There's an interesting comment on the page of the Battery University site that discusses AGM batteries:

"AGM and other sealed batteries do not like heat and should be installed away from the engine compartment. Manufacturers recommend halting charge if the battery core reaches 49°C (120°F). "

 

I have no particular reason to doubt the truth of that, but it does seem to be widely ignored, especially the battery siting aspect.

 

Not sure* if the same applies to EFB batteries.

*Edit, actually, the 'and other sealed batteries' bit probably suggest that it does apply.

 

 

Edited 18 February, 20197 yr by Wino

The issue is the battery is a consumable item and it's lifespan is dictated by usage patterns.

It's the same as many other car component. If you brake heavily you need to replace your pads/discs more often. If you use more right foot, your tires need to be replaced more often. etc etc.

In terms of your EV. That will have protections or warning against deep cycling and worse still, it'll log those and any warranty may be invalidated.

I think it's down to battery not been sized correctly for stop/start or the charging circuit is badly designed to meet emission regulations. Whatever usage pattern, the battery should last at very least 10 years, all my previous cars did. One of which (2002 Volvo) was ~11 years old when only used once a week for 2 miles drive to Asda, on original battery.

 

EV battery won't get warranty invalidated, it doesn't matter how you use it. The very early 2011 Leaf had problems dealing with heat in hotter American states, people are known to get warranty replacement by abusing their battery to trigger warranty. I having been keeping a close eye on my EV battery health, I see no problem it lasting 10+ years. Same with its 12v battery, where it even gets topped up from drive battery when the EV gets parked for a long time.

 

Whereas with latest emission strangled Internal Combustion Engine (ICE) cars, we have to spend and spend to keep everything in working order: Change the battery, buy charger to top up the tiny Flintstone-era battery. Change the engine oil. Change the gearbox oil. Change the timing belt. Listen for DMF failure which costs ££££, DPF gets blocked will also cost £££. I can't wait to ditch the ICE.

However you are not complaining when your car costs 5-10% less in fuel.

 

19 minutes ago, abaxas said:

However you are not complaining when your car costs 5-10% less in fuel.
 

Driving fossil fuel is costing 3 times more in fuel than would have cost driving EV using clean electricity.

So I'm still complaining  

 

For modern ICE car, a lot of the fuel saving end up in dealer/manufacturer's pocket: battery change, only 5 year timing belt interval, DMF and DPF replacement costs. I'm getting rid of this money pit before 2022, when timing belt is due, before it hits 150k miles to avoid DMF/DPF issues. I am hopeful I can drive long distance in full electric by 2022.

Ahh those evil double over had can engines. So more more to break.
Those evil injectors. Damn electronics I wan't my carb back.
****** DMFs that make the engine quieter and put less stress on gearboxes.
The DPF that stops people getting cancer. What a bunch of cocnuts people are for having those.
Ever increasing in reliability. W*nkers.

 

12 hours ago, Wino said:

There's an interesting comment on the page of the Battery University site that discusses AGM batteries:

"AGM and other sealed batteries do not like heat and should be installed away from the engine compartment. Manufacturers recommend halting charge if the battery core reaches 49°C (120°F). "

The battery in my car has a (insulating?) jacket around it. Is that to keep it warm, keep it cold, or for some other reason? I'd not seen that before.

1 hour ago, Rodge said:

The battery in my car has a (insulating?) jacket around it. Is that to keep it warm, keep it cold, or for some other reason? I'd not seen that before.

 

The freezing point of the electrolyte is proportional to the state of charge, the jacket gives it extra protection in cold environments so it doesn't freeze, especially if the charge level is on the low side. Probably does keep it cooler to come extent as well.

 

I'm pretty sure there was an old Jag that had a thermostat and a big fan aimed at the battery to keep it cool back in the day

 

We all need one of these https://www.worthpoint.com/worthopedia/jaguar-xj6-12-series-3-battery-box-246961015

Edited 18 February, 20197 yr by SuperbTWM

The jacket is to prevent temporary absorption of heat into the battery from  the engine bay during low speed stuff such as slow traffic or heat soak after keying off at the end of a journey. That’s when underbonnet temps away from the engine hit their peak. It slows the rate of change in temperature within the battery.

 

As soon as there is air flow in the engine bay from vehicle movements heat is dumped out from under the bonnet, battery temps will still be warm but they are managed. 

 

If left long enough, the battery / whole vehicle will always normalise to the adjacent ambient temperature, whatever it is at that time.

 

The vehicle, battery included, is rated from -20’c to something like +50’c ambient to cope with 95% of likely operating environments. Interior trim will go beyond 100’c. Take it past those temps and expect issues! 12v lead acid batteries are replaced more frequently in hot climates due to decay though, which is unavoidable. 

Found this interesting:

 

 

Would be cool if someone with VCDS could do some logging of system voltage on one of these 'micro-hybrids', and put some numbers to the proportion of time the system voltage is/isn't above (resting) battery voltage.  Any volunteers?

 

They are not hybrids by any stretch of the imagination. 

 

They do what i said, they overcharge the battery during slow downs and braking, very briefly, then take alternator load off the engine during acceleration by reducing regulator voltage, again very briefly. At no point is electrical energy used to propel the car, there are no  motors. 

 

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. How many cars have flat batteries in the showroom, a lot! Those batteries will be shagged. Excessive charging and overheating do damage too but should never happen unless the car has a fault, even then it's unlikely as that would was cause all sorts of other problems too and your car should never allow that to happen

To add. A battery also has a finite number run down/charge cycles. In the case of a standard lead acid battery the cycle is to about 40% charge and no lower, below this damages the battery. An AGM can cycle down to about 20% remaining charge. All pretty irrelevant in a car as the don't do cycles, they stay fully charged in normal use. So their life span is dictated by natural erosion and sulfation, about 10 years, the same as good quality UPS batteries which are also kept fully charged 99% of the time. 

On 18/02/2019 at 10:20, abaxas said:

However you are not complaining when your car costs 5-10% less in fuel.

 

A would question that ! Be lucky if it 1-2 mpg. We have a euro 5 pre stop start stop Galaxy and my daughter a face lift Euro 6 stop start version. Ours gets a very constant 42-44 mpg around the doors which is most of its use. Hers is the same sort of use with more longer runs maybe. She gets about 37-38 mpg. Other things come into play here too, like the strangulation of Euro 6. 

5 hours ago, Wino said:

Would be cool if someone with VCDS could do some logging of system voltage on one of these 'micro-hybrids', and put some numbers to the proportion of time the system voltage is/isn't above (resting) battery voltage.  Any volunteers?

 

 

Its not just micro-hybrids, any car with start/stop will do this.

 

According to a friend who works at JLR on power and charging systems, the usual target capacity is around 80% full, after that the BMS will reduce the voltage and stop charging (presumably brining the voltag down to a point of equilibrium with the battery so its still powering all consumers but no current going into battery), apparently if its particularly cold (under 5C) the car will fully charge the battery

Edited 19 February, 20197 yr by SuperbTWM

5 hours ago, Wino said:

Would be cool if someone with VCDS could do some logging of system voltage on one of these 'micro-hybrids', and put some numbers to the proportion of time the system voltage is/isn't above (resting) battery voltage.  Any volunteers?

 

Juts plug one of those cheap 12 volt adapters with a volt meter built in. I had one in my Mitsubishi and it was literally 15 volts braking or slowing and back to nominal the rest of the time with a slight dip accelerating. My question is and wonder what they have done about the lights as they would be expected to be dimming and brightening quite a bit. Need to look into it, I as an engineer would assume they would fit a DC to DC converter to maintain a constant light voltage, I wonder.

Maybe, but a log over a journey would give a much clearer picture of the extent to which this is useful technology as opposed to 'trendy' technology and shrewd marketing.

3 minutes ago, SuperbTWM said:

 

Its not just micro-hybrids, any car with start/stop will do this.

 

According to a friend who works at JLR on power and charging systems, the usual target capacity is around 80% full, after that the BMS will reduce the voltage and stop charging (presumably brining the voltag down to a point of equilibrium with the battery so its still powering all consumers but no current going into battery), apparently if its particularly cold (under 5C) the car will fully charge the battery

I would like to see some evidence of that. I measure alternator outputs quite regular on various cars. I never see much under 14.2 volts coming from the alternator, more around 14.4v that is charging a battery to full capacity. 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. 

7 minutes ago, Wino said:

Maybe, but a log over a journey would give a much clearer picture of the extent to which this is useful technology as opposed to 'trendy' technology and shrewd marketing.

Or, come to think of it, more about achieving nice emissions type testing results than anything else. Always seems to be  solid fall-back guess...

Just now, teescom09 said:

I would like to see some evidence of that. I measure alternator outputs quite regular on various cars. I never see much under 14.2 volts coming from the alternator, more around 14.4v that is charging a battery to full capacity. 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. 

 

I guess the only way to find out would be to run one of those cheap displays like you mentioned above. You never know, if you actually use stop start the battery may rarely get to 80% charge unless you are on a long run.

 

I have also been informed that they used the system to get round emissions on the NEDC drive cycle as you are allowed to discharge the batteries to 12v. So if you start off with a 100% battery and it doesn't start charging while it gets under 80% you have effectively saved using any engine power to run the alternator and thus reduces emissions.

20 minutes ago, teescom09 said:

My question is and wonder what they have done about the lights as they would be expected to be dimming and brightening quite a bit. Need to look into it, I as an engineer would assume they would fit a DC to DC converter to maintain a constant light voltage, I wonder.

 

I have been told there are decent sized capacitors on the VW platforms to support the electrical systems during the engine restart phase when the starter kicks in robbing all the energy it can. Dash and exterior lights remain stable but wipers still stall whilst the engine cranks over. 

I can understand an averaging scenario and also it may be they have slowed the charge rate ever so slightly to allow for more overvoltage boosts. By their nature stop start systems if used in an urban environment will have the average battery state somewhat below capacity as there is not just the starting to consider, there is the power consumption sitting with lights, blower radio etc draining away. Hence the need for a superior AGM lead acid  which can handle this better and also provide higher cold cranking current as they have lower internal resistance.  On out of town runs the battery is eventually fully charged and stays that way.

1 minute ago, SuperbTWM said:

 

I have also been informed that they used the system to get round emissions on the NEDC drive cycle as you are allowed to discharge the batteries to 12v. So if you start off with a 100% battery and it doesn't start charging while it gets under 80% you have effectively saved using any engine power to run the alternator and thus reduces emissions.

 

At that is the real reason for all this complication!

 

The car industry claims anything between 5% and a ludicrous 15% saving in fuel/emissions but you can bet your bottom dollar that marketing have done multiple rounding up of imaginary numbers based on unrealistic/excessive use of stop/start and totally fictional energy recovery numbers which I reckon is virtually zero in manual transmission cars (due to the modern way drivers use the clutch/gearbox when braking, i.e. no changing down gears)

 

I switch off stop/start which is a very annoying feature as often it restarts half a second after it stops (just the way I drive).

 

A realistic number is 1 to 2% for manual boxes higher for dsg.

 

The saving never recoups the extra cost of the technology or the extra cost (monetary and environmentally) of more regular battery chnges and the dealer recoding charges.

Just now, BigEjit said:

 

I have been told there are decent sized capacitors on the VW platforms to support the electrical systems during the engine restart phase when the starter kicks in robbing all the energy it can. Dash and exterior lights remain stable but wipers still stall whilst the engine cranks over. 

There always has been, but capacitors are potentially very dangerous things. They have virtually zero internal dc resistance. Short them and the flash is an explosion, will melt the end of screwdriver off. A bit scary

6 minutes ago, BigEjit said:

 

I have been told there are decent sized capacitors on the VW platforms to support the electrical systems during the engine restart phase when the starter kicks in robbing all the energy it can. Dash and exterior lights remain stable but wipers still stall whilst the engine cranks over. 

 

With dash lighting being LED, you wont notice voltage dips as they have their own regulators. All electronic modules etc have regulated power supplies running at low voltages. Climate control has electronically controlled fan speed, etc etc.