Follow up on my 3 step regulated cheepo charge [the LiDL one will also do Gel Cell & AGM batteries which arw charged differently] of my S5 de-sulph was in fact an exact 22 days in total to get the SOC [6x2.1] to 13.7 volts. My feedback conclusion for the group on 'lifestyle' is that two 15 minute trips once a week meant the battery will never ever get to absorption mode, and subsequently the plates at the bottom level of the battery will flake & sulphate. we all know how important the state~of~charge plays in modern computer driven cars is in general and in the particular how critical it is when control is determined by the PCM in CRD GV's. For myself I might one day get around to making a super-capacitor starter / lifepo4 [Li-ion not li-Po] hybrid, but I'll have to think through transitient voltage spikes and current current fluctuations not just for the battery but for the 3 on board puter modules. There has to be an alternative to these great big antiquated heavy battery lumps that should have been obsolete 50 years ago, designed for carburettor engines that took 5 minutes of spinning to pull petrol into their cylinders and engine oil that was as gloy as araldite, the modern ignition off draw is also huge by comparison with permanently running memories - radio - compass - keyFOB - alarm functions etc, years ago we had only one tiny clock and even then only if you owned a Jag or similar.

27 days in total, before I took it off charge. 2 hours later I connected the invasive old school drop tester :

- 1st pic was just a voltage only [it showed a worrying sleight overcharge] reading, no load applied and showed approx 13.5v
- 2nd pic after a 10 second load was 11.8 well in the green and not dropping
- 3rd pic after a 10 minute wait was given a 10 second load and was 11.4 well in the green and not dropping
- NOTE - you are wasting your time, and a garage is wasting your money unless a drop-test is done ONLY at near or at full charge.

- images for the drop test in order 1 2 3

1st image
2nd image
3rd image

- well in the green and no further needle drop after both drop tests - well happy
- connected to the car [with the BMW battery on it] and the alternator showed 14+ volts - well happy
- the second and third pic on 'drop' show ∓ spot on 800 CCA's - well happy
- tested again 3 days after coming off charge even after the drop tests - still showing a full float at 13.8v [800+CCA] as per image 1

Conclusion : My lifestyle and lack of use cased the problem and will cause the same problem again, a spare full size backup battery on 'maintenance mode' will work. The works well in a jam, is an expensive but instant 'get out of jail card'. Last point you can not do a desulph in less than 3 weeks - it just does not work - and unless you use a 3 step charger you will never get past 98% and a regulated voltage output of not more than 13.4 volts with usually less than 1 amp of current to achieve 2% before float mode.

Sorry the images are so large.

x3 edits none are revisionist

1st was to inset the URL links because the above pics did not [link] work. 2nd and 3rd are to complete my battery check.
2nd - to easily monitor the alternator input on the move, you can find a cheaper one for £2 delivered to your door.
3rd - I bought this new school non-invasive conductance tester just because I could and I've just tested the S5 Bosch and my de-sulph after 4 days off charge returned 12.87 volts @ 809CCA En.


Now I am concluded ...... no more edits !

 

nice bit of testing.

Richard

 

Keep your lead-acid battery whether starter or leisure battery on permanent 13.8volt float charge, (when it will draw only milliamps and gas is so microscopically small the hydrogen channel can easily accomm.) and the battery's life will be exceptionally long. This we found with lead-acid backup batteries used for alarm bell-boxes in the security business. Many-a Yuasa battery at 15 years old plus would still light my heavy current test lamp brightly for a long time, and these were all jelly batteries, all kept at 13.8volt by a small regulated charger. In fact I used 6volt scrap ones to power my Sony vintage camcorder of its day, and they were far better and powered it far longer than the nickel-cadmiums.

Leedsman.
n.b.
What Quinteq calles a "drop-tester" I think we used to call a "leg-tester", last used by me in the late 1950s. Usually the battery was on the floor after charging, and this gadget was propped against one's leg in use. It had two heavy brass prongs to push into the lead battery terminals, a power resistor across drawing about 100 amps, plus wooden handles of course to hold it, and a kind of swivel action to adjust the prongs to fit any battery. Across the resistor there was a cheap moving coil voltmeter as part of the assy.
This voltmeter had green for good and red for bad in its window. The gadget soon sorted out the bad batteries, as they wouldn't keep the voltmeter deflected for more than a few seconds. In those days there was a 6volt version! Oh yes, there were a few 6volt Beetles about. My boss at the time showed me around Doric Batteries in Heckmondwike where he used to work once, I found it fascinating. Apart from the smell of sulphuric acid everywhere...

 

I well REM the leg tester only just a couple of years ago millions of garages still owned one. Now the price of 100a delivered to your door is only about £20 so may have ditched the leg tester although as Leedsman says they both do much the same thing and are a lot cheaper than a 500 AmpCarbon Pile Battery Load Drop Tester.

- thanks, tfb.