XK 120 Battery / Voltage Questions
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Joined: Jan 2024
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From: Sonoma, CA
XK 120 Battery / Voltage Questions
(I think this is what the forum is requesting.)
Just won a BAT auction for a 1953 running, drive-able XK-120 roadster. I'm 85 years old, and have been involved with autos all my life, but this is my first "historic" car. The WSJ, many years ago, said folks like me want cars that they envied when teenagers but couldn't afford at the time. The XK-120 fits the description! I always envied the 120 with wire wheels, but I settled for discs, and have been advised that wire wheels come with maintenance issues.
I don't plan to restore, but just bring it up to a reliable vehicle for regular use, about which I won't worry when I park it. I will leave restoration to my co-owner-son, who will inherit it. I look forward to learning what I need to know from other forum members. I've asked a local Jaguar shop to provide an assessment and recommendations.
One question that comes to mind relates to the battery. There is one, 6V battery in place, in one of two battery boxes behind the seats, said to be positive ground. Should I add a second, to be wired in parallel, or is it customary to rely on just one battery? The agent for the seller suggested converting to 12V, negative ground. What components, other than bulbs, are polarity-sensitive or voltage sensitive, that would have to be replaced or modified?
Thanks.
SFRobo
Just won a BAT auction for a 1953 running, drive-able XK-120 roadster. I'm 85 years old, and have been involved with autos all my life, but this is my first "historic" car. The WSJ, many years ago, said folks like me want cars that they envied when teenagers but couldn't afford at the time. The XK-120 fits the description! I always envied the 120 with wire wheels, but I settled for discs, and have been advised that wire wheels come with maintenance issues.
I don't plan to restore, but just bring it up to a reliable vehicle for regular use, about which I won't worry when I park it. I will leave restoration to my co-owner-son, who will inherit it. I look forward to learning what I need to know from other forum members. I've asked a local Jaguar shop to provide an assessment and recommendations.
One question that comes to mind relates to the battery. There is one, 6V battery in place, in one of two battery boxes behind the seats, said to be positive ground. Should I add a second, to be wired in parallel, or is it customary to rely on just one battery? The agent for the seller suggested converting to 12V, negative ground. What components, other than bulbs, are polarity-sensitive or voltage sensitive, that would have to be replaced or modified?
Thanks.
SFRobo
Junior Member
Joined: May 2021
Posts: 16
Likes: 1
From: Kansas
Wheels
(I think this is what the forum is requesting.)
Just won a BAT auction for a 1953 running, drive-able XK-120 roadster. I'm 85 years old, and have been involved with autos all my life, but this is my first "historic" car. The WSJ, many years ago, said folks like me want cars that they envied when teenagers but couldn't afford at the time. The XK-120 fits the description! I always envied the 120 with wire wheels, but I settled for discs, and have been advised that wire wheels come with maintenance issues.
I don't plan to restore, but just bring it up to a reliable vehicle for regular use, about which I won't worry when I park it. I will leave restoration to my co-owner-son, who will inherit it. I look forward to learning what I need to know from other forum members. I've asked a local Jaguar shop to provide an assessment and recommendations.
When I was 85 (two years ago) I got an XKI-140 FHC with wires. The adapter hubs have been a real pain to work with/replace. Consider yourself lucky with the disk wheels. At the time, I felt that the Jags of friends drove like pickup trucks. I still feel that way - there is a reason for the steering wheel being so large in diameter ! But they do look great. Enjoy !
One question that comes to mind relates to the battery. There is one, 6V battery in place, in one of two battery boxes behind the seats, said to be positive ground. Should I add a second, to be wired in parallel, or is it customary to rely on just one battery? The agent for the seller suggested converting to 12V, negative ground. What components, other than bulbs, are polarity-sensitive or voltage sensitive, that would have to be replaced or modified?
Thanks.
SFRobo
Just won a BAT auction for a 1953 running, drive-able XK-120 roadster. I'm 85 years old, and have been involved with autos all my life, but this is my first "historic" car. The WSJ, many years ago, said folks like me want cars that they envied when teenagers but couldn't afford at the time. The XK-120 fits the description! I always envied the 120 with wire wheels, but I settled for discs, and have been advised that wire wheels come with maintenance issues.
I don't plan to restore, but just bring it up to a reliable vehicle for regular use, about which I won't worry when I park it. I will leave restoration to my co-owner-son, who will inherit it. I look forward to learning what I need to know from other forum members. I've asked a local Jaguar shop to provide an assessment and recommendations.
When I was 85 (two years ago) I got an XKI-140 FHC with wires. The adapter hubs have been a real pain to work with/replace. Consider yourself lucky with the disk wheels. At the time, I felt that the Jags of friends drove like pickup trucks. I still feel that way - there is a reason for the steering wheel being so large in diameter ! But they do look great. Enjoy !
One question that comes to mind relates to the battery. There is one, 6V battery in place, in one of two battery boxes behind the seats, said to be positive ground. Should I add a second, to be wired in parallel, or is it customary to rely on just one battery? The agent for the seller suggested converting to 12V, negative ground. What components, other than bulbs, are polarity-sensitive or voltage sensitive, that would have to be replaced or modified?
Thanks.
SFRobo
Have fun
Veteran Member
Joined: Dec 2009
Posts: 9,555
Likes: 2,553
From: Crewe, England
(I think this is what the forum is requesting.)
Just won a BAT auction for a 1953 running, drive-able XK-120 roadster. I'm 85 years old, and have been involved with autos all my life, but this is my first "historic" car. The WSJ, many years ago, said folks like me want cars that they envied when teenagers but couldn't afford at the time. The XK-120 fits the description! I always envied the 120 with wire wheels, but I settled for discs, and have been advised that wire wheels come with maintenance issues.
I don't plan to restore, but just bring it up to a reliable vehicle for regular use, about which I won't worry when I park it. I will leave restoration to my co-owner-son, who will inherit it. I look forward to learning what I need to know from other forum members. I've asked a local Jaguar shop to provide an assessment and recommendations.
One question that comes to mind relates to the battery. There is one, 6V battery in place, in one of two battery boxes behind the seats, said to be positive ground. Should I add a second, to be wired in parallel, or is it customary to rely on just one battery? The agent for the seller suggested converting to 12V, negative ground. What components, other than bulbs, are polarity-sensitive or voltage sensitive, that would have to be replaced or modified?
Thanks.
SFRobo
Just won a BAT auction for a 1953 running, drive-able XK-120 roadster. I'm 85 years old, and have been involved with autos all my life, but this is my first "historic" car. The WSJ, many years ago, said folks like me want cars that they envied when teenagers but couldn't afford at the time. The XK-120 fits the description! I always envied the 120 with wire wheels, but I settled for discs, and have been advised that wire wheels come with maintenance issues.
I don't plan to restore, but just bring it up to a reliable vehicle for regular use, about which I won't worry when I park it. I will leave restoration to my co-owner-son, who will inherit it. I look forward to learning what I need to know from other forum members. I've asked a local Jaguar shop to provide an assessment and recommendations.
One question that comes to mind relates to the battery. There is one, 6V battery in place, in one of two battery boxes behind the seats, said to be positive ground. Should I add a second, to be wired in parallel, or is it customary to rely on just one battery? The agent for the seller suggested converting to 12V, negative ground. What components, other than bulbs, are polarity-sensitive or voltage sensitive, that would have to be replaced or modified?
Thanks.
SFRobo
Veteran Member
Joined: Nov 2012
Posts: 1,131
Likes: 1,208
From: Joyner, Queensland, Australia
The XK120 originally had two 6-volt batteries wired in series for 12 volts.
If the car is currently running as Fraser says it may be on just one compact 12-volt battery in place of the two 6-volt batteries.
Those earl circa 1950 batteries were quite inefficient and very bulky compared to modern batteries.
Conversion from positive earth to negative earth is quite simple on these early model Jags. I have done it many times on my own cars as well as friends' cars.
The battery connection needs to be reversed.
The generator fields need to be re-flashed to the desired polarity.
The ammeter leads need to be reversed.
You need to check the fuel pump. Very early SUs were not polarity sensitive but later ones have a diode which needs reversing and the latest models using hall effect have to be changed.
You DO NOT need to change anything in the ignition system if it is still standard, general lighting and things like windscreen wiper motors.
Cheers
If the car is currently running as Fraser says it may be on just one compact 12-volt battery in place of the two 6-volt batteries.
Those earl circa 1950 batteries were quite inefficient and very bulky compared to modern batteries.
Conversion from positive earth to negative earth is quite simple on these early model Jags. I have done it many times on my own cars as well as friends' cars.
The battery connection needs to be reversed.
The generator fields need to be re-flashed to the desired polarity.
The ammeter leads need to be reversed.
You need to check the fuel pump. Very early SUs were not polarity sensitive but later ones have a diode which needs reversing and the latest models using hall effect have to be changed.
You DO NOT need to change anything in the ignition system if it is still standard, general lighting and things like windscreen wiper motors.
Cheers
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