How to tell if Battery is charging

[esad789]

Hi

Just wondered if i could test to see if the Dynamo is charging the battery as i has has difficulty starting the ol girl the last few night when coming home from work in the dark.
I have a meter but not sure where to place the probes

Cheers

Jason

[Jefftav]

Turn meter to read 20v and with a largeish crocodile clip attach the negative probe on battery negative terminal and positive probe on positive terminal of battery. Note reading on meter - should be 12.5V

Start car and look at reading again it should go up to 13.5V or maybe even 14V with car at fast tick over to indicate that the dynamo is charging the battery.

Leave battery overnight and before starting the car check reading again and compare from previous readings.

You could have a battery on it's way out or the dynamo may not be charging the battery enough. Cleaning terminals is a good idea and checking the fan belt tension may also be useful.

[kennatt]

simply,wait till dark ,point car at garage wall,start car ,switch headlights on .then rev the engine if its charging you will see the lights get brighter ,if not then you have a problem,

[lambrettalad]

if in doubt get a decent battery shop to test it ,and show you the results on their meter .I did last week and it was fine.
the display will tell you what % of its potential out put the battery has ,it's state of charge and if your dynamo is charging.Good luck

[esad789]

I have placed a meter across the 2 terminals and got 12.5 volts, I then started the car and it went up to 12.9.
Its seems worse in the mornings when its cold

Any ideas

Jason

[lambrettalad]

thats a little low ,well worth a check up ,do not go to a well know large chain

[bmcecosse]

You have to start the engine - and then REV UP.... Should go to 13.5/14 volts. Then repeat with headlights and heater fan ON. Again - should go to at least 13.5 volts....... Make sure the fan belt is tight enough - but not too tight...

[rayofleamington]

A lead acid battery will perform less well in cold conditions - and very poorly if it is on the way out!

However if you've been using the car a lot with lights, heater and wiper on, and been in a lot of congested traffic, then chances are that the battery may just be discharged. The dynamo will usually just keep up, but do remember that it's not keeping up when you're sat with the engine at idle when you're in a queue. Therefore in winter when you turn the consumers on on, it can slowly discharge.
When I ran my minors as everyday cars all year round I would use a trickle charger on the battery* part way through winter. That was far less hassle and much more reliable than an alternator conversion.

If you've got a driveway, don't mess about removing the battery! Just leave the charger under-bonnet on an extension lead from the house/garage. Don't forget to remove it before you start the car!! However just in case you might forget, make sure none of the cables are near the fan / fan belt!

[Bazzalucas]

I have fitted a voltmeter to my car. I've checked the belt tension, and the dynamo is a recently rebuilt unit. At speed, the voltmeter will read approx. 14v. When I switch on lights, heater fan, etc, the reading drops to between 10v to just below 12v. Recently I drove it for about 2 hours in this condition, through cold and rain, with lights, wipers & heater fan all going. When I arrived at my destination, I thought perhaps my battery would have lost enough grunt to start the motor, but it spun it over quite happily. I later drove home in the same conditions, with the same results. Is my gauge duff, or my battery just do full of reserve that it can sustain this kind of prolonged drain?

[bmcecosse]

Odd - because the volts seem to read ok when nothing much on. I suggest a new fan belt, pulled up TIGHT may solve the problem....

[lambrettalad]

[quote="rayofleamington"]A lead acid battery will perform less well in cold conditions - and very poorly if it is on the way out!

and much more reliable than an alternator conversion.


Ray why is it more reliable ? I'm not convinced

[bmcecosse]

Me neither....

[kennatt]

I for one could NOT be bothered with messing about with extention leads and chargers,A good battery and alternator conversion will do for me thank you very much.My minor stands sometimes for three or four weeks,and the battery spins it over well enough to start,and with an alternator it very soon tops the battery back up.