if you find you put off necessary jobs

Chat about your 2018+ AW/BZ model Polos here!
grazuncle2
Silver Member
Posts: 350
Joined: Thu Aug 23, 2018 5:40 pm
Drives: Polo 1.0 TSI SE 2019
Location: Birmingham

Re: if you find you put off necessary jobs

Post by grazuncle2 »

I had batteries lasting over four years. with no detectable state change that I noticed..(I used to change the car often then so would never know the actual longevity of them..
However since having the previous Polo for 15 years, and change of job .. I did well to get 2.5 years out of them before getting power anxiety.( Sluggish turn over the next day after a good run) and then you are putting the batteries on charge more often.
Charging system checked out many times in that period. Starter checked ok and always spun over really quickly after changing the battery.

So I'm not too pleased to have had this car only 4.5 months and have a low standing voltage and having to hook up the charger.. again.
It is due for a service towards the end of the year.. I'll ask VW to test it.. The car will still be under the 3yr warranty.. Not sure if that will mean anything at all..
Andy Beats
Bling Bling Diamond Member
Posts: 2012
Joined: Tue Nov 13, 2018 1:12 pm
Drives: Nissan Leaf 40KW (and Polo United)
Location: aberdeen

Re: if you find you put off necessary jobs

Post by Andy Beats »

2.5 years and struggling to turn over the car is bad, not had that in any car.
grazuncle2
Silver Member
Posts: 350
Joined: Thu Aug 23, 2018 5:40 pm
Drives: Polo 1.0 TSI SE 2019
Location: Birmingham

Re: if you find you put off necessary jobs

Post by grazuncle2 »

Something you might expect from parasitic draw but no.

The draw when off was 0.2/0.3 amp.. if you leave the car for 5 days.. That adds up to 25 amp.. nearly half of the 60amp battery capacity (when new) that was fitted..Presuming the battery was fully charged most of the time.

If not then that would equal struggle. Again, not realising that batteries don't like being left in a low state only compounds the problem.

I know differently.

Admittedly a new battery cost order 2 or 3 that's is not a lot of money compared to total running costs.. But I don't like the inconvenience of charging.. Hence this project
Johntheo1
Bronze Member
Posts: 138
Joined: Mon Jan 11, 2021 8:52 am
Drives: 2018 MK10 AW1
Location: Cork

Re: if you find you put off necessary jobs

Post by Johntheo1 »

grazuncle2 wrote: Fri Sep 10, 2021 3:14 pm Something you might expect from parasitic draw but no.

The draw when off was 0.2/0.3 amp.. if you leave the car for 5 days.. That adds up to 25 amp.. nearly half of the 60amp battery capacity (when new) that was fitted..Presuming the battery was fully charged most of the time.

If not then that would equal struggle. Again, not realising that batteries don't like being left in a low state only compounds the problem.

I know differently.

Admittedly a new battery cost order 2 or 3 that's is not a lot of money compared to total running costs.. But I don't like the inconvenience of charging.. Hence this project
A parasitic loss of 200/300 ma is excessive IMO, nearly all my VWs had a parasitic loss of 40/60ma, the 2005 Polo has the highest of all at 90ma but
it could still be left parked up at the airport for a full week (15 AH draw off from a 36AH battery) even when the battery was 10 years old. You also say
"I had bought an accurate volt meter and connected permanently hence I know running voltages; my standing voltages were low. 11.8 which suggested very low charge...", even if the battery is practically flat after starting the alternator should have no problem in charging at > 13.5V so you should never have seen the voltage at 11.8V with a running engine even if the battery was/is knackered, if, by standing charge you mean the terminal volts after stopped for a hour or so then the battery has only approx 25% charge or so. I will post a rough guide to battery capacity in a few minutes.

Volts Capacity % volts/cell
11.51 10 1.918
11.66 20 1.943
11.81 30 1.968
11.96 40 1.993
12.10 50 2.017
12.24 60 2.040
12.37 70 2.062
12.50 80 2.083
12.62 90 2.103
12.73 100 2.122
grazuncle2
Silver Member
Posts: 350
Joined: Thu Aug 23, 2018 5:40 pm
Drives: Polo 1.0 TSI SE 2019
Location: Birmingham

Re: if you find you put off necessary jobs

Post by grazuncle2 »

Sorry.. It think my math was off by a factor of 10x.. should have been. 0.02/0.03 amp and so my total draw is off too.

I don't have a proper better tester to give it a high amp short test..any battery seller should though I suspect... Could try that.

Ps. The standing charge voltage standing was indeed 11.8 after charging over night. The charging voltage with engine running is usually as high as 14.5.

After a couple of weeks left on maintenance charging the standing voltages is now 12.3 after surface charge dissipated.

It is improving so I leave it on maintenance whilst it is parked up.
RUM4MO
Bling Bling Diamond Member
Posts: 5859
Joined: Sat Dec 30, 2006 9:12 pm
Drives: B8 S4 & 6R/6C1 1.2TSI 110
Location: Mid Lothian

Re: if you find you put off necessary jobs

Post by RUM4MO »

I agree that 50milli amps is a typical figure for when all the systems have been forced into sleep mode for certainly older VW Group cars, I've never had to check anything under 10 years though, maybe something that I should do on both our cars to get to know what the drain is under "good" conditions.
grazuncle2
Silver Member
Posts: 350
Joined: Thu Aug 23, 2018 5:40 pm
Drives: Polo 1.0 TSI SE 2019
Location: Birmingham

Re: if you find you put off necessary jobs

Post by grazuncle2 »

Thankyou Johntheo1

This is very useful information...

Some info on the 'net' suggested that 11.8 v was discharged whereas your list suggests morel like 30% charge hold! (I should have been a bit more sceptical as the car does/did start with no struggle when it was @ 11.8v..

I see also from this that, following 3 weeks of maintenance charging, is now close to 12.3 standing charge.. hence a more respectful 60% charge holding

Volts Capacity % volts/cell
11.51 10 1.918
11.66 20 1.943
11.81 30 1.968
11.96 40 1.993
12.10 50 2.017
12.24 60 2.040
12.37 70 2.062
12.50 80 2.083
12.62 90 2.103
12.73 100 2.122

Thanks for this!
Johntheo1
Bronze Member
Posts: 138
Joined: Mon Jan 11, 2021 8:52 am
Drives: 2018 MK10 AW1
Location: Cork

Re: if you find you put off necessary jobs

Post by Johntheo1 »

It's reasonably easy to check if a battery is on the way out by using your charger, on a healthy battery if terminal voltage is say 11.8 and you put it on normal charge, it will keep charging until the voltage rises to ~ 14.3v and c/o to trickle charge, if a 36AH battery is 75% discharged@11.8V then it should take your 5A charger about 5/5.5 hours to reach full charge, if it c/o to trickle charge in say 30 minutes or so, then the battery is kaput.
A neighbour of mine recently called me as his 2011 diesel Opel Insignia would not start (original battery so not bad really). The terminal voltage was 11.8V so I attached my 3.8A charger to it, this is a 95AH battery so one would expect it to take around 17 hours to reach full charge but it didn't, after about 10 mins on charge it went to full charge but reached 14.3 volts in 32 minutes which means it inputted 2 AH, the terminal voltage a few minutes after removing the charger was 12.4V and the car started instantly but the terminal voltage then fell again to 11.8v and obviously no start.....battery kaput, new battery bought/installed. You might say how could increasing the charge by 2AH in a basically flat battery still start the car, well, I don't know but if one assumes say 400A for 3 secs while cranking then this only requires (400*3/3600) 0.33AH so maybe this explains it? although one might expect the internal resistance of a failed battery to be too high to pass sufficient current to crank or even engage the start solenoid.

That little 7.5AH house alarm battery that I use on my fountain lights takes ~ 1.5 hrs to reach full charge from 11.9/12V. so must still be in A! condition.
Post Reply