Can a bad Battery impact Alternator output?

[DT-P38]

If my battery has reached the end of its useful life, and is unable to sustain a decent level of charge, will it affect the performance of the alternator?

Further info. The last 3-4 days the pig has had some trouble turning over at cold start up's. The first couple of cranks are almost like its not gonna get there and then it seems to build some momentum, spin a bit more freely-normally, and then fire up. The battery is about 6-7 years old. WHen I put a multimeter over the battery this arvo after running for about 5-10min's and it was hovering around 12.6-12.7V. Output from the alternator at idle was 13.98V and at steady 1800 revs approx. 14.1-14.2V. When engine and ignition completley off, I tested the battery and watched it drop from 12.76 down to 12.43 in the space of 20 -30 seconds.

As I understand from reading similar AULRO experiences here, that Alternator output is a bit low... so I am wondering if the low battery drags the output down or if the alt senses its off par and reduces output to help it catch up slowly or something?

Either way a new battery goes in tomorrow morning (when the muddies get fitted up!), I guess I am just wondering if I also need to put new/reco alternator on the VERY SOON list.

Any thoughts/comment appreciated, Dave

[PhilipA]

I would think all that is normal.
Just put in a new battery.
Regards Philip A

[wayneg]

Well a few weeks ago it was water pump season, now its Battery week. I had a perfect battery one day , the next similar to your description then failed to start. Tested myself and thought alternator was not pumping out to good. No time to spare so jump started the car then dropped into an Auto electricians for free check. Alternator good, battery bad.
The old battery was a 600cc amp no idea how old but never missed a beat till now, New one is 750cc amp Exide. $225 later and no issues for 6 days

[poleonpom]

Exactly the same thing happened to me. New battery was all it took. Didn't save me from all the other frigging non-electrical problems tho'

[boofdtl]

Yes if you want to call in to work i can test it all for you..

[wrinklearthur]

Well a few weeks ago it was water pump season, now its Battery week. I had a perfect battery one day , the next similar to your description then failed to start. Tested myself and thought alternator was not pumping out to good. No time to spare so jump started the car then dropped into an Auto electricians for free check. Alternator good, battery bad.
The old battery was a 600cc amp no idea how old but never missed a beat till now, New one is 750cc amp Exide. $225 later and no issues for 6 days

I have not long brought a 750cc amp Exide battery at 'your local bloke' for under $200.
So its not only the fuel prices that are taking a hike. But hey ! it's definitely not inflation you understand !
.

[DT-P38]

Yes if you want to call in to work i can test it all for you..

She's already booked in to your place tomorrow morning. Need to fit up some off road tyres I have had under the house for a while (and an alignment if req'd) and get a new battery...

But I will take you up on the offer of testing that Alternator for sure, thanks Boof! I hope your mob know how to be gentle with old rangies!

[PeterAllen]

Follow this link to some useful insight on testing for bad earths,battery state and alternator.
Sticky: Electrical Troubleshooting Updated 2010

[wayneg]

I have not long brought a 750cc amp Exide battery at 'your local bloke' for under $200..

I did not have the luxury of being able to shop around but the place I went to did have 2 types of Exide 750cc amp. One was $180 and the other $225 with some fancy colour changing charge level device and no maintenance. The cheaper one was not available until the following days delivery so no real choice.

[DT-P38]

To update... the alternator tested out completley ok although I did get some good advice to upgrade the main charge feed to the battery and the positive. Both are editinon the list for tomorrows tidy ups.