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Old 23rd November 2021, 11:18   #1
Rev Jules
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Default Strange one. Flat Battery??



I have had a C-Tek trickle charger on the car for the past three days, this morning I go to check the car and there was a clicking noise coming from the alarm sounder, the air conditioning was running and the fuel gauge was moving slightly side to side in the empty, this was with no key in the ignition, the charger yesterday was showing in the fully charged mode, obviously the battery is flat this morning.
Any ideas please.

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Last edited by Rev Jules; 23rd November 2021 at 11:22..
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Old 23rd November 2021, 11:23   #2
MSS
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I would start the process of elimination by removing the battery terminals and putting the ctek on the battery to see if it will achieve and retain full charge.
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Old 23rd November 2021, 12:53   #3
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Quote:
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I would start the process of elimination by removing the battery terminals and putting the ctek on the battery to see if it will achieve and retain full charge.
Please refer to above, it had achieved a full charge, just wanted to know why things had turned themselves on with out a key in the ignition??.

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Old 23rd November 2021, 13:06   #4
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My reasoning behind the suggestion was that perhaps things turned themselves on because the battery voltage fell below a certain threshold that is required for normal operation. This could be due to the battery becoming discharged for some reason. Charging the battery whilst not connected to the car would help you eliminate with some degree of confidence there being a fault with the battery+charger.
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Old 23rd November 2021, 18:28   #5
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The ECU will throw a fit at very low voltage.

My battery failed in August, no response to key when I tried to unlock with the button. Found the battery voltage 'floating' around 9-10v so thought I'll try and start it as didn't want to go looking for leads.

What surprised me was that despite the starter struggling it managed to start, great I thought. Pressing the windows button to confirm all was ok not so great. I can only compare it to pressing the detonate button. All hell let loose, fuel gauge & stereo died, wipers came on then stuck midway, you get the picture.

With the engine running the battery now had a whopping 6v. So thought alternator What to do next? I should have switched it off but as I had it booked in for another master cylinder & radiator with the worlds slowest mechanics (I got it back last week btw !) I drove the bl**dy thing instead and decided I'll fit the spare when I got her back later that day (Ha ha). when I got to the garage I checked it again and it had 5v. At 5v the engine was still running but I had no wipers, no horn, no stereo or indicators

Turned out to just be a U/S battery, all fine once it was swopped out. Didn't even store any fault codes though which given all the low voltages I found very strange indeed.

TLDR if battery drops below 9v ECU/Canbus doesn't like it.
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Old 24th November 2021, 21:22   #6
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Quote:-- the charger yesterday was showing in the fully charged mode.

What do you mean by the above quote ??

Does your charger have lights to show things like power on, or battery charged ??
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Old 24th November 2021, 22:36   #7
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Ctek chargers have lights to indicate the stages through which the charger has progressed. This includes a light for the fully charged, monitoring/topping-up stage.
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Old 25th November 2021, 00:17   #8
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Question

Not really my forte but maybe if I pose a daft question or two someone in the know might respond, so here goes. If the bonnet is up while trickle charging would the bonnet switch prevent the bcu from going to sleep? If so and the bcu is kept awake then what would be the possible result (if any) of say a drop in ambient temperature? Could it, for instance, trigger the operation of the rear screen heater? For something to be triggered in the absence of a fault, assuming the battery and charger is proven to be ok, what system/item would draw sufficient current to flatten the battery overnight?
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Old 25th November 2021, 21:39   #9
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Quote:
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Ctek chargers have lights to indicate the stages through which the charger has progressed. This includes a light for the fully charged, monitoring/topping-up stage.
I'm sure that you are aware that the full charged green light rarely tells the truth. It can tell blatant lies about the CAPACITY of the charge held in the battery.----

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Old 25th November 2021, 21:43   #10
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Quote:
Originally Posted by COLVERT View Post
I'm sure that you are aware that the full charged green light rarely tells the truth. It can tell blatant lies about the CAPACITY of the charge held in the battery.----


Yes but not a complete lie. On the whole when the light is green the battery has a reasonable amount of stored charge.

Would you by any chance be trying to show off that you know something about batteries?
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