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Flat battery

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have been driving my Herald about 50 per week since the weather got drier so say march.  Just tried to start it today and battery was flat.  A couple of question please 

how do I check the battery is charging from my dynamo ( ignition light goes out when I got it going from a jump start)

 how do I ascertain my battery does or does not need replacing as it is five years old

After my jump start took it for a five mile run and it would still not start would a run of this length charge the battery up to full

any other suggestions what it might be.


thank you in advance.





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If you have either a volt meter or an ammeter - either will indicate whether the alternator is charging OK.   If you have neither.. then start the car and turn on the headlamps.  At tickover the lights will be dimmer than when you rev the engine anything more than 1400 rpm.  1200 - 1400 rpm the alternator should make your headlamps much brighter than a partially charged battery. 

Very likely it's either the connection to the battery, or to the starter solenoid that's not allowing enough current to start the car.  The charge from your alternator is much lesser current flow so even a poor connection will turn your charge warning light out, but perhaps it's not enough to properly charge the battery.  So, the first thing I would try is to remove the battery terminals, clean up both the posts and the inside of the clamps with wet n' dry, then wipe them around with Vaseline (to prevent bi-metal corrosion) and refit them.    

Does the battery need replacing ?  Suggest you clean the battery terminals, and then see if the battery holds a decent enough charge.  Loudness of horn, brightness of headlamps, are often a good indication that the battery is good, even when there are starting issues.


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it's a dynamo! :) Not that that it makes any difference, your good advice remains the same. 



If you haven't got a multi meter, why not! :lol: They're only a tenner from Halfords, a must have tool.


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As  "rule of thumb". it used to be said that a minimum of 20 to 30 min open road running was required to replace what the starting takes out. I guess your 50 would qualify unless it was "stop start" urban?. Doug is right, an Essential tool is a good multimeter. BFG`s advice is very sound as first steps to proving battery viability and charging. Just a thought?. Have you any aftermarket devices, Clock`s for example or a permanent feed to a radio/alarm or similar?. These are Ghost drains and can take down a Battery surprisingly quickly.

If you get access to a Meter. a Standing (rested) battery with a full charge will show around 12.5+ish Volts. Measured accross the Pos/Neg terminals, No ingnition on. When running, If charging, the voltage can rise initially to 13 to even 15 Volts. I regularly "see" 14 on my Modern, and should fall back as the battery charge rises.

Best of Luck.



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1 minute ago, PeteH said:

I regularly "see" 14 on my Modern

Many moderns are higher than that (15+) to reduce current for a given power - so high that they have to soft start halogen bulbs so they don't blow on startup!

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a battery can seem fine and overnight it dies  

age doesnt come into it  its lack of use is the best battery killer ( coupled with the quality of the battery has a part in all this)

but you have a few  things to think about 

the battery has sulphated a and the plates are dead in maybe one cell(most suppliers can use a controlled programed tester to check this .

there is a serious earthing problem. a good clean of earthing points   may help

something is draining the battery but if its been ok in the past its  unlikely ie clock radio or a boot lamp is on ( is there a lost lamp that might be on all the time ,  alarms  etc 

with everything off, link   a meter or small bulb put it between a battery terminal and the battery lead  if it lights you have a drain 

with side /head lights on does it dim when you attempt to crank or there are no lights coming on

it may be the starter is failing not the battery 


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15 hours ago, Andrew said:

ignition light goes out when I got it going from a jump start)

It happened to me, I thought the battery was gutless but the ignition light I thought went out. It was only driving through a tunnel that I could see a dim red light. Fortunately I got home and sorted out the problem which was a duff new alternator! 


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Hi Guys just thought I would inform you all what I did. Multimeter showing the car was charging  in the battery.  So as instructed took of the battery terminals and found lots of crud.  Cleaned all of re greased with petroleum jelly now all is good.  Thank you for the tips on her.    

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