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Old 03-14-2014, 03:24 PM   #1
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Battery Question

About 8 months ago I bought an engine battery from O'Reilly Auto. Normally I keep it connected to a 3 stage trickle charger but for the last 3 days I didn't have it connected to the charger. I checked yesterday and today and I'm getting a reading of 12.2. If I let the house batteries set for 4-5 days without being connected to shore power, I normally get a reading of 12.6--12.7. Do you think the chassis battery is going bad?

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RJ
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Old 03-14-2014, 04:09 PM   #2
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At 12.2v your batter is only 50% charged. This is extremely hard on
a starting battery and shows that you do indeed have a problem.

There are several possibilities: charger is
not working correctly, or you are unaware that you have a load on
the battery, or the battery is bad/has a weak cell/low on water.

We all have had batteries that were bad, especially the cheap ones.
You should have a warranty, and O'Reilly should be able to test
the battery for you, and that would help diagnose the problem.
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Old 03-14-2014, 04:50 PM   #3
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You can take the battery to most Auto parts shops and get the battery tested free. You need a load test, not just a voltage reading. You could also test with a specific gravity tester. Chassis batteries often have phantom loads on them, radio/clock memory, ECU, electric steps, etc. Try taking a cable off and put a test light or meter in the gap, see how big the parasitic draw is. While the cable is off, you might clean it up and do the same to the other cable too. Did you take the voltage reading directly from the battery terminals? If not, also clean ground connections.
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Old 03-14-2014, 07:36 PM   #4
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There are several loads that may be on the Engine battery.. On my motor home the steps are on the engine battery.. of course if I lock them in position they do not suck much, but if you leave them on automatic and open/close the door they draw power big time while moving. (motors are like that). The Engine control computer (Optional the Transmission control) the Dash Radio, and assorted other systems may be partially powered up all the time.
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Old 03-16-2014, 05:23 PM   #5
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To check for a parasitic draw draw do I disconnect the positive or negative cable? And then which end of the meter goes where?
Thanks
RJ
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Old 03-18-2014, 04:04 AM   #6
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There are two types of ammeters. One type you disconnect the + lead and insert the meter in series in the circuit. The second type you don't connect to the circuit. ..it has two half-round arms you simply open and close around a wire. It reads the current through induction.
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Old 03-18-2014, 10:01 AM   #7
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What I have is a volt meter which at one end is a small box which I place on the negative terminal and then a lead which I place on the positive terminal. I get a reading, 12.5v etc, on the small box. Is this something I can use or do I need to get a different/better meter? How would I use this one, if I can.
Thanks,
RJ
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Old 03-18-2014, 10:10 AM   #8
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Quote:
Originally Posted by Full.Monte View Post
There are two types of ammeters. One type you disconnect the + lead and insert the meter in series in the circuit. The second type you don't connect to the circuit. ..it has two half-round arms you simply open and close around a wire. It reads the current through induction.
Battery current measurements should not be attempted unless you know exactly what you are doing. It is not a simple task and must be done correctly.

Most of the second type (clamp meters) you find will only measure AC and don't work on DC. Better to open the circuit by removing the negative cable on an RV from its battery post and with everything off and the motor home unplugged from shore power, measure between the negative cable you removed and its post for any current. If using a decent digital meter you won't have to worry about polarity of the test leads. Don't use one of those Harbor Freight piece of crap meters to measure current draw.

If you are uncomfortable with using a meter for measuring current or still not sure what you are doing then don't do it. Take it to a garage and have them measure it. It is possible to do damage to the meter, battery, wiring, or yourself if a current measurement is attempted incorrectly and more likely than not, you won't get a second chance.
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Old 03-18-2014, 10:17 AM   #9
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Originally Posted by RJEV View Post
Full.Monte
What I have is a volt meter which at one end is a small box which I place on the negative terminal and then a lead which I place on the positive terminal. I get a reading, 12.5v etc, on the small box. Is this something I can use or do I need to get a different/better meter? How would I use this one, if I can.
Thanks,
RJ
You will need a meter that measures current although a volt meter will show if there is any voltage flowing once the battery circuit is opened.

From your questions I think you would be better off taking it to a garage and having them check it. As I said above it must be done correctly and you can do considerable damage if things are hooked up and tested incorrectly.
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Old 03-18-2014, 03:49 PM   #10
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"You will need a meter that measures current although a volt meter will show if there is any voltage flowing once the battery circuit is opened."

Voltage never has and NEVER will flow

Voltage is a measurement of pressure it does NOT FLOW
Current flows - NOT Voltage
When current flows a voltage drop is seen due to resistance

A simple current measurement which is indicated in Amperes aka Amps can easily be done with a low cost Clamp on DC meter (Temna - Sears- Etc.. many available for less than $50.00) however very low current levels will be difficult to see with a clamp on meter. Most DMM's will have a 10amp current measurement capability - Remove the negative battery cable - Hook the meter in series with the negative battery cable and where it was connected the ground. If more than 10amps is being drawn most likely nothing more than a fuse in the meter will blow.
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Old 03-18-2014, 04:28 PM   #11
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You are correct. I should have said if there is any voltage present. If there is then there should be some current also but you will not know how much by just measuring the voltage as it is only an indicator that something is drawing current and discharging the battery.
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Old 03-18-2014, 04:57 PM   #12
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Most clamp meters that will measure dc current are worthless for small currents in dc.

You can test by checking for light bulb change, if you can see the current change with one light turning on the meter may work.

The Fluke model we use is about 4 hundred bucks...

A harbor freight meter will work for this BUT read the instructions TWICE.

The voltage reading is static and no measurable current flows through the meter.

Think "thermometer", you are simply measuring amount of voltage.

For amps the lead is moved on the meter to a different position.

NEVER LEAVE IT PLUGGED IN HERE AFTER USE AND REMOVE IT ASS SOON AS YOU MAKE YOUR MEASUREMENTS!!!!!

REASON FOR WARNING...
The meter measures flow of electrons in the wire.

Think "gas pump", as electrons or current flows through the wire it is indicated in units called amps. Gas pump indicates gallons...

The meter acts like a jumper and connects the two points together...try to measure a voltage while configured for amps and you let the smoke out of something and it cannot be put back.

And just like food...let the smoke out and you are done...

Next issue is rush current.

There are usually filter caps that clean up the power residuals from alternator and switches.

These can draw some surges that can damage low buck meters.

You also may have a large load on that you are not aware of.

So a "spark test" is done.

Simply touch the cable back to see if you get a spark.

If it sparks repeat...sparks indicate a load and tiny sparks are small cap or noting to worry about while big one needs to be turned off.

Now with the general stuff stated...

You first turn everything off.

Locate all of your batteries and take photos first.

Now only the ground will be removed first as it is the safest way.

Remove ground on first battery to test.

Measure voltage on battery and note it.

Change configuration of meter to 10 amps.

Do spark test on ground wire.

Place red lead on battery "-" and black lead to ground wire.

Write down number.

Now leave this ground loose and reconfigure meter for voltage.

Check voltage on other battery.

Record this number .

Remove ground from battery and spark twst.

Configure meter for 10 amps.

Red to battery"-" and black to ground wire.

Read and record this number.

Repeat this process for every 12 volt battery system. (Two 6 volt count as 1one 12 volt) .

When all batteries are done then all ground connections should be disconnected at each battery.

Now safe to work on the positive post.

Check your photo so you can put everything back.

Masking tape makes good labels if needed.

Loosen the bolts and make it so all of the wires can be removed from the battery.

Once all of the wires are loose or disconnected from the positive side reconnect the ground wire for only that battery.

Now spark test each wire.

Configure meter for 10 amps.

Connect meter red lead to battery "+"

Connect the meter black lead to each wire that was connected to positive post one at a time and record that value.

Repeat until all wires done then remove ground.

Reconnect all wires then do rest of the batteries.

Reconfigure meter for voltage.

You now should have loads in amps for every wire from the battery.

If you have fuses you can remove fuses and use the meter in place of the fuse to measure current on the fused load as well.

This is a long post but it provides safe process to measure tye loads on the batteries.

Plenty of threads on taking it from here to chase the loads down.
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Old 03-24-2014, 04:19 PM   #13
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Thanks tony for your explanation. I have been having some battery issues myself, and your post was very helpful.
Chris
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Old 03-24-2014, 07:01 PM   #14
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You are welcome.

There are a ton of battery threads to read to help.

What issues are you having?
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