I have an 1963 MGB. It has two 6 volt batteries in series behind the seats. I need to hook up my charger to it because the batteries have died. I understand this car has reverse polarity so I was thinking I need to hook up the positive from my charger to the negative and the same for negative. But, which battery? Do I use the poles only or should I hook the positive to the car chassis or other metal?
When I tried originally, I got a spark. So, now I’m skittish. Any advice for this newbie MGB owner?
It must be a '63, because they didn’t make MGBs in 1953.
If this were my car, I’d get a 6 volt charger and charge each battery separately. Positive is positive, and negative is negative, regardless of which is the vehicle ground.
I don’t know what will happen is you try to charge the batteries when they are connected. If you want to try it connect the positive lead from the charger to the positive terminal on one battery, and the negative lead to the negative terminal of the other battery. The batteries must still be connected to each other for this to even have a chance of working.
I’d remove the batteries from the car, or at least disconnect them from the car’s electrical system, before charging them.
FORGET which is the ground. Positive ground or negative ground does not matter when you’re talking about charging the batteries. The charger must be hooked up positive to positive and negative to negative. Otherwise disaster will result.
You will have one cable that goes from the positive terminal of one battery to the negative terminal of the other. Do not connect the charger to either of these terminals, that will not be good for the charger.
If the car is a positive ground, then there will be a cable from the positive post on one battery that goes to the body or frame. The positive clamp from the charger goes to this post or to ground, then the negative clamp of the charger will go to the negative terminal of the other battery.
A lot of old british cars were positive ground, but I don’t remember the MGB being one of them. ind the cable that goes to the body or frame and check which terminal it is attached to.
One more thing, I believe that you can easily change it to a single 12 volt battery if you want. Todays batteries are a lot more powerful so they don’t need to be as big.
Is the charger set on 6 volts or 12 volts?
The positive lead from the charger goes on the positive battery terminal and the negative lead goes on the negative terminal. This is true regardless of which terminal is connected to the car’s chassis. North American cars use negative ground, which means the negative terminal is connected to the chassis. British cars, like the MGB, use positive ground, which means the positive terminal is connected to the chassis.
The MGB is one of the nicer cars in a generation that included the Austin Healey Sprite and MG Midget (a second generation Sprite with an MG badge), the Austin Healey 3000 and the Triumph TR3 and TR4.
Using two 6-volt batteries in series (end to end) was a dumb way to make a 12-volt electrical system. Even when 6-volt batteries were relatively common, you still had to buy two of them instead of just one 12-volt battery.
You might be able to get away with using a 12-volt charger to recharge both batteries at once, but it would be better and safer to do them one at a time. My old Sears charger has a switch to select either 12 or 6 volts. If I remember correctly, an MGB’s batteries are located behind the seats. Set your charger to 6 volts and connect positive to positive and negative to negative on the same battery. You do not need to remove the batteries from the car or disconnect them from the electrical system. If the engine will not turn over briskly after each battery has been charged for 3 or 4 hours, at least one of them is junk. To determine which one (or both), find an auto parts store that can still get 6-volt batteries and have them test yours.
The MGB was originally positive earth/ground until the change from generator to alternator in 1967, but a lot of cars got repolarized over the years to be able to run negative-ground radios, etc. You can either charge the batteries individually (disconnected from everything and with the charger set for 6 volts) or as a single unit. The batteries are hooked up in series (negative on one to positive on the other) so it is electrically equivalent to one 12v battery.
As mentioned earlier, a popular approach to the MGB battery situation is to simply replace the two 6-volts with one 12-volt. There’s plenty of room in one of the battery boxes for a much more powerful 12-volt, and it’s going to be cheaper than buying two 6-volts. Of course, if it’s a show car, just keep it stock.
Changing to one 12-volt just requires a longer battery cable to reach where the other battery was. Doing this also frees up the other battery compartment. Moss Motors sells a plastic insert that lets you convert it to a storage container-just right for the supplies you will want to carry around with you.
Converting to negative ground is also a good project. Go to Mossmotors.com and download their catalog. It has step by step instructions.
Don’t be discouraged by the naysayers who will say you should have gotten a used Corolla instead. With proper car and maintenance, these cars can actually be pretty reliable. Virtually anything you need can be had from Moss or Victoria British. You would also be surprised how much can be found locally. There are some excellent MGB web sites and discussion forums on the web. Just google MGB.
By the way, my first new car was a 1965 MGB and I’ve seldom been without a LBC since 1962.
Yes one 12 volt battery can be substituted for the pair you have now. MG placed them where they are for balance and to improve the center of gravity. Note how close they are to the ground. Remember many of these cars were raced in competition. Some still are.
Be sure a former owner has not already changed your MGB over to negative ground. Just trace the - cable from either battery to see where it goes. Most were changed for the installation of negative ground stereo equipment. Try finding a positive ground CD player. I doubt they exist.
You certainly can charge both batteries at the same time. No problem. Just be sure you are attaching the charger + to + and - to -, and have it set for 12 volts. I’ve done it literally dozens of times in nearly 40 years of MG ownership. I do mine from under the bonnet, but describinig where to connect the charger would be difficult in this forum.