12v battery maintenance, issues, etc.

[r44flyer]

40 minutes ago, hind said:

The thing is, it will not charge it to 100%, by design. You can charge the battery to 12.7V, drive a car for 100 miles, let it rest and after 30 minutes you will read 12.5V. Meaning that this drive effectively discharged your battery. This is the issue with relying on the car. 

As an electronics engineer with much experience in charging batteries, I respectfully don't agree.

Charging a Battery requires a voltage higher than the normal state of the Battery to charge it.
Normally you would charge a 12V lead acid Battery at 2.25V per cell i.e. a 13.5V to 13.8V charge voltage would be considered a normal range.

When the charging voltage is removed the battery will then settle to it's normal state, typically 12.5V to 12.7V.
This is called sag. However, it doesn't mean the battery is not charged to 100%, when in fact it may well be.
That lower voltage is considered the battery's normal steady state voltage when fully charged, governed its' chemical construction, temperature etc.

If systems are connected to the battery, which they are of course even when the car is off, a small discharge current will still occur, and further reduce the battery steady state voltage slightly.
How long it takes to fully discharge a battery in good condition is then decided by the quiescent discharge current.

A battery in poor condition may settle to a lower state, and might even appear normal around 12.0V to 12.5V (our rubbish battery measured 12.5V off load), but it will not have any capacity left.

So a reasonably long journey around town will always fully charge the 12V battery.
Hence why I have never had to boost ours with a mains charger in 9 months since it was replaced.

[Dala]

21 minutes ago, r44flyer said:

...So a reasonably long journey around town will always fully charge the 12V battery....

[r44flyer]

42 minutes ago, Dala said:

Context is everything so I'll play along anyway...
Assuming this is a monitored 12V Battery on a car and the X axis is hours.
I don't know how old the Battery is, don't know the state of the Battery capacity before hour 0 so I've no idea whether it had been on charge/driven/or how long before hour 0.

All we can see is that at hour 0 the battery was around 12.7V and was settling to a steady state of 12.43V by hour 7, assisted by a small quiescent discharge current by the car's 12V systems.

Just after hour 7 the car was driven/charged for just over 1 hour during which a charge voltage was applied.

From hour 9 to 21 the battery settled back to its steady state around 12.4V
The quiescent discharge current would have resumed and the battery stayed at a steady state, albeit with some percentage loss of capacity up to hour 21.
The flat line indicates that the 12V battery was reasonably charged, but this graph cannot reveal at what capacity.
You would have to do a discharge test down to the correct voltage to prove what capacity the battery actually had left, which in this case could easily be anywhere from 20% to 95%, depending on the state of charge, battery condition and temperature. So the graph doesn't actually prove anything for me.

I'm not saying that a 1 hour journey will fully charge a flat battery, I'm saying a reasonable journey, yes 1 hour would do, will top up a good battery, and replace a fair proportion of its capacity since its previous use. 

My original point that the 12V battery is being charged every time the car is driven stands, evidenced by the fact that my replacement Yuasa battery has not been charged in any other way since January.

[Dala]

5 hours ago, r44flyer said:

...Just after hour 7 the car was driven/charged for just over 1 hour during which a charge voltage was applied...

12.8V is not "charge" but "maintenance" voltage

--------------------------------------------------------

the day before

How the system evaluates charging and maintaining the car Battery by driving is still a mystery to me.

[hind]

8 hours ago, r44flyer said:

As an electronics engineer with much experience in charging batteries, I respectfully don't agree.

With charging lead acid batteries? If yes then you will know that the Battery capacity is linked with the electrolyte density. And you increase it with charging, but it takes time. The higher the voltage the faster the process, but above some point the electrolysis process becomes more intensive, turning water part of the solution into hydrogen and oxygen. That's why you rarely charge the Battery with the voltages higher than 14.4V. With the Battery out of the car you can crank the voltage to 16V, keep it like that for a few hours, refill with demineralised water and you are good to go. But with the battery inside the car you can't do that easily, so you have to rely on the absorption phase of the charging, which is based on keeping the voltage on the maximum safe level and letting the battery to rebuild the electrolyte density and it's capacity. 

But for some reason the charging algorithm in Yaris doesn't always use maximum voltage, dropping it to 12.7V. Could you imagine what's the charging current then? How long would it take to not only charge it but restore the correct electrolyte density? In no way you can restore what's lost during parking. And because of that to keep the battery in a good shape, regardless of the manufacturer, in Toyota Yaris IV you need to charge it manually from time to time. Otherwise it will degrade over time and fail sooner than it should 

[HarryW2024]

I do wonder what the charging algorithm is as used by Toyota. It’s not as if it’s constrained by the simple constant constant voltage (CV) charging of an alternator system of a normal car. Ergo it should allow for phase charging which is a combination of Constant Current (CC) and CV as it swtiches between Bulk, Absorbsion and Float phases.
Also being a Calcium Battery (Ca/Ca) it has to manage sulfation of the terminals/plates, which the type is particularly prone to, giving a false voltage level readout due to surface charging at too low levels and hence not actually fully charging it.

[dash]

Charge holds at 14V while the car is parked and is in Ready mode (as evidenced using BM6). So half an hour parked in Ready mode is more beneficial to the charge state of the 12V Battery than half an hour's driving. Go figure... 🤔
 

[152bobby]

This topic is now on Page 122, it's going to continue until the cows come home 🥺😄

[r44flyer]

4 hours ago, Dala said:

12.8V is not "charge" but "maintenance" voltage

--------------------------------------------------------

the day before

How the system evaluates charging and maintaining the car battery by driving is still a mystery to me.

Any voltage applied to a lead acid Battery above its steady state is charging.
Call it what you will but 'maintenance' is just another mode of charging.

The art of charging is more algorithm based now with either pre-programmed responses or real time analysis done by 'AI' electronics.

[r44flyer]

2 hours ago, hind said:

With charging lead acid batteries? If yes then you will know that the battery capacity is linked with the electrolyte density. And you increase it with charging, but it takes time. The higher the voltage the faster the process, but above some point the electrolysis process becomes more intensive, turning water part of the solution into hydrogen and oxygen. That's why you rarely charge the battery with the voltages higher than 14.4V. With the battery out of the car you can crank the voltage to 16V, keep it like that for a few hours, refill with demineralised water and you are good to go. But with the battery inside the car you can't do that easily, so you have to rely on the absorption phase of the charging, which is based on keeping the voltage on the maximum safe level and letting the battery to rebuild the electrolyte density and it's capacity. 

But for some reason the charging algorithm in Yaris doesn't always use maximum voltage, dropping it to 12.7V. Could you imagine what's the charging current then? How long would it take to not only charge it but restore the correct electrolyte density? In no way you can restore what's lost during parking. And because of that to keep the battery in a good shape, regardless of the manufacturer, in Toyota Yaris IV you need to charge it manually from time to time. Otherwise it will degrade over time and fail sooner than it should 

Yes I agree with all that.
I've plenty of experience charging all kinds of batteries.

I just wonder about the quality of the factory fit batteries and their decision to only use 35Ah capacity.
As I said my Yuasa 45Ah Battery has not needed or had any off car charging in 9 months.
Time will tell over the coming winter.

[r44flyer]

32 minutes ago, dash said:

Charge holds at 14V while the car is parked and is in Ready mode (as evidenced using BM6). So half an hour parked in Ready mode is more beneficial to the charge state of the 12V battery than half an hour's driving. Go figure... 🤔
 

That must be Toyota's way of dealing with a request to charge rather than driving.
i.e. parked and idling is telling the car system to charge more aggressively.
But we've not had to do that the last 9 months.

Unfortunately a simple Battery voltage monitor is never going to tell the full story.
Ideally we would need to monitor the voltage and current vs time to determine what is really happening.
Plus we'd need more info on how Toyota's charging system is programmed to respond to circumstances.

[PortlandBill]

24 minutes ago, dash said:

So half an hour parked in Ready mode is more beneficial to the charge state of the 12V battery than half an hour's driving. Go figure... 🤔
 

So switching the air conditioning on remotely while the cars at the airport and I'm sunning myself in the Bahamas will work! 

[hind]

33 minutes ago, r44flyer said:

my Yuasa 45Ah battery has not needed or had any off car charging in 9 months.

My already agonal Mutlu which holds the 11.6V after one day of parking and with measured effective capacity of 15Ah still works fine even if the car is not driven during weekends. But I won't risk leaving the car in the airport parking lot when going for the two week vacation. Anyway I won't defend Mutlu because their quality is rubbish, the Battery lost more than half of the original capacity after 2.5w parking and was driven daily before, but it might have survived if it was charged to 14.4V all the time when the car is Ready. Yuasa not only has bigger capacity and doesn't lose it that fast when the voltage drops but probably handles the charge better and is less prone to failing. But nevertheless it's still used far from ideal conditions, because it's the car charging algorithm. 

[r44flyer]

15 minutes ago, hind said:

 holds the 11.6V after one day of parking 

Agree with all that, but 11.6V steady state, really? It's not worth the risk so I would be changing that Battery.

[Yaris_Cross]

2 hours ago, dash said:

Charge holds at 14V while the car is parked and is in Ready mode (as evidenced using BM6). So half an hour parked in Ready mode is more beneficial to the charge state of the 12V battery than half an hour's driving. Go figure... 🤔
 

That is good to know i can show the other half that post when i tell her she needs to do the supermarket shop on her own while i wait for her in the car park in "Ready Mode" as the car needs to do its thing to stay reliable 😉

[Fergusson]

Clearly I’m not alone with my Yaris Battery issue.  You guys seem to be well up on it, so please tell me how I can leave my car in an airport car park and come back to the car starting ok.  I ask because Toyota’s official response is that the car needs to be run / charged weekly.  They seem to think this is acceptable.

Please help !

Angela

[hind]

2 hours ago, r44flyer said:

I would be changing that battery

I have to convince the dealership that they should pay for it. Right now, of course, the Battery is ok, just needs a little charging 🙂

Here is a readout after opening the car and waiting for a few minutes (sorry, don't have time to wait for everything to go to sleep). It was parked 24h ago. 

[r44flyer]

1 hour ago, hind said:

I have to convince the dealership that they should pay for it. Right now, of course, the battery is ok, just needs a little charging 🙂

Just checked mine for you for comparison, 12.34V, parked overnight.
In my opinion 11.76V is too low and a sign of a failing Battery.

You also mentioned "an effective capacity of 15Ah", how do you know that? That could be good evidence for a failing Battery.
Trouble is the dealer will likely only fit a 35Ah version but  pester them for a replacement anyway.
Or get an independent Battery test then pester them to contribute to a Yuasa 45Ah battery.

[r44flyer]

1 hour ago, Fergusson said:

please tell me how I can leave my car in an airport car park and come back to the car starting ok.

One solution would be to buy/borrow a suitable 12V boost Battery pack and keep it in the car for that occasion.
Learn how to use/connect it before hand.

[Dala]

Remove D/C cut fuse. Removing this fuse cuts off all the parasitic drains on the 12 volt.It is used at the factory during transport and can be removed for long term storage.

[PortlandBill]

40 minutes ago, Dala said:

Remove D/C cut fuse. Removing this fuse cuts off all the parasitic drains on the 12 volt.It is used at the factory during transport and can be removed for long term storage.

Would  that effectively do a factory reset and lose all settings? 

[einfachGaer]

I don't remember where I've read it but, you can avoid the car going into 12,8v maintaining mode by turning on the lights manually!

The option directly above AUTO is sufficient, the car goes immediately to 14,4v and doesn't drop.

Weirdly enough, if you are on that setting and in P it drops down to 12,8v for whatever reason.

 

Conclusion:

You want to charge the Battery while driving? Lights on!

You want to charge the Battery while in P? Select AUTO!

[PeteChat]

19 minutes ago, einfachGaer said:

I don't remember where I've read it but, you can avoid the car going into 12,8v maintaining mode by turning on the lights manually!

 

Weirdly that used to be the case if I wanted our caravan fridge to work on 12v when towing with my Honda CRV. Apparently the current draw was not enough to engage the “smart” alternator otherwise.

[Chas G]

@hind your post brought back memories of unscrewing the plugs on top of the Battery and using a hydrometer to check the electrolyte specific gravity and occasionally topping up with distilled water. I dont recall ever adding acid.

I seem to remember sg 1.250 being the target. Seemed to work at the time and wonder why we don't do it now as some batteries still have the plugs. 

[hind]

4 hours ago, r44flyer said:

You also mentioned "an effective capacity of 15Ah", how do you know that

I'm using the charger which measures the mAh's when charging or discharging. I charged with starting voltage of 11.6V (literally 0% according to the diagrams) and finished when the charging current dropped to 0.1A upon reaching 14.4V. So actual capacity would be even smaller because I omitted <100% charging efficiency. 

4 hours ago, r44flyer said:

In my opinion 11.76V is too low and a sign of a failing battery.

I agree 🙂 but when I drove to the dealership, the Battery recharged on the way and when they tested, it was "OK - discharged", according to the procedures. Because yeah, it produced enough cranking current, had proper voltage etc. As I've pointed out multiple times in this and similar threads, the dealership does not check the capacity because they are unable to do that during regular service visit. And of course the need to jump start it after vacation was ignored, as "the car has to be driven regularly". So I hope it dies soon so I can call them and ask to take the car and replace the Battery. This is not a covid Battery, the car was made in 2023 and first failure was 6 months later while it was driven daily, various lengths. 

1 hour ago, Chas G said:

wonder why we don't do it now as some batteries still have the plugs

Back then we didn't have any smart charging and the batteries were not that sophisticated. I mean, the tech behind was the same, but now the plates are much thinner (weight and cost saving) and porous to produce larger contact area with the electrolyte. Another thing is - we don't trust people to notice that the freshly brewed coffee in a paper cup is hot, why would we trust them with the sulphuric acid? 😉 

I bet that Mutlu have plugs to fill the batteries in factory, as a part of car assembly process. That way they can supply dry batteries and electrolyte separately. They are not intended for the user maintenance.