Do I Need to Replace Battery Yet?

[ap87]

Hi all, so i've been working from home for a few months now so not using the car as much, just the odd trip to the shop and back, nothing more than 15-20 minutes. I then went to start it over the weekend after a couple of days in the freezing cold and although it started first time, it chugged a little bit and took a good few seconds to finally start.

I checked voltage of the battery the next morning after sitting all day and it was 11.8 at the time and then when starting the car the cranking voltage dropped to around 9 then back up to over 14.

Is it just the cold thats not helping here and if I take it out for a proper driveevery now and then, can I still live with this battery for many more months to come if I keep an eye on it?

Its a stop start model so you are looking at £150+ for a new battery, something I could do without buying at the moment unless really needed.

 

[ap87]

How old is the battery? Anything in the car drawing a small amount of power?

Unsure of age to be honest, i've only had the car 2 years but its been in since then. Not sure of anything drawing power. I do have an aftermarket stereo in the car but not sure if anything on that could be drwaing power?

11.8v resting is flat get a charger for it. Loads of people need one these days. Solar is even easier

I do have a smart charger, will get it hooked up today. Hypothetically, what if it fully charges but then shows 11.8 again tomorrow?

 

[ap87]

If it fully charges then drops again then its battery replacement time.
Mines behaving like that. Full charge then after 1 week sitting in garage battery lost a load of volts and down to 12.2v. high self discharge probably sulfated up inside or other issues.

Ok, ill go whack her on charge now and leave it on and give it another test in the morning

 

[ap87]

Sooner the better get it on charge.
If you end up replacing battery you dont want same to happen again so if car not used much keep on charge or get solar panel. Since you said its i stop start battery it could be agm and those are not cheap and also those are supposed to be able to rapid recharge from alternator too. Very odd

Yeah its an AGM one. I was all ready to go out and buy one thinking batteries were only around £50 but then when I saw the price it got me thinking if I do really need to change. Ill see how it goes then for now, thanks

 

[ap87]

leave the battery disconnected otherwise you won't know if the voltage has dropped cos the battery is bad or because of voltage draw from something.

Ok, can I do this just by removing the neg terminal rather than taking it out? Will the car lose all its memory?

 

[ap87]

To be honest, it doesn't sound like you need a new battery, it just sounds like the car needs a good run. By only running the car short distances over the last few months, each time with a stone cold start, you've almost certainly taken out more of the charge from the battery than you've put in. If the internals of the battery were on their way out, when you tried to start it in the freezing cold, it would have just failed. Those -3c morning when the car hasn't been started for a few days are the toughest time for batteries, and if they're a bit weak, they just won't start.

My advice - either use the car for a good journey or put it on charge (make sure you use the AGM setting on the smart charger too)

How old is the car?

Car just turned 9 years old, cant say whether the battery has ever been changed as ive only had it just under 2 but has been fine in that time. I've got it hooked up to the smart charger on AGM mode now so ill let that complete and will also take it outf or a drive this week and monitor for the next week or so before buying anything. Hopefully wont be required.

 

[ap87]

Morning all, so I hooked up to the smart charger yesterday at 9.45ish and by 23:45 it had completed (14 hours). Checked voltage again this morning and it was down to 12v. Unfortunately I couldn't leave the negative terminal disconnected to test whether something in the car was draining the battery or not as I needed to use the car early this morning, so i'll charge it back up now and then leave the neg disconnected and then check voltage tonight.

So far though it seems that the battery probably isnt holding charge so a new one is probably needed.

p.s Car is a VW Passat, there is nothing clear stating a date on the battery, not by looking at the top anyway. Condition looks great, very clean.

 

[ap87]

Just ordered a Bosch for £115 delivered. Decent price so just got it anyway to save faffing about

 

[ap87]

Battery has just arrived. Brand new too by the way. Out of interest I just had a look at he manufacture date by decoding the numbers etched into it. Seems that it was manufactured a year ago Jan 2020. Is this still ok? any downside to it being a year old