Alternator issue. again...
Laughing Gas
Joined: Sep 2014
Posts: 830
Likes: 39
From: Whittier
Also, don't forget to start with fully charged batteries. Alternators are just to maintain the charge, not for recharging the batteries. Get your alternator checked and if needed, get the correct alternator.
Postmaster
Joined: Sep 2010
Posts: 3,472
Likes: 2
From: Southern Cal
Also, why does an alternators charge at about the same rate as a battery charger, starting about 14.4 - 14.6 volts?
Why are there regulators built in to ensure top charging and yet still adjust to not overcharge?
Why if you have a drained battery, can you drive it for a bit and recharge?
Looking forward to an explanation?
Certified Thread Hijacker
Joined: Aug 2001
Posts: 14,441
Likes: 60
If alternators are only used for "re-charging" then why is there a need for a variety of different amp sizes?
Also, why does an alternators charge at about the same rate as a battery charger, starting about 14.4 - 14.6 volts?
Why are there regulators built in to ensure top charging and yet still adjust to not overcharge?
Why if you have a drained battery, can you drive it for a bit and recharge?
Looking forward to an explanation?
Also, why does an alternators charge at about the same rate as a battery charger, starting about 14.4 - 14.6 volts?
Why are there regulators built in to ensure top charging and yet still adjust to not overcharge?
Why if you have a drained battery, can you drive it for a bit and recharge?
Looking forward to an explanation?
Josh
Postmaster
Joined: Sep 2010
Posts: 3,472
Likes: 2
From: Southern Cal
With all said...
I do understand the need to not rely on an alternator as a battery charger.
Putting a drained battery into a vehicle and running with the intent to fully charge the battery can overheat the alternator and cause premature failure.
It can be a Solution, just not a good one.
I do understand the need to not rely on an alternator as a battery charger.
Putting a drained battery into a vehicle and running with the intent to fully charge the battery can overheat the alternator and cause premature failure.
It can be a Solution, just not a good one.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Right, the battery is only for starting purposes. It does act as a filter or surge protector. But, the alternator is responsible for all power requirements - ignition, lights and accessories.
The exception to this was the archaic generator system, at idle the headlights would dim as the cutout removed the generator from the electrical system, generators could not provide current at low RPM. Alternators replaced generators for some good reasons and this was a big one.
I've never owned a vehicle with two batteries in parallel - but it has to be problematic for short trips especially. Electrically they are a single, very large capacity battery so any mismatch in voltage or, internal impedance is going to mean different cells start drawing excessive current. Larger alternators will be able to provide the current necessary to efficiently recharge quicker.
I suspect this is the problem, as the cells become mismatched over time within the battery and they stay that way. Keep the cables and connections absolutely clean and tight, periodically "equalizing" individual batteries using an outboard charger capable of providing 25 to 35 amperes should help maximize battery life.
The exception to this was the archaic generator system, at idle the headlights would dim as the cutout removed the generator from the electrical system, generators could not provide current at low RPM. Alternators replaced generators for some good reasons and this was a big one.
I've never owned a vehicle with two batteries in parallel - but it has to be problematic for short trips especially. Electrically they are a single, very large capacity battery so any mismatch in voltage or, internal impedance is going to mean different cells start drawing excessive current. Larger alternators will be able to provide the current necessary to efficiently recharge quicker.
I suspect this is the problem, as the cells become mismatched over time within the battery and they stay that way. Keep the cables and connections absolutely clean and tight, periodically "equalizing" individual batteries using an outboard charger capable of providing 25 to 35 amperes should help maximize battery life.
Token Redneck
Joined: Jun 2007
Posts: 9,339
Likes: 350
From: Breckenridge, TX
Jeep apparently sizes their alts better than Ford)Jeep died while running and battery showed flat at 10V on a DVM. Load test wouldn't complete, just flashed "charge". Can't leave it on the side of the road so I jumped it and drove is a couple miles to a friend's house. When I opened the hood while it was idling to check voltage I saw the alt literally smoking, and it was flashing/arcing inside.
I load tested the battery and checked charging volts a month before and every was good at the time. Not sure if the battery lost a cell and killed the alt, or if the alt died and killed the battery.
Either way it got a reman and a new battery, and it's fine now. Dead batteries are just bad news all around, use a real charger on them.
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