Battery size for xj6

Hi guys
. What is the minimum amount of ca. And col cranking amps i should get for my 4.2 litre engine?
My mechanic says the one i have is not enough and could do damage to starter. I have 750cca. And 690cca

That sounds like plenty to me. My cars range from 590cca to 675cca - 3.4 litre, 3.8 litre and 4.2 litre. Living in Sydney means 5 degs (Celsius) is a cold winter’s morning. Paul

Nothing wrong with that battery specs, Stan - it’s more than ample…

Cant really see a battery causing starter damage - insisting on holding key to ‘crank’ with the engine not turning will. The starter is a very robust item - battery size is immaterial as long as it charged enough to crank and start the engine…

That said; get the biggest battery that will fit in the tray - particularly in a cold climate. Actually, the physical size of the battery hides secrets; high storage capacity and high cranking amps in the same physical size means denser packing. and a less mechanically robust one…

xj6 85 Sov Europe (UK/NZ)

Thanks paul and frank…you just saved me 250.00.sounds like mechanic wanted to sell me new battery.

I’ve always thought of batteries in the terms of weight. Lead isa heavy. Objective, the “heaviest” battery that will fit the allotted space.

Circa 1954, I served in Northern Germany. My Belgian assembled 50 Chevrolet featured two 6 volt batteries, in parallel. Not the best arrangement, But, it never failed to crank there. When I came home, each battery had expired, "somewhere aboard ship on the N. Atlantic !!!

Fixed. bought one new big battery !!! NY to El Paso in three days.


My father’s 52 Oldsmobile hat the same dual battery set-up, Carl…

With two discharged or iffy batteries barely able to turn the engine - coupled in series they sure spun the engine for a certain start. Of course there were drawbacks - any bulb ‘on’ was likely to blow…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

And 24 is even better, sorta!!!

  1. decades ago, my son completed assembling the very much “hotted” up Ford 429 for his "scratch built "T’ roadster.
    Too much compression and initial friction to crank on 12.
    auto box prevented a push or pull start. Old tech for a “tight” engine.

“Well, it may cost a starter, but, let’s give it 24”. A decent crank and it fired with a roar. Fortunately not enough cranks ot cook the starter. Let run for a bit with added cooling at 2K RPM to seat the cam and other stuff. From then on it fred nicely on a mere 12v.

Decades later, I built my scratch built, but with mere warmed up flat head Ford V8. Set it up on 12. The 6v starters do OK on 12. But, prolonged cranking not advised. Not good any way… Starters have no cooling fans!!!


Hi: I have 2x 1991 XJ6’s and other vehicles. The only battery I put into any of them is a Energizer 12v battery 108-700N - h9.72"xw7.24"xh8.15" 850 cold cranking amps. It has both top terminals and side terminals. I live in Canada where the temperature varies from minus 30F to 90F. I have never had any starting problems. Battery is about $100 CDN at any local Walmart.


If you have two 1991 XJ6s then they are what are called XJ40 and they are discussed on the Jag-Lovers XJ40 and not here. The XJ40s were a major new development by Jaguar first delivered in 1988 in the USA and they have very few parts or systems in common with the Series I, II and II XJ6s and XJ12 discussed on this list.


Paul M. Novak

1990 Series III V12 Vanden Plas

1990 XJ-S Classic Collection convertible

1987 XJ6 Vanden Plas

1984 XJ6 Vanden Plas

1969 E-Type FHC

1957 MK VIII Saloon

Ramona, CA USA

Hey guys, getting back to my jag project, and I need a battery. What size is appropriate for a series 1 XJ6? The online battery finders are returning mixed results.

Go to Costco and read their app book which actually lists cars, years, and models. I bought a battery from them for my series 3 XJ6 in 2013, and it lasted until January 2022

Just get the biggest battery that fits in the tray, Rob - and ensure it is not too high - hitting the bonnet…:slight_smile:

Due to changing battery sizing through the years; it may be difficult to find the original specs - or a perfect fit…

xj6 85 Sov Europe (UK/NZ)


not sure about SI - do you have the metal battery box? I do, but have discarded it because I found it hard to find a suitable battery. For some years I have been using a 50300, which is said to be a long and wide as the original, with good success. Only due to the different height I omitted the box and used a Jaguar bracket instead, maybe from a SIII car, maybe from an XJS. It works absolutely trouble free.

Good luck


75 XJ6L 4.2 auto (UK spec)

The original battery box had a cooling fan built in. I never did understand why?

Yeah, most of them tell you to get a Group 26 which while it works fine it looks odd because it doesn’t fit the S1 battery tray and hold down very well. Super tiny. After a ton of looking at size specs I found that a Group 85 fits better (not perfect) and is usually readily available. The super geniuses at auto parts stores probably can’t find it if you say Group 85 so tell them you want a battery for a 2006 Pontiac GTO.