Parasitic Demand?

[outback]

My '02 Trailblazer EXT had a dead battery. I was surpised since it was a 72 month battery. The truck is only two and a half years old with 36000 highway miles on it. I have heard that GM trucks are very succeptable to "parasitic demand". I'm not real familiar with this term. The truck is equipped with OnStar and a DVD player. I understand that the OnStar can be a drain on the battery, but I was very surprised to see it dead in only a short time. What is "Parasitic Demand?" And are GM trucks more prone to this problem?

[GM-Tech]

My '02 Trailblazer EXT had a dead battery. I was surpised since it was a 72 month battery. The truck is only two and a half years old with 36000 highway miles on it. I have heard that GM trucks are very succeptable to "parasitic demand". I'm not real familiar with this term. The truck is equipped with OnStar and a DVD player. I understand that the OnStar can be a drain on the battery, but I was very surprised to see it dead in only a short time. What is "Parasitic Demand?"  And are GM trucks more prone to this problem?

 

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Parasitic draw on a battery is a fact of life with all vehicles these days, not just GM or Chevy. Clock and radio presets need to be retained, other modules in the system (and there can be many of these!) require tiny amounts of power. I'm sure Ford, Chrsler, Toyota, etc., use just as many computers and therefore have the same parasitic loads.

 

However, in a properly operating Trailblazer, I typically see somewhere in the range of a 15 mA (milliamp) drain. This is almost nothing and would take several weeks to drain a fully charged battery. With Onstar, it's a bit complicated, but initially, the Onstar wakes up every 9 minutes. That's because all modules in the vehicle "go to sleep" after a short time so they don't cause excessive drain. If the Onstar module didn't periodically wake up, Onstar could not unlock your vehicle for you when you leave your keys inside because the module would be asleep and unable to receive commands. So, it wakes up occasionally and then goes back to sleep. After so many hours of inactivity (40 I think, but don't quote me) it doesn't even do that. So if you lock your keys in your TB at the airport and go away for a week, don't expect that Onstar will be able to unlock it when you get back.

 

More likely, it's just battery time. 2.5 years is actually pretty darn good. I'm surprised it hasn't been replaced at least once for an acid leak. I'm not quite sure where you got that it was a 72 month battery. You get that kind of warranty if you purchase a delco battery, certainly not on the original battery, but in any case, that doesn't mean it actually lasts that long! That'll be the day.

[outback]

My '02 Trailblazer EXT had a dead battery. I was surpised since it was a 72 month battery. The truck is only two and a half years old with 36000 highway miles on it. I have heard that GM trucks are very succeptable to "parasitic demand". I'm not real familiar with this term. The truck is equipped with OnStar and a DVD player. I understand that the OnStar can be a drain on the battery, but I was very surprised to see it dead in only a short time. What is "Parasitic Demand?"  And are GM trucks more prone to this problem?

 

<{POST_SNAPBACK}>

 

 

 

 

Parasitic draw on a battery is a fact of life with all vehicles these days, not just GM or Chevy. Clock and radio presets need to be retained, other modules in the system (and there can be many of these!) require tiny amounts of power. I'm sure Ford, Chrsler, Toyota, etc., use just as many computers and therefore have the same parasitic loads.

 

However, in a properly operating Trailblazer, I typically see somewhere in the range of a 15 mA (milliamp) drain. This is almost nothing and would take several weeks to drain a fully charged battery. With Onstar, it's a bit complicated, but initially, the Onstar wakes up every 9 minutes. That's because all modules in the vehicle "go to sleep" after a short time so they don't cause excessive drain. If the Onstar module didn't periodically wake up, Onstar could not unlock your vehicle for you when you leave your keys inside because the module would be asleep and unable to receive commands. So, it wakes up occasionally and then goes back to sleep. After so many hours of inactivity (40 I think, but don't quote me) it doesn't even do that. So if you lock your keys in your TB at the airport and go away for a week, don't expect that Onstar will be able to unlock it when you get back.

 

More likely, it's just battery time. 2.5 years is actually pretty darn good. I'm surprised it hasn't been replaced at least once for an acid leak. I'm not quite sure where you got that it was a 72 month battery. You get that kind of warranty if you purchase a delco battery, certainly not on the original battery, but in any case, that doesn't mean it actually lasts that long! That'll be the day.

 

<{POST_SNAPBACK}>