Charging battery with alternator

[Soundguy]

timely for this thread.

my mom called me at work this am with a dead battery in her 07 cady SRX

that's the one with the battery up by the windshield, and the alternator burried in the middle right front of the engine..

anyway.. I go over to her house. this happened previously about 2ys ago... battery was warrientied then.. but she got charged 150$ to install it ( ?? nice warranty gm.. )

anyway.. thus battery is 2ys old.

I get over there.. no lamps on.. nothing that should have made the battery die.. but yet it was stone dead.. 10v showing on my dvm.

anywho.. I had brought over a charger and let the bat charge up over lunch, came back and hooked up jumper cables to my diesel just to make sure there was no strain upon starting.

started up fine.

put one of those loaded 2 probe charge system analyzers on.. said bad alt. I let the car run 10 minutes just to make sure it wasn't reading a dip from the low battery / starting draw. tested again.. same deal.. low charge output. ( this is the metal kind with a nichrome? load resistor and a scale for testing bats and alts.. ).. put my dvm on and read.. car idling.. varried charge voltages from 13.2 to 13.45 had my mom rev it up and it actually dropped to 12.9 one time.. after 5 minutes of idleing and on and off again looking.. charge voltage never made it up over 13.45v.

since nominal bat voltage is 12.6, it -IS- charging.. but low...

I shut the car down and have now let it set a couple hours. bat shows good nominal volts and car started fine.. same low charge volts..

that's making me think alt is taking a dump.. and bat is good for now since it charged up and did not self discharge... also makes me thing there is not a heavy parasitic draw in the car killing it. gosh that alt looks like it is going to be fun to remove.. there is a tensioner on a ? 3 bolt bracket at the al mount, and then also a lower rad hose.. looks like it might come out the top with the lil plastic engine shroud slightly interfering.... yummy... and here I thought the bat was hard to get to...

soundguy

 

[JDgreen227]

Interesting post, Soundguy...many times I think they intentionally design components like that alternator to be hard to access so you will give up and take it to the dealer for servicing.

 

[Soundguy]

sure.. same with using specialty bolts or fasteners, or require the use of special tools. they figure people won't buy a 60$ tool to do something maybee once, and will instead take it to the dealer...

 

[Hollow]

" anyway.. I go over to her house. this happened previously about 2ys ago... battery was warrientied then.. but she got charged 150$ to install it ( ?? nice warranty gm.. ". WOW, it would have been cheaper to buy a battery at Autozone and let them install it for free... I know how it feels though. I've got an 07 Avalanche that the odometer and information display went out in a couple of weeks ago. The only way to replace it is to replace the whole cluster, $285 for the part alone and they said they wouldn't warranty the new one unless they install it. I'll never buy another GM product as long as I live!

 

[Soundguy]

same here... I mentioned to my mom it would have been cheaper for us to install a store battery.. but she was worried about warranty issues... that just beats all.. bat goes out in warranty.. vehicle under warranty.. and yet 150$ to do it

I doubt autozone would have installed that bat in that srx... it's tough to get to...

but yeah.. no more GM for me either. wife has a yukon.. when it bellies up finally.. we will have learned our lesson many times over. I shoulda learned my lesson back when i had a pontiac... go figure... guess I wanted practice turning wrenches and repalcing odd parts and stuffing cash byt he pocket fulls into a vehicle.. oh well.. knock on wood.. the yukon runs.. though uses oil about as fast as a 2stroke... even though gm tech says that is within book spec for the 5.3 in it.. .. no leaks.. it drinks it....

soundguy

 

[JDgreen227]

" anyway.. I go over to her house. this happened previously about 2ys ago... battery was warrientied then.. but she got charged 150$ to install it ( ?? nice warranty gm.. ". WOW, it would have been cheaper to buy a battery at Autozone and let them install it for free... I know how it feels though. I've got an 07 Avalanche that the odometer and information display went out in a couple of weeks ago. The only way to replace it is to replace the whole cluster, $285 for the part alone and they said they wouldn't warranty the new one unless they install it. I'll never buy another GM product as long as I live!

Neighbor of ours and two friends have the Impalas with the haywire speedometers, the ones that read 40-50 mph fast. Have to replace the cluster for a fix, not warranty repair either. They are really ticked about it and have LOTS of company.

 

[GolfAddict]

timely for this thread.

battery was warrientied then.. but she got charged 150$ to install it ( ?? nice warranty gm.. )

soundguy

Off topic, but I think the dealer is pulling something here and I'd hesitate to let your mom use them again, or maybe go with her. My last three cars have been DTS's, and their bumper-to-bumper warranty covers dang near anything except oil changes or typical wear items. I had a left front headlight go out on my 07 and thought I'd just change it myself. Owners manual said take it to the dealer. Looked on-line and you have to remove a bunch of bodywork. Took it to the dealer - parts and labor no charge. They even shuttle you anywhere you want to go in town if you don't want to wait there and pick you up later. Wonder if they were pulling a fast one on a little ol' lady...

 

[Soundguy]

dunno. we called the selling dealer ( 1 hr away) and the local caddy dealer.. got about the same 'info' from each..

I think it's a scam for sure.. but a scam by gm.. not so much the dealers... probably no reimbursement for that sort of warranty work from corp to dealer.. so the dealer bills for it.. IMHO...

 

[LBrown59]

I've never heard of that before. Never had a problem with it ether...

Same here and I've owned cars and trucks since 1958.

 

[JakeBrake]

I think we need to distinguish between a discharged battery and a defective battery.

The OP left the ignition key on and the battery discharged completely eventually. If he jump started the tractor and let it recharge on the alternator, the alternator would put out maximum amps, which may damage the alternator.

On the other hand, most of today's "maintenance free" batteries fail suddenly with no warning. In other words, it starts fine one time and then next time, maybe five minutes
later, it's dead as a hammer. In most cases you can jump start the vehicle and move the vehicle to a convenient location. When you try to start it again, it's dead. In this case the battery will not take a charge. "Maintenance free" batteries almost always fail open. The battery is open even if you can measure 12VDC across the battery terminals. So, the alternator cannot charge the battery and will not have an excessive amp drain. So the alternator should not be harmed by jump-starting and moving the vehicle to a convenient location.

By the way, the "maintenance free" battery on my Kubota is over 6 years old. I start the tractor in the barn and I don't turn it off until it's back in the barn.

I worked with industrial lead-acid batteries during my working career. These batteries are never allowed to discharge completely. If the batteries do discharge completely during a natural disaster or some such, the batteries are recharged when power is restored but replaced as soon as possible.

 

[JDgreen227]

OP here, excellent post, Jake Brake....:thumbsup:

 

[BobRip]

I think we need to distinguish between a discharged battery and a defective battery.

The OP left the ignition key on and the battery discharged completely eventually. If he jump started the tractor and let it recharge on the alternator, the alternator would put out maximum amps, which may damage the alternator.

On the other hand, most of today's "maintenance free" batteries fail suddenly with no warning. In other words, it starts fine one time and then next time, maybe five minutes
later, it's dead as a hammer. In most cases you can jump start the vehicle and move the vehicle to a convenient location. When you try to start it again, it's dead. In this case the battery will not take a charge. "Maintenance free" batteries almost always fail open. The battery is open even if you can measure 12VDC across the battery terminals. So, the alternator cannot charge the battery and will not have an excessive amp drain. So the alternator should not be harmed by jump-starting and moving the vehicle to a convenient location.

By the way, the "maintenance free" battery on my Kubota is over 6 years old. I start the tractor in the barn and I don't turn it off until it's back in the barn.

I worked with industrial lead-acid batteries during my working career. These batteries are never allowed to discharge completely. If the batteries do discharge completely during a natural disaster or some such, the batteries are recharged when power is restored but replaced as soon as possible.

Jake. I don't think the alternator will put out max amps for very long. At idle the alternator will only put out limited amps. Alternators only put out rated amps with the engine reved up. Also the battery voltage will quickly climb to limit current.

 

[Soundguy]

"Maintenance free" batteries almost always fail open. The battery is open even if you can measure 12VDC across the battery terminals. So, the alternator cannot charge the battery and will not have an excessive amp drain. .

that in and of itself can also be an issue.

an unloaded alt / vreg can suddenly spike with changes in the vehicles electrical load. ie running with lamps on alternator with an open battery, and then you turn lamps off.. load suddenly drops.. v can spike before reg makes a recovery and clamps it... not great ont he rest of the electrical system IMHO..

soundguy

 

[Soundguy]

Jake. I don't think the alternator will put out max amps for very long. At idle the alternator will only put out limited amps. Alternators only put out rated amps with the engine reved up. Also the battery voltage will quickly climb to limit current.

i think you may be surprised about an alts rated output vs rpm..

dc generators are terrible about low rpm charging.. alt's on the other hand are quite efficient at it.

soundguy

 

[BobRip]

i think you may be surprised about an alts rated output vs rpm..

dc generators are terrible about low rpm charging.. alt's on the other hand are quite efficient at it.

soundguy

I looked this up. This link Alternator Output vs. Engine RPM
Shows that at 575 rpm engine speed the output of a 63 amp alternator is only 16 amps. Yes they are better than generators, but they do drop. At idle and a few loads on you may be discharging your battery.

 

[jmurray01]

What Bill is doing is 100% correct.

An alternator should never be used to charge a battery from dead.

OK, if you are away from home and the only way to get going again is to get a jump start, fine, but if you have the means of putting the battery on a slow charge, do it!

An alternator is designed to keep a battery topped up, not charge it from flat, however if will charge it from flat if necessary, but that doesn't mean you should let it.

 

[Soundguy]

how many cars you got that idle at 575 rpm?

all my vehicles are around 800.

specs i see show up to 60% of rated amps at normal idle speeds.. least a 10/12SI gm does..

soundguy

 

[Soundguy]

An alternator should never be used to charge a battery from dead....

...An alternator is designed to keep a battery topped up, not charge it from flat, however if will charge it from flat if necessary, but that doesn't mean you should let it.

yep.. just like.. you can pull a choke knob and choke an engine to shut it down.. but it's not a good idea..

 

[JDgreen227]

What Bill is doing is 100% correct.

An alternator should never be used to charge a battery from dead.

OK, if you are away from home and the only way to get going again is to get a jump start, fine, but if you have the means of putting the battery on a slow charge, do it!

An alternator is designed to keep a battery topped up, not charge it from flat, however if will charge it from flat if necessary, but that doesn't mean you should let it.

Pretty hard to find an outlet for a charger many times, so to say I am 100% correct is not always right. And how many of us carry a charger around? So far I have not seen anything about how much a charge jump starting puts back into a low battery, although one member said it's a good idea to connect the two batteries together for a period of time and let the good battery charge the run down one.

Problem is, in the very rare cases I have asked a stranger to help me jump start my vehicle (once in the last 25 years) I pretty much hate to ask them to stick around an extra 5 or 10 minutes.

 

[Mark Page]

I've jump started other vehicles many times. If you hook up your cables and let the charging vehicle run for 10 or 15 minutes the dead battery will absorb enough juice to put a lesser load on the charging battery when you start it. I can't say I've ever had an alternator problem as a result.
Chances are I'll be replacing the once dead battery in short order.