OK, that was a bit of a Rabbit Hole!

 

Following off on a side passage, I had never heard of Lead Crystal batteries: (https://greenrhino-energy.com/crystal-batteries/). They look interesting, but expensive (over life, they list the lowest cost of ownership, but they list Lead Acid as having a 2-3 year life, which isn't really representative of anything but the absolute cheapest, and I'd bet the price that they've used isn't for the cheapest).

 

(There is also another table here, which might be slightly fairer about cost...still using unrealistic numbers for 'good' Lead Acids, though)

 

More substantively:

 

"AGM has very low internal resistance, is capable to deliver high currents on demand and offers a relatively long service life, even when deep cycled."

 

Some AGM batteries are specialist at deep discharge, some aren't. Low internal resistance is certainly possible, but is a function of geometry, so just because a battery is AGM doesn't necessarily mean low IR.

 

(Incidentally, I once killed supervised the killing of a set of Optima AGM batteries in a lab application in about a year. Now they were, occasionally, in deep cycle mode, but I was disappointed. 'Elf and safe knees would only allow leak-proof, in that circumstance.)

 

"AGM batteries are less prone to sulfation" - possibly true, Lead-Calcium are reputed more prone to sulfation, and it is unclear which they mean.

 

Note that the 'spider diagram'  comparison is with Gel cells, and that isn't really relevant here.

 

"AGM is the preferred battery for upscale motorcycles."

 

Not totally. They may have got away with "AGM is the preferred battery for OEM fitting in upscale motorcycles.", but Lithium has quite a following in the aftermarket, and is generally seen as the most desirable as they are lighter. Whether the weight saving causes any discernible difference is questionable.

 

"AGM is making inroads into the start-stop function of cars. The classic flooded type is simply not robust enough" 

 

Well, fair enough really, but mentioning EFB would have made a fairer comparison.

 

"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)."

 

That may be true, but they are regarded as suitable for engine compartment use, with appropriate measures. The controller has to limit charging based on temperature (which it doesn't know, but at which it can make an educated guess, bearing in mind recent charge history)

 

I have to say i was a little disappointed with this considering they have 'University' in the name, but maybe I shouldn't be. 

 

 

Sorry, wino, but that may not have been an adequate answer; my comment about their info is based on looking at their site ~5 years ago, and I can't remember what exactly I looked at, at the time- probably something to do with Calcium and non-Calcium, but I'm not sure (and I'm not really prepared to dig around their site generally for other problems, unless it directly affects something I am considering here and now).

 

It is a shame, as I think they know their stuff, just have been a bit careless in the writing.

 

In any case, I think there has been some thread drift and that we are probably no longer doing anything to help the OP. If you want to continue the discussion about technical battery matters, a new thread may be indicated?

Edited 24 October, 20205 yr by Camlobe
extra info

1 hour ago, Wino said:

^ Interesting and good info about reducing both weight and hazardous substance content by going smaller. 

All you tend to hear about is car manufacturers fitting smaller batteries to 'penny-pinch' but it seems there are other pressures too.

 

Do you @BigEjit know of a source of reliable freely available info about charging AGMs etc. optimally? Every time I look it up I seem to find more conflicting info. One site suggests that they must be protected from overcharge more so than conventional lead acids, and protected from heat by avoiding fitment in engine bays - https://batteryuniversity.com/learn/article/absorbent_glass_mat_agm

Based on that it seems that poor lifetimes may be partly due to car manufacturers siting of these batteries near engines? 

There’s not that much info out there for looking after batteries which is surprising considering every car for the last 90 years or so has one. I guess it’s not that interesting as a subject. BU pages are probably the best available for free. 
 

For AGM, the charging should be voltage limited to 14.8v max, current can fluctuate within this limit. Flooded batteries are charge current limited.

 

All batteries need protection from overcharging so they don’t dry out. AGM naturally hold less electrolyte over wet flooded batteries and need more protection from this but certain duty cycles will force a loss of moisture from the assembly regardless of tech. Pressure valves in the lids aim to stop this water loss (Valve Regulated Lead Acid - VRLA) and in-vehicle charging strategies hold the battery in a confined charging window to protect it from overcharge and try to recover it from undercharging depending on available engine run time. 

 

Excess heat is also a silent battery killer from overcharging and environment and is bad for all lead acid batteries. Too much heat and the lead plates decay and turn to mush, it takes a while for this to have a noticeable effect but once started, it’s not reversible. Equatorial markets go through batteries quicker than temperate climate markets. It’s also the reason for the module on the neg post has temperature sensor so that charging is restricted relative to battery temp. 

 

General mis-information leads folks to think cold weather kills batteries. It doesn’t! It shows up weak batteries damaged from summer heat/discharge/overcharge. The insulation bag the battery is covered in is to reduce the speed of heat soak from the engine bay when stationary or slow moving with no airflow underbonnet. Regulations only allow AGM to be fitted inside a vehicle cabin for occupant protection from spraying acid in a crash situation. It usually ends up in the load space somewhere accessible but then needs to be bigger to overcome the losses in heavy high performance cabling stretching the length of the chassis adding more weight.

 

Then you get those folks pulling the fly lead off the battery module to inhibit S/S and throw all these carefully engineered compensation factors out the window! 🤦‍♂️ Dried out batteries go pop!

Usual blah blah blam Youtube video.

 

I skipped through it but think that I can sum it up.

 

Bloke has flat car battery, he charges it (or maybe used a jumpstart pack) and was good to go, to carry on with his life.

 

Except life for him is staring into a screen so 99% of the video, the blah blah blah is precisely that!

 

@J.R.

Point of video is even in 2020 VW have snagging faults, and not the battery, software and hard wear in the vehicles.

They build cars for over a century and still manage to **** things up because they are always aiming at low emissions under testing (range with EV's, and penny pinching with the production of the vehicles. 

Then there is the 3 week wait for Dealerships, yet VW Group supposedly had all these Mobile Techs that could go out and do the Emissions Fix.

They might well need to be doing the same again if their latest models are going to strand owners. VW Assist going out with all the gear and more than a rough idea type thing.

Edited 24 October, 20205 yr by e-Roottoot

On 24/10/2020 at 08:18, Camlobe said:

 

That may be true, but they are regarded as suitable for engine compartment use, with appropriate measures. The controller has to limit charging based on temperature (which it doesn't know, but at which it can make an educated guess, bearing in mind recent charge history)

 

 

The current monitor on the battery post also measures the temperature which is near as you are going to get to actual battery temperature without a sensor built in the battery.  

It’s weird ... my dpf keeps regenerating and when it does the oil temp gets high, if I turn engine off the battery dies and car won’t start... but after about 30 mins when engine cools it starts. Maybe it’s overheating the battery, starts first time every morning. Really confusing