battery drain / 3 month old battery unhealthy already?

[mc999]

Hi,

I picked a 2018 2l diesel toyota proace up a few months back. It frequently said energy efficiency mode active which seems to be caused by a low 12v battery. I have also never to this day seen the stop start functionality work.

I had a cheap odb scanner and multimeter which both indicated that the alternator was fine but the battery voltage would get low when left for a while.

So i replaced the 70ah 760cca oem efr battery with a numax agm battery with the same specs.

Everything was fine for a while but i was disappointed to see the energy efficiency message creeping back when the van wasn’t in frequent use. a few weeks ago before the really cold weather it wasn’t used for a week and the battery fully died, i fully charged it and it was left another week during the really cold weather and it died again.

At this point in thinking a parasitic drain and started checking for that but i’m coming up with nothing. which now makes me think the old battery was bad and coincidentally i got a new bad battery? (or a fault in the van has damaged the battery)

currently the battery will deplete to the point of not being able to start in 4 days from a full charge and i have not seen it stay above 12.54v even after fully charged.

any ideas? was it a bad idea to replace with an agm battery? is it likely i got a dud battery? is it likely a problem with the van could kill a battery? is the battery tester wrong?

i think next steps might be an auto electrician or going back to the parts place with the battery if it’s still under warranty.

any advice would be great

[mc999]

seems like i can’t link images of the battery tester but it says:

health 45% 511cca (should be 760)
charge 73%
internal resistance 4.85
cranking low 9.21ms 8.81v
charging normal
loaded 12.27v
unloaded 12.28v
ripple 94mv

[GreenV8S]

12.54V is a little low for fully charged but does indicate the battery is more or less charged.

If it's going flat in 4 days then you would be losing of the order of 10Ah per day, or an average of a few tenths of an amp. That's significantly higher than normal.

You could start by doing a residual current test across every fuse you can see. Note that you may need to have the car completely shut down and closed for 10 minutes before the electronics quiesce. You could be looking for a courtesy light switch not opening when the door is closed and holding a relay closed, or something plugged into an OBDII port you haven't noticed, poorly designed USB socket, that sort of thing.

If you aren't familiar with doing a residual current test then read up on the process and make sure you have a sufficiently accurate volt meter.

[E63eeeeee...]

I had a phone charger that used to do this, the 12v cigarette lighter port apparently sidesteps all the battery management tech and doesn't get turned off when the battery gets lower unlike most of the systems in the car itself. Any chance it's something like that?

[mc999]

GreenV8S said:

12.54V is a little low for fully charged but does indicate the battery is more or less charged.

If it's going flat in 4 days then you would be losing of the order of 10Ah per day, or an average of a few tenths of an amp. That's significantly higher than normal.

You could start by doing a residual current test across every fuse you can see. Note that you may need to have the car completely shut down and closed for 10 minutes before the electronics quiesce. You could be looking for a courtesy light switch not opening when the door is closed and holding a relay closed, or something plugged into an OBDII port you haven't noticed, poorly designed USB socket, that sort of thing.

If you aren't familiar with doing a residual current test then read up on the process and make sure you have a sufficiently accurate volt meter.

thanks for replying, i did attempt this. i disconnected the alternator for a day or so and also started testing the fuses but i only saw zero values. because of what you said im now thinking perhaps my multimeter doesn’t have the required millivolt accuracy to do this work? it’s this cheapo from screwfix:

link removed but it’s item 95426 on screwfix

there’s nothing obvious at all, the only thing i noticed was one fuse for the 12v accessory socket was clearly not the oem one so i pulled that just incase but it didn’t help.

one question i have though, every youtube video on this has the car locked, sleeping and the doors latched but open before looking at the fuses but how do they stop the alarm going off in this state?

[mc999]

E63eeeeee... said:

I had a phone charger that used to do this, the 12v cigarette lighter port apparently sidesteps all the battery management tech and doesn't get turned off when the battery gets lower unlike most of the systems in the car itself. Any chance it's something like that?

unfortunately not, there’s nothing plugged in anywhere. it was formerly a hire van so i’m wondering if there are any weird devices left behind.

but it was cheap so i wouldn’t think they’d leave any trackers behind or anything fancy

[GreenV8S]

mc999 said:

how do they stop the alarm going off in this state?

Tape over the door switches so it thinks the doors are closed.

You can verify the meter accuracy and your test method by picking a fuse which you know supplies some low power circuit and confirming that you can measure the expected voltage difference across the fuse when the circuit draws power.