Dream car or Budget, which comes first? Tell us your thoughts | No thanks
Mazda CX-5 - Modern stop start battery. - xtrailman

I'm having charging problems with my CX_5 diesel, battery volts should be showing i believe around 12.6 volts when stood overnight, but i have never seen that, currently its showing around 12.4 volts.

But on two occasions the volts have been down to 12.1 volts, shortly afterwards the car failed to turn over.

I am monitoring the volts with a plug in voltmeter, which does read slightly low compared to my fluke meter, but its near enough to monitor what's going into the battery.

Sometimes the charging volts appear to be what i would expect, other times not, too low. For example immediately after starting i would expect around 14 volts plus, sometimes it never goes above 12.9 volts.

So the fault isn't consistent. Really it would help if i had some criteria to indicate what sort of charge volts to expect.

The volts are always high on the overrun, but not on acceleration, if i put the lights on volts usually also increase.

Any help would be appreciated, mr google doesn't seem to help.

Mazda CX-5 - Modern stop start battery. - elekie&a/c doctor

It is not possible to test a battery using a voltage only reading.A flat battery can show 12 volts at the terminals.The only proper way to test a modern battery is with a conductance tester.This measures the ability of the battery to store a charge and its present capacity against rated capacity value.It is also a good idea to check the alternator charge voltage.hth

Mazda CX-5 - Modern stop start battery. - Peter.N.

It should though be showing around 14.4 volts with the engine running, if it isn't you would seem to have an alternator problem.

Mazda CX-5 - Modern stop start battery. - xtrailman

Thanks Doc, yes i realise that, really i'm just seeing the voltage as an indicator that some charge is going to the battery.

I've also checked all the cell with a hydrometer, got 1.25 approx from each one, just one was only very slightly different.

As you say a conductance tester appears to be the modern test tool. Is this one worth buying?

http://www.obd2express.co.uk/wholesale/launch-bst-460-battery-tester-in-mainland-china.html

Irronically the dealer tested the battery with a magic box he had and pronouced the battery ok, but asked for the car to be booked in next tuesday, immediatly afterwards i jumped into the car and got another fail to start, he jumped it for me and it started immediatly.

Mazda CX-5 - Modern stop start battery. - elekie&a/c doctor

This is the type of tester reqd,not sure how good this one is.Good video here on testing a battery.www.youtube.com/watch?v=FTvRl19mjdg

Mazda CX-5 - Modern stop start battery. - Liliflower

yes, definitily worth to get one, and good quality in obd2express.co.uk/

Mazda CX-5 - Modern stop start battery. - FP

Once again I feel cynicism rearing its head.

A thread that has been dead for well over a year suddenly gets a plug for a particular product.

 

Ask Honest John

Value my car