low internal battery voltage Newbie question

[tbird]

CSR 200 10K miles, new battery recently fitted by CC prior to purchase, just been out for a quick blat as sunshine final here , Started fine, drove about 20 miles, stopped for a couple of hours, started again first time, after about 5 mile stack warning low voltage, cleared after about another couple of miles, monitored voltage all way home ran at 14.2v - 14.3v consistently. Happened after a particularly bad gear change

should I

1 worry this is a precursor to a problem

2 just check connections for loose or corroded connections (nothing imediately visible)

or is it a case of TADTS

 

cheers

 

Tim

[Phil]

If you have ever tried to take a reading off a battery and you have had to scratch the surface to get a decent connection, think about this when fitting a battery.

The alternator is supplying 14 ish volts but does the battery accept this?

The lead is lead colour, grey because of oxidation on the surface, this creates a barrier, resistance, sometimes resulting in a flat battery.

Extreme cases can cause you to think the battery is dud or the starter is on the way out as the starter struggles to start the car.

It will also give you false readings on equipment running off the battery.

Add to this vibration from running and changes in the weather, problems can be intermitent

Simple and not costly, sand down the terminals before you fit the battery, do not think because it is new it will be OK.

If you wish to add grease do it after and on top of terminal and connections, if you grease before connecting everything you may re insulate the connection.

Hope this helps

 

FreeRange7

 

http://good-times.webshots.com/photo/2404840560089816983khvSRw

 

[tbird]

Phil hi

thanks for the info, I am ok with the general theory etc and maybe I made the queation too simple, I guess what I was interested in was, where the voltage is sensed, as the engine was running what would differentiate between the Voltage the Alternator is running at and the voltage the battery is sitting at and what is the Vdiff that is used to trigger the dash warning , or does it use a calculation based on current being supplied by Alternator which I guess could be a more accurate measure of the state of the battery. or has anybody had a similar problem just prior to a diode pack giving up the ghost, Mainly, as its still under CC warranty, if it has been seen before I could monitor/test for specifics and maybe save some money

 

but thanks for taking the time to reply all knowledge is useful

 

cheers

 

Tim

[Phil]

The most common way to test an alternator output is to go to the positive an negative on the battery and run the engine, then load the system up with lights, stereo, heater etc to see if the output remains the same around the 14.5 volt mark, if it does the alternator should be good.

This still does not mean that the battery is accepting the charge as stated.

If the voltage drops as you load it up the alternator is failing to do its job.

The battery gives out 12 volts to the stater turning over the engine and then the alternator spins supplying power to the starter helping to start the engine.

The battery is then redundant as the alternator takes over supplying power to run the engine and keep the battery topped up.

If the volt meter on your car is attached to the battery in any way, a bad connection could give the problem you are experiencing, as the gauge reads the battery voltage then the alternator voltage this maybe the case.

If not check the earth on the gauge, remove clean and replace even if it looks OK and then check the connection to the alternator, again clean and replace.

You may know all this Tim, if so forgive me as I am only offering an opinion based on problems encountered from years of selling batteries, I wish you the best of luck.

 

 

FreeRange7

 

http://good-times.webshots.com/photo/2404840560089816983khvSRw

 

[geko]

Hi,

 

another case of voltage warning in a CSR:

here

 

 

Best regards

Gerhard

 

Caterham CSR 200

MAZDA MX-5, NB, 1840ccm

 

Edited by - geko on 2 Aug 2009 19:34:58

[tbird]

Phil Hi,

thanks again I am always pleased people volunteer personally experienced knowledge we can all learn from everyone's experience

 

 

Geko Danke SchÖn, interesting, will look at wire types used in circuit

 

Tim

 

Edited by - tbird on 2 Aug 2009 20:01:31

 

Edited by - tbird on 2 Aug 2009 20:05:00