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Stilllearning

Just how dead is a really flat battery?

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My car (a Mazda) flattens its 90Ah battery completely in less than a week when unused. When I complained to Mazda, they said that if the car is to be left unused for more than 3 days it should either have the battery disconnected or be connected to a charger. If disconnected it takes half an hour to reset and recalibrate everything (including the radio, Bluetooth, brakes, steering, windows, etc), but my "smart" charger refuses to charge the battery (even from full) because the apparent self-discharge rate registers as a fault. So generally I'm stuffed.

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1 hour ago, roland elsdon said:

Skoda fabia vrs. To change headlight bulb remove front bumper. Which contains spotlights that have no remote connectors.

Specialist did it for me by removing ‘bits’ under bonnet. 45 mins labour.

That must be the new vRs as my old one, 2006 diesel wasn't like that.

I didn't even need to find someone with small hands ;)

 

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50 minutes ago, Machpoint005 said:

Isn't that a case of his preferring the better option, but the cheaper one prevailing? Think Sony Betamax vs VHS.

 

Absolutely.  Just think how much better the rail system (worldwide) would have been if the gauge had been built to a seven (and a 1/4”) foot gauge.

 

Back on topic, I left the boat without isolating the batteries and with the fridge door open the batteries were almost completely flat  after a few days.  Went back after a couple of weeks and voltmeter showed nothing.  Recharged over the next few days cruising and I expected them to be knackered but they continued another couple of years  with no obvious loss of capacity.

Edited by dor

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When I had to replace the battery of my Vectra a decade ago, the manual warned that disconnecting the battery  would mean having to reprogram the radio with a security code, this being an anti-theft feature. To save myself the trouble I connected a small 12V SLA battery to the battery cables with strong crocodile clips before removing the old battery and fitting the new one, and had no probems. As long as you turn off everything, such as lights and radio, first, the additional 12V battery does not need to have a large Ah capacity as it only needs to supply a small current to keep the electronics alive while the main battery is being changed.

 

It is best not to attempt to charge a really flat battery with a fast, high current, charger. The high current density caused by current having to flow in the small conductive areas between the sulphated areas can lead to local heating of the battery plates. The consequential differential thermal expansion between the sulphated and non-suphated areas can force active material from the plates and lead to loss of  capacity. 

 

Something similar to the French train problem happened to London Transport some decades ago. I think it was the Piccadilly line, where they ordered new trains with fewer, but longer, carriages to get new trains of the same length as the old ones but with greater capacity. They correctly calculated that the new trains would negotiate the curves in the tunnels, but forgot that tube tunnels bend up and down and well as from side to side: the longer carriages of the new trains fouled the tunnel roof at some of the sharper vertical bends, meaning that the track bed had to be dropped at those locations before the new trains could run.

Edited by Ronaldo47
Typos, clarification

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34 minutes ago, Keeping Up said:

My car (a Mazda) flattens its 90Ah battery completely in less than a week when unused. When I complained to Mazda, they said that if the car is to be left unused for more than 3 days it should either have the battery disconnected or be connected to a charger. If disconnected it takes half an hour to reset and recalibrate everything (including the radio, Bluetooth, brakes, steering, windows, etc), but my "smart" charger refuses to charge the battery (even from full) because the apparent self-discharge rate registers as a fault. So generally I'm stuffed.

Interesting as our mazda was left for 3 months while we were boating...admittedly in a garage so it was left unlocked with the electronic handbrake off and it started (diesel) without fuss and operated its istop after a 5min journey. I was quite impressed. 

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3 hours ago, roland elsdon said:

Skoda fabia vrs. To change headlight bulb remove front bumper. Which contains spotlights that have no remote connectors.

Specialist did it for me by removing ‘bits’ under bonnet. 45 mins labour.

Same as the Mrs' Skoda Yeti. Can't change a headlight bulb without removing half the front end of the car. And by then it's cheaper to replace the whole headlight, complete with running lights, as it's a combined unit. £300 later...  I believe that the EU banned the design and construction of cars like that a couple of years ago because it doesn't meet the requirements of a lot of continental countries (we always carry spare bulbs but a bit pointless when you need a workshop to change the bulb).

 

I'll stick with my collection of Land Rovers (20 year old Defender and a 60 year old Series truck). £3.50 last time I changed a headlight bulb and took me less than 2 minutes.

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5 hours ago, Stilllearning said:

I beg to differ: 2cvs and Dyanes etc are very simple, just not like any old British cars. For example all you need to adjust the ride height of a 2cv etc is an 8mm spanner and a ruler :)

 

Or 4  very large adults 😂

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1 hour ago, Ronaldo47 said:

 

Something similar to the French train problem happened to London Transport some decades ago. I think it was the Piccadilly line, where they ordered new trains with fewer, but longer, carriages to get new trains of the same length as the old ones but with greater capacity. They correctly calculated that the new trains would negotiate the curves in the tunnels, but forgot that tube tunnels bend up and down and well as from side to side: the longer carriages of the new trains fouled the tunnel roof at some of the sharper vertical bends, meaning that the track bed had to be dropped at those locations before the new trains could run.

The Central Line was built to a smaller diameter than the other contemporary tube lines. And also originally had shorter stations, later lengthened. When London Transport was doing a widespread fleet replacement in the 80s/90s they wanted to standardise the fleet to allow more flexible use of the rolling stock and simplify maintenance arrangements etc. Surveys of the tunnels showed that only a few areas were so tight that tunnel reconstruction was necessary, so the whole plan was deemed feasible. Much of the reconstruction was done in short overnight possessions, by unbolting the relevant cast iron tunnel segments, excavating the clay from behind then putting the segment back with some extra packing pieces in the joints. A few rings done each night. Once the tunnel was sorted the track was completely renewed, with the alignment optimised to suit the new tunnel layout.

A colleague of mine at the time was responsible for much of the survey work and track alignment design.

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1 hour ago, frangar said:

Interesting as our mazda was left for 3 months while we were boating...admittedly in a garage so it was left unlocked with the electronic handbrake off and it started (diesel) without fuss and operated its istop after a 5min journey. I was quite impressed. 

Yes, Mazda said only 1 or 2 models are like it. Mine unfortunately, a Mazda 6 diesel, is one of those models.

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2 minutes ago, Keeping Up said:

Yes, Mazda said only 1 or 2 models are like it. Mine unfortunately, a Mazda 6 diesel, is one of those models.

Oh ours is a 2019 CX5 so I think it’s the same 2.2d engine...must just be different other systems. I have to say I was amazed it started after the lay up

as due to unforeseen circumstances I wasn’t able to put a ctek charger on it which was the original plan. 

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Last summer I left my Kia Sportage for three weeks on the drive.  I fully expected to need to charge the battery due to the alarm, but it started happily.

 

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Just now, Stilllearning said:

This morning the charger is showing about 1 to 1.5 amps, does this imply a healthy and charged battery? It’s an 80 ah battery.

Without the charging voltage the current alone is meaningless.

 

If it is 14.6v at 1 amp then it is charged, but you will have an unknown capacity (it may now be a 40Ah battery) until you do a capacity test.

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This is why we all need to switch to Electric cars.

Never again will you have to worry about not flattening your engine start battery ........as you wont have an engine. QED!

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18 minutes ago, Dr Bob said:

This is why we all need to switch to Electric cars.

Never again will you have to worry about not flattening your engine start battery ........as you wont have an engine. QED!

 EV 12v battery can suffer if car is used for short journeys, it takes its charge from main batt when car is being used or charged, a long slow charge (or long run) is needed occasionally to top it up. 

 

ETA: Unless it has a 12v li-on of course. 

Edited by nb Innisfree

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Update. I and my local garagiste were amused to note that when he put his electronic battery diagnosing gizmo on the battery it said to replace the battery. It also said the battery was capable of holding 564 Ah, and it s a 600 Ah battery. So it’s going back on the car.

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11 minutes ago, Stilllearning said:

Update. I and my local garagiste were amused to note that when he put his electronic battery diagnosing gizmo on the battery it said to replace the battery. It also said the battery was capable of holding 564 Ah, and it s a 600 Ah battery. So it’s going back on the car.

I never yet met a battery diagnosis gizmo nor a smart charger worth the space it takes up.

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2 minutes ago, Sir Nibble said:

I never yet met a battery diagnosis gizmo nor a smart charger worth the space it takes up.

All those I have seen (HRD testers) really excel at persuading customers with well discharged but serviceable batteries that they need a new one.

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15 minutes ago, Sir Nibble said:

I never yet met a battery diagnosis gizmo nor a smart charger worth the space it takes up.

Which is why Didier chuckled when he pointed out the reading to me.

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12 minutes ago, Tony Brooks said:

All those I have seen (HRD testers) really excel at persuading customers with well discharged but serviceable batteries that they need a new one.

I once saw a car that had three new batteries on warranty before I pointed out the missing fanbelt.

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