How can you check your battery is ok.

[John Mason]

My car is not starting on the battery.  The starter does not turn when the starter is pulled although on checking the battery there is a large voltage drop and soon the battery is flat. All through this procedure  the amp meter shows nothing also there is not enough power to operate the horn or indicators.  The car starts on the handle but on tick over again the horn and indicators do not operate. However with a few revs on the engine both horn and indicators work correctly.
Forum readers  will now be aware that I am in no way familiar with auto electrickery. Do I need a new battery or is it something else. Should it be the later advice on a replacement please. I would also be appreciative of how you can check your battery. At the moment my all singing all dancing charger is supposed t check the condition of the battery before it starts the charging cycle. This it does without showing any problems.

Sorry for going on a bit. John Mason.

[Robert Leigh]

You do not say whether your battery is old or bought recently, and whether the problem has appeared suddenly or got worse over time. In my experience Austin Seven batteries can last from 18 months to 6 years, but the use of the car and the state of the charging system are relevant. Have you checked the condition of the main battery connections; they should be clean and without any corrosion around them. Also is the acid level in the battey just above the separators in all cells? If the car gets regular use the battery should stay charged if it is in good condition. If less regularly used it may be advisable to use a charger. Once all the cells are gently bubbling the charger should be disconnected. A bit more information would help in diagnosing your problem.

[Tony Griffiths]

If you do end up needing a new battery, no doubt there will be many and varied recommendations. I've just bought two of this type; it has a plain body with no lugs or other fittings that have to be removed to get it into an A7 battery box and is a large capacity, 80-Amp hour job. Sold in a ready-to-use form by the MG Spares Company. https://www.mgocspares.co.uk/product/d004w/battery-421-6v-80ah-600cca-wet

[andrew34ruby]

John, this is how I was taught to test a battery, and I have tested thousands using this method.

Charge the battery with a fair bit of charge. Use your charger for a few hours or drive the car for at least half an hour.

Disconnect the charger and with battery disconnected put a voltmeter across the battery. It should read about 6.4 volts. If it's down at 6.1 then charge it for longer.

Re-connect the battery to the car and put voltmeter across the battery. Pull the starter for maybe 6 seconds and what does the voltmeter read? If starter motor is cranking the engine it might read around 5.0 volts for 6 or even then seconds. If it reads less, then the battery has failed the test.

If it does not crank the engine what voltage do you get? Less than 5 volts means battery has failed. No cranking and a voltage of 6 or more volts indicates there is a problem with connections somewhere or the starter motor itself. If you are at this stage, you simply do not know about the battery.

[Colin Morgan]

As you might know, the voltage reading of a battery shows its state of charge.*  

I find this chart useful - just halve the values for 6v!  

From experience, leaving the battery at a low charge - less than 50% or so - is not good for its long term health.


  Battery Voltage v Charge.jpg (Size: 90.89 KB / Downloads: 193)

*When isolated, as per Andrew's comment below.

[Graham Barker]

Hi John,
My Ruby recently showed all the symptoms of your car, including an alleged "smart" charger not identifying a battery fault. Horn wouldn't work unless the motor was racing. Started easily on the crank handle. 
Graham O did the battery test described in the thread and voltage plunged to 4Volts as soon as I pulled the starter. He pronounced that my battery was useless!
A new battery immediately fixed all the faults.

[andrew34ruby]

As you might know, the voltage reading of a battery shows its state of charge.  

I find this chart useful - just halve the values for 6v!  

From experience, leaving the battery at a low charge - less than 50% or so - is not good for its long term health.

Agreed Colin, but I would clarify this by saying...

" the voltage reading of a battery with everything disconnected shows its state of charge. "

[John Mason]

Thank you all who contributed with suggestions and advice. I did the checks Andrew outlined and all led me to the conclusion that the battery had given up the ghost. I think the cause was not giving it a low short charge during the winter to keep the charge good. Colins chart confirmed this with the voltage readings and chart. As if I had not got enough evidence to make things really certain Grahams last post just added to the certainty. Then my son (who has much better eye sight than me) put his twopence worth in and said,”There are only two of the cells making bubbles dad.”
Tony thanks for the advice on where to buy a new battery. I will be contacting them.

John Mason.