Alternator good or Bad ?
#1
Alternator good or Bad ?
Hey guys,
Last week my truck started to get kinda hard to start. Then one morning it was completely dead and did not even fire off.
I cleaned the terminals and tried again and still no result. So i checked the Batt Volts and both had about 12.5
Got out my load tester and the passenger side failed, Picked up a new motor craft battery from orilleys and all is good again.
The batteries i had or still have one in there were interstate 850cca 1000ca they are from Feb of 2014
Im Just curious if a week alternator could have been the culprit. Seems as I'm replacing my batteries every 2 to 3 years. Now i know how that goes but curious after watching my volt readings on my edge evolution monitor which is plugged into the obdll port. Just wondering if these are normal.
On start up i see 11.4v
after running for 5 min or so it creeps up to 12 or 12.5 and stays there for 10 min or so
Once i start driving it get up to 13 to 13.4
After driving for 30 or 35min to drop my son off hen i park or stop at a red light it drops to 12.4 12.6 volts.
So i started fooling around with a few things and heres what else i noticed
Driving @ 1500rpm with no ac and no lights i see 13.7 to 13.9
at idle no ac no lights 12.7
Driving with lights on and ac full blast 13.2 to 13.5
at idle with lights on and ac 12.2 to 12.4
This just dose not seem right. The alternator is pretty old but i don't want to replace it if its not broke kinda thing
So what do y'all think
Last week my truck started to get kinda hard to start. Then one morning it was completely dead and did not even fire off.
I cleaned the terminals and tried again and still no result. So i checked the Batt Volts and both had about 12.5
Got out my load tester and the passenger side failed, Picked up a new motor craft battery from orilleys and all is good again.
The batteries i had or still have one in there were interstate 850cca 1000ca they are from Feb of 2014
Im Just curious if a week alternator could have been the culprit. Seems as I'm replacing my batteries every 2 to 3 years. Now i know how that goes but curious after watching my volt readings on my edge evolution monitor which is plugged into the obdll port. Just wondering if these are normal.
On start up i see 11.4v
after running for 5 min or so it creeps up to 12 or 12.5 and stays there for 10 min or so
Once i start driving it get up to 13 to 13.4
After driving for 30 or 35min to drop my son off hen i park or stop at a red light it drops to 12.4 12.6 volts.
So i started fooling around with a few things and heres what else i noticed
Driving @ 1500rpm with no ac and no lights i see 13.7 to 13.9
at idle no ac no lights 12.7
Driving with lights on and ac full blast 13.2 to 13.5
at idle with lights on and ac 12.2 to 12.4
This just dose not seem right. The alternator is pretty old but i don't want to replace it if its not broke kinda thing
So what do y'all think
#3
Agreed but my question was about the charging system not how to replace batteries. I normally do it that way and have my entire life. But the 900cca tractor battery plus my 2 woulda put me up to 400 bucks and i was not in a position to drop that kinda coin. Years past always bought 2 at the same time even try and get the same month if i can. Just like chain and sprockets on a motorcycle they wear together i get that. But the funds went there to spend
#4
Hey guys,
Last week my truck started to get kinda hard to start. Then one morning it was completely dead and did not even fire off.
I cleaned the terminals and tried again and still no result. So i checked the Batt Volts and both had about 12.5
Got out my load tester and the passenger side failed, Picked up a new motor craft battery from orilleys and all is good again.
The batteries i had or still have one in there were interstate 850cca 1000ca they are from Feb of 2014
Im Just curious if a week alternator could have been the culprit. Seems as I'm replacing my batteries every 2 to 3 years. Now i know how that goes but curious after watching my volt readings on my edge evolution monitor which is plugged into the obdll port. Just wondering if these are normal.
On start up i see 11.4v
after running for 5 min or so it creeps up to 12 or 12.5 and stays there for 10 min or so
Once i start driving it get up to 13 to 13.4
After driving for 30 or 35min to drop my son off hen i park or stop at a red light it drops to 12.4 12.6 volts.
So i started fooling around with a few things and heres what else i noticed
Driving @ 1500rpm with no ac and no lights i see 13.7 to 13.9
at idle no ac no lights 12.7
Driving with lights on and ac full blast 13.2 to 13.5
at idle with lights on and ac 12.2 to 12.4
This just dose not seem right. The alternator is pretty old but i don't want to replace it if its not broke kinda thing
So what do y'all think
Last week my truck started to get kinda hard to start. Then one morning it was completely dead and did not even fire off.
I cleaned the terminals and tried again and still no result. So i checked the Batt Volts and both had about 12.5
Got out my load tester and the passenger side failed, Picked up a new motor craft battery from orilleys and all is good again.
The batteries i had or still have one in there were interstate 850cca 1000ca they are from Feb of 2014
Im Just curious if a week alternator could have been the culprit. Seems as I'm replacing my batteries every 2 to 3 years. Now i know how that goes but curious after watching my volt readings on my edge evolution monitor which is plugged into the obdll port. Just wondering if these are normal.
On start up i see 11.4v
after running for 5 min or so it creeps up to 12 or 12.5 and stays there for 10 min or so
Once i start driving it get up to 13 to 13.4
After driving for 30 or 35min to drop my son off hen i park or stop at a red light it drops to 12.4 12.6 volts.
So i started fooling around with a few things and heres what else i noticed
Driving @ 1500rpm with no ac and no lights i see 13.7 to 13.9
at idle no ac no lights 12.7
Driving with lights on and ac full blast 13.2 to 13.5
at idle with lights on and ac 12.2 to 12.4
This just dose not seem right. The alternator is pretty old but i don't want to replace it if its not broke kinda thing
So what do y'all think
If you have a DVOM. The attached may help with diagnosis.
#6
Agreed but my question was about the charging system not how to replace batteries. I normally do it that way and have my entire life. But the 900cca tractor battery plus my 2 woulda put me up to 400 bucks and i was not in a position to drop that kinda coin. Years past always bought 2 at the same time even try and get the same month if i can. Just like chain and sprockets on a motorcycle they wear together i get that. But the funds went there to spend
The problem COULD be a bad alternator killing the batteries, or bad batteries could have overworked/cooked the alternator. Either way, it sounds like something is wrong. Since you say you keep gong through batteries, I would guess the alternator is bad.
Many auto parts stores can test both the alternator and the old battery for you. I would pull the alternator, and have them test it in the store. Advance Auto Parts and Autozone both have the machines.
Break out the credit card and just fix it right the first time. You really should not have one brand new battery along with one that is 2 years old.
#7
If the other battery tested fine, it's fine. Yeah it may shorten the life of the new battery but one good 2 year old battery is not going to going to destroy a new battery. You load tested the old battery and it passed so I think it's time to forget about it.
You definatally have a charging system issue, and possibly a starter issue that may be the root cause of all the battery failures. The Starter may be pulling to many amps and shortening the life of the batteries. Check ALL connections real well and inspect the condition of the cables.
Someone on here will probably show up soon and post the procedure for checking the starter AMP draw, I can't find it at the moment.
And have the alternator tested, preferably by an auto electric shop. The parts store testers have let me down a few times on warranty issues, but for low output SHOULD be surficent to test your alternator.
You definatally have a charging system issue, and possibly a starter issue that may be the root cause of all the battery failures. The Starter may be pulling to many amps and shortening the life of the batteries. Check ALL connections real well and inspect the condition of the cables.
Someone on here will probably show up soon and post the procedure for checking the starter AMP draw, I can't find it at the moment.
And have the alternator tested, preferably by an auto electric shop. The parts store testers have let me down a few times on warranty issues, but for low output SHOULD be surficent to test your alternator.
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#8
#9
It isn't "necessary" to do a whole bunch of things, but it's best practices and will save money in the long run. Ya do what ya gotta do, but people should be informed about what's likely to occur.
Two batteries connected in series or parallel are just a larger battery. That's how they all work, whether in a flashlight or TV remote, a collection of cells is connected in various configurations to get the voltage and ampere specification desired. But each cell must be closely matched or there will quickly be trouble, the mismatched cells will start to leak or go into reverse polarity.
The problem with mixing and matching auto batteries (cells) is the internal impedance and state of charge won't be matched close enough and they will start to "fight" each other and start to outgass and boil electrolyte. It presents a difficult load for the alternator and voltage regulator.
Battery maintenance is very often neglected, and especially when multibattery setups are involved. It can get pretty spendy replacing alternators and batteries back and forth.
Two batteries connected in series or parallel are just a larger battery. That's how they all work, whether in a flashlight or TV remote, a collection of cells is connected in various configurations to get the voltage and ampere specification desired. But each cell must be closely matched or there will quickly be trouble, the mismatched cells will start to leak or go into reverse polarity.
The problem with mixing and matching auto batteries (cells) is the internal impedance and state of charge won't be matched close enough and they will start to "fight" each other and start to outgass and boil electrolyte. It presents a difficult load for the alternator and voltage regulator.
Battery maintenance is very often neglected, and especially when multibattery setups are involved. It can get pretty spendy replacing alternators and batteries back and forth.
#10
The statement seems to indicates to me the other battery (referring to both batteries) being deficient rather than just one.
There is no economic reason to replace a Battery that passes testing unless it is just over the acceptable limits of testing. And then, its always the customers choice when informed.
By this standard, every time I replaced a Battery in early Cummins V8 the customer would have spent over $2,000 + Labor for two banks of parallel 6v batteries in a series configuration on a 12v System. I would have been asked to leave. Or, for that matter $400 + Labor on every Powerstroke I worked on.
That's not accurate. Parallel Batteries achieve the same Volts while doubling the Ampere Hours (ah). For instance, our Trucks only require 12v and no more than 740 amps to start. But, the specification is for 2 (two) 800+ ah Batteries. By doing this, when the batteries fall below 50% amperage while cranking, the reserve 50% of each produce 800 ah (amps) (720 + 10% additional reserve).
Series Battery configurations double the Voltage and maintain the same single rated ah capacity. This is seen on many OTRT from before the 50's thru the 80's. And, still used in several heavy-duty applications such as Back-Up Generators, Golf Carts, Hybrid, etc..
Reversing Polarity of a FLA / SLA Battery is a general myth. The only way for this to happen would be to completely discharge the battery, either by leaving the key on, or by an unnoticed dead short that completely dissipated the charge over a few days. After that happened it would appear to be a dead battery, nothing more.
Cells is FLA / SLA Batteries must be within .50sg or 0.05v. during the testing process to pass. Any more and they would fail. Therefore, replacing the battery is a waste of dollar$.
The regulator on our trucks (differ than todays PCM/ECM controlled units) is either open or closed, charging or not when operating properly.
All FLA / SLA Batteries "Off-Gas", all the time, when being charged. But, more noticeable when voltage is in excess of 15v. Its a by-product of the cells chemical reaction when the ion process is occurring with two dissimilar metals. This is how Sulfation (the by-product) occurs which eventually leads to an exhausted battery life because the plate area is covered and electrolysis no longer occurs. The best way to prevent this is by for the average owner is to ensure the batteries have the correct level of denatured water and not lower than 55/45 Acid to Water Ratio.
* On a side not, charging a battery intermittently at 16v helps reduce the process when done correctly over several hours.
Many Battery Maintainers offer this function over the counter.
Many, if not most of the OTRT and Hybrid Vehicles have them installed at the factory as a combination maintainer / conditioner to get maximum life.
With the only special tool being a Paper Clip, and a Soldering Iron, they're rebuilt rater easily for about $20.
#12
What is likely to occur? I see this as mixing Apples and Oranges referring to the OP. Or, Battery replacement as a whole. The statement seems to indicates to me the other battery (referring to both batteries) being deficient rather than just one. There is no economic reason to replace a Battery that passes testing unless it is just over the acceptable limits of testing. And then, its always the customers choice when informed. By this standard, every time I replaced a Battery in early Cummins V8 the customer would have spent over $2,000 + Labor for two banks of parallel 6v batteries in a series configuration on a 12v System. I would have been asked to leave. Or, for that matter $400 + Labor on every Powerstroke I worked on. That's not accurate. Parallel Batteries achieve the same Volts while doubling the Ampere Hours (ah). For instance, our Trucks only require 12v and no more than 740 amps to start. But, the specification is for 2 (two) 800+ ah Batteries. By doing this, when the batteries fall below 50% amperage while cranking, the reserve 50% of each produce 800 ah (amps) (720 + 10% additional reserve). Series Battery configurations double the Voltage and maintain the same single rated ah capacity. This is seen on many OTRT from before the 50's thru the 80's. And, still used in several heavy-duty applications such as Back-Up Generators, Golf Carts, Hybrid, etc.. Reversing Polarity of a FLA / SLA Battery is a general myth. The only way for this to happen would be to completely discharge the battery, either by leaving the key on, or by an unnoticed dead short that completely dissipated the charge over a few days. After that happened it would appear to be a dead battery, nothing more. Cells is FLA / SLA Batteries must be within .50sg or 0.05v. during the testing process to pass. Any more and they would fail. Therefore, replacing the battery is a waste of dollar$. The regulator on our trucks (differ than todays PCM/ECM controlled units) is either open or closed, charging or not when operating properly. All FLA / SLA Batteries "Off-Gas", all the time, when being charged. But, more noticeable when voltage is in excess of 15v. Its a by-product of the cells chemical reaction when the ion process is occurring with two dissimilar metals. This is how Sulfation (the by-product) occurs which eventually leads to an exhausted battery life because the plate area is covered and electrolysis no longer occurs. The best way to prevent this is by for the average owner is to ensure the batteries have the correct level of denatured water and not lower than 55/45 Acid to Water Ratio. * On a side not, charging a battery intermittently at 16v helps reduce the process when done correctly over several hours. Many Battery Maintainers offer this function over the counter. Many, if not most of the OTRT and Hybrid Vehicles have them installed at the factory as a combination maintainer / conditioner to get maximum life. The problem with Alternators failing can be in correlation to batteries. Most fail because of cheap Rectifiers. Or, Rectifiers which aren't sufficient for the amperage they're outputting. Any Alternator above 120 amps will last twice as long, if not indefinitely, with one, or preferably two or more external rectifier in the system all dependent upon the ah the system requires. With the only special tool being a Paper Clip, and a Soldering Iron, they're rebuilt rater easily for about $20.
Any collection of individual cells connected in various configurations can give us whatever voltage and amperage spec we want in a battery.
Exactly the same thing applies in an automotive battery. It's made up of six cells, in series connection. Once we further connect these automotive batteries in series, or parallel or a combination of the same it is yet again simply part of a larger single battery, from an electrical standpoint, even though they may be in separate locations, and separate cases. Perhaps this is where many people are unclear.
We always want the internal impedance and charge level and temperature for each individual cell of the larger battery to be as close as possible, this isn't a matter of debate or opinion.
Battery theory is well over a hundred years old at this point and very well hashed out, there's no mystery involved.
#13
Your accessories have an RPM above idle where they reach their max performance so you might not see 14VDC out of the alternator at idle. IIRC it is somewhere around 1900 RPM for the alternator. Just because you're voltage is low at idle does not immediately point to a bad alternator. On a hot day I'm less than 14VDC even at cruising speed. Even if it's not at 100% health there are other issues that can cause a voltage drop. While I won't beat a dead horse, a bad battery can be a large draw (load), especially at startup, that would give you a low voltage indication as it is supplying current to try and charge the battery.
Without replacing both batteries at the same time you have two batteries in different conditions (one new and one aged) that have two different characteristics. They can work against each other instead of with each other (not evenly sharing the load) and the stronger battery will age quicker and, thusly, put an excessive load on the alternator. There are also other loads that may have electrical issues that place a load on the battery when the truck is off or take a higher than normal draw on the alternator.
IMHO the best way to do a "quick check" of the alternator is to disconnect both batteries after you start the truck then take a voltage reading (VDC) across the terminals of the alternator. If you're seeing anything over 13VDC, while not the strongest, I would consider it at least performing and look at other possible options. Are the terminals clean on your batteries? Is the cabling in good condition? I chased a gremlin for a couple of years that was killing my Optimas and it turned out to be my starter. Electrical issues are difficult to pinpoint until something completely fails so it's hard to come up with a list without starting somewhere and following the indications.
I hope this helps a little.
Without replacing both batteries at the same time you have two batteries in different conditions (one new and one aged) that have two different characteristics. They can work against each other instead of with each other (not evenly sharing the load) and the stronger battery will age quicker and, thusly, put an excessive load on the alternator. There are also other loads that may have electrical issues that place a load on the battery when the truck is off or take a higher than normal draw on the alternator.
IMHO the best way to do a "quick check" of the alternator is to disconnect both batteries after you start the truck then take a voltage reading (VDC) across the terminals of the alternator. If you're seeing anything over 13VDC, while not the strongest, I would consider it at least performing and look at other possible options. Are the terminals clean on your batteries? Is the cabling in good condition? I chased a gremlin for a couple of years that was killing my Optimas and it turned out to be my starter. Electrical issues are difficult to pinpoint until something completely fails so it's hard to come up with a list without starting somewhere and following the indications.
I hope this helps a little.
#14
#15
I'm going to guess starter was killing his BATTERIES.
Massive amperage draw every time you start your truck ( with a failing starter) is like stick welding with a 12v battery. The batteries don't last to long in that situation.
Massive amperage draw every time you start your truck ( with a failing starter) is like stick welding with a 12v battery. The batteries don't last to long in that situation.
Last edited by clem1226; 07-23-2016 at 01:46 AM. Reason: To remove my snarky tone.