47 minutes ago, teescom09 said:

It would be extremely difficult to measure the actual charge in a battery without load testing it and very precarious to do it via charging current against voltage. 

 

Interesting comment .

Do you believe the notion that the battery monitoring modules (or whatever they call them) are doing a meaningful job of Coulomb counting and assessing battery SOC that way? 

 

 

Edited 19 February, 20197 yr by Wino

@WinoHave you fallen asleep whilst listening to 'battery university' story tapes again 

 Whut, did someone say something?

Used to be SOC was available in infotainment (now removed) but possibly still accessible in VCDS.

 

Edited 19 February, 20197 yr by xman

Wouldn’t bother chasing the SOC reading from the vehicle. By turning on the electrics to get a reading, you are changing the status of the electrical circuit and measuring the battery plus varying losses from the ignition being on.

 

Better off just sticking a digital voltmeter across the battery terminals. Better still if the battery is disconnected first as there will be nothing leaching off the battery affecting the reading. 

12 hours ago, teescom09 said:

Regarding the battery and stop start. It has little if any impact on the life of the battery. The stop start only comes to play if the battery is pretty much fully charged and the brief pull from the starter motor will not impact the battery whatsoever. The only thing that kills batteries prematurely is being allowed to go totally flat and remain flat, most common cause in fields and showrooms awaiting buyers and delivery.

Here's a case study:

I drive my Octavia about once a week, 30 miles mostly motorway commute, but close to home is start-stop traffic. 60 miles a day.

During summer, stop-start kicks in soon after started driving in the morning. During winter, stop-start would gradually kick in later until would only happen when almost arriving home. On return journey, if I turn off S/S, the next week I drive it, S/S would kick in sooner.

 

True, S/S only happen if battery is at high SoC. But it is a very bad implementation in the way it draws more power than the car generates over a moderate journey. Isn't a reliable engineering solution when combined with the fact how these 12v batteries prefer to be kept fully charged, not 80% charged.

 

Isn't there some manufacturer that stops the piston in a position to allow ignition start, rather than a bodge job by using the starter motor?

Why isn't Li-on battery used instead? Li-on prefer to be kept charged at 50%.

Why are 12v cars even called micro-hybrid? Even those new 48v equipped cars are hardly hybrid, just another Band-Aid on ancient + polluting internal combustion engine.

 

 

 

Regarding the voltage drop when starting. Exterior lights do dim when starter motor is being used, whether during stop-start or initial start. I have seen it happening on my front door camera. All non-LED VAG cars seems to do this if you look closely.

Lead acid is superior to li-ion in almost all ways other than density and deep cycling.

This is especially true for temperature. At normal spring/summer temperatures the li-ion will have ~3x the energy density of the lead acid but at -20c it'll be the same or lower. Also at those low temperatures you won't be able to charge the lithium based batteries very fast, if at all, without damage.

Fine is you live somewhere that's always warm. But if you live in the highlands, might as well invest in a flat bed. You'll need it in winter :P

 

On ‎20‎/‎02‎/‎2019 at 08:18, wyx087 said:

Why are 12v cars even called micro-hybrid?

The clue is in the 'micro' bit, it means 'millionth of'.

On 20/02/2019 at 08:18, wyx087 said:

True, S/S only happen if battery is at high SoC. But it is a very bad implementation in the way it draws more power than the car generates over a moderate journey. Isn't a reliable engineering solution when combined with the fact how these 12v batteries prefer to be kept fully charged, not 80% charged.

 

AGM batteries are much less fussy about the SOC than the standard Lead Acid, 80% or in fact much lower is not an issue.