Charging battery with alternator

[Hollow]

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

 

[Oldawg]

I was a GM dealer mechanic for years (went to GM Training Center on alternators when they first came out) and never heard of damaging an alternator by charging a dead battery. Also the charging circuit on an automobile is more sophisticated than most battery chargers and does a fine job keeping the battery fully charged, providing the vehicle is driven fairly often for a reasonable distance.
Small tractors with the alternator coils under the flywheel are a different animal. I think these are more easily damaged by overworking them, and I would use a charger to restore a flat battery in this case.

 

[Keoke]

The best way to charge a battery is with the alternator in your car, it stops charging when the battery is full. The alternator in my Jeep interacts with battery temperature! Cheap chargers ruin your battery by overcooking. I think using the jump start function from a charger is really bad for your battery.

If you need to jumpstart a car, let the helping car run for a while so that the dead battery gets charged thru the full battery and alternator of the helping car.

Then start and charge the battery in your vehicle. The alternator is your best charger. Your battery life is longest if you use your vehicle frequently.

This is my experience.

The best way to charge a battery is to keep the amps low for a very long time. This will remove the max sulfation from battery plates and give the fullest charge. Best formula is to use amp hrs rating. EG, a 60 amp hr battery chg for 12 hrs @ 5 amps for best results. Even better would be 3 amps for 20 hrs.
An alternator will not likely destroy itself charging a battery simply because the battery, by itself, will not be conducive enough to allow the alternator to rise to it's max amperage.
Now, a dead battery in parallel with high vehicle loads may, but not likely, force an alternator to it's max rate. But this, unless carried on for a long time, is not likely to do any damage.
A dead or very weak battery will keep the alternator charge very low until the battery's electrolyte becomes more conducive to current flow across pos and neg plates. A non conducive battery will also give high alt voltage and cause voltage reg to reduce field current in alt and lower chg rate. Most voltage regulators run between 13.8 to 14.6 volts.
Bottom line, the chance of burning up a good alternator by charging a weak battery is almost nil.
cheers,
keoke

 

[AKfish]

The best way to charge a battery is to keep the amps low for a very long time. This will remove the max sulfation from battery plates and give the fullest charge. Best formula is to use amp hrs rating. EG, a 60 amp hr battery chg for 12 hrs @ 5 amps for best results. Even better would be 3 amps for 20 hrs.
An alternator will not likely destroy itself charging a battery simply because the battery, by itself, will not be conducive enough to allow the alternator to rise to it's max amperage.
Now, a dead in parallel with high vehicle loads may, but not likely, force an alternator to it's max rate. But this, unless carried on for a long time, is not likely to do any damage.
A dead or very weak battery will keep the alternator charge very low until the battery's electrolyte becomes more conducive to current flow across pos and neg plates. A non conducive battery will also give high alt voltage and cause voltage reg to reduce field current in alt and lower chg rate. Most voltage regulators run between 13.8 to 14.6 volts.
Bottom line the chance of burning up a good alternator by charging a weak battery is almost nil.
cheers,
keoke

Hey George;

Good to hear from you... And a very timely message as well! :thumbsup: Hope you're keeping 'ol Sea biscuits pasture well taken care of!

Regards,

AKfish

 

[Soundguy]

The best way to charge a battery is to keep the amps low for a very long time. This will remove the max sulfation from battery plates and give the fullest charge. Best formula is to use amp hrs rating. EG, a 60 amp hr battery chg for 12 hrs @ 5 amps for best results. Even better would be 3 amps for 20 hrs.
An alternator will not likely destroy itself charging a battery simply because the battery, by itself, will not be conducive enough to allow the alternator to rise to it's max amperage.
Now, a dead in parallel with high vehicle loads may, but not likely, force an alternator to it's max rate. But this, unless carried on for a long time, is not likely to do any damage.
A dead or very weak battery will keep the alternator charge very low until the battery's electrolyte becomes more conducive to current flow across pos and neg plates. A non conducive battery will also give high alt voltage and cause voltage reg to reduce field current in alt and lower chg rate. Most voltage regulators run between 13.8 to 14.6 volts.
Bottom line the chance of burning up a good alternator by charging a weak battery is almost nil.
cheers,
keoke

you are not taking into account bats with a bad cell, dragging system volts low, making the alt charge higher to keep voltage in the correct range. Battery is toast anyway.. but toasts even faster, and why abuse the alt with a higher than 'NEEDED' charge rate, plus the fuel usage.

nothing is for free. if you are charging higher you are using more fuel.

remember guys.. most devices have a tolerance range. you can operate outside the tolerance range for some amount of time and get away with it.

you do it often, and that's where you get into problems. same applies to other machines too. shoot normal range loads in your gun for target and experience, and a couple +P loads to know what it feels like, then load it for +P for self defense.. that's one thing. Only shoot +P day in and day out and you are likely to have a loose piece before it's time..

the more time you spend at the extreme edge of a decices tolerance, the more chance you have of a failure.

if you have 2 identical 63 amp alternators, and one is charging at 25a full time, with occasional higher demand, and the other is at 63amps full time, with occasional higher demand... I lay odds that the one running at the edge of it's rated tolerance will have a shorter working lifespan. Will that be true in all cases.. no.. it a law of averages type of deal. Same with High early failure rate on electronics..e tc..

soundguy

 

[Keoke]

In order for a "bad cell" to force an alternator to high charge you would need physical connection (dead short) between a positive and negative plate. This would cause boiling and self draining of that particular cell. In most, but not all, cases this connection would melt open long before the alternator would heat up from overcharging.
A low-conducive (sulphated) cell, the most common battery fault, or open cell would not cause overcharging of alt because both of these faults would limit current flow.
Alternators, because of mutual induction in the stator cannot be made to charge beyond their rated amperage. Old DC generators on the other hand can charge beyond rating and self destruct if fld current is not controlled by the regulators current limiter relay. Alt voltage regulators do not have or need a current limiter because of mutual induction.
None the less, running an alt a low charge rates (cooler) will give longer life to unit and is the smart way to go.
cheers,
keoke

 

[Keoke]

Hey George;

Good to hear from you... And a very timely message as well! :thumbsup: Hope you're keeping 'ol Sea biscuits pasture well taken care of!

Regards,

AKfish

Ak, Happy New Year, to my buddy up there in the tundra.
Hopping all is well with the JD110.
Hey, we will taking a cruise to coastal Alaska in August.

take care bud,
george

 

[Soundguy]

In order for a "bad cell" to force an alternator to high charge you would need physical connection (dead short) between a positive and negative plate. This would cause boiling and self draining of that particular cell. In most, but not all, cases this connection would melt open long before the alternator would heat up from overcharging.
A low-conducive (sulphated) cell, the most common battery fault, or open cell would not cause overcharging of alt because both of these faults would limit current flow.

While I have not taken a battery apart to physically determine what the fault was, I have seen plenty of batteries that read 10v, and when you charge them with an alt, the charge voltage would be on the high side.. say 15v, turn off vehicle and battery bleeds down to 10v extremely fast. My wifes yukon did this recently. the 2v difference makes me thing of a bad cell. charge voltage exceeded 14.7 of wich most gm alts don't go past. my good lab grade dvm verified 14.9/15 charge volts. I have heard of a vreg module that will do 15.. ( like for a 10si model ).. just havn't seen one.

again.. not sure what the bat issue was ( walmarts problem now... I was just past the 3yr free replacement and just 6m into the pro rate.. so dot a new 100$ battery of 38 $.. 1 week old now.. etc.. ).. but it deffinatley bleed to 10v within 30 seconds of shutting the vehicle down.

soundguy

 

[BobRip]

I remembered earlier today about the alternator issue I had on my Olds 98 that had a digital dash, I had replaced the OEM alternator at about 100,000 miles, the rebuilt replacement had a lifetime warranty and after about 3 years, I was on the way to work and the digital gauge readout began flashing "Battery 14.9 Volts Overcharging" and the normal readout was supposed to be "Battery 13.7 Volts". Well when I got home I removed the alternator and returned it to the seller and asked for a replacement they gave me a hard time about that saying their tester showed no overcharging but the replacement I got went another four years and never read over the normal 13.7 volts. I always wondered just how many batteries get ruined when alternators overcharge batteries and the cars have only a useless idiot light that furnishes no real useful information.

I once bought a rebuilt alternator that did this. It would erratically go to high voltage. I finally captured this rare event after I blew my ignition module. When they rebuild they are very unlikely to find an erratic problem during their test. I replaced the regulator and never had a problem. I hate to buy rebuilt parts for this reason.

 

[Johnp33]

First off you can damage an alternator with an unregulated charge spend the extra dollars and buy one that is regulated. The diodes in an alternator can be damaged by voltage above 16.
I have seen many a unit with a bad alternator that they just change the alternator boost it to start and tell the customer to drive the long way home 3 months later he is back for warranty.
If you have a single battery charge it, by itself.
If you have multiple batteries separate them and charge them independently.
I have a Duramax and use the truck to boost equipment, when this fall I separated them and charged them one took about 2.5 hours to come to light on charge the other 20 minutes. This is with a 10 amp regulated charger. I have an 80 amp charger that I use on some units to bring batteries back from the dead, when sulphated.

 

[BobRip]

First off you can damage an alternator with an unregulated charge spend the extra dollars and buy one that is regulated. The diodes in an alternator can be damaged by voltage above 16.
I have seen many a unit with a bad alternator that they just change the alternator boost it to start and tell the customer to drive the long way home 3 months later he is back for warranty.
If you have a single battery charge it, by itself.
If you have multiple batteries separate them and charge them independently.
I have a Duramax and use the truck to boost equipment, when this fall I separated them and charged them one took about 2.5 hours to come to light on charge the other 20 minutes. This is with a 10 amp regulated charger. I have an 80 amp charger that I use on some units to bring batteries back from the dead, when sulphated.

My alternator had a built in regulator. Are there any unregulated alternators out there? Certainly not on cars or trucks. Are you referring to tractors?

 

[Johnp33]

Unregulated Charger,

 

[BobRip]

Unregulated Charger,

Got it. Thanks. I agree. You can also damage a battery.

 

[Keoke]

Hi JD & folks, The alternator on the Olds has a built in regulator that reads the alt output voltage at it's 1/4" output stud. The digital voltage reading showing at the dash most likely is coming from the accessory terminal of the ignition switch. This voltage is quite a ways downstream from the alt itself is subject to proximity load draw as well. Bottom line, this is not a good way to check your VR setting. Best best is hook a quality DVM to the output stud on the alt for true VR setting. Alternator output in amps should be low (minimum loads) for this test so that the VR can start to clip field current and thus regulate amperage output. Most VR units set between 13.8 & 14.6 volts, although some OEM's go cheap with small gauge wire will run as high as 15.0 volts
cheers,

 

[Keoke]

Hi John, when two batteries are in parallel, as in your truck, the alt voltage regulator will only see the stronger of the two and thus set the alt charge rate to that battery.
Bottom line, the weaker battery will never get to control the charge rate but will serve as a sump for alt current flow even though this flow may be at lower levels then desired.
Rv's are a classic case of the above. Camping overnight runs the camping battery down but when you start the vehicle in the morning it is the truck battery that directs the the alt output. If the alt VR was to only see the weak camping battery voltage then it would charge it up at a much quicker rate.
cheers,

 

[Johnp33]

I worked on class eights and use to separate them all 4 and charge them separately, to give the best battery life and starting ability. BUT of course as a mechanic i guess I thought my batteries were exempt, at least it was not suphated. That was a bonus.
They Did also make Alternators that did not have integral alternators, Dodge and Ford both used them. As did Lucas.

 

[AKfish]

Ak, Happy New Year, to my buddy up there in the tundra.
Hopping all is well with the JD110.
Hey, we will taking a cruise to coastal Alaska in August.

take care bud,
george

Thanks, George. Used the 110 yesterday (my son, actually) to clean up a 9" snow dump.

August, huh? Well, I've been doing hay in August the past 2 years (later than I'd prefer) and I'm always lookin' for help....

I'll be waitin' at the dock in Seward.

AKfish

 

[JDgreen227]

Hi JD & folks, The alternator on the Olds has a built in regulator that reads the alt output voltage at it's 1/4" output stud. The digital voltage reading showing at the dash most likely is coming from the accessory terminal of the ignition switch. This voltage is quite a ways downstream from the alt itself is subject to proximity load draw as well. Bottom line, this is not a good way to check your VR setting. Best best is hook a quality DVM to the output stud on the alt for true VR setting. Alternator output in amps should be low (minimum loads) for this test so that the VR can start to clip field current and thus regulate amperage output. Most VR units set between 13.8 & 14.6 volts, although some OEM's go cheap with small gauge wire will run as high as 15.0 volts
cheers,

THanks for info you supplied, ditto to everyone else who has contributed to this thread, I have learned a lot from the replies.

 

[Soundguy]

Hi JD & folks, The alternator on the Olds has a built in regulator that reads the alt output voltage at it's 1/4" output stud. The digital voltage reading showing at the dash most likely is coming from the accessory terminal of the ignition switch. This voltage is quite a ways downstream from the alt itself is subject to proximity load draw as well. Bottom line, this is not a good way to check your VR setting. Best best is hook a quality DVM to the output stud on the alt for true VR setting. Alternator output in amps should be low (minimum loads) for this test so that the VR can start to clip field current and thus regulate amperage output. Most VR units set between 13.8 & 14.6 volts, although some OEM's go cheap with small gauge wire will run as high as 15.0 volts
cheers,

Yes, I realize the remote sense function is there to up alt v output so that at the end of the line of the small wire it is close to correct.

when i measured I was measuring at the alt output. Apparrently GM is still going at it with the big hammer and making 15v charge outputs possible.. I like the old 14.4-14.7 jobs.. IMHO.. easier on electrical systems...

soundguy

 

[BobRip]

Yes, I realize the remote sense function is there to up alt v output so that at the end of the line of the small wire it is close to correct.

when i measured I was measuring at the alt output. Apparrently GM is still going at it with the big hammer and making 15v charge outputs possible.. I like the old 14.4-14.7 jobs.. IMHO.. easier on electrical systems...

soundguy

GM drops the voltage as the system warms up. It settles down to around 14.2 volts. I have seen seven years on an original Chevrolet battery. I doubt they are damaging them.