[Tagara]

I have a 2008 trail blazer 4.2 engine
this morning i went to start vehicle and starter had clicking sound no start but lights were dim and i dont drive this vehicle very often at all. i do have battery on a trickle charger ( optima 1 .5amp)
1) Battery showed 20 percent charge on my battery charger. I than charged it to 100 percent..vehicle started. i let it run for about 15 minutes and shut off..i did not drive it

2) I restarted vehicle and looked at the gauge and it was showing 14.4 volts i shut off and restarted showed about the same voltage..i turned the headlights on and fan blower on 5 setting and voltage voltage went down to around 13.5 rising climbing to around 14.2 on dash gauge.

3 shut vehicle off,,tried to restart and battery was dead

4 i know i should have probably driven vehicle as to maybe let it charge battery better.

5 i bought this vehicle 2 years ago with only 117 thousand miles on it..i have only put about 1200 mile on it since i bought it.the battery was replaced two years before i bought vehicle.

6 so i just recharged battery too 100 percent and vehicle started right up..let vehicle run for 20 minutes at idle shut off and once again dead..do i need an alternator ??

 

[TJBaker]

At 4 years old you may need a new battery more than a new alternator.

 

[Tagara]

At 4 years old you may need a new battery more than a new alternator.

TY for the quit response,,,i am still up so i just ordered an obd2 kam that i can connect to my motorcycle battery in case i have to change battery,,i have paid attention to what can happen to the ac actuators if i dont have a backup battery source prior to removing battery.i wish i knew if i could jumpstart the trailblazer and remove one cable and see if truck would keep running on the alternator..than i would know for sure, i wont dare do that unless i was advised lol

 

[TJBaker]

have paid attention to what can happen to the ac actuators if i dont have a backup battery source prior to removing battery

Well you just had the experience of trying to start the truck and the battery was dead. Twice (correction, 3 times) if I read your message correctly. This is exactly the same situation that will exist when you remove your battery. The HVAC system resets. In fact even if there is still some power in the battery and the dash lights and such come on but when you try to crank the engine there is not enough battery power,, the voltage drops too low and if you have a CD player you will likely hear that recycle also.

In short, when trying to crank the engine, a 'dead' or very low battery is equal to removing the battery insofar as all the various controller modules like the HVAC system and such will reset due to the voltage dropping below the required threshold.

So you quite likely have zero to gain here with the KAM at this point.

 

[Mad Russian]

Why not charge the battery fully and keep it on a trickle charge.
Get a "smart" trickle charger that won't overcharge the battery.

 

[Ravalli Surfer]

i wish i knew if i could jumpstart the trailblazer and remove one cable and see if truck would keep running on the alternator..than i would know for sure, i wont dare do that unless i was advised lol

Never let the alternator run without the battery as a load on it to keep it from frying either its inside electronical parts and pieces ---- or damaging the computer that drives it.

Alternators, among other things do NOT LIKE not having a voltage reference from the battery to keep it from jacking itself up trying to compensate from what it can only assume is a dead battery.

The battery, as a great big choke and capacitor, is also the repository of Voltage and if you take that information away --- well ... $$$ goes outta your account on account you killed some expensive parts -- and secondarily --- NOW you cannot diagnose them as individuals --- 'cause you damaged too many or too much of the support staff.

The parts stores make enough money as it is --- don't feed the ex-burger flipper inmates.

 

[Tagara]

Never let the alternator run without the battery as a load on it to keep it from frying either its inside electronical parts and pieces ---- or damaging the computer that drives it.

Alternators, among other things do NOT LIKE not having a voltage reference from the battery to keep it from jacking itself up trying to compensate from what it can only assume is a dead battery.

The battery, as a great big choke and capacitor, is also the repository of Voltage and if you take that information away --- well ... $$$ goes outta your account on account you killed some expensive parts -- and secondarily --- NOW you cannot diagnose them as individuals --- 'cause you damaged too many or too much of the support staff.

The parts stores make enough money as it is --- don't feed the ex-burger flipper inmates.

After i read your reply,,i decided deff not to jump start and remove battery cable to see if it would run. i then went down and bought a new battery..plugged my OBD2 Kam into data port and hooked up my motorcycle battery to it. installed battery and all is normal. I have to admit the pcm controlling alternator is very new to me..I did a lot of research on it...when i first started the truck was about 14 volts and after driving for 30 minutes it went down a lot lower,,restarted truck and voltage jumped back. all is working as advertised.I could have old battery was about 5 years old.when i removed it..was an AAA battery dated 12/15 so is over 7 years old..

1) last question i used to keep my optima trickle charger on it because sometime i do not drive it as much,,should i keep that on it or i would i be better off driving it for a good 30 minutes once a week or more. The reason i ask this,,on my 2009 miata i went through two batterys in two years..i very seldom drove it and left on trickle charger,,when i bought last battery my wife started driving it all the the time for last 3 years and no battery problems. i think i just answered my question..i need to drive my trailblazer a lot more,,

 

[Mad Russian]

The computer on the TB measures how much is taken out of the battery and then controls the alternator to put back what is taken out, that's why you will see the voltmeter drop when the battery is charged.
If you use a dumb maintainer it can overcharge the battery, that's why I suggest a smart maintainer, like this one:
NOCO GENIUS5, 5A Smart Car Battery Charger, 6V and 12V Automotive Charger, Battery Maintainer, Trickle Charger, Float Charger and Desulfator for AGM, Motorcycle, Lithium and Deep Cycle Batteries https://a.co/d/3Erf69A

 

[Ravalli Surfer]

Did you read about the High Freq excitement of the alternator to induce it to charge much harder at idle?

It's very fascinating ... and IIRC ... it was available on the Cads and big Buicks/Olds/Pontiacs in 1975 or so.

 

[miketexas]

I have a 2008 trail blazer 4.2 engine
this morning i went to start vehicle and starter had clicking sound no start but lights were dim and i dont drive this vehicle very often at all. i do have battery on a trickle charger ( optima 1 .5amp)
1) Battery showed 20 percent charge on my battery charger. I than charged it to 100 percent..vehicle started. i let it run for about 15 minutes and shut off..i did not drive it

2) I restarted vehicle and looked at the gauge and it was showing 14.4 volts i shut off and restarted showed about the same voltage..i turned the headlights on and fan blower on 5 setting and voltage voltage went down to around 13.5 rising climbing to around 14.2 on dash gauge.

3 shut vehicle off,,tried to restart and battery was dead

4 i know i should have probably driven vehicle as to maybe let it charge battery better.

5 i bought this vehicle 2 years ago with only 117 thousand miles on it..i have only put about 1200 mile on it since i bought it.the battery was replaced two years before i bought vehicle.

6 so i just recharged battery too 100 percent and vehicle started right up..let vehicle run for 20 minutes at idle shut off and once again dead..do i need an alternator ??

I got an idea, test the bat and the alt.

 

[Tagara]

The computer on the TB measures how much is taken out of the battery and then controls the alternator to put back what is taken out, that's why you will see the voltmeter drop when the battery is charged.
If you use a dumb maintainer it can overcharge the battery, that's why I suggest a smart maintainer, like this one:
NOCO GENIUS5, 5A Smart Car Battery Charger, 6V and 12V Automotive Charger, Battery Maintainer, Trickle Charger, Float Charger and Desulfator for AGM, Motorcycle, Lithium and Deep Cycle Batteries https://a.co/d/3Erf69A

TY for that info..read 5 reviews and that will come in handy,,it is now on order from amazon thanks again..love the features it has

 

[Mad Russian]

TY for that info..read 5 reviews and that will come in handy,,it is now on order from amazon thanks again..love the features it has

I have one of their jump-start units. Pretty small, but cranks my diesel generator like it was nothing.

 

[dougp01]

You might try checking at your local automotive parts house (AutoZone, O'Reilly, etc.). They often have a battery tester behind the counter and will help you to learn if the battery is good or not. However, you need to put good a topping charge on that battery before it's tested. That is, more than just a few minutes of idling in the driveway. If you can, try an overnight charge, at the 2 Amp setting. And, do not leave it on the High Rate, Fast Charge, or the Start setting for more than a few minutes.

Often as not, I've found some economical solutions that are fairly common. First of all, check the belt that drives the alternator pulley. If it's at all loose, frayed, or its surfaces are glazed, it may not be able to charge the battery. Second, clean the battery posts and cable connectors with a brush specifically made for that job, any contamination or corrosion can be resistive to charging current. Take note of the cables too, if they are damaged or not. If all this and a battery test checks out, then your alternator may indeed be the problem, which is the most expensive answer, so don't just start swapping out.

One tip, if you put the battery on a charger, in a fully discharged state, and it indicates fully charged in only a few minutes, it is likely the battery no longer has the capacity to hold enough charge to reliably start your car, regardless of how young or old it is. Same goes for any type of rechargeable battery (even your cell phone), if it used to take a few hours and now it recharges way too fast, it's likely no good.

Modern low maintenance batteries have a way of going out unexpectedly. If the battery fairly new, then the auto parts should be able to pro-rate it for you.

~doug

 

[Tagara]

You might try checking at your local automotive parts house (AutoZone, O'Reilly, etc.). They often have a battery tester behind the counter and will help you to learn if the battery is good or not. However, you need to put good a topping charge on that battery before it's tested. That is, more than just a few minutes of idling in the driveway. If you can, try an overnight charge, at the 2 Amp setting. And, do not leave it on the High Rate, Fast Charge, or the Start setting for more than a few minutes.

Often as not, I've found some economical solutions that are fairly common. First of all, check the belt that drives the alternator pulley. If it's at all loose, frayed, or its surfaces are glazed, it may not be able to charge the battery. Second, clean the battery posts and cable connectors with a brush specifically made for that job, any contamination or corrosion can be resistive to charging current. Take note of the cables too, if they are damaged or not. If all this and a battery test checks out, then your alternator may indeed be the problem, which is the most expensive answer, so don't just start swapping out.

One tip, if you put the battery on a charger, in a fully discharged state, and it indicates fully charged in only a few minutes, it is likely the battery no longer has the capacity to hold enough charge to reliably start your car, regardless of how young or old it is. Same goes for any type of rechargeable battery (even your cell phone), if it used to take a few hours and now it recharges way too fast, it's likely no good.

Modern low maintenance batteries have a way of going out unexpectedly. If the battery fairly new, then the auto parts should be able to pro-rate it for you.

~doug

ty for all the info..i replaced the batter and all is well now,,,old battery was toast,,old battery was going on 8 years old.

 

[Ravalli Surfer]

3 years is typically 1/2 life for modern batteries.

If you test the battery - install a KAM FIRST and remove one of the battery cables AT THE BATTERY and make sure the battery tester knows what he's doing.

A good friend who runs an RV parts outlet, sells big-expensive Deep Cycle L/A batteries all day long to people who had them tested elsewhere by "reputable" shops.

They test out perfectly when I get to check a few out once in a while at his place. I use a carbon pile to load them sufficiently to test their top and bottom charge .... something the digital testers cannot do ---- because the Deep Cycle batteries are only used for the living area of the RV ... not starting them.

Selling new, expensive batteries to ignorant people because of faulty testing procedures is big business at parts houses.

Me selling perfectly good-previously misdiagnosed batteries is big business too.

 

[Tagara]

3 years is typically 1/2 life for modern batteries.

If you test the battery - install a KAM FIRST and remove one of the battery cables AT THE BATTERY and make sure the battery tester knows what he's doing.

A good friend who runs an RV parts outlet, sells big-expensive Deep Cycle L/A batteries all day long to people who had them tested elsewhere by "reputable" shops.

They test out perfectly when I get to check a few out once in a while at his place. I use a carbon pile to load them sufficiently to test their top and bottom charge .... something the digital testers cannot do ---- because the Deep Cycle batteries are only used for the living area of the RV ... not starting them.

Selling new, expensive batteries to ignorant people because of faulty testing procedures is big business at parts houses.

Me selling perfectly good-previously misdiagnosed batteries is big business too.

Ok i was not going to tell this story..The other day when i was changing out my battery ( on the advice of others and yourself ) my neightbor who lives about 7 houses down saw me changing out my battery He owns a 2009 4.2 trailblazer.

I had just finished the install and he ask me why i did it..so i tell him and sees my OBD2 Kam hooked up to my motorcycle battery.

I tell him why it is needed to keep memory alive and most importantly for the famous HVAC control system

So he proceeds to tell me how his alternator is over charging his battery at 14.8 and he has been jump starting his car everyday.. I instantly cringe. as he tells me he is going to pick up a new alternator at advance auto. i said how about i take off the battery cover and check date on battery. he agrees..the battery is over 8 years old..so i tell him got get a new battery and bring it back. I will put it in for you and hook up my KAM. that will most likely fix it

so he goes to advance auto..buys an alternator and new battery. puts them in himself comes back and tells me his heat and ac is all messed up..he has gone back to Advance and told them..guy at advance says his alternator burnt up actuators.

i said this is why i told you why a KAM is needed. his trailblazer has 192 k miles on it. i told him this will be an expensive fix.

 

[miketexas]

I disconnected batteries all time at my shop and never had any problems.