Can a battery charge kill an alternator?

[Nick Micale]

I never considered that charging a battery could kill the alternator?

For the past few months I had issues with one of my street cars that had intermittent starting issues, and the new battery needed occasional charging, and many times the voltage was too low to fire the ignition?

The engine is fresh as is the alt and battery.

It had not been started in a couple weeks, so I tried starting it yesterday but needed to again charge the battery as cranking voltage was bellow 11v.

After a few hours charging, it fired up but the alt voltage was below 12V and for a second or 2, it would drop to 7V?

So I installed a fresh reman alt, and voltage was 14V at the alt and battery.

The alt tested bad and failed all the analyzer tests as the diodes and rectifier and regulator were all bad.

Did some research today and many experts and literature stated do not let the alt charge a dead battery as it does put a very heavy load on the delicate internal electronic components, always dis-connect the battery when charging.

Another piece of this puzzle came from a local reman electronic shop is there is a position of the armature when not rotating that a charging current can and damage the delicate electronics in that era our alternator design.

Later alternators versions were safeguarded from this weird issue.

I am not an electronic expert, but it did not make sense that an alt with 5 mile use from out the box would die so quickly?

My conclusion is no matter if the moon, stars and armature are all in the right position will kill a good alt, I will disconnect a battery before I charge it!

 

[gdsims231]

It is always best to fully charge the battery before starting. If your battery is discharged, you start the car via jump box or charger, then disconnect the outside source, the alternator not only has the load of the entire car but the additional load of the dead battery.

 

[Dennis Kirban]

Your rite Nick as we have had it happen with customers that buy new alternators from us matter of fact we put that info with each unit so owners can avoid having that problem wit a new alternator.

They put the blame on a bad new alternator when in fact the battery was the culprit.

Learned all this from my guy who rebuilds our alternators as my electronic skills are like my mechanical skills.....very low on the scale.

denniskirban@yahoo.com

 

[ScottHeidinger]

Most alternators I have replaced have a warning like this in the box with them. Never made a lot of sense but seeing how they find any excuse to void a warranty I have always completely charged the battery before putting a new alternator on and have never had a issue.


Sent from my iPhone using Tapatalk

 

[SS/GN]

We use to run Reactor Batteries in the race car and they told us to keep the charging voltage at 13.8v but not more than 14.4. I talked to many other suppliers of ignition boxes, alternators and other battery companies and they all said the same things. Many off the shelf chargers, even the Snap on one we had would go higher.

 

[mikeelia]

I would assume that keeping a trickle charger on the car is fine when it comes to this [no 'dead battery' load, ever]. I think mine has been on the car almost continuously for more than 15-years...

 

[Frederickdav]

Years ago when I lived out in the country, hardly a winter went by that I needed to jump start my car or somebody else's. We didn't wreck alternators doing that. I'm sure many times the battery was dead. We'd just give it a jump and all would be fine until the next time.

 

[TurboWh1]

I've seen many alternators fail prematurely on our cars primarily due to old factory wiring not necessarily charging a battery.... I couldn't tell you how many times I've had a battery charger hooked up while working or tweaking something on my car. Most remanufactures replace the failed component only to have the next weakest link fail. It's crazy what you find when you open them up. Loose parts, obviously bad parts, bad bearings, etc...They clean it up and make it look pretty so you feel good when you open the box.

My question would be... What is causing your battery to drain? It might be a paracitic drain of some sort. I put 5 alternators on my car when I bought it about 15 years ago. The culprit ended up being the dash light causing the charging issue / failed alternator. Any intermittent short circuit to the voltage regulator is almost immediate failure. My symptoms were very similar to your scenario. I've had a few other Turbo Regals since, they all get my own personal rebuilt alternator and a stand alone wiring system. I've never had an alternator fail since.

 

[rodruckus]

Alternators aren't designed to charge batteries, but instead to maintain a charge level. You would probably have to drive your car for about 6 hours to achieve the same fully charged level of a battery charger. Not the bs, "just 30 minutes."

If you wanna use your alternator to charge a battery, you better only do this to a partially discharged battery. Plus, you better be driving, not just sitting at idle. Idling only is gonna put an extra heavy load on your alternator. You need higher rpms to attempt to offset the load.

However, a big, big no-no, is trying to charge a totally dead battery with only your alternator. Again, alternators aren't designed to charge batteries. You better put that battery on a charger or if you have access to a spare, swap it out while you wait for the dead one to charge back up.

While a battery is in a totally dead or close to fully discharged state, I've seen alternators give bad readings. Even the battery light come on for extended periods, too. It can easily fool you into thinking you may have damaged something. Especially if you just jumpstarted your car, and didn't have any problems beforehand. If your car has a voltage gauge or if you have another way of reading voltage, you'd be surprised at how they sometimes read and initially act.

 

[Gary Durden]

I thought we were taught old school "the battery charger is used to charge the battery and the alternator is used to maintain the charge".

 

[vacuum 6]

Something I've used for many years. When charging I "disconnect" the + side.