Dead Battery.

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Dead Battery.

Postby nang » Sat 28 Jan, 2017 02:56

I don't use my Z3 every day so keep a little trickle charger hooked up. Done this for many years with no adverse results with other cars.
However this morning, after two weeks unused the battery was dead flat. No warning lights, nothing. Little red light on charger also not on. So seems like I have a buggered charger. Power in nothing out.
Would a not working trickle charger flatten a battery in two weeks ?
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Re: Dead Battery.

Postby colb » Sat 28 Jan, 2017 09:23

How old is the battery? If the charger failed then quite possible for the battery to die due to old age especially in this cold weather here in UK. Maybe not cold where you are so its probably down to age of battery and failed charger.
The draw on the battery would be the clock and the radio memory and the alarm if operating, should be able to cope with that if a charger or conditioner is put on a good battery. Must admit I try and start mine up and run it up to temperature at least fortnightly and if needed put a conditioner on it until it gets to maintenance level and takes what it wants.

Worth checking out what your alternator is putting out when you get it running by putting a volt meter on the battery posts, you should see a good voltage of 14.5 volts with nothing switched on.
Last edited by colb on Sat 28 Jan, 2017 09:36, edited 1 time in total.
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Re: Dead Battery.

Postby peter2b » Sat 28 Jan, 2017 09:33

I use to use a battery conditioner on my kit car over winter when I didn't use it worked fine car started on the first press on the start button, I think I got it from car builder solutions
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Re: Dead Battery.

Postby therealdb1 » Sun 29 Jan, 2017 00:41

It depends also on how the charger has failed.
If the output circuit has gone short then this would place an additional load on the battery and could flatten it in two weeks. It could be like leaving the lights on.
First test ought to be trying another charger, a faster one not trickle, on the battery and see if it takes a charge but it is not uncommon for batteries to die without warning these days especially if they have been allowed to deep discharge.
If the trickle charger is designed for being continuously connected to the car then there should be no problems you have just suffered bad luck.
I have three of the Accumate type with four LED's that I have left connected to the fleet for months on end over many years with no issues.
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Re: Dead Battery.

Postby mich » Sun 29 Jan, 2017 04:11

The same type of thing has happened to me but my battery is only 3 yrs old approx, but car seldom used. The battery has a powerprobe indicator window which changes colour with the condition of the battery:
Black = charge
Green = charged
White = replace
How accurate are these and do you view in the shade or sunlight?
I have had mine on trickle charge for 12 hrs and the colour has not changed from black.
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Re: Dead Battery.

Postby Rory4711 » Sun 29 Jan, 2017 12:58

Am not convinced about the indicator on the battery, unless I've a duffer. The Carcoon I keep the car in winter months comes with a built-in constant trickle charger which is always on. The car starts first turn of the key but on checking the battery indicator it's either black, or possibly blank.
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Re: Dead Battery.

Postby motco » Sun 29 Jan, 2017 17:37

I strongly recommend you do not switch on the ignition even to position 1 or 2 until you have a fully charged battery in place and the charger is removed. I had a flat battery, put it on charge in the car, and turned on the ignition to check whether I had lost my radio code with the charger still connected. I hadn't, but in doing so it damaged the coding plug in the instrument cluster and put EEP_1 in the odometer display until I replaced the coding plug. There's threads on the subject of EEP_1 :shock:
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Re: Dead Battery.

Postby mich » Sun 29 Jan, 2017 23:27

Rory4711 wrote:Am not convinced about the indicator on the battery, unless I've a duffer. The Carcoon I keep the car in winter months comes with a built-in constant trickle charger which is always on. The car starts first turn of the key but on checking the battery indicator it's either black, or possibly blank.

The indicator is still showing black but the car starts so easily and the battery feels full of punch so I guess the powerprobe indicator is rubbish.
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Re: Dead Battery.

Postby z3ddie » Wed 01 Feb, 2017 15:06

I bought one of these off Amazon - for £1.99 worth its weight in gold - you see standing voltage and also if the alt is putting charge into the battery

https://www.amazon.co.uk/gp/product/B00 ... UTF8&psc=1
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Re: Dead Battery.

Postby colb » Wed 01 Feb, 2017 18:07

Snap, I have one of these, got it after my alternator started to fail and had to be replaced. Ideal for monitoring the output by simply plugging it in the cig lighter socket. I see the Amazon link is over 4 quid, got mine off ebay for 1.99.
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Re: Dead Battery.

Postby lightning » Wed 01 Feb, 2017 18:21

mich wrote:The same type of thing has happened to me but my battery is only 3 yrs old approx, but car seldom used. The battery has a powerprobe indicator window which changes colour with the condition of the battery:
Black = charge
Green = charged
White = replace
How accurate are these and do you view in the shade or sunlight?
I have had mine on trickle charge for 12 hrs and the colour has not changed from black.


The battery in my 3.0 Z3 is 60Ah.

lf the battery was flat, then a trickle charger at (say) 0.5A would take over 100 hours to fully charge it. However most "Smart" chargers can deliver a boost current of between 1A and 4A and at 2A for instance it's still going to take 30 hours to fully charge.

Even with a higher powered charger the battery will draw less current as it begins to charge. On my 16A charger the current starts at the maximum but rapidly drops to below 3A (on the charger's digital readout) remaining around 2A until the battery is fully charged.
This is on a disharged (won't engage the starter) but not completely flat battery.

If the battery is completely flat the "Smart" charger may in fact do nothing as the internal resistance of the battery is so high that it cannot detect it being connected.
Unless the charger has a "recovery" mode a way round this is to connect a 12v lamp across the battery, say a sidelight bulb, this will fool the charger into kicking in, after a few minutes the bulb can be removed.
That's effectively how the "recovery mode" does it, if fitted, using a resistor rather than a bulb.
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Re: Dead Battery.

Postby mich » Wed 01 Feb, 2017 20:53

lightning wrote:
mich wrote:The same type of thing has happened to me but my battery is only 3 yrs old approx, but car seldom used. The battery has a powerprobe indicator window which changes colour with the condition of the battery:
Black = charge
Green = charged
White = replace
How accurate are these and do you view in the shade or sunlight?
I have had mine on trickle charge for 12 hrs and the colour has not changed from black.


The battery in my 3.0 Z3 is 60Ah.

lf the battery was flat, then a trickle charger at (say) 0.5A would take over 100 hours to fully charge it. However most "Smart" chargers can deliver a boost current of between 1A and 4A and at 2A for instance it's still going to take 30 hours to fully charge.

Even with a higher powered charger the battery will draw less current as it begins to charge. On my 16A charger the current starts at the maximum but rapidly drops to below 3A (on the charger's digital readout) remaining around 2A until the battery is fully charged.
This is on a disharged (won't engage the starter) but not completely flat battery.

If the battery is completely flat the "Smart" charger may in fact do nothing as the internal resistance of the battery is so high that it cannot detect it being connected.
Unless the charger has a "recovery" mode a way round this is to connect a 12v lamp across the battery, say a sidelight bulb, this will fool the charger into kicking in, after a few minutes the bulb can be removed.
That's effectively how the "recovery mode" does it, if fitted, using a resistor rather than a bulb.

Thanks that is useful info I must check the charger which is over 30-35 years old, and when I said trickle I may have used the wrong term It may be about 4 amps I will check
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Re: Dead Battery.

Postby lightning » Thu 02 Feb, 2017 08:20

Probably a standard battery charger of the type sold for decades.

A transformer, two diodes and if you are lucky a meter on the front. Nothing "Smart" in there, connect it up and it drops about 16 volts of unsmoothed rectified AC into the battery at whatever current it will accept.

If the battery is good, then the current demand will drop as it reaches full charge. If the battery is sulphated, the charger will continue to dump 2-4A into it.
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Re: Dead Battery.

Postby therealdb1 » Thu 02 Feb, 2017 09:50

You wouldn't want to leave that charger connected indefinitely!
In this case you have already had a faster charger connected and your battery is flat so it is probably stuffed.
If it were me I would buy a new battery anyway at this point, get the car started and check the charging circuit, and then if the car is only used infrequently acquire a proper smart trickle charger that you can leave connected full time.
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Re: Dead Battery.

Postby nang » Sun 05 Feb, 2017 03:27

Took my battery to my friendly mechanic. Came up fully charged overnite. Seems that my charger is stuffed .Tried it on other batteries and no flashing red light. Got another coming. I've got 2 others on the rest of my fleet which have given no trouble.
I've always been led to understand that letting batteries discharge over time is no good for them.
Said mechanic, well versed in things BMW tells be he'll need the car to reset air bag light after my little episode.
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Re: Dead Battery.

Postby bertiejaffa » Sun 05 Feb, 2017 13:10

Im interested to know what trickle chargers people have/recommend?
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Re: Dead Battery.

Postby Rory4711 » Sun 05 Feb, 2017 13:30

Have has a CETEK for years, can safely be left on all winter. Currently ( no pun intended ) I don't use it since the charger that comes with the Carcoon indoor cover is a clever little beast; if it's brought your battery up to speed and is still connected, if there is a power cut - we've had a couple - it takes over the running of the fans to keep the carcoon inflated, using your battery. It can keep this up for a couple of days, and when the power comes back on it reverts to charging up the battery.
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Re: Dead Battery.

Postby nang » Tue 07 Feb, 2017 04:15

Just bought a replacement...Connecnet (probably Chinese)Charging Current 1500mA.
Fingers crossed :roll:
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Re: Dead Battery.

Postby nang » Fri 10 Feb, 2017 03:38

Looks like I was lucky, put charged battery back in this afternoon. Reset clock and radio, no warning lights have lit up. :o
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Re: Dead Battery.

Postby mich » Sat 25 Mar, 2017 03:58

I have now brought a “Power Train” trickle charger it says 3 stage charge system 12v 1.6 amp, has been on for about 26 hrs and still showing charging. Battery had enough charge in it to start car easily so must be nearly there. The manual says it brings the battery up to 95% charge then goes into float stage which keeps it at this level.
Cost NZ$49.95 free delivery.
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