At those prices, I think I’ll stick with the trusty zero maintenance SLAB in my annex 1 plane :-) (Which I think has already lasted double the lifetime of the Gill it replaced).
I wonder whether anybody puts enough value on the weight saving to pay the extra?
IMHO Gill wet batteries (the cheapest – at £440+VAT) are crap and not worth using, except possibly in a scenario where you never fly past the crease in the map (as in say flight training, or a lot of GA “club” profiles) and thus rarely have to start up away from base, and then starting issues aren’t a worry. But they also cost c. 2x more in effect because they tend to pack up 2x sooner than Concorde.
A Concorde RG24-15, at £617+VAT, is a much better battery. Mine was installed Jan 2013 and will probably test to spec at the next Annual, Jan 2021! The previous one lasted 6 years and I think this one is doing well because I use the CTEK reconditioning charger at each Annual.
I don’t know how much the ETX680 would retail for in Europe but $1000 = £724 today, so (assuming the mfg actually supports the reseller pipeline with discounts) you are paying perhaps £150 extra inc VAT. LAS sell some but not this one, and their ETX900 price shows a $1=£1 conversion with 20% added 
which leads to the ETX680 going for £1200 inc VAT which is £460 extra inc VAT over the Concorde.
For that £460, you are saving an astonishing 13.4 – 3.7 = 9.7kg! A slight loss of capacity of 13.6Ah down to 11.7Ah.
The big Q is: who will pay the extra to save ~10kg. Admittedly $1 → £1 is a ripoff and shows that either (a) Extra are sticking a middle finger to Europe and not supporting resellers here or (b) LAS are printing money 
I know a guy (no longer flying) who paid 5 digits to certify a composite oxygen cylinder for a TB21, to save something similar in weight.
You also get a far lower self discharge rate; the ETX680 is likely to start the plane after a year… well after the engine is rusted up solid, so maybe not
The counter argument is that this battery contains, ahem, e-l-e-c-t-r-o-n-i-c-s and we know the history of electronics in GA I mean, look, everybody is ripping out magnetos and installing electronic ignition which has proved to be 100% reliable < cynicism off >
The sealed ($595) Gill batteries are said to not be as bad as the conventional wet ones ($464), says MooneySpace – that said, they also vastly prefer Concorde RG ones ($679).
Peter wrote:
For that £460, you are saving an astonishing 13.4 – 3.7 = 9.7kg!
Yes, which is well and good for some types; there are planes where people are putting in lead weights into the tail to make CG issues work better.
I’m all for new technologies and all that, but one should check if they actually get anything for their 460#’s ;-)
Big cost differences between the US and Europe
Yes indeed in some types you want the extra weight. But not in a TB20, where the battery directly subtracts from the luggage compartment loading, which is already compromised by the TKS fluid tank.
I would go for the lithium battery if it was proven in the GA marketplace. Is there any data? I guess any data would come from the US homebuilding community.
Peter wrote:
I wonder whether anybody puts enough value on the weight saving to pay the extra?
No, because if I used a lighter battery, I’d need it replaced with ballast weight to make the CofG envelope work (I think I’ve mentioned this before).
In any case, looking around a typical pilot’s lounge, I think there are much cheaper ways of saving weight :-)
Peter wrote:
Big cost differences between the US and Europe
Yes, but if you look at what Spruce US ask for shipping the battery over here (~$250) and add the non-zero risk of getting slapped with VAT, you end up with $1000 for the Gill any way you slice it… Same with oil.
There are cheaper ways to ship than what Spruce offer, but it gets complicated fast, probably not worth the hassle for a single battery.
It shows that Spruce EU are, as you put it, printing money.
Spruce EU (Sandelving.de; not related to Spruce US) are marking up US prices heavily, but often one has to use them because it is the only way to import the item (say, PR1422 and related “hazardous” sealants).
The real issue is that due to a lack of reseller support from the US vendor(s) nobody is going to commit to shipping stuff in bulk, by sea freight. Air freight shipping batteries is daft. I reckon LAS is buying the lithium batteries at the 1-off US retail price.
Peter wrote:
Air freight shipping batteries is daft.
Why? I can have a 10″ × 10″ × 10″ package weighing 40 lbs (an approximation of the new Gill) shipped to Poland for an estimated $125. Takes about a week. So say $750 delivered. Spruce EU want 650 EUR + 20 EUR shipping. Both are without VAT. So I save about 50 EUR by buying straight from Spruce. And I’ll surely find what I need for less than Spruce US charge, or, worst case, use my A&P’s discount.
