12v battery maintenance, issues, etc.

[Chas G]

46 minutes ago, jthspace said:

Reverse car into garage? Easy to access fuse box / boost connector.

I fitted a 12v socket in the battery cover under rear seat that can be used for charging or for connecting a boost pack.

Excellent job. Well done.👍

[Pete Ilk]

I have an optimate trickle charger, connected to socket lead attached to 12v Battery. I checked a couple of times voltage before charge, after 4/5 days non use, at 11.2 and 11.9. After a day or two on the trickle charger the voltage reaches a maximum of 12.5 v.. What does this indicate re the state of the Battery?

Could anyone confirm, again, the largest capacity and size of potential replacement batteries? what would the expected voltage readings be on a larger capacity replacement Battery. Many thanks, and apologies if the questions have previously been answered.

 

[jthspace]

This is what I fitted following recommendations in this thread.

https://toyotaowners.b-cdn.net/uploads/monthly_2023_11/Screenshot_2023-11-03-08-30-33-180_com.android.chrome.jpg.5257211c3ee27348faa19c82db24e107.jpg

 

[Roy124]

1 hour ago, Pete Ilk said:

I have an optimate trickle charger, connected to socket lead attached to 12v Battery. I checked a couple of times voltage before charge, after 4/5 days non use, at 11.2 and 11.9. After a day or two on the trickle charger the voltage reaches a maximum of 12.5 v.. What does this indicate re the state of the battery?

Could anyone conpfirm, again, the largest capacity and size of potential replacement batteries? what would the expected voltage readings be on a larger capacity replacement battery. Many thanks, and apologies if the questions have previously been answered.

 

Pete, first question, to me, that your 4/5 reading suggests either some deterioration in the Battery or your meter is under reading.  I found my meter read lower than a Battery monitor attached directly to the Battery.  When my charger has been on I get a similar reading. In other words probably no problem. 

I can't give an opinion on the capacity for YC batteries but my garage replaced the original  battery on my Corolla from the 35Amp for a 42Amp which was the same size.  The voltage readings should follow the same profile of a longer time scale.

Simplistically,   35AHr battery supplying 10A for one hour would drop to 25A. The 42A would drop to 32A.  The former would be at 71% and the larger 76%.

[Mooly]

2 hours ago, Pete Ilk said:

I checked a couple of times voltage before charge, after 4/5 days non use, at 11.2 and 11.9.

11.2 volts across the Battery terminals is a very low state of charge and leaving a Battery in that state will see it deteriorate due to sulphation of the plates.

11.9 volts is still a low state of charge but if that were encountered in say a traditional combustion engine car it would start the car as normal and give no real hint it was in fact 'low'.

2 hours ago, Pete Ilk said:

After a day or two on the trickle charger the voltage reaches a maximum of 12.5 v.. What does this indicate re the state of the battery?

While the charger is connected the voltage should go higher than 12.5 volts and typically would be around 14 to 15 volts while on charge. If the charger has a low current output then it might take a while to climb higher. 

 

2 hours ago, Pete Ilk said:

what would the expected voltage readings be on a larger capacity replacement battery.

If you activate any of the cars electronic systems while measuring the voltage then it would typically fall down from a high of 14 to 15 volts down to around 12.5 volts because the charger could not supply the additional current.

 

2 hours ago, Pete Ilk said:

what would the expected voltage readings be on a larger capacity replacement battery.

The chemistry of the Battery defines the voltages. Fully charged batteries of 10Ah, 30Ah, 60Ah and 100Ah will all show similar voltages at similar states of charge.

Think of that like a tank of water. A 10 gallon or a 100 gallon tank are both 'full' when full and both half empty when half the contents have been removed, however the half empty 100 gallon tank still has much more 'content' available than the half empty 10 gallon one.    

[Pete Ilk]

1 hour ago, Mooly said:

While the charger is connected the voltage should go higher than 12.5 volts and typically would be around 14 to 15 volts while on charge. If the charger has a low current output then it might take a while to climb higher.

Thanks for info. My voltage tester is separate to the charger. The charger will be charging at 14 plus v when on top boosting charging phase, and lower on maintenance phase . When I disconnect the charger and measure the volts it is about 12.5v. Are you saying that it should be higher when disconnected after a long charge?

[Roy124]

Pete, your 12.5v  might not be that accurate.   Are you using an analogue meter?  An OBD reader or the BM2/6 give digital readings to 0.01v, in my car they give different readings.  The former is instantaneous whereas the BM is a short term average reading.

[Mooly]

When you remove the charger, the voltage across the Battery terminals will fall back fairly quickly although how quickly depends on how much background current draw there is pulling it down. In reality It could easily be just a matter of a few tens of seconds or alternatively if there were no current draw at all the Battery would remain at perhaps 13v or more for many hours. A quick flash of the headlights or operating the central locking would pull that 13v down instantly though. 

At this point and given a healthy and fully charged Battery what happens next depends on the background current draw and this is where all the problems occur...

...it takes a surprisingly long time for a battery to fully charge because the charge current taken by the battery naturally tails off as the charge level rises. All the evidence form all the many threads and users with battery issues points to the fundamental problem being that the background current draw takes more from the battery than can be put back by normal use (normal time spent driving).

This is what I believe happens...

If the battery starts at 100% and you see it down at 80% after say 5 days standing then a few minutes charging (the cars own charging circuit) will see that 80% rise very quickly to say 90% but then the battery itself stops taking all that the charger can deliver and the charge level then climbs ever more slowly. Lets say 80 to 90% after 10 minutes but then it takes another 10 minutes to bring that to say 92% and another 30 minutes to reach 95% and ever longer to put that last few percent back.

Now the same scenario happens again only now you are starting from say 95%. The overall consequence is the batteries overall state of charge falls over time. As the charge level gets ever lower the battery starts to 'age' more quickly due to sulphation and at this point it becomes a downward spiral. The same background current draw now seems to pull the voltage down ever more quickly and the battery just never gets a prolonged charge to recover it. After a while it is past a point of no return.

In a conventional car it is less of a problem because there is not this highish level of background current draw. The battery may be deteriorated and in poor state but because there is no current draw it stays in that same state day after day and will still start the conventional car normally. It may be old and way down on capacity but it is 'enough' given that nothing is discharging it when it it is parked up. 

 

[Mojo1010]

27 minutes ago, Pete Ilk said:

Thanks for info. My voltage tester is separate to the charger. The charger will be charging at 14 plus v when on top boosting charging phase, and lower on maintenance phase . When I disconnect the charger and measure the volts it is about 12.5v. Are you saying that it should be higher when disconnected after a long charge?

I have a measurement of 12.8v fully charged Battery. 12.5v is ok. You have a charger so wouldn't need to put a bigger Ah Battery in unless current one fails. 

[hind]

1 hour ago, Mooly said:

if there were no current draw at all the battery would remain at perhaps 13v or more for many hours. A quick flash of the headlights or operating the central locking would pull that 13v down instantly though. 

The voltage will drop as the chemical reaction (movement of the hydrogen ions) will stop after we stop charging and the electrolyte saturation (measured by the density where 1.28g/ccm indicates fully charged) stabilises. It doesn't depend on the current draw. It will of course be affected if we take any current out of it (how much voltage will drop depends on the internal resistance of the Battery and the current). 

Anyway the problem with car batteries is based on the fact that it's really time consuming to charge it fully, most of the time we are ok with letting the alternator / charging circuit to charge to something like 80% when the current is still big enough to put significant charge and we are still underneath the 14.4V maximum voltage level. 

Ignoring Battery temperature corrections, we cannot charge with more than 14.4V as we risk hydrolysis (bubbling) and loosing water from electrolyte (not to mention producing hydrogen) but as the Battery voltage rises, with constant max voltage the current has to fall to even less than an amp. So it might take days of charging to get that remaining 20% back. 

That's why it is adviced to charge the battery with the charger from time to time, especially if we risk having negative energy balance (we use up more than we put back when driving). It happened previously with the cars with ICE that were doing short trips with many engine start/stop cycles. No matter how big the battery, it would eventually run out.

Now it's different because the modern car uses the energy when it is parked and even with hybrid engines we don't use up that much of the energy to start but the small battery makes it easy to deplete it if we drive occasionally (or we are doing short trips) 

[Pete Ilk]

Thanks for all replies. Makes it a bit clearer.

[Roy124]

Mooly,  I disagree only about 'conventional' car.  I would say older traditional car to differentiate from modern connected cars which will have not dissimilar current draws while not in use.

The only difference between ICE and Hybrid may be the alternator doing a rapid recharge after engine start. 

[Mooly]

Its just a choice of words... so I mean ICE without such things as keyless entry and it not phoning home all the time. The only drain on these is the tiny draw of the remote receiver for a normal 'WiFi' key with lock and unlock buttons on it plus the normal background draw of the ECU and immobiliser and alarm (if fitted) which is very low indeed.

38 minutes ago, Roy124 said:

The only difference between ICE and Hybrid may be the alternator doing a rapid recharge after engine start. 

That's a fair point under certain conditions although I see so many times in these threads that owners say that they see 14.4 volts or close to that value when charging in ready mode or when driving. If that is so then it doesn't matter whether it is a high output alternator or the DC/DC convertor in a Hybrid doing the charging, the Battery doesn't care. All it sees is the 14.4 volts and if that is present then it is the Battery itself determining the charge current, not the charger (alternator or the DC /DC convertor). That to me is the problem.

The batteries seem to have accelerated aging due to the type of usage and an insufficient charge time to maintain them in good shape. A new  Battery has a very low internal resistance and that means it can draw lots of charge current even as the terminal voltage approaches 14.4 volts. A deteriorated battery can not allow (or accept if you prefer) this current to pass.

I hope this below makes some kind of sense. It is a simple simulation I set up to show how the internal resistance of a battery greatly affects charge acceptance and current delivery. In reality there is more going on because the internal resistance also varies with charge level but it illustrates the point. The aged battery can not take much charge current and so it would take a very long time bring a moderately discharged battery back to full charge through driving alone.   

The batteries differ only in the internal resistance figure I set. First image shows charge current for each. Second image shows the terminal voltage under the same loading.

The old and new batteries are labelled and the alternator or DC/DC convertor is at the right producing a constant 14 volts. The second image separates the two as they now discharge into their respective loads.

The reality will be a bit different in raw numbers but the principle of the issue remains the same. 

 

[Chas G]

Please come back. All I had to do was put Petrol in you and get you serviced

I wish I hadn't traded you in for a load of anxiety even though I have disabled "smart" entry, taken out the Dashcam and disabled MyT cloud. From fully charged at 12.7 volts to dip below 12 volts -

6 days of none use (0.1v/day)

2 weeks of my normal mileage of mixed journeys at best.

Took them a week to sell my immaculate 2020 Petrol Yaris Y20. 

 

 

[Chas G]

I need to get the BM2 Battery monitor fitted ASAP with alarms to my phone when it reaches 12 volts so I can effectively manage the state of the charge. 

[Eddie G]

1 hour ago, Chas G said:

Please come back. All I had to do was put Petrol in you and get you serviced

I wish I hadn't traded you in for a load of anxiety even though I have disabled "smart" entry, taken out the dashcam and disabled MyT cloud. From fully charged at 12.7 volts to dip below 12 volts -

6 days of none use (0.1v/day)

2 weeks of my normal mileage of mixed journeys at best.

Took them a week to sell my immaculate 2020 Petrol Yaris Y20. 

 

 

Know what you mean, do mainly short trips and ended up trading in my 2022 Yaris Hybrid Design for a 2020 Yaris Y20 and while the 2022 Yaris was better to drive am more than happy with the Y20 and am planned on keeping it long term.

[jthspace]

12 hours ago, Chas G said:

I need to get the BM2 battery monitor fitted ASAP with alarms to my phone when it reaches 12 volts so I can effectively manage the state of the charge. 

I’ve seen my Battery drop to mid 11’s and still fine to start. If your dealer can’t/wont fit charge lead/BM2 and you fancy a drive up to South Cambs near Duxford Imperial War Museum M11 Jct 10 then I will happily fit both for you. 

[Chas G]

46 minutes ago, jthspace said:

I’ve seen my battery drop to mid 11’s and still fine to start. If your dealer can’t/wont fit charge lead/BM2 and you fancy a drive up to South Cambs near Duxford Imperial War Museum M11 Jct 10 then I will happily fit both for you. 

Thank you for your very kind offer. Have a very happy Christmas best wishes Chas 

[Max_Headroom]

5 hours ago, jthspace said:

I’ve seen my battery drop to mid 11’s and still fine to start. If your dealer can’t/wont fit charge lead/BM2 and you fancy a drive up to South Cambs near Duxford Imperial War Museum M11 Jct 10 then I will happily fit both for you. 

What a brilliant gesture.

[Chas G]

The Nextbase dash cam I disconnected in my Yaris Cross appears to consume quite a lot of Battery power (see Nextbase data below). The dash cam was wired to a fuse under the glove box which I am not sure is live or dead when the car is off.

However if it is live 24/7 and I simplistically use their figure of 100mAh in standby mode for the 3 days (72hrs) my car often sits idle, that is 7.2Ahr out of the 12 volt 35Ahr Battery which might be only 80% charged. No doubt the camera would also be charging some of the time on standby :-

"On average, our Series 2 Dash Cams use approximately 300mAh (Milliamp Hours) of power while turned on, recording and charging, 200mAh while in standby mode (charging) and around 100mAh in standby mode (fully charged)."

 

[Dala]

Are you not using a Hardwire Kit?

https://nextbase.com/accessories/series-2-hardwire-kit/

[Graham47]

2 hours ago, Chas G said:

The dash cam was wired to a fuse under the glove box

Highly likely that this is a fuse that’s only live in READY mode.  That’s by far the normal way.  But it’s very easy to check, does/did the Dashcam switch off when the ignition was switched off ?

[Chas G]

1 hour ago, Dala said:

Are you not using a Hardwire Kit?

https://nextbase.com/accessories/series-2-hardwire-kit/

I don't know, I didn't install it.

[Chas G]

45 minutes ago, Graham47 said:

Highly likely that this is a fuse that’s only live in READY mode.  That’s by far the normal way.  But it’s very easy to check, does/did the dashcam switch off when the ignition was switched off ?

I only know its connected to a fuse under the glove box because the fuse box lid was lying in the bottom of it. Need to be more supply than me to ferret about down there.

I just unplugged the camera  and put it in the house so it wouldn't use any power. In normal use 200-300ma

[jthspace]

3 minutes ago, Chas G said:

I don't know, I didn't install it.

Any chance of a photo, it’s a bit awkward to see but if you or someone could take a pic with a smartphone we can work out if it’s a permanent live or ignition controlled depending which fuse slot its piggybacking off.
Sometimes they are wired to permanent live if you want it working when parked. Mine is ignition controlled as it piggybacks off the windscreen sensor.