Fried Battery Question

[paulo57509]

The VR in the Lumina went bonkers so the alternator was putting out max for a week or so....undetected. The only thing that clued me in was I was hearing the alternator "whine" was pretty loud.

I put a volt meter across the battery with the engine running and got close to 16.5 volts. With the engine off, the battery was reading over 14 volts.

I replaced the alternator and voltage reading-wise, all seemed back to normal. I didn't check battery voltage with the engine off after the alternator replacement. :

:

That evening in the grocery store parking lot, the car wouldn't crank - dead battery symptoms. AAA gave me a jump and I was on my way.....for two blocks when the car completely dies. AAA comes back to tow me the three blocks home.

Next day I measure battery voltage. +14 volts and no juice to operate any electrical device on the car.

I don't know much about fried battery behavior, but obviously getting over-charged did something. I'm thinking an internal short. What do the electrical gurus say? BTW, my turn signals still blink slow...it's has an electronic (vs. mechanical) flasher.

 

[Quest]

You should have looked into both the battery and the alternator instead of focusing on just replacing alternator.

In your case: I would have the battery load-tested first, and if deemed faulty: replace the battery.

Alternator: get another battery (known good one) and then mount it on the car along with the new alternator and see what happens. Normally, when running with battery fully charged, it should idle above 12.6V (more like 13.0V +). Anything lower/higher than that, I would have the alternator looked at and replaced as well.

It's not normal to have delco-remy alternators go bonkers and some "exotic" spiral cells go along with the party...

Q

p.s. I'm old-fashioned so give me any ordinary thin plate lead-acid cell and I'm done for years...

 

[Colt45ws]

It should be 12.6V no load battery voltage and a little over 14V charging.

 

[fsskier]

You said the battery has 14 volts, and "no juice", does that mean the battery voltage drops to near zero when you hit the starter?
If the Battery voltage remains high, then you have other problems, bad terminals, faulty connection to the starter, failed starter, whatever. Turn on the dome light and watch it... if it goes out or stays on it gives you a pretty good visual indication of instantaneous voltage.

The second reply above gives the correct charging voltage, all modern systems run a little over 14 volts when charging.

 

[tonycarguy]

An internal short would cause it to read very low , like 9v to 10.5v, not high. Undercharging or old age are likely to cause an internal short. Overcharging is likely to cause loss of electrolyte; hence check your water level.

Remove the neg terminal, wait 12 hrs, then measure the voltage w/ the battery disconnected. What does it read?

12v lead acid batteries should have resting voltage between 12.65v and 13.15v depending on the type of battery. They should be charged between 14 and 14.7 depending on temperature and type of battery.

 

[tonycarguy]

Another thing is, it is not meaningful to measure the voltage of a car battery immediately after it is charged or discharged. You get useless results. You need to obtain its resting voltage -- let it sit disconnected overnight. Or alternatively, you can turn on your headlights for 10 seconds, turn them off, then wait 2 hrs. Either way will give you an accurate voltage.

The 14v you read was probably immediately after driving it. Which is what I'd expect. I'd be willing to bet your battery lost a lot of electrolyte. If you measure its resting voltage it's probably below 12v, which is dead.

 

[The_Jeff]

If you overcharged it you may have boiled off some water. See if there are vent caps... you may have to use a screwdriver or even scrape off the label.

I would NOT trust that battery though. Went through this wtih a hyundai accent. Sometimes it will goof around and give you enough surface charge to start, but, it's shot.

Also it's a good time to look for burnt out bulbs.

 

[oilboy123]

Batteries can do a lot of weird things. A battery with 14 volts that can't start the car is toast. Unless have you a bad connection or starter/relay.

If overcharging for to long too high a charge can toast the battery. When I used to work in shops I would notice that batteries getting near the end of their life would have higher voltage readings, like closer to 13 volts. This is after sitting overnight or for a certain amount of hours. Which should be closer to 12.6 volts.

The acid will get more concentrated as the battery plates get more sulfates built up on them.

 

[UNC017]

Originally Posted By: paulo57509

Next day I measure battery voltage. +14 volts and no juice to operate any electrical device on the car.

I don't know much about fried battery behavior, but obviously getting over-charged did something. I'm thinking an internal short. What do the electrical gurus say? BTW, my turn signals still blink slow...it's has an electronic (vs. mechanical) flasher.


I'd be more inclined to think that youve got a blown fuse link (or whatever GM uses if not a fuse link). Its highly unlikely the battery would read 14v if it really were dead, although if the voltage immediately plummets to <10 when you put a load on it, then I would guess the battery got boiled dry. If its serviceable, try adding distilled water (not likely to make it last real long, but worth a shot).

 

[dwendt44]

What eljefino said.

Been there done that.. Overcharging will boil the water out.
Even some 'sealed' batteries can be opened and filled with distilled water. Done that too.
Fill and charge. Battery may be usable for a while. You are in a warm climate so it could last quit a while.
Damage was done however, and even if you 'save' it, I'd start saving for a new one.

 

[mechtech2]

How can you have 14V at the battery [which is 1-2 V HIGHER than normal] and not have power for "any electrical device on the car"?
Start checking fuses, relays, and fusible links.
Normally, a high battery V is not a sign of battery problems.
Low battery V is.

 

[oilboy123]

High battery volts and bad battery is not unheard of. I have probably had a dozen or so over the years in shops. I have probably had at least 3 or 4 working on vehicles on the side.

 

[tonycarguy]

Originally Posted By: oilboy123

The acid will get more concentrated as the battery plates get more sulfates built up on them.


You have that backwards. As the plates become sulfated, the electrolyte becomes less acidic (ie, turns more like water). The specific gravity falls as the battery ages.

 

[sunfire]

Originally Posted By: tonycarguy

Remove the neg terminal, wait 12 hrs, then measure the voltage w/ the battery disconnected. What does it read?


Can you please explain what the purpose of disconnecting the negative terminal?

Why can't I leave the battery connected and measure the voltage the next day?

 

[paulo57509]

Just to close the loop, I replaced the battery (after replacing the alternator) and all is well. Thanks for the replies.

I wouldn't looked at the battery first, given the voltage across the battery with the engine running was over 16 volts. IIRC, alternators should cut off at around 14.5 volts max. Also, there was no symptoms of a weak or failing battery at that time.

BTW, before I returned the battery core, I took voltage measurements across it 14 hours after it was removed from the car. It still read 14.5 volts.

Oh yes, I replaced the flasher and the turn signals are working as they should too. It was a mechanical and not an electronic one.