Doing a 12V battery test

[Corollanutter]

Following all the hullabaloo about flat 12V batteries on these hybrids I have started to do a few tests using a BM6 on-battery voltage monitor. I have a standard car, with any accessories (dash cams etc) fed via the "ignition" feed (so no discharge when engine off). The BM6 itself takes at max 2mA average, so a very negligable load.

To date, I'm seeing around a 20% level of discharge (based on voltage readings) over a 24 hour period if the car isn't used. This is on a 12 month old Bosch 54Ah replacement battery - so the Battery "should" be in a reasonable state. This seems abnormally high. The charging system actually seems quite robust with a good charge being put into the batteryt when running. The next step is to try turning off /disconnecting some of the features that are known to drain the Battery, which as far as I know, are the remote locking and the DCM. Does anyone know which fuse controls the DCM? Also, does turning off the remote (hands-free) locking via the cluster acually stop the car polling the remote? (as this is what causes the power drain). 

Another test I will need to do is a controlled discharge test over time to give me some idea of the batteries existing capacity. Otherwise my estimated discharge measurements are pretty meaningless (and I don't want to invest in a new Battery just for the test!)

I'll feed some results out on here when I get them.

BTW, it is a 2019 1.8 Corolla TS Excel.

[Roy124]

Chris, I presume that 54 Ah Battery has not been fully discharged?  My MY19 had a 35 Ah Battery replaced with a 42 Ah after 22 months.  Your 54 should have capacity to spare. 

Anyway, does your new Battery not have a guarantee? 

[Roy124]

BTW, where did you get your BM6?  Do you like it?  What sort of range are you getting from it? 

[Corollanutter]

3 minutes ago, Roy124 said:

Chris, I presume that 54 Ah battery has not been fully discharged?  My MY19 had a 35 Ah battery replaced with a 42 Ah after 22 months.  Your 54 should have capacity to spare. 

Anyway, does your new battery not have a guarantee? 

Hi Roy. I’ve not had a problem with a flat Battery as yet, however when I fitted the BM6 just after Christmas, the SOC was under 30% - probably because it hadn’t had an decent run for a few days. A full day charge soon put that right. It’s most unusual that the car doesn’t have at least a 1 hour run every couple of days - so that has avoided any problems. And yes, the Battery has a guarantee, however I’m not sure (at the moment) that is actually low capacity! 

[Corollanutter]

18 minutes ago, Roy124 said:

BTW, where did you get your BM6?  Do you like it?  What sort of range are you getting from it? 

It was purchased from Amazon. It seems to work very well, however the SOC % shown seems a bit pessimistic compared to the voltages shown. The bluetooth range is quite short - really no more than a few yards (probably as it’s shielded by the bonnet). From your phone app you can download a complete file, month by month, of the SOC, voltage and temperature taken every 2 minutes. 

[Roy124]

I was considering one of the 3 BM2 but will probably go for BM6 then. 

I have a little feeling I may be returning it when it arrives.  I downloaded the App, tried to log in, it said I had to agree terms and privacy.  I can't tick the box or log in.

did you have a problem Chris?

 

[Derek.w]

I am using BM2 used its load test just after charging Battery this was the result.

 

[Derek.w]

I prefer to know the Battery voltage but at least a hour later or next day.

Just keep it at 12.2 volts or higher to prolong Battery life.

 

[Corollanutter]

4 minutes ago, Derek.w said:

I am using BM2 used its load test just after charging battery this was the result.

 

Don’t forget that the cranking test doesn’t apply to Toyota hybrids. The HV Battery starts the engine, not the 12v. 

[Derek.w]

Chris, Its still a load test without a starter motor on the 12 volt system.

 

[AndrueC]

Does it really matter? If the car starts drive it.

It seems to me like some people are just worrying about something for the sake of it.

[Corollanutter]

58 minutes ago, AndrueC said:

Does it really matter? If the car starts drive it.

It seems to me like some people are just worrying about something for the sake of it.

Just want to understand how long I can leave the car without problems (not long I think) - and as someone who has worked for many years in automotive electronics design,  what is causing this problem? 

[Dala]

2 hours ago, Derek.w said:

I am using BM2 used its load test just after charging battery this was the result....

 

Interesting, I can't measure the cranking voltage on the BM6, only the charging voltage.

4 hours ago, Corollanutter said:

.....however the SOC % shown seems a bit pessimistic compared to the voltages shown.....

I reset the SOC according to the charts for my Battery

    

[Derek.w]

I can measure the charging voltage under two load conditions to simulate increasing engine speed

on a alternator.

[Derek.w]

Charging voltage BM2 test using diffrent load conditions instead of engine speed.

I have no info. on ripple valtage voltage.

[Derek.w]

Andrue The idea is you monitor it so you know it will start when you go out.

[Corollanutter]

14 hours ago, Roy124 said:

I was considering one of the 3 BM2 but will probably go for BM6 then. 

I have a little feeling I may be returning it when it arrives.  I downloaded the App, tried to log in, it said I had to agree terms and privacy.  I can't tick the box or log in.

did you have a problem Chris?

 

I think you may need to register the app to a device before you can do this. No problems encountered here - it just started to work. 

[Dala]

because the car is still drawing voltage from the car Battery,
maybe this SOC setup will suit better

[Hibird]

19 hours ago, AndrueC said:

Does it really matter? If the car starts drive it.

It seems to me like some people are just worrying about something for the sake of it.

I think you may be more worried than the OP, I look forward to whatever conclusions may come out of the investigation of a 20% Battery capacity loss a day

[Roy124]

I set up the App yesterday.  The BM6 arrived today.  I fitted it, started the App, and a few moments later got the SOC reading RED and 12.53v.  That was strange as I had just driven the return journey today, 2x25 minutes.

However looking at Dala's figure from yesterday the SOC relates exactly to the measured voltage.  Need to do more readings but very impressed so far.

I checked the voltage using a volt meter and got 12.95v

I see DALA has customised the readings.  Can Dala run through the process?  I have the AGM Battery, then selected custom and found the Voltage SoC table.  Where do I go from there?

[Corollanutter]

So, first findings for those who are interested. But if you aren't interested, just move on.. 🙂 
 

With the car in it's normal state, keyless locking on etc, this is the graph of Battery SOC over a 5 day period. It is subject to the algorithm in the BM6 app, which seems to try to level out the SOC when on charge. I'm believing the SOC displayed to be about correct after about 1 hour of being switched off (allowing for surface charge dissipation, temperature drop etc). It is showing a rough 15-20% total capacity loss (discharge) per 24 hour period when the car is off and locked. The charging regime seems to be quite good, with a sensible on-charge voltage of around 14.37 Volts, restoring about 35% of the total capacity within about 90 minutes of the car being in Ready mode. Assuming this Battery is in a reasonable condition (A 52Ah Bosch S4, only one year old) - and allowing for a 20% loss of total capacity from new (another assumption I know...)- this Battery should have a capacity of at least 41 Ah. So, as a very, very rough estimate I am seeing an average current draw from the battery of around 250 - 300mA. 

Where this may be in error is the assumption of the total battery capacity. If, as I'm suspecting, the battery is more than 20% degraded due to the quite severe exercising it is getting (i.e. fairly deep charge / discharge cycles) then the calculations will all be out. However, as I'm currently using the car daily for the next couple of weeks I will have to leave doing a controlled discharge test until I have a suitable slot in my diary.

Also, as the battery seems to be subject to a average continuous load, the battery voltage measurements to determine the SOC are not truly open-circuit - which would of course be giving more errors.

However what does seems to be certain, even allowing for the above mentioned errors, is that there is a significant drain when the car is off and locked. In my time (albeit some years ago) in automotive design, the acceptable total car quiescent draw from the battery was in the order of a few 10's of mA. It seems that this has changed significantly. 

I just need to do more work to find out exactly how much current is leaching away - and where to. I know people have mentioned current clamps etc, however, a) I don't have one, and b) it would need connecting to a recording device to monitor things over an extended period (and I don't have one of those either)

It does bear out many other comments (and Toyotas own guidelines issued in lockdown) that the car, if left for more than a few days, will be so low in charge that it simply will not enter Ready mode.  And IMHO, it is NOT acceptable for a modern car not to start after it has been left at (say) an airport for a couple of weeks. 
 

To be continued....

[Corollanutter]

1 hour ago, Roy124 said:

I set up the App yesterday.  The BM6 arrived today.  I fitted it, started the App, and a few moments later got the SOC reading RED and 12.53v.  That was strange as I had just driven the return journey today, 2x25 minutes.

However looking at Dala's figure from yesterday the SOC relates exactly to the measured voltage.  Need to do more readings but very impressed so far.

I checked the voltage using a volt meter and got 12.95v

I see DALA has customised the readings.  Can Dala run through the process?  I have the AGM battery, then selected custom and found the Voltage SoC table.  Where do I go from there?

Do a search on t'internet for 12V AGM SOC tables and update the SOC/voltage settings in the app to those given by the Battery manufacturers (or similar). I have a "conventional" Battery and have done the same. The voltages have + and - buttons each side to modify them. Then hit OK at the bottom of that screen to store them

[Roy124]

2 minutes ago, Corollanutter said:

Do a search on t'internet for 12V AGM SOC tables and update the SOC/voltage settings in the app to those given by the battery manufacturers (or similar). I have a "conventional" battery and have done the same. 

That was the  question.  How do i update the settings? 

[Corollanutter]

2 minutes ago, Roy124 said:

That was the  question.  How do i update the settings? 

Sorry, I realised that was what you were maybe asking and edited / updated my reply. Hope that helps. 

[Roy124]

Looks like I had done that, I tweaked the 100% SoC to 12.95v.  I have SoC 64 and 12.44v  Lower voltage, higher SoC but the displayed voltage is what is wrong.