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[Dusty]

Flat battery on my miggy yesterday.

Charged it up from completely flat to full charge in about 40 minutes.Everything then O.K .car starts first time. Then.....

Flat battery on my miggy today and yes you guessed it flat to fully charged in about 40 minutes or so.

As the battery charges so quickly is the fault likely to be the battery itself or something causing it to go flat so quickly.

Any ideas

Thanks  Dusty.
  

[dbug]

Probably dodgy battery - could be duff alternator though.  Check voltage across battery with engine running @ 2000 rpm.

[Andyb]

i would say battery has gone kaputt only other thing u could check is to see if the is a drain on the battery when not connected and when connected to the car if there is a drain when connected then u have a fault in the car either a light staying on or such like but there will be some drain when connected cos of the cars electric circuits but i think its no more than .5 volts i might be wrong

[iainb]

Hi, Sounds like its only doing a surface charge
Best thing to do is put it on a trickle charge over night and then in the morning disconect it and leave it for half an hour, so that the surface charge can clear and then test it

[Dusty]

Probably dodgy battery - could be duff alternator though.  Check voltage across battery with engine running @ 2000 rpm.

Sorry I don't know how many volts I should get and how would I test it?

Thanks

[Kevin Wood]

How do you know it's fully charged? Indicators on chargers can be fooled by a weak battery. Best thing to do is charge it then put a voltmeter across the terminals. You should see 12.5 - 13.0 volts from a healthy, fully charged battery. Now switch on the headlights and watch it for a minute or two. It may drop slightly but should settle comfortably above 12v. If it gradually decreases and drops under 12 volts within a few minutes, battery is toast.

Now start the car and check voltage under the following conditions:

Idle, no load: 13.8 - 14.5v
2500RPM ish, no load:  13.8 - 14.5v
2500 RPM ish, lots of electrical accessories on: 13-14.5 v

If the voltages are outside these limits the battery is not charging correctly.

Crimps on the battery terminals can work loose. Check they are secure and not getting hot.

Kevin