I get intermittent warnings that my battery is low and systemns will be shut down in 3 minutes - usually just before I start the engine.

Battery is one year old and maintains a steady voltage.
The pic is of my bluetooth voltage monitor taken immediately after the low battery warning appeared on the screen prior to starting the engine.

Battery resting voltage was 12.4v which dropped to just under 11v during starting, then charged up at 15v. Car starts and runs fine.




Anybody got any ideas why I should keep getting these warnings when the battery appears OK. Jules

I think that charging at 15 volts is too high, I would do some tests on the alternator

Any resting battery voltage that's below 12.6 volts could indicate a weak or damaged battery.

15 volts is too high. Should be 14.4 volts. At a stretch 14.7 volts occasionally, but this is too high for the long term on a regular basis.

Once the battery is charged. Disconnect it, say overnight, about 12 hours minimum to stabilise the resting voltage, 24 hours would be better, & while still disconnected measure the voltage. Should be low to mid 13 volts.


Is the Bluetooth monitor good quality. I use a proper Kyoritsu meter. Are you actually measuring at the battery terminals. Measuring somewhere throughout the car is a waste of time. Procrastination, mankind's greatest labour saving device!

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I had one (warrantied) battery that developed apparent short ignition only running and then unexplained starting failures.

It was relatively newish and passed the Kwikfit Quick Battery Test.

However I do believe that it probably had a failing cell and the resulting internal high resistance mucked up the various tests and readings.

The new 12v Battery, bought elsewhere, has since been trouble free.

https://www.freel2.com/forum/topic38965.html?highlight=battery

Unfortunately another new battery may be the only way of proving this.

(if charging problem -- dont forget the uncommon Blue Wire) FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 79k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

Im charging the battery up now and will check the voltages with the bluetooth device and my multimeter tomorrow.

The alterrnator may well have a problem - the charging voltage on the bluetooth is oscillating between 14.7 and 15v - Is that normal ?





with the multimeter showing 14.7v

I know the battery was low on charge; did several very short journeys this morning towing the trailer - hence im charging before re-testing. Jules

Jules,

Obviously 15v is too much……..possibly the Bluetooth device is over-reading……your multimeter with 14.7v sounds right…….possibly there is nothing wrong with the electrics……..
Look on the bright side……  FL2 SD4 HSE Lux Auto MY 2012— current
D2 TD5 HSE Man MY 1999 470kmls….gone 2014 ….lovely engine..chassis rotten
D1 300TDI Man MY 1996 56kmls….gone 1999…D2 much better
Wife’s FL1 1.8P MY 2001 32kmls …gone 2007…has Mini since.

yes that may be so and the battery is actually just rather low on charge.

It will be interesting to see what the morning test is like. Jules

Lightwater wrote:

Are you actually measuring at the battery terminals. Measuring somewhere throughout the car is a waste of time.

Further to this.

The mulitmeter consistently reads 0.1v lower than the bluetooth voltmeter.

The battery seems fine and happily holds a charge of 12.5v on the multimeter after being left overnight.

However the car continues to charge the battery at 14.9v even after several miles of driving (15.0v on the bluetooth device)

This seems too high from what people have said on here.

I guess next step is to get the alternator checked over. Jules

I presume you don’t get the ‘low battery’ warnings now Jules………….
The alternator on my FL2 charges at 14.7v whilst the engine is running……I think it’s supposed to.
So if you trust thé multimeter reading it’s slightly over that……whether it’s acceptable, within the parameters for the battery to not overcharge……I don’t know. Alternator could need a new regulator I suppose. As you say perhaps it needs checking-out.
Looks a bit of pig to remove……! FL2 SD4 HSE Lux Auto MY 2012— current
D2 TD5 HSE Man MY 1999 470kmls….gone 2014 ….lovely engine..chassis rotten
D1 300TDI Man MY 1996 56kmls….gone 1999…D2 much better
Wife’s FL1 1.8P MY 2001 32kmls …gone 2007…has Mini since.

jules wrote:

Im charging the battery up now and will check the voltages with the bluetooth device and my multimeter tomorrow.

The alterrnator may well have a problem - the charging voltage on the bluetooth is oscillating between 14.7 and 15v - Is that normal ?




with the multimeter showing 14.7v

I know the battery was low on charge; did several very short journeys this morning towing the trailer - hence im charging before re-testing.

Correct me if I'm wrong but shouldn't the BMS shut down charging the battery after the battery achieves full charge, then when the demand requires the battery topping up it switches back to charging the battery, if the battery terminals are continually at 14.7 volts when the engine is running then it must be assumed the battery or the system has a fault. The object of the BMS is to reduce alternator load and therefore reduce fuel consumption, would the voltage show different values after a reasonable run before switching off.. my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.

^^^^^This, all day. Mine, a 850cca AGM, ranges to 14.8 down to just under 13 volts. But, I have no idea if the alternators are different on mine.

If it was me, I would do a hard battery reset before exploring other possibilities.

Dartman the one wrote:

Correct me if I'm wrong but shouldn't the BMS shut down charging the battery after the battery achieves full charge, then when the demand requires the battery topping up it switches back to charging the battery, if the battery terminals are continually at 14.7 volts when the engine is running then it must be assumed the battery or the system has a fault. The object of the BMS is to reduce alternator load and therefore reduce fuel consumption, would the voltage show different values after a reasonable run before switching off..

I am sure the whole description is in the Repair and Wiring Manual. (Use the 'Find on Page' function of your browser --for 'BMS')

You will also find tests using (I think) the rear window heater as a load, looking for a 14.8v output.

I haven't got time at the moment to get details or extracts, but I think you will find that no clutches, or contact points are used to interrupt the output. Almost certainly the alternator power generated will be incrementally adjusted to keep a set voltage as measured by the BMS.
This may be adjusted in response to engine power requested by throttle position.

If you have time, please read the Manual and let us know what you find.

Thanks Ian

This picture is the description but the Forum interface is cutting it down in size. - Sorry

 FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 79k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)