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 Post subject: Battery Warranty - Claims, real SOH?
PostPosted: Wed Apr 16, 2014 3:27 am 

Joined: Wed Apr 16, 2014 3:14 am
Posts: 1
Hi All,

I've been in the market for EV for some time but still hold some concerns over the battery warranty, are they really prepared to shell out to replace it and more to the point how do they really check and manage this?

1) I wonder if anyone has had any experiences with having to claim on the 8year/99,360 mile (unstated capacity protection!?)battery warranty? or know of any cases? It would be interesting how VW deal with this, check this etc.

2) I have heard they deal with the SOH (state of health) of the battery? As I understand this is the 'real' capacity of the battery pack after any reserve they have calcualted in (think this is about 20% on the e-up). Can anyone shed more light on this?

Michael ;)

 Post subject: Re: Battery Warranty - Claims, real SOH?
PostPosted: Wed Apr 16, 2014 8:44 pm 

Joined: Thu Dec 05, 2013 2:54 pm
Posts: 11
Those are very good questions - unfortunately, since this is Volkswagen's first electric vehicle, there isn't really a precedent on how well VW will honor their battery warranty.

Were you thinking of leasing or buying? If you aren't buying outright, I'm not sure it really matters...

Also, since they just announced that the e-Golf uses a super-special battery that doesn't get affected at all by high ambient temperatures, chances are the VW e-Up will be heaps better than the first generation Nissan Leaf ever was anyway.

A large consideration for buying an EV for me was that my savings in fuel would pay itself off within the first 4 or 5 years. Anything after that period is bonus.

 Post subject: Re: Battery Warranty - Claims, real SOH?
PostPosted: Mon Jul 21, 2014 10:46 am 

Joined: Mon Jul 21, 2014 10:32 am
Posts: 6
It's my impression that VW are using NMC battery chemistry (nickel manganese cobalt), though I've not seen that stated explicitly by VW. This has a longer lifetime than the LMO (lithium manganese oxide) cells that Renault/Nissan/GM/Mitsubishi have used so far.

Problem with serial battery packs is that if one cell goes down then the whole pack is faulty. Oops. So the battery management system has to be very clever and nurse all the cells individually, else if one starts drifting low when all the others are fully charged, the battery is only as good as the least charged cell. VW must be pretty confident of their battery pack as they are talking about a warranty of 8 years and an expected lifetime of 10 years at better than 80% capacity retained. Compare that with Nissan who say 6 years to 70% retained.

The problem with better longevity is that the cells have a lower energy density. The e-Up pack is as heavy as Leaf, but has 15% less capacity. Difficult to tell how much of that is the management electronics, but you get the idea. The longest lived cells of all are lithium titanate, which Mitsubishi has used on Japanese (domestic only) MiEV taxis, as they will get a hammering from rapid charging all day long. Consequently, this MiEV has a minuscule range.

NMC is a good compromise and a wise choice on cost/weight and safety, but it's just a bit more expensive yet with worse range. I guess VW want to get a reputation for reliable EVs with those for whom the range is sufficient. Are they expecting to sell many?

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