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MG MGA - Battery charging

I have just installed a hood on my '58 roadster after 25 years without one (old age catching up) and never realised just how valuable the space behind the seats was without it. A problem I have encountered when the hood is stowed apart from the lack of storage space and difficult access to the boot release is gaining access to the battery for maintenance and charging.
My query is, can any damage result if the battery is charged by connecting the charger positive lead to frame(ground) and the negative lead to the starter solenoid negative lead?
D. J. Barron

DJ,
You must have good cables and connections, and insure that you don't accidently touch negative to chassis. If you are trickle charging the circuit will never draw much amperage, and should be ok, but if you are attempting to charge a dead battery, or start the car, you must have good cables and connections.
mike parker

Like Mike said, the main problem is that it is easy to short to the chassis when connecting the charger to the solenoid. If the wires are good enough to handle the 100 or more amps of starting, they are good enough for charging. One advantage to charging at the solenoid is that you are far from the battery. Many car batteries have exploded from inadvertant sparks during charging.

During the winter when I don't drive mine as much, I clip a float charger to the solenoid to keep the battery charged.

Jeff Schultz

Jeff has made a good point regarding blowing up batteries. It is far better to charge with the cables as far from the battery as possible, due to the hydrogen gas emitted by the battery. Also, since it wasn't stated before, insure that your battery electrolyte level is correct (for those that aren't aware) and make sure that the cap vents are venting.
mike parker

Another word of caution. When connecting charger leads directly to the battery it is easy to spot the +ve and -ve terminals. When connecting under the bonnet it is not. Probably just as many As are now negative earth as there are positive. Check before you connect.

Steve
Steve Gyles

What brand of float charger are people using. Last year I left my batteries i the car and tried keeping them up using a trickle charger. Positive to the frame, negative to the battery soleniod. The charger never went on float (have new batteries) and whenever a metal portion of my shop light touched the car a spark jumped. I was using a trickle float charger from Moss-(Schumaker).
This year I took the batteries out to clean the trays and am charging them out of the car.
What was I doing wrong?
John
John

If you got a spark when a metal part of the shoplight touched the car, I would say the charger or the shop light or both was broken and dangerous. I would check out both of them before using either again.
Jeff Schultz

You could have an open circuit from the charger that is then earthing through the shoplight earth. Do you have a battery isolator on your MGA? If so, where is it positioned in the circuitry? e.g. Is it between the battery +ve terminal and chasis and you had the battery isolated from the chasis while attempting to charge?!

Steve

Steve Gyles

Since you have a positive ground car and a negative ground electrical system, this is what one would expect to happen. It is the same thing that could happen when jumping a neg ground car with a pos one if anything touches.
John

A properly operating charger should have both black and red wires electrically isolated from the charger's chassis. The shoplight should have the metal cage connected to the earthing pin of its plug. under no circumstances should there be a spark when the shoplight metal touches the car. Time to check the charger. If there is a problem there, it may be why it never goes to float charge.

A second note: When I store my car, after a 1/2 hr run that tops off the battery, I simply pull it into its final resting place, remove the key and walk away. When I get back to it 5 months later, I put in the key, turn it, pull the choke and the starter. It starts right up. The point is, with these cars, there is NO electrical drain on the battery. Just its internal self discharge takes place. In 9 years, I have never had the car not start. I do not use trickle chargers. This is in northern Illinois winters.

I am running a std generator, std point-type ignition, std point-type fuel pump. The only thing I do is unplug the CD/radio power which does pull a slight (mA) current from the battery. Otherwise it is as stock as it can be. A slight load can fully drain a battery over several months.

Chuck
Chuck Schaefer

Chuck

He says that he connects the positive output from the charger to the frame of the car(for a pos ground car). Under these circumstances I think it would be normal to spark when the body of the car is touched by the ground side of the building's electrical system.
John

John (Canada)
I think you may have hit on it?!
Since my positive ground MGA was grounding to my house ground - which is negative- through the shop light, a circuit was made and current flowed between the car and the house ground.
Does this make sense?
Following this logic, I need to find a trickle/float charger which has internal circuitry that can handle either polarity. That or change the car to negative ground.

As to charging at all.. Here in Wisconsin the car can be off the road from November to April because of snow and salt on the road. I have found that if the batteries are charged regularly during this time my batteries last far beyond the 3 year warrenty. The last pair were good for 6 years! Really!
John
John

John,Canada, The house wiring is an AC system, not a DC system. It's ground is not negative. Nor is it positive, it is "Earth", sometimes called Ground. This "Earth/Ground" is not to be confused with the Chassis Ground on our cars which is simply a return path for the DC current.



In order for the light to create a spark when touched to the car's metal,there must be an existing electrical connection within the charger to its case or Earth conductor. The light's metal cage completes the electrical path and, Violla, a spark occurs. This should not be. If it does, either the charger is very old and not designed to the safety requirements of the last 30-40 years, or it is defective. Its output, the wires connecting to the car, should not be referenced to its case. It makes no difference if the Chassis Ground is positive or Negative.



John(WI), I too, get around 6 years of use on a single 12V battery anbd I do not float charge the battery thru the winter. I see no use for the float charger since there is no electrical load on the system.

Chuck
Chuck Schaefer

Correct me if I'm wrong, but normally the battery charger has a ground on the plug, and this is tied into the neutral on the plug. The positive and negative reduced voltage(6 or 12 volts) should be isolated from the AC line power, although it may not be. The rectifiers are grounded to the case, and in this case wouldn't the negative and the AC ground be equal? If so, then you would complete a circuit when a connected to an AC neutral or ground. Regarding a shop light, the steel cage around the bulb is grounded (earthed) for safety reasons, and this would cause an arc.
mike parker

Mike, You said "....battery charger has a ground on the plug, and this is tied into the neutral on the plug". The ground and neutral wiring are not tied together at the pulg. They are, or should be in the USA, tied together at the electrical service entrance breaker box. This prevents the neutral current from creating a voltage on the equipment chassis that could cause a shock hazard.

You are correct that the DC voltage to the battery should be isolated from the AC line power. I suspect that this is where John,WI is having a problem. Some very old chargers, I'm talking maybe 40 yrs ago, may have had the rectifier tied to the case of the charger. In this situation, whether the negative or positive are tied to the chassis would depend on the type of circuit used in the charger.I doubt if any charger with an automatic float control would be like that. In John's instance, I suspect that the problem is also drawing enough current to prevent the charger from switching to "float".

My charger is maybe 30 years old and has an isolated output.

Chuck
Chuck Schaefer

Chuck,
I am referring to the neutral and ground on the charger. Obviously this would be on a 3 wire AC line on the charger, where usually the ground is just tied to the case, as you stated. This is what I thought was the problem with John's charging system.
mike parker

This thread was discussed between 11/01/2005 and 13/01/2005

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