why have the battery in the boot?–
TTopGun
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At 02:26 2010-09-05, TTopGun was heard to say:
why have the battery in the boot?
Weight distribution. The battery is a heavy object. The front of
the car already has the engine. The midsection has the driver and
transmission (and the driver is on one side). Thus it makes sense to
move some weight to the rear passenger side.
You might gain something by downloading Kirby’s XJ-S Experience in a
Book eBook from the website - I’m quite certain this is discussed in there.
— '88 Jaguar XJ-SC 5.3L V12 (LHD) ‘Black Cat’
Sean Straw '85 Jaguar XJ-S 5.3L V12 (LHD) ‘Bad Kitty’
Sonoma County, California '91 Jaguar XJ40 4.0L (LHD) ‘Trevor’
http://jaguar.professional.org/ '69 Buick GranSport 455 V8
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In reply to a message from TTopGun sent Sun 5 Sep 2010:
With the XJ-S I reckon it was to do with ‘‘no room in here, plenty
of room back here’’, and I tend to agree somewhat.
The heat in the engine bay also was not kind to batteries, well
documented in the '70’s when I worked for Lucas Batteries here.
The early XJ40 had them under the bonnet, then went to boot, so
maybe weight, heat, room, all played a part in it. My BMW 740iL had
it under the back seat, just like the early VW Beetles, and that
was simply room, as the engine bay was full of engine and stuff,
and the boot was woeful for that size car.–
The original message included these comments:
why have the battery in the boot?
–
Grant Francis 85 XJSV12 (Hers), '96 X300 XJ6 3.2l (My Cat)
Adelaide South Austarlia, Australia
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In reply to a message from TTopGun sent Sun 5 Sep 2010:
Early XJ 12 had the battery under the hood but it had to
have a cooling fan.
As heat affects battery performance the it was re located on
the 12 cylinder cars to the trunk.
As far as weight is concerned the weight of the battery is
negligible compared to the rest of the car.
Alex P–
alex paterson
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In reply to a message from alex paterson sent Sun 5 Sep 2010:
Cars like the XJS, BMW and Lincoln LS have the battery in the trunk
due to weight distribution…battery weight is
not ‘‘negligible’’. XJ12’s had the battery under the bonnet and
utilized a special cooling fan (and six’s too) to reduce
heat…only when they introduced the ABS system did they move it to
the boot because the ABS took up too much space.–
1986 XJS, 5.3 Litre V-12, 1974 Triumph TR-6
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TTopGun wrote:
why have the battery in the boot?
My suspicion is: no other place to put it. Perhaps it’s worth
noting, though, that the XJ12 has the battery in the engine
compartment, and it has its own little cooling fan!
– Kirbert
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In reply to a message from Kirbert sent Sun 5 Sep 2010:
space, the engine bay is busy
heat, definitely because it comes with a cooling fan, and
these engines are one of the hottest around, I don’t know
about trunk temps on a hot day though.
weight distribution, 100litres or petrol weights about 80kg
and that when the tanks are full, there isn’t much back there,
but a battery adds 20kg-40kg which aint that much more.–
TTopGun
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In reply to a message from TTopGun sent Sun 5 Sep 2010:
It’s a ''constant…where passengers, fuel, cargo, drivers weight
can change…the battery weight doesn’t…engineers consider
the ‘‘car’’ and all it’s components when designing it within it’s
weight distribution. BMW’s claim a 50/50 distribution which the
battery placement plays into…why this seems to be something
people can’t grasp is beyond me…in our aircraft ANYTHING that
weighs more then 5 lbs that is gear attached to the plane HAS to be
added or deleted and the whole plane re-skewed…yet I can freely
bring on more the 5 pounds worth of food…books etc and it’s not
that big of a deal…they consider the things they DO have control
of which is how it leaves the factory NOT your weight/loading/fuel
state.–
1986 XJS, 5.3 Litre V-12, 1974 Triumph TR-6
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JT wrote:
…in our aircraft ANYTHING that weighs more then 5
lbs that is gear attached to the plane HAS to be added or deleted and
the whole plane re-skewed…
Balance of an airplane is critical. One thing interesting to note is
that aircraft designers generally try to position variable weights
centered over the wings so they don’t affect the balance. For
example, in old two-seat biplanes the pilot sat in the rear, the
passenger got the front seat. That wasn’t just to give the passenger
a great view. It was primarily because the pilot had to be rearward
of the wings to counter the weight of the engine forward of the
wings. The plane would presumably never fly without a pilot, but it
might very well fly without a passenger; the passenger seat is the
variable weight here. With the passenger seat directly centered over
the wings, didn’t matter if there was a passenger or not, it didn’t
affect the balance.
– Kirbert
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In reply to a message from Kirbert sent Mon 6 Sep 2010:
More to Kirbert’s point is the fuel loading and burnoff off of the
fuel. Generally, the fuel is in the wings and some fuselage belly
tanks located as near as possible to basic CG of the aircraft.
However, a perfect setup is rarely possible and there is variation
of the CG based on fuel loaded on the aircraft. Therefore, not
only is the weight of the fuel part of the total takeoff weight of
the aircraft, but the effect of the fuel load on the takeoff CG is
used in calculating the takeoff CG of the aircraft which must be
between the fore and aft CG limits of the aircraft for takeoff.
This gives a trim setting (horizontal stabilizer setting) for the
aircraft at liftoff speed - no sudden nose up or nose down pitch at
liftoff (remember the commuter aircraft that crashed into the
hangar in the NE a few years ago because the pilot coudn’t get the
nose up?). Although the CG varies during flight as the fuel is
burned off, it does not normally (except for some very unusual
circumstances) exceed the fore and aft CG limits and is therefore
not calculated inflight or for landing as it will be within limits
and the aircraft is kept in trim by the pilot or autopilot.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Miami, FL, United States
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In reply to a message from lockheed sent Mon 6 Sep 2010:
I was simply using the 5 lbs on our A/C to show that the battery
wouldn’t be ‘‘insignificant’’ to the car engineers…not to start a
whole aircraft W/B discussion…I think that belongs on another
board entirely.–
1986 XJS, 5.3 Litre V-12, 1974 Triumph TR-6
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In reply to a message from JT sent Mon 6 Sep 2010:
Let’s say a car battery weighs 40lbs (I think most are heavier than
that.) In a 4000lb car that’s 1% of the weight. But moving it from
front to rear causes a 2% shift in balance. That’s significant when
the manufacturer is aiming for 50/50. There’s plenty of room for
the battery under a BMW hood but they still choose to put it in the
trunk.–
1990 XJ-S V12 Convertible, 86 XJ6, 01 XJ8
Santa Clara, CA, United States
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At 16:12 2010-09-06, Mark H was heard to say:
Let’s say a car battery weighs 40lbs (I think most are heavier than
that.)
Yup. I see a variety of group 34 batteries coming in around
54lbs. The lighter ones are Optima, rather than conventional plate
design, and since the original design wouldn’t have been an Optima,
the heavier weight would be more appropriate when figuring the intent
of the manufacturer.
— '88 Jaguar XJ-SC 5.3L V12 (LHD) ‘Black Cat’
Sean Straw '85 Jaguar XJ-S 5.3L V12 (LHD) ‘Bad Kitty’
Sonoma County, California '91 Jaguar XJ40 4.0L (LHD) ‘Trevor’
http://jaguar.professional.org/ '69 Buick GranSport 455 V8
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In reply to a message from sean.straw%2BJaguar@mail.professional.org sent Mon 6 Sep 2010:
I recently replaced the battery in my Jeep. Up in the right front
corner of the engine bay. Heavy, but probably not 50 pounds!!
Enjopys some air up there for cooling, I suppose. But, makes it’s
removal necessary to change a head lite bulb!! all the emmories
then have to be reset!!
I installed an Optima yellow top in the Jaguar. Not light by any
means. Sure glad it has a strap to m an handle it into place.
As a side note, I put a meter on the red top that was ginving me
trouble. It has been sitting on the bench a few months. 12.4 V!!!
surprise!!
One of my projects is to make my antique power generator electric
start. The red top and a darn good starter I have from a Ford 8N
tractor might be just the ticket. They are almost like flat head
ford starters, but just a tad different.
Early drag racers used to remove the light weight batteries from
the engine bay and use big diesel truck batteries in the left rear
of the trunk/boot. Two fold objective. Change weight distribution
to get better traction hook up and allow the alternator/generator
to be taken out of service for just those little extra horses.
Not a bad idea for RWD cars in snow conditions.
Carl–
The original message included these comments:
Yup. I see a variety of group 34 batteries coming in around
54lbs. The lighter ones are Optima, rather than conventional plate
design, and since the original design wouldn’t have been an Optima,
the heavier weight would be more appropriate when figuring the intent
of the manufacturer.
–
Carl Hutchins 1983 Jaguar XJ6 with LT1 and 1994 Jeep Grand
Walnut Creek, California, United States
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