Battery or alternator? Which do you think?

[Mikaelse]

I can recommend putting in a combined Battery voltage meter , phone charger in the cig lighter socket. cost 10 £ or so and shows you what is going in. Strongly recommend AGM type Battery if you need to change. A 70 Ah one is fine if it has got start spec. They cost more but charge up several times faster after start and self discharge more slowly. Last longer and tollerate deep discharge better. My oldest car Battery of that type is more then 10 years but I guess that is not to expect.  

[rich1068]

Battery seems to be holding out but the winter will be the real test I suppose. And I do have a meter of sorts. One of those FM/BT transmitters for streaming music and calls. On start up it shows Battery voltage and how much charge the alternator is putting back.

[brendangeorge]

Hi Richard

The Battery voltage is critical - if it is low then you have a problem.  However, it is not the only or best indication of the battery's health.  The Battery's ability to hold charge and deliver CCA or CSA if you are English (Cold Cranking Amps or Cold Starting Amps) are key.  To test CSA you need a special meter - I think you mentioned Lexus RSA tested your alternator etc.  they probably should have performed a CCS test (the AA would have done) - did they give you the results?  I called the AA for a jump start of my old 430 (I needed to make my tee time at Woburn) and my started pack was duff.  We got it running and charged a little but the CCA was low - bought a new bat on the way to the golf club.

The Battery life is a function of the number of charge discharge cycles and the depth you discharge to.  It is not a great idea to flatten your Battery it will affect its life.  Temp is a big factor.  If the car won't start don't keep cranking fix the problem and charge the Battery after a few goes at cranking. Somebody mentioned using an AGM Battery - check the spec and make sure of the CCA.  My RX450h has one because of the stop start nature of the engine - however, it is not used to crank the engine only run the electronics - the engine is cranked using the traction Battery but nothing works with out the ECUs.  My neighbour has a RX450h and the AUX bat went flat - the car would not run.  I showed him how to sort it out (the local dealer did not help).

Your charging tester idea is neat - with moder car alternators you should never see the light dim and brighten with engine speed - takes me back to my old MKII Cortina in 1978.  That was a cold winter :).

Good luck with the bat - my apologies for the lecture, if it was boring - I am a test manager for a living.

Bren

[Thackeray]

47 minutes ago, brendangeorge said:

I am a test manager for a living

What do you test?

The thing that irritates me is that a lot of big companies don't bother with Document Testing. So they issue user manuals that users can't understand.

It's a pity after all the work that has gone into producing their product that they don't understand it's vital to explain to the buyer how all the functions work. Same thing applies if you're only producing products for internal use - the accompanying user guides need to be tested to make sure people can understand them.

[brendangeorge]

Hi William

I am an Electrical and Electronics engineer (Degree etc.) and these days spend most of my time testing large IT programmes - Data Centers, Networks etc.  The whole thing from the designs to user acceptance, including the security.  Clearly I don't press all the buttons (some I do) but manage the process.  I am the annoying so and so you have to have on the programme to keep everybody honest.  You are correct about documentation - the people who deisgn and build things see it as an embuggerance and probably run out of time to do it.  The other challenge is the assumption of knowledge on behalf of the user/customer.  On a big project we have a hadover built into the cost - if it is not done the customer does not pay.

When we run a big project we have something called a RTM - a requiments tracking matrix and one of the requirements is the docs.  One type of deocument we have to produce is called a run book - what you have to do to get something reinstalled or up and running quickly with out reading all the designs and manuals - a bit like stickies on the forum.  Big IT projects are like new cars (not so relevant here because a lot of run old ones) thinks change all the time.  My next gig will be all new version, loads of new features that don't work, unclear requirements, rubbish documentation => loads of testing which keeps me in work.

I should add I often work on projects that are tough or a bit broken - plenty of room for being a hero and there is always work - I love it really.  I should also say testing is a process based on critical thinking so I can manage the testing of anything - experience makes it easier.

Cheers

Bren

[Thackeray]

15 minutes ago, brendangeorge said:

the people who deisgn and build things see it as an embuggerance and probably run out of time to do it.  The other challenge is the assumption of knowledge on behalf of the user/customer.

You are so right. There was a time (many decades ago) when software writers would write the user documentation and for an intelligent user it read like a foreign language. When the documentation is done, it needs to be tested on intelligent users who have never encountered the system before (detailed previous knowledge means the test may not be valid). A document test manager needs to monitor how the user follows the document, makes false steps, gets stuck when a vital step is not spelt out etc. Then the document can be changed to account for these mis-steps.

The problem can be that the software designer may just excuse the documentation by implying that the user is stupid. This is wrong. If the user can't get the product working from the documentation, then the documentation needs to be fixed!

In the project plan, there needs to be a task headed Document Testing! If there isn't, the documentation is unlikely to be as good as it could be. (I hope you can tell your project manager to put this heading in!)

[Mikaelse]

There is limited need for rocket science and exaktness here unless you are an engineer like me.  IF you can see what happens with the voltage after starting and it goes up after a few minutes to say 13.5V or so at least that is reasoanbly ok concerning the charger function.  Then the question is if the Battery is recieving charge descently fast or alternatively is damaged or tired so that it des not perfrom even if it is fully charged as far as it goes.  You can have any of those problems. 

1. Charger weak,  2. Battery recieving charge slowly or 3. weak even if charged for a long time. 

If it sounds tired when running the starter from cold even after say an hour long trip at least previous day it is probably time to change it. You can also of course charge it with a charger over night  to be sure it is full. 
In the SAAB cars ( for engineers and nerds , now gone mostly) in the dash display they  showed lowest voltage during start for a few seconds. There were indication in manual what was OK depending on temperature.  I seem to remember 8,5 Volts if it was very very cold - 20C perhaps. 11 V or so in summer.