The only person I've heard of having a problem with a 12V battery in an EV was Hal (BYD) but I think that was just a simple replacement.
Mad in technological terms, perhaps... but, in reality, the whole EV thing is a bit mad, Ted. Inter cert physics tells us that moving more weight requires more energy. Does the proportion of electricity we generate from renewables even compensate for the extra energy an EV requires? Then there's the environmental cost of mineral extraction, manufacture, shipping, scrapping more energy efficient (i.e. lighter) petrol and diesel cars, etc....
"Does the proportion of electricity we generate from renewables even compensate for the extra energy an EV requires?"
Yes ... the energy harvested from inertia an gravity tru deceleration is all down to or dependent on mass or weight ... the heavier the vehicle the more energy is harvested from degenerative brakin .... tho I prefer to say degenerative deceleration because any braking is a 100% energy conversion to heat ( 1st law of thermodynamics) .
To explain it in taxi driver terms ... if yur ev weighed nuttin an you inside weighed nuttin ( i know thats a stretch of the imagination but bare wit me 
) wer driving it an yu took yur foot off the accelerator.... you wud come to a immediate stop with out braking .... like as if you hit a brick wall sort o ting ....the energy saved tru degenerative/ deceleration is dependent on 2 tings ..... the apes drivin style .... an the mechanical efficiency of the yoke yur drivin ... an as we all know mechanical efficiency can never achieve 100% which is why perpetual motion is impossible....
Now... any questions ?
I guess we have to go back to primary school science to remember that you can't get more energy out than you put in. Hybrids (and presumably EVs) are good at recovering some of the extra energy they consume through regenerative braking and such like but they're not manufacturing free energy. A good example might be recovering energy going downhill but it's not going to recover more than the extra energy (compared to a petrol or diesel car) it took to get up the hill in the first place. Where hybrids come into their own is in Urban centres when they don't need to either keep the engine running or constantly stop and start it.
When SB said he'd buy me a lottery ticket a while back I had a look at the price / specs of new Octavias. As far as I recall the diesel (manual transmission) version achieves (albeit marginally) better mpg than the hybrid version. Stealership figures are based on "mixed" driving so it's likely that the hybrid would be better in an urban environment and certain that the diesel would be significantly better on the open road / motorways. When I bought my MKIII I had a look at the Prius. It's published mpg figures were higher than what I was getting from Gretta hence I concluded that all that extra technology was pointless for me.... although, I opted for the DSG Octavia in the end which also consumes slightly more diesel than Gretta! Ifn SB ever buys me said lottery ticket and if it won I'd still buy a new diesel Octavia or maybe (ifn it's a particularly high jackpot) a new diesel Superb.
Yuod be surprised how many dont understand basic inter cert physics rat
"Does the proportion of electricity we generate from renewables even compensate for the extra energy an EV requires?"
Obviously if your driven a hybrid or ev on the motorway all day at constant velocity ....energy harvestin/ regenerative deceleration ...as i like ta call it is very limited an Obviously a diesel bein more efficient than a petrol engine will possibly do better .... but passengers live in city's not the motorway .... which is why ya drive there to work ... I tink yur confused a bit cause ya live down the bog an have to drive to civilisation to work ....
As for winnin the lotto you cud buy a diesel cause ya wont be puttin a taxi roof sign onit an cartin the riff raff , workin class an junkies that ya normally carry round in yur taxi ....an ya wont be fixing it in the shed neither up all nite havin the luv o yur life wonderin wen yur comin to bed
