I stop battery voltage

[xtrailman]

My cars been stood for a couple of days, today I've checked a new cd in the player and noticed my plug in voltmeter is only showing 12V dc.

I've checked its accuracy against a professional fluke meter, I'm a retired electrician, and that reads 12.16v dc across the battery.

Normally I would be looking for around 12.6v.

From what I've read 12.2v usually equates to 50% capacity, so I'm a little concerned that the battery may be faulty, or maybe just under charged.

My driving routine is no different to any other car I've owned, and I've not had any battery issues for a very very long time.

Just wondering if this Istop is worth using?

Or has anyone had a battery fail?

I did phone the dealer but didn't get much out of them, apart from them saying they had changed a few on the fords, but none on the Mazda.

 

[squibcakes]

I use the iStop all the time - accept when the temp is hot - rather keep the air con going. What is the SG at this voltage?

I think that if the car has been off for a while then voltage would drop and what you see is normal - there are electronics always depleting the battery even when the car is off.

You should charge the battery over night and then check the SG. If the SG is still low, then the battery is on the way out.

 

[Sassimac]

I had a battery go flat after a few days. And considering I only had the car for a very short time, I thought that very unusual.

The Dealer did tests on the battery, and declared it faulty. The car still showed that the i-Stop function was available. In fact it never stopped showing it..!! Nonetheless, it was declared faulty.

Consider trying a specific gravity test as mentioned. This is how the battery is tested in the manual.

The Dealer did replace the battery.

 

[xtrailman]

Thanks for the replies, I don't have a SG tester except for checking wine!

So maybe time to buy one for the battery, I'm doing a 200 mile trip today so will monitor the voltage.

Is it ok to connect a smart charger across the battery while its in the car connected?

It must be over 30 years since I've charged a car battery, and I've never had to do a sg test either.

 

[Perusal]

According to the 'blurb' in the CX5 Brochure the iStop restarts the engine using, and I quote, "combustion energy rather than the starter motor" so I don't think this could be the cause of any drop off in battery performance.

I have used the iStop since new and find that it has 'a mind of its' own' in so far as it will operate when it thinks fit, by which I mean it's an intelligent system that will not operate when the conditions are inappropriate. For example I was surprised some time back that after a long run on the M-Way when I came to a junction the engine remained running. I thought this odd until somebody explained that the last thing you want to do after a high speed run when the engine is at high temperature is switch the engine off with red hot oil in the turbo i.e. lacquer the turbo bearings. The engine should not be stopped until the oil has had a chance to cool slightly.

On another occasion after only driving 800 yards in hot weather I stopped at a set of traffic lights, the engine stopped and then after a minute or so re-started of its' own accord, I suspect to provide sufficient electrical power via the alternator to feed the A/C without draining the battery.

Interestingly, I have now done 4500 miles in the car and like you am retired so don't commute, most of my driving is on country roads with perhaps 20% in built up areas. My wife asked me the other day whether the system had saved us much fuel. Upon checking via the instrument dial I noticed that in those 4500 miles the engine has been off for 1 hr 39 mins..........now that must have saved some fuel!

So, in my case I am a complete convert. Of course, if you are a grand prix type of driver at the traffic lights (I am getting a little old for that now) it doesn't contribute to racing starts but the engine does fire back up extremely quickly and has never held me up when pulling away (nor has it EVER stalled as one road test commentator suggested it was prone to)

 

[xtrailman]

Went to start the car today, voltmeter showing only 11 volts, car failed to start.

Manage to start the car using a power pack and set off on a two hour plus trip, still wasn't happy with the charging voltage. so booked it into the dealer at Newcastle.

technician came back and said at some time the battery had been disconnected, possibly when the towbar was fitted and wired, but afterwards the alternator smart charging hadn't been reinitialised.

Technician reset the system and the charging voltage is now noticeably higher, typically 14 volts on idle, were as prior it was seen as low as 12.3 volts with the engine running.

 

[xtrailman]

According to the 'blurb' in the CX5 Brochure the iStop restarts the engine using, and I quote, "combustion energy rather than the starter motor" so I don't think this could be the cause of any drop off in battery performance.

I believe that only applies to the petrol engine, I'm pretty sure the diesel uses the starter motor.

Disconnecting the battery also affects the istop according to the Mazda tech, he reset that as well, said something about it having a learning curve.

 

[Perusal]

I believe that only applies to the petrol engine, I'm pretty sure the diesel uses the starter motor.

Disconnecting the battery also affects the istop according to the Mazda tech, he reset that as well, said something about it having a learning curve.

No, my brochure clearly states that combustion power is used for both the diesel and the petrol engines, the only difference being that the petrol engine starts 0.05 seconds quicker.

( 4/12 - Actually I was wrong, so apologies, further digging reveals that the it's the injection of fuel into the gasoline engine that restarts it whilst in the diesel the engine has to be turned to compress and ignite the fuel/air mixture hence the need for a larger starter motor and I guess additional drain in the battery)

Nonetheless, glad to see you got sorted.

Had some discussions with Hodgsons in Gateshead when I was looking to buy. Very helpful, wasn't bothered about the distance to travel but in the end they didn't have the right model in the right place at the right time so ended up buying somewhat closer to home.

 

[xtrailman]

Bit of a conflict here with what the dealer say and the car manual.

Manual says if the car is stood for long periods remove the battery and periodically charge it.

Says nothing about reinitialising after a battery is removed, or about a special battery charger being required to charge it.

But the dealer service manual clearly does.

Cars been starting ok since it failed, although battery voltage isn't showing 12.6 volts yet after been stood over night.
But again the dealer manual says nothing about what voltage should be seen.

Anyway I'm now armed with a SG meter and will take cell readings today.