trooper2481

positive ground batteries

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Are positive ground British batteries any different then the normal American battery or is it just the positive ground wiring systems in British vehicles just different. Can I purchase a normal USA 12 volt battery and install it into my positive ground vehicle ?  thanks  trooper2481

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It is not the battery that is +ve ground, it is the electrical system of the vehicle. The frame, body etc. act as a "wire" attached to the + terminal, the wires are attached to the - terminal. Electrickory flows from one side to the other through any conducting medium, whether it is a wire or a car body or frame.

 

Many American vehicles had +ve ground too. Both of mine are, 1930 and 1939.

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Just make sure the terminals are in the right place so the cables reach. I picked up a lawn mower battery last summer thinking it was the right physical size it would work. The terminals were on the opposite side of the battery and the cables barely reached.

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On 1/28/2017 at 6:31 PM, Jim Bollman said:

Just make sure the terminals are in the right place so the cables reach. I picked up a lawn mower battery last summer thinking it was the right physical size it would work. The terminals were on the opposite side of the battery and the cables barely reached.

Or, alternatively, make sure you have cables long enough to reach the terminals on the battery you buy.

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I totally agree with what others have said.

 

Interesting info on the 1961 thru Jan 65 Triumph TR4 with Positive ground battery verses the Feb 65 on Triumph TR4A with Negative ground battery.

 

Both used the exact same battery mounted on a shelf to the rear of the engine on the firewall with the starter to the right side of the engine.  

 

For the earlier TR4 both battery posts are to the rear near the firewall with a shorter positive ground terminal to the left (drivers side) and used a longer negative cable down to the solenoid  next to the starter.

 

For the later TR4A they turned the battery around to place the posts forward nearer to the engine.  The Neg ground cable was now slightly longer and the Pos cable slightly shorter.  When the battery was turned around this also put the Negative terminal to the left and Positive terminal on the Solenoid / starter side.

 

 

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As stated earlier, the electrical system is set up either positive or negative ground. The battery doesn't care either way. I worked for a number of years in the British car industry. We converted many, many cars to negative ground so the owners could install stereos. Positive ground radios were difficult to find, expensive and lacked the features that the more common, negative grounded, unit had. The term "ground" is actually incorrect. Either one is grounded. The lead going to the chassis just completes the circuit. The electrons flow from the negative side to the positive side

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All the above are more or less correct, Auto electrics are DC, Direct current that is the current only runs in the one direction termed "Polarity"

It is relatively simple to change the polarity ie from negative earth to positive earth or vice versa. Any Auto Elect service man can do it for you in minutes. This is especially so with older vehicles with a Generator (Dynamo). 

 

Mr Google tells us:-

 

IF YOU DO NOT UNDERSTAND ANY OF THE FOLLOWING DO NOT ATTEMPT TO DO THIS JOB YOURSELF!

ENLIST THE ASSISTANCE OF YOUR AUTO-ELECTRICS SERVICE MAN.

 

Many owners of earlier models are discouraged by the hassles associated with positive ground electrical systems. Seemingly simple tasks, such as mounting a C.B. or tape deck, can become major projects when you have to keep them from touching other metal parts. But unlike other problem areas, though, this one has a solution that is actually very straightforward: reversing the polarity of the charging system. For all models except those with radios, electrical tachometers and clocks, there is little more to it than reversing a few wires.

The procedure is as follows:

1. Disconnect both terminals of the battery 
Lift the battery from the box and put it back in so that the terminals are at opposite ends from the original position. Positive will now be where negative was and vice-versa. Do not reconnect the battery yet, but make sure the existing cables are long enough. Sometimes the positive cable may be a bit too short, depending upon the battery in your car. Usually though, enough extra length can be obtained by taking up some of the slack where the cable runs under the boot.

2. Coil 
Unplug the wires at the ignition coil and replace them on the opposite posts. The wire from the distributor should now be to the negative (-) side of the coil, and the wire from the ignition switch will be to the positive (+) side.

3. Ammeter 
For the ammeter, simply switch the two plug-on wires as was done with the coil.

4. Radio 
If your car is equipped with a radio, it must be disconnected and removed. Depending upon the radio you have, the polarity must be changed either by a switch on the case, or by internal wiring changes. In either case, most radios that operate on positive ground have instructions for polarity reversal somewhere on the case. If equipped with a switch, the change is easy. If the reversal is internal, it is best left to a radio repair person.

5. Electrical tachometer (series IV only) and clock 
These two guages were not designed for polarity reversal so it must be done by internal modification. Local electrical shops who are not familiar with the changes necessary may not wish to attempt the job. This service is available, however, from Tiger Tom for a nominal fee of $5 per guage, plus shipping.

6. Reconnect the battery

7. Repolarizing the regulator 
Use a small piece of wire and momentarily (about one second) touch it between the regulator terminals marked "Al" and "F". It will make a few sparks so don't think you've hurt something.

At this point, you're finished with the polarity changes. The only thing left is to test the charging system output.

Ideal specifications are: No-load (all electrical items off) - output should be 14.5 to 14.7 volts at 2000 to 3000 RPMs.

Loaded (all electricals on, such as wipers, heater, lights, etc.) - output should not drop below 13 volts at 2000 or more RPMs.

If your readings do not fall into this range, the regulator will need to be adjusted.mets in the

CHANGING THE POLARITY OF THE GENERATOR  (When changing to Negative Ground) 
by Phil Roettjer

Whenever you are changing your car from a positive to a negative ground you must remember to polarize the generator's field to positive. If you don't, you can destroy  your regulator. In such a case, your ignition light will stay on because your generator can  no longer charge.

To polarize the generator when making change the ground OR when you install a new generator (to make sure it is polarized correctly), all you do is quickly swipe a wire to the field terminal (the smaller of the two) that is connected to +12 Volts. There will be a small spark and the job is done. 
  

IF YOU DO NOT UNDERSTAND ANY OF  THE ABOVE DO NOT ATTEMPT TO DO THIS JOBYOURSELF  BUT ENTRUST IT TO YOUR AUTO-ELECTRICAL  SERVICE MAN.

 

Bj.

Edited by oldcar (see edit history)

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I never understood  old car owners that think it is better to change the original equipment of antique cars-------9 volt batteries and play with polarity --------------if the wires are in good shape 6 volts are all you need        I put a negative ground radio in a positive car   just by isolating ground of car and radio when mounting     in my case    put in glove box and used a small volt reducer mounted behind dash------and used the CHICKEN WIRE above head liner as antenna -----works good enough

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