient test, where a load of 1/2 the cca of the battery is placed on the battery for 10 seconds at which voltage must remain above 9.6 volts if it falls below 9.6 volts you could use a new battery.
that being said it is perfectly normal for most engines to crank over a little slower in cold weather if you have had temperatures below 0 and you have not ever had to jump start your vehicle your battery is probably ok, but if you want it tested try a parts store or shop that can put a load test on it as it is the only way to tell if its up to par.
 
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Old 01-28-07, 10:40 PM
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bejay
Yes you can test a battery with just a voltmeter while cranking over the engine. One has to disable the engine from starting by disabling the ignition. In most application if voltage on the battery drops below 11v while cranking the engine the battery is weak for winter time when temp are 0 and below. In this test if the battery is down to 10v (cold weather) while cranking the engine the starter will turn the engine very slow and most likely not start. With your test on putting 1/2 the CCA load of the battery the voltage will drop even more. Most starters will not put that much of a load on a battery. That is why the voltage will be higher if the battery is in good shape. In the summer with a weak battery my work truck would start (5.8L 351 Ford engine) with only 10-10.5 volts while cranking and it better start fast. I had better have it replaced when it gets cold. That is why Voltmeters are put in cars today instead of charge/discharge gauges. A Voltmeter not only tell you if the battery is being charged. It also if you watch the voltmeter while cranking the engine will tell you the condition of the battery. If you have been keeping an eye on this you won't be stuck with a car that will not start on a cold morning.

When I have check batterys this way and went to get a new one, it was conformed by where ever I purchased the new battery. They would put their load tester on the battery.
 
  #9  
Old 01-29-07, 12:13 AM
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[1. Battery
If 3 years and older. Batteries loose their peak cranking amps as they get older due to the plates in the battery being ate up. With your voltmeter you can test your battery to see what kind of shape it is in. First make sure it has a full charge. Pull the spark plugs wire off the plugs or disable the ignition system. Be sure that all cable connections on the battery and starter are clean and tight. Hook the meter to the battery and using the key turn to start and hold for 5 seconds while watching the voltmeter. If the volts drop below 11.5 volts replace the battery. ]
I would say you replace alot of good batterys as i dont know of many vehicles that while cranking wouldnt drop below 11.5 volts or is it 11 volts as you 2 posts in this thread seem to differ, while the starter doesnt usually put as much load as 1/2 the cca its not uncommon for them to draw 100-300 amps and with the varying load a starter puts on a battery from one vehicle to another it isnt really a good test. think I will just stick with 1/2 the cca as its specific to the battery being tested and it is the common method used for years and hasnt failed me yet.
havent seen many vehicles with an accurate enough voltage guage that it would be of much use.
 
  #10  
Old 01-29-07, 06:53 AM
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I have stated that when taking the battery in for replacement I have had their load tester check the battery also.

When I run into a problem I don't run down to the nearest shop to have a bunch of tests done when in just 2-5 minutes I can have a very good idea what the problem is, battey condition and starter condition by doing a amp draw test on the starter by hooking up my amp meter in line with the battery and starter. In dash volt gauges are in most cases just a good indication of voltage, but if you know what the gauge reads when the battery is new and later on the voltage drops while cranking I would say the battery is becoming weak, the starter is dragging and/or a combination of both. Maybe not a true reading of the voltage but a very good indication of what is happing to have more accurate test done. So far I have bat 1000 with the above tests and has alway kept me on the road. In store/shop tests have alway confirmed the problem.

Maybe at times I assume too much of those asking questions with a problem. I assumed that Cyzpro knows that in zero weather the starter would turn the engine over slower and would be common knowledge.
 
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