Battery life

[SD1too]

Originally Posted by freewheeler

... then check the voltage drop on the battery over a couple of days whilst still disconnected.

The open-circuit battery voltage may not tell you much. What matters is how much the voltage drops when the battery is required to deliver a large current to the starter motor. Anything below about 10.5 volts is a bad sign.

Simon

[freewheeler]

Originally Posted by SD1too

The open-circuit battery voltage may not tell you much. What matters is how much the voltage drops when the battery is required to deliver a large current to the starter motor. Anything below about 10.5 volts is a bad sign.

Simon

I was hoping it might show how much it's dropping over 24 hours, I'll check the voltage drop after starting tomorrow. Cheers, Dave

[freewheeler]

Originally Posted by freewheeler

I was hoping it might show how much it's dropping over 24 hours, I'll check the voltage drop after starting tomorrow. Cheers, Dave

Right so this morning I took a reading on the battery and it was 12.18 volts across the terminals then following advice (SD1too) I took a reading during starting and it went from 9.odd volts momentarally (it was so fast I couldn't catch it all) and then jumped to 10.3 volts across the terminals before the car started. I stopped the engine and the voltage read 11.9. So it looks like the battery is not quite dead but very poorly I still intend to try to rejuvinate the battery with the smart charger and leave it off the car for a few days to check the voltage drop before shelling out for a new battery. The RAC fitted the battery two years to the day more or less and charged me £30 to come and check it yesterday because I'm no longer a member (but thats another story) but found nothing wrong on his box of tricks, makes me wonder if the software is designed not to report a faulty battery if it's borderline

[Ed3]

my cdti battery was borderline due to age and I followed Arctic's advice with buying a new Tayna battery (around £90 delivered). Which has been very good for my low miles with occasional long trips often standing for 3 weeks without use but remains strong.

[Synchromesh]

You measured 12.18V this morning but I am not sure when you last charged it. If it was fully charged recently and hasn't been loaded then 12.18V is very low, it should be approaching 13V. Google 'battery university lead acid state of charge' and look at the graph. Even though your battery is only 2 years old if it has spent a long time below 90% state of charge it may have sulphated and despite what you read on the internet I don't think significant sulphation of a lead acid battery is reversible. I think if you carry on using it it will let you down. When my dad was still driving in his 70s and 80s he used to ask me to fit a new battery on his Rover 45 when it was 3 years old even if it tested OK. He said he would rather pay a bit more than be stuck somewhere away from home in the dark and the rain. I could see his point.

[SD1too]

Originally Posted by freewheeler

I still intend to try to rejuvenate the battery with the smart charger and leave it off the car for a few days to check the voltage drop before shelling out for a new battery.

Yes, use your smart charger Dave. Taking voltage readings with the battery on the bench will not be helpful, as I explained earlier (my battery currently reads 12.14 v after standing uncharged for 10 days and it will start the engine tomorrow!). My second car's battery reads 12.47 v and is also reliable.

Following charging for 24 hours, you'll have to return it to service to find out if it can deliver starter motor current reliably. Is that practical or do you rely on the car every day for work?

Simon

[freewheeler]

Originally Posted by SD1too

Yes, use your smart charger Dave. Taking voltage readings with the battery on the bench will not be helpful, as I explained earlier (my battery currently reads 12.14 v after standing uncharged for 10 days and it will start the engine tomorrow!). My second car's battery reads 12.47 v and is also reliable.

Following charging for 24 hours, you'll have to return it to service to find out if it can deliver starter motor current reliably. Is that practical or do you rely on the car every day for work?

Simon

Leaving it off for a few days is no problem Simon but after reading comments here I think I'll purchase a new battery, eurocarparts have a Bosch with better specs than the Varta I have currently for about £123.oo so I'll opt for that. Cheers, Dave

[SD1too]

Originally Posted by freewheeler

... after reading comments here I think I'll purchase a new battery ... for about £123.oo so I'll opt for that.

You prefer to shell out £123 when your current battery might be able to be saved with a proper charge?

Out of interest, which comments have resulted in this change of mind?

Simon

[Ed3]

are these links of use?

https://www.tayna.co.uk/car-batteries/varta/e44/


https://www.the75andztclub.co.uk/for...d.php?t=308641

[Synchromesh]

I hope my post 35 doesn't push you to prematurely replace your battery. I returned to your post 1 and noted that you weren't actually having battery problems you just wanted to know if it would still start after being parked for a prolonged period. I mixed your post up with another where the op was actually having battery problems. If your alternator is charging and the battery is fully charged when you reach the airport and your car's sleep current is similar to mine (16mA) you should be alright. After two weeks your battery will have lost approximately 20% of its charge. Despite keeping an eye on the condition of my car battery I still have a lithium-ion jump starter in my boot just in case.