Rep Power: 0

Hi all,

I have a 2018 civic with original battery as was advised by my mechanic to replace the battery soon as its getting old, the battery read 12.3v, 10.4v cranked, 14.2v idle. I thought i would get one before the winter comes so replaced 2 weeks ago. All well, last week went on a long trip for a few days came home and left the car sitting for two days. Then Monday gone comes and tried to start car only to be given a battery warning light. The battery now reads 12.4v, 11.9v cranked and idle. I have done 40k miles. could it be the alternator or do you think its something to do with the new battery?
Any help would be welcome. I have tried to put the multimeter on the alternator but dont know how to get to the positive post.

With thanks.

 
Rep Power: 125

Did you drive the car around at all after or did you only let it idle? It takes time for the alternator to charge the battery, and it's typically only done when the alternator is under load.

 
Rep Power: 221

Could be the alternator, although its pretty early for that to fail. New battery could be bad

 
Rep Power: 0

Thanks.

Yes, once the new battery was installed i drove around for about 50mins, all was good, then few days later drove up to the lakes and around 3hr journey there and after a few days up there drove all the way back. i have checked to see if the battery grounded and it is.
If it was a bad battery or the battery not getting charge from the alternator when it was installed i dont think i would have made the journey i did.

 
Rep Power: 125

That would tell me the alternator is okay. Could be that the battery was weaker than it should have been, but it's probably fine.