Any battery experts?

[Micky 32]

Hi all. My apologies that i don’t own T6 but mechanical something similar, 2024 Skoda Octavia vRS diesel , same engines, battery and smart alternator. I see a lot of battery info on here so thought i’d post a question.

Not sure what to make of my battery, car is 18 months old. I put my Topdon BT600 battery tester on my battery. It’s a Clarios Varta EFB+ 700 A EN. The tester will not pass it. Keeps telling me to “Replace” it measures an average reading 550 amps.

There are no physical signs. The starter sounds brisk and the start stop works flawlessly everytime.

However everytime i connect my obdeleven to the car i keep getting communication errors etc, a few times i saw a low voltage code in the brake booster module. Today i connected up my bm2 battery monitor. I get good resting voltage but a few times today it recorded a low cranking voltage of around 9 volts. The car has done 47,000 miles. I do 30k a year so the car is used daily never lying up.

Is my battery on it’s way out after only 18 months??

 

[roadtripper]

I wouldn't pay too much attention to the BM2 cranking tests - they're great devices for long term monitoring and spotting trends but take the accuracy with a pinch of salt.

Start Stop works a battery hard and it doesn't take too many deep discharge events to damage a starter battery (literally a handful) because the plates are so close together and thin.

18 months is shorter than I would expect, but 47000 miles is a lot of start stop cycles. Yours is an EFB rather than an AGM and they tend to be less robust. A low cranking amps and a low cranking voltage are consistent with the way a starter battery will age and fail as the plates wear/get damaged.

My standing advice if you're experiencing electrical weirdness is start with a known good new battery once you've checked the basics - don't spend weeks and hundreds of quid on testers and other kit when you can replace the battery for little more than a tank of diesel.

If you do replace it go for an AGM if you can, with heavy mileage they will probably stand up to it a bit better. The charging profiles for EFB/AGM are the same.

 

[Micky 32]

Thanks for the reply. I wasn’t sure if there was trouble ahead with my current battery. My work entails calling to an average of 7/8 houses a day so my starter probably gets more use than the average car.

My last car a VW Passat came with an AGM battery. It did show signs of aging at 3 years but it made it to 7 years and 200,000 miles. It was a slow degradation.

 

[Salty Spuds]

If you didn’t own all the battery testing gadgets, you wouldn’t be worrying. If it starts briskly and the stop/start is working (it’s the first thing to go with a dodgy battery) then stop looking for problems that ain’t there.

 

[Lubrown]

Current online buzz from ‘mechanical influencers’ seems to be around stop/start - I see it all the time on YouTube at the moment.
Personally it doesn’t pass my BS filter as my golf (also with pretty much the same engine as the van) is eleven years old, I never turn the stop/start off and it’s still on the original battery.
As above - if your car starts fine there is no major issue.

 

[Micky 32]

LoL. I only have one battery tester gadget and rarely use it. I guess i shouldn’t be worried so despite it fails my battery and i get error codes.

BTW the start stop system still worked on my last car with a worn out battery.

 

[Micky 32]

 

[Micky 32]

A quick question about the smart alternator. I did a round trip of 40 miles yesterday. 20 miles there and 20 back. The first 20 miles the alternator charged at a constant 15v. On the way back it was 14.9. Last night on a 20 mile round trip around14.5/6. Is that normal behavior? There’s no reason for my battery to be low as i do 600 miles a week.

 

[whodat]

It'll depend on whether your lights, fans, AC, radio etc were on as well as revs, uphill/downhill/wind etc.
It won't have been exactly the same conditions.
Think realistically - if there is a low voltage problem if you have left it for a couple days, then there is a problem. Stop looking for problems. If you are worried, just change the f'ing thing.
9v is way too low for a battery to go but I'm no eggspert.

Mine is 3 years old and sits at 12-12.1v after a couple of days in the cold. Still starts although takes a fraction of a second longer. Think maybe this summer it is time to invest in a new one.

 

[Salty Spuds]

A quick question about the smart alternator. I did a round trip of 40 miles yesterday. 20 miles there and 20 back. The first 20 miles the alternator charged at a constant 15v. On the way back it was 14.9. Last night on a 20 mile round trip around14.5/6. Is that normal behavior? There’s no reason for my battery to be low as i do 600 miles a week.

Just because the alternator was putting out c15V, doesn’t mean the battery is down. As @whodat says, lights/heater/aircon will all cause the alternator to do its thing. How are you monitoring the voltage?

 

[Micky 32]

Just because the alternator was putting out c15V, doesn’t mean the battery is down. As @whodat says, lights/heater/aircon will all cause the alternator to do its thing. How are you monitoring the voltage?

I always have the AC on set to 22 degrees and rarely see 15v. Even brake recuperation mode can work with the AC on. It was daytime on that drive and no lights on etc just normal.
That’s ok if no issue was worried in case 15v was a bit too high and would overcharge the battery. I have a BM2 connected.

 

[Salty Spuds]

I always have the AC on set to 22 degrees and rarely see 15v. Even brake recuperation mode can work with the AC on. It was daytime on that drive and no lights on etc just normal.
That’s ok if no issue was worried in case 15v was a bit too high and would overcharge the battery. I have a BM2 connected.

The charging voltage can reach around 17V in certain circumstances, 15V is normal for modern stop/start systems.

 

[roadtripper]

Also the BM2 is good for monitoring over time and seeing patterns and trends, I wouldn't trust the absolute voltage unless I had checked it against something more trusted like a decent quality multimeter