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Old 04-27-2012, 08:57 PM
 
13 posts, read 33,069 times
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I have a 1998 isuzu rodeo and the battery in it is only 1 year old. i have ran parasitic draw tests and that is not the case here. the battery holds its charge no problem. the battery will read 12.6 volts with the negative terminal disconnected, when i reattatch the negative terminal the voltage coming out of the battery immediately drops to 10.2 volts; i read this is caused by a short somewhere in the wiring. how do i find this short? does anyone know?

--Thanks, Charlie
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Old 04-27-2012, 09:11 PM
 
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Assuming that the key is off when you connect the negative battery cable, there are only a few power consumers that are "live" when you make the connection. So you can isolate the large draw on the battery to those areas of the car.

Other than looking around for obvious failed cables, burned through insulation areas, and so forth ..

The best tactic would be to get a power distribution wiring diagram for the car and start isolating the main power supply cabling until you eliminate the power draw.

Have you had the battery draw tested so that you know how many amps it requires to drop the voltage down to the lower value? It would take a rather large draw ... probably on the order of several hundred amps at 12v, to drop a fully charged battery down to 10.2 volts. That requires some large cabling to deliver that much power, such as the positive cable to the starter.
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Old 04-27-2012, 10:22 PM
 
13 posts, read 33,069 times
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It isn't actually constantly drawing power I have tested it. I think somewhere the POSITIVE and NEGATIVE wires are touching somewhere so when there is power flowing through both wires, the battery (POWER SUPPLY) is shortening out, but no fuses are being blown. Any Ideas?
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Old 04-28-2012, 05:43 AM
 
11,548 posts, read 52,908,820 times
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Quote:
Originally Posted by cstuaa View Post
It isn't actually constantly drawing power I have tested it. I think somewhere the POSITIVE and NEGATIVE wires are touching somewhere so when there is power flowing through both wires, the battery (POWER SUPPLY) is shortening out, but no fuses are being blown. Any Ideas?
Re-Read Post #2 above.

No fuses being blown yet a large power draw means that there's a short in a positive cable between the battery and the unfused places which can draw power. A positive cable to the starter could be such a location, or a positive cable to a power distribution box.

Did you draw test the battery yet to know how many amps of current it takes to drop the battery voltage down to 10 volts?
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Old 04-28-2012, 10:01 AM
 
2,025 posts, read 4,139,756 times
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I don't think you really understand the concept of a parasitic draw test. And a fully charged battery is closer to 13.2 than 12.6.
Here's the reality, if you had no draw the voltage would not drop when you connected the cables. Dropping to 10 volts is a significant power draw and quite frankly you would see sparks and the cable would heat up very quickly. What I'm thinking is that you have a battery with a bad cell that drops to 10 v under the normal parasitic loads a modern vehicle has, clock, security system, remote locks, etc. A fully charged healthy battery will maintain over 10 volts when engaging the starter, your battery won't hold 10 volts running the clock. Start there!
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Old 04-28-2012, 11:11 AM
 
13 posts, read 33,069 times
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Parasitic Draw Test showed that there was 25MA being drawn when the car was off. Is that too much?
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Old 04-28-2012, 11:28 AM
 
2,025 posts, read 4,139,756 times
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Quote:
Originally Posted by cstuaa View Post
Parasitic Draw Test showed that there was 25MA being drawn when the car was off. Is that too much?
that's not much at all, about right for a clock. That's not enough to drain a healthy battery.
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Old 04-28-2012, 11:39 AM
 
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Then any idea on what the problem is?
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Old 04-28-2012, 11:58 AM
 
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Can you try a different battery and see if you get the same results? Maybe borrow one from another person's car for testing?

Have you tried jump starting?

I think a battery can fail in a way that it shows pretty much charged (full charge is 12.75 volts of more with nothing connected), but then you connect anything, even a small load, then the voltage drops quite a bit and it will not power anything.

So I am wondering... Is it the car or is it a bad battery. (Don't assume anything! Just because the battery is new does not mean it is not bad. A wise person once told me that whatever you are assuming is good... Well that is probably what is bad in some situations! )
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Old 04-28-2012, 12:03 PM
 
13 posts, read 33,069 times
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Quote:
Originally Posted by Billy_J View Post
Can you try a different battery and see if you get the same results? Maybe borrow one from another person's car for testing?

Have you tried jump starting?

I think a battery can fail in a way that it shows pretty much charged (full charge is 12.75 volts of more with nothing connected), but then you connect anything, even a small load, then the voltage drops quite a bit and it will not power anything.

So I am wondering... Is it the car or is it a bad battery. (Don't assume anything! Just because the battery is new does not mean it is not bad. A wise person once told me that whatever you are assuming is good... Well that is probably what is bad in some situations! )
-Jump Starting Works Instantly
-Borrowed a Brand New Battery From my dad, he just bought it and hasnt used it yet. When i use the battery i borrowed the car works fine.
- But i have a feeling it's not the battery because the one that i have that was in the car is the second battery i have bought in the last 3 months...the original stopped working so i put this battery in and this battery doesnt work either..both batteries did hold charge when i put them in.
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