Car Battery

Destination · 30 Jan 2022 at 18:58

Due to illness my mother's car hasn't moved for a year.
I tried to start it, but the car is completely dead, no lights/radio noise, nothing on dashboard when turning ignition.
Assumed the battery was flat, so stripped it out, and put it on a charger which reported the battery (which is about 2 years old and close to unused) was at 100% charge.
Somewhat confused I replaced it into the vehicle, and tried again, nothing as previous.

If the car is jump started from a running vehicle, then the car turns over, starts, and run until switched off.

Can a completely dead battery report being full?
Something else likely to be the issue?

paradigm · 30 Jan 2022 at 19:04

I guess it depends on how bad the charger is. If it’s using an old “peak detect” method for determining full charge, it will be looking for the voltage climbing then tailing back off (fallback voltage). A dead cell can make a peak detect charger think a cell is charged almost immediately.

A more modern or smart charger will actually measure the voltage, so will know if you are at the right voltage for a flat or charged battery.

My guess is (given I replaced my mum’s battery twice in the last two years) that the battery is completely dead and that no amount of charging will make a difference.

Destination · 30 Jan 2022 at 20:06

Thank you.

jpaul · 30 Jan 2022 at 21:23

Did you leave it on charge nonetheless ?, even if it was saying it was full - I have an old charger which afaik just limits the current applied to the battery,
other than that you just leave it charging for a reasonable time, based on the current and battery capacity - I never pay much attention to its meter showing charge level.

paradigm said:
I guess it depends on how bad the charger is. If it’s using an old “peak detect” method for determining full charge, it will be looking for the voltage climbing then tailing back off (fallback voltage). A dead cell can make a peak detect charger think a cell is charged almost immediately.

sure you are not describing an nimh charger ?

lordrobs · 31 Jan 2022 at 17:08

It could be suffering from stratification where the electrolytes effectively settle at the bottom of the battery.

The fact that it is dead as a doorknob even when charged though indicates either it, or the charger, is scrap.

Rroff · 31 Jan 2022 at 17:21

I've got a 12V sealed lead acid battery out of a UPS which acts sort of like that - seen a few too many charge cycles with full depletion - stick it on a charger it quickly shows 100% charge and measures 14.4V but within about 5 minutes of being taken off charge it drops to 1.165V.

(Need to get around to disposing of it - for some reason I keep sticking it to one side).

BUDFORCE · 1 Feb 2022 at 20:14

If the battery was left for any length of time flat that almost certainly a dead battery.

Car batteries don't like being left at anything other than 100% charged

Obviously in practice, it is unlikely to be 100% at all times , but leave it flat or low charge for any length of time and you'll nuke it.

brendy · 1 Feb 2022 at 20:35

Plug everything back as it should, beg borrow or buy a lithium jump pack (not overly expensive for them over on rainforest) as they come in handy especially in winter when batteries tend to expire. Use it to start the car then let the engine charge the battery for a few minutes then take it for a short drive. Stop the engine and try to restart it, if you get nothing then it's a duff battery.

Alibaba99 · 1 Feb 2022 at 22:52

The OP has already stated that he can start the car using a jump start and it runs fine until switched off. It then appears that it doesn't want to start again.

phil675 · 2 Feb 2022 at 11:03

I've just had this with a motorbike battery, bike not used since November, battery wasn't in great working order anyway and must have been killed by the cold, it was on charge whenever not being used, charger says full, never had a fault light. Not enough juice to start the bike, new battery sorted it.

brendy · 2 Feb 2022 at 11:17

Alibaba99 said:
The OP has already stated that he can start the car using a jump start and it runs fine until switched off. It then appears that it doesn't want to start again.

He never mentioned driving it to put a better load on the alternator.

Janesy B · 2 Feb 2022 at 14:01

brendy said:
He never mentioned driving it to put a better load on the alternator.

Doesn't matter, if the battery gets to that state it'll need replacing.

jpaul · 3 Feb 2022 at 11:36

I'll bookmark V on amazon now , in case of a £20 repeat
https://www.hotukdeals.com/deals/noco-genius1uk-1-amp-fully-automatic-smart-charger-3880634
the comment, there, that maintenance trickle charge on some cars which have Lion batteries(f80), is not recommended, interesting though.

wolfie138 · 3 Feb 2022 at 13:20

just having much the same issues w/ mine, VW battery. started getting warnings when in traffic queues w/ the music on etc, seems i need a new one. thought i could give it a bit charge but the handbook goes on about volt-limiting stuff, and as for changing the battery it says nothing but "go to the dealer" :-/
thought it a bit off that i need a new one after about 4 years but after a lot of scouring and looking on VW forums this is getting the norm, seems start-stop tech knackers batteries.

Rroff · 3 Feb 2022 at 13:52

jpaul said:
the comment, there, that maintenance trickle charge on some cars which have Lion batteries(f80), is not recommended, interesting though.

IIRC generally for long term maintenance Li-ion batteries are best kept at around 70% charge, with a full charge every ~4 months or so, keeping them constantly at 100% will reduce lifespan though how much depending on temperature - typical UK outdoor temperatures probably less of an issue compared to electronics in constant operation like say a laptop.

Cyber-Mav · 3 Feb 2022 at 14:08

sitting for 1 year dead id say time for new battery.

Deleted member 651465 · 3 Feb 2022 at 18:55

If you’ve got access to one, try trickle charging the battery for 48hrs and then give it a go.

I wouldn’t hold out much hope though.

Semple · 3 Feb 2022 at 19:01

Do you have a multimeter to check the voltage the battery is reporting?

Rroff · 5 Feb 2022 at 13:00

jpaul said:
I'll bookmark V on amazon now , in case of a £20 repeat
https://www.hotukdeals.com/deals/noco-genius1uk-1-amp-fully-automatic-smart-charger-3880634
the comment, there, that maintenance trickle charge on some cars which have Lion batteries(f80), is not recommended, interesting though.

Currently £24.99 - not quite as good as the £20 deal - I just grabbed one as it looks like it could be useful for one of my setups.

Thebug · 6 Feb 2022 at 11:35

wolfie138 said:
just having much the same issues w/ mine, VW battery. started getting warnings when in traffic queues w/ the music on etc, seems i need a new one. thought i could give it a bit charge but the handbook goes on about volt-limiting stuff, and as for changing the battery it says nothing but "go to the dealer" :-/
thought it a bit off that i need a new one after about 4 years but after a lot of scouring and looking on VW forums this is getting the norm, seems start-stop tech knackers batteries.

i had this on my octavia , stop start batteries only seem to last around 4/5 years so ii got a bosch battery from ebay new for £100 and used the carscanner pro app on my phone with a bluetooth dongle to reprogram it in, so about £113 all in the dealer wanted around £300 if I remember correctly

Car Battery

Deleted member 651465

Deleted member 651465