12v battery maintenance, issues, etc.

[CruxisCore]

2 hours ago, Roy124 said:

Why?

I have a BM6 and its readout is different my voltmeter by a couple of points.  In fact I have 3 voltmeter as sometimes the voltage will jump all over the place. 

There is no reason to suspect that the plug in sensor would be inaccurate.   However while it might be inaccurate by a point or two you will be looking for difference rather than absolute.

This. 

It's kinda what I often tell people about smart watches, that it's not that important whether it factually records that 10k steps accurately. But usually the device is still consistent with itself. Yeah, maybe when it says you did 10k steps its only really 8k steps, but that day when it tells you you have only 8k steps, you know that it's still less than what you usually walk kinda thing.

Same thing, a cheap 12v socket voltage meter might be off by a point or two compared to a professional multimeter, but so what? If you know that it is, that means that instead of freaking out at 12,1v you can freak out when it says 11,9v 😄

[Cyker]

4 hours ago, Roy124 said:

Why?

I have a BM6 and its readout is different my voltmeter by a couple of points.  In fact I have 3 voltmeter as sometimes the voltage will jump all over the place. 

There is no reason to suspect that the plug in sensor would be inaccurate.   However while it might be inaccurate by a point or two you will be looking for difference rather than absolute.

I can imagine cheap ones being quite bad - They have terrible contacts and connections which create a lot of extra resistance, throwing the readings off.

I had a particularly bad one you had to twist around in the socket a few times to try and get a good contact or it read something stupid like 7v  

That's why I like to buy stuff people recommend here - It turns out my usual tactic of buying the cheapest one doesn't always give the best results. Never fathomed why!   

[Roy124]

Cyker. I loved a destructive comparison between two 'identical' Apple charger plugs.

Simply both used identical Chinese plastic mouldings of the destroy to open design.  Both output the required voltage.  The internals were similar though the knock off had fewer components.

Bottom line, they were probably both knockoffs. 

[Cyker]

Ah, you might like bigclive's channel on Youtube, he likes dismantling things like that.

He has a variety of useful equipment, like his custom X-ray machine (A hammer), and an explosion-containment device (Pie dish)

 

[CPN]

I would have thought that the car's own systems would be the most accurate measurement of all coming via the OBDII port...

...bear in mind that this is with the car "at rest" in the garage switched off and fully locked up. Also, my Battery is currently 3 years old since the car was built.

(also bear in mind that a fully charged conventional (sealed or otherwise) 12v car Battery made up of 6 cells should be 6 x 2.2v = 13.2v when fully charged at 100% health - i.e. just about new)

... and finally, that displayed voltage matched my calibrated Fluke 77 multimeter reading across the Battery. 

Edited July 25, 2023 by CPN
The last bit...

[Dala]

I use this Light Car Adapter , I like this method of measurement, measurement via this adapter is quite accurate.

https://youtu.be/FeN8ULJnIas

 

 

I use BM6 for more accurate calculations : https://www.aliexpress.com/item/1005004458755180.html

According to my all available data - driving the car over day -battery cannot be guaranteed charged. Only external charging (wired, solar ...) or "READY" mode. Driving in night is charging car Battery OK - headlights are is ON (voltage 14,2-14,4V)

[Roy124]

9 hours ago, CPN said:

would have thought that the car's own systems would be the most accurate measurement of all coming via the OBDII port...

It will be an accurate source, the limitation is with the display system specification and its circuitry.

[TopGeek]

Cigarette lighter voltage indicators do not and cannot give a true measurement of the voltage at the Battery terminals. The only type of device that can do that is a laboratory calibrated voltmeter connected directly to the Battery terminals. Consequently, references to the SoC levels are meaningless, except when measured under controlled conditons. Anything else is subject to variable factors such as the votage drop between the Battery and the cigarette lighter, current drawn by other systems along those several metres of cable, the accuracy and consistency of the measuring device.

Cheap  voltage indicators are inherently inaccurate, non-linear and subject to temperature variations. At best, they can only give an approximation of the true battery voltage.

Those devices only give a relative indication of the SoC of the 12-volt battery. The voltage indicated cannot be regarded as true battery voltage.

So yes, they are useful but only in relative terms.

[CPN]

4 hours ago, Roy124 said:

It will be an accurate source, the limitation is with the display system specification and its circuitry.

I disagree in this case when the display is simply that. A display that just shows the reading that it's given. No translation or calculation involved. 

[Roy124]

CPN, we must agree to disagree.

[CPN]

6 minutes ago, Roy124 said:

CPN, we must agree to disagree.

OK. I'll agree that you're wrong in this case. 😉😁

[Dala]

There are two variants for the Toyota hybrid:

1/ fully charged car Battery has 12.2V
2/ charging voltage is normal 12.8V

In my opinion neither option is correct
there is a mistake somewhere

3 rides today
14.0-14.3V were only at the beginning of the drive for about 2 minutes and at the end when parking

[CPN]

7 minutes ago, Dala said:

There are two variants for the Toyota hybrid:

1/ fully charged car battery has 12.2V
2/ charging voltage is normal 12.8V

In my opinion neither option is correct
there is a mistake somewhere

Totally agree with you. Nothing has changed in basic principles of wet-cell Battery technology since I did my C&G 1st Year back in the late 60's. An ordinary 12v car Battery with 6 cells fully charge should be 2.2v per cell and it should sit all day at 13.2v when new. Even dynamos in cars (as well as alternators later on) where commonly regulated to 14.4v while charging the Battery. So both of those Toyota figures are a bit weird. 

I suspect they are applying the same charging principles that have been tested and recognised as good for longevity in the case of either Li-Ion or NiMh whereby the optimum range of SoC is between 40%-80% and never at a fully charged condition. 

Trouble is, it doesn't work for wet cell batteries!! 

[CruxisCore]

It's probably just a case of a "sweet spot". CaCa batteries requiring over 16 volts means the car wouldnt charge it full anyways, but just cos it doesnt necessarily push it over 12,2v or 12,3v doesn't mean that Toyota thinks it's a full Battery. The hybrid efficiency is all about just that, efficiency. If the car was pointlessly charging the Battery all the time at +14v, it would hamper the EV driving.

So chances are Toyota have done a fair share of testing and decided that 12,3v is an acceptable charge (at some 60'ish% SoC) and they dont want to waste energy pushing it much above that. It doesn't hurt the Battery either, but yeah, it'll run dry and take damage easier that way.

It'd be almost certainly a simple software fix if they wanted to sacrifice some of the EV driving for higher charge rate on the 12v, but again, they probably found this to be the soft spot. I've seen enough flat batteries on non-smart ICEs over my years of driving to know that it's not a bulletproof solution either for people who dont drive much/drive short trips. It could be nice though if they allowed for some options, the car could even have a user setting for "battery reconditioning" or something where for a limited time it charges the battery at higher rate and notifies the user that EV driving % will be temporarily hampered by it or something. Would also be good for people who dont have a chance to use mains chargers. Also, for the love of God, let us monitor 12v voltage from infotainment lol

That said, I've noticed using my 12v socket voltage monitor on my (purely ICE) Aygo X and noticed it doesnt necessarily work much different to that graph. The alternator only kicks in when the voltage drops below 12,3v. And it does seem to have 2 different charge modes at least, one at/around 13v and one around 14v. Of course this voltage meter could be off somewhat, but its probably consistent with itself. It's a 65 Ah battery and the voltage meter usually shows 12,3-12,5v or then one of the charging voltages when driving.

As for the theoretical full charge voltage of a 12v battery, can't say I've ever seen that in real world scenarios and there's probably a reason why 12,7-12,8v is touted as a full charge. I suppose it's possible in practice as an open circuit voltage and in isolation, but likely not ever a reality when actually connected to a somewhat modern car with passive load on the battery

EDIT: Another ICE story. I had a Toyota Proace (dont do the same mistake as I did, it presents the worst of french engineering as a PSA car). It broke an alternator, but it behaved weirdly for a while (the alternator died gradually) so instead of suspecting the alternator, I bought a brand new battery for it. I didnt switch it until it left me on the road at which point I switched the battery on the fly. The brand new, full battery was within critical levels 30 minutes minutes of no help from the alternator. This is kinda interesting as it gives an idea of how small those batteries are if they arnt being charged. Or alternatively just how much electricity modern cars use. This also likely makes the idea of regular just-in-case charging of the battery with a main charger quite futile, as anything you probably gained might be wiped away after an hour of driving IF the smart charger decides to not step in before 12,3v. As such, it kinda also makes sense that in the search of optimal efficiency, the battery is charged just enough and not a bit more (unless you drive less than the magic limit and end up with a dead battery 😄 )

[Charliewatch]

I feel a tad disappointed with the 12v Battery issue with my toyota yaris.

Do members think an upgrade or modification might come from Toyota.

TIA

[FROSTYBALLS]

1 hour ago, Charliewatch said:

Do members think an upgrade or modification might come from Toyota.

Maybe for a future model, but not retrospectively for existing.

[CruxisCore]

Toyota has changed some problematic 12v batteries under warranty, but that will really help if the Battery is defective or just gone bad from too many times running dry, but the cause of the problems is still probably elsewhere

[Cyker]

8 hours ago, Charliewatch said:

I feel a tad disappointed with the 12v battery issue with my toyota yaris.

Do members think an upgrade or modification might come from Toyota.

TIA

The fixes are basically to use the car more, fit a higher-capacity Battery or use a trickle-charger.

I haven't had any problem with the 12v in mine in nearly 2 years of ownership, but I use it every day for work; I even accidentally left the lights on all day once, but it fired up first time in the evening so I didn't get stranded at site.

From what I've gleaned, you're only likely to have 12v problems if you hardly use the car, or if you had a duff Battery from the start (I suspect a lot of the earlier ones were left sat for a long time unattended during the pandemic times, and subsequent transport issues caused by new customs red tape following Brexit, and the batteries were allowed to discharge, which does a lot of damage to lead-acid batteries. Newer ones shouldn't have this problem tho'.)

 

 

[TopGeek]

I bought a cigarette lighter monitor (despite my doubts about their accuracy) and the results are interesting. On starting Ready mode, the device momentarily indicates 11.9 volts and then immediately goes to 14.0 volts, without the ICE starting. When the ICE does start or when driving, the voltage remains with the range of 14.0 - 14.2. This presumably reflects the regulated charging voltage. When stationary, if I switch off and immediately go into ACC mode the voltage goes down progressively from 14.0 to 12.0 but I've not dared to let it go further down due to my previous experience in ACC mode.

Indeed, it seems to me that the current drain in ACC mode is likely to flatten the 12v Battery rapidly. It's probably safer to use Ready mode if you have to sit stationary in the car while, for example, waiting for your passenger to arrive.

[Derek.w]

Your 11.9 volts reading is the equivalent of a 12.2 volt reading before you opend the doors to the car and moved key to acc mode if you weighted for a couple of seconds this display will soon drop even more say a extra 0.1 or .2 volts SO your 12.2 may be 12.4 volts before you opend the door.

Charging can be 14.0 volts or above.

 

[Max_Headroom]

9 hours ago, TopGeek said:

It's probably safer to use Ready mode if you have to sit stationary in the car while, for example, waiting for your passenger to arrive.

It has been said many times in the thread if you don't drive much leave it in ready mode when parked (supermarket etc) and this will keep the 12v Battery charged. 

[MaDProFF]

@Charliewatch One of my questions was about the charging issue for the new 2024 yaris, but they would not comment, one thing for sure is they know about the issue so I would like to think that they have improved the issue some how, even with just a more powerful larger capacity Battery would help.

[Roy124]

3 hours ago, Max_Headroom said:

It has been said many times in the thread if you don't drive much leave it in ready mode when parked (supermarket etc while your other half goes shopping) and this will keep the 12v battery charged. 

Fixed it for you.  Your can't leave in Ready mode and lock it.

[TonyHSD]

Of course they know about any issues these cars has. They have employees that only stay on the computer all day and read every single complain, post, or anything here and in any other media available to the public.
However Toyota will not come and say: “ hey guys sorry but your cars has faults in the 12v system or some production cars has faulty batteries installed or our dealers seems not following exact procedure for transportation and storage of our cars or they doesn’t do proper PD inspections etc” . No, but if you have any issues after new car purchase they will take care of. They will also look into it and improve with the time. They can’t improve owners uses, maintenance habits or drivers styles., or perhaps anything that doesn’t need actually being improved. 👍

[TonyHSD]

4 minutes ago, Roy124 said:

Fixed it for you.  Your can't leave in Ready mode and lock it.

I think he meant with the driver inside the car waiting. You can lock in ready mode with the key but it will be against the law.