Yuasa AGM battery, a conversation with Yuasa tech support.

[mikejt]

Eighteen months ago, a cold and frosty morning and we were about to start 165mls journey the 12v Battery failed, luckily the Lexus breakdown arrived quickly and jump started us. We completed the journey ok and assimed the 12v Battery would have charged ok. The next morning, about to start our return journey, the Battery exibited the symptoms of low voltage but luckily the hybrid system came to life after a couple of tries.

Had new Battery fitted by Lexus Hatfield and on their recommendation I purchased the CTek 5.0 smart charger. With the charger I bought an LED Comfort indicator which is permanently wired and provides a two pin socket connection for the CTek.

I asked the deskbound service tech what the Ah rating of the Battery was and couldn't get an answer, which I though was a pathetic response.

As a precaution I asked the workshop techs to check the charging voltage and all seemed ok.

As a follow up to this I monitored the Battery voltage with high impedance digital meter.

I also contacted Lexus support and Yuasa ltd for some information on the AGM Battery fitted and the expected voltage and FYI I include here an email correspondence with  Yuasa Tech support guy.

It's interesting and frustrating to note these AGM batteries never operate in the 85 -100% range of a conventional lead acid starter Battery and at 12.4 volts  and  max of 45Ah when fully charged the actual available Ah capacity is considerably lower.

Email text with Yuasa.................

"Good Afternoon, 

Apologies for the late reply, just catching up after the holidays. 

The CTEK LED comfort indicator is designed for a starter Battery profile not a hybrid type auxiliary Battery. 

The micro hybrid Battery profile is different to a starter Battery as it operates within the 40%-80% partial state of charge range compared to a starter Battery which typically operates between 85%-100%. 

The below state of charge reference is very simplistic, and I would be cautious to use it.

12.5 V or higher: Fully charged

11.0 – 12.4 V : Half charged

10.9 – or lower; Discharged

(Check the voltage 20minutes after the hybrid system and all lights are turned off)

Kind Regards, apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";'> 

GS Yuasa Battery Sales UK Ltd Unit 13, Hunts Rise, South Marston Park, Swindon, Wiltshire, SN3 4TG

REPLY

Hello, 

Further to my email below, Lexus Customer Relations state this'.... I have spoken again to our Product Technical department, who have confirmed that it is the Hybrid Battery which only charges to a maximum of 80%, not the 12V Battery..... '  

So that's cleared that up.  

I have perused your website and discovered this, which seems to be my Battery :- 

https://www.yuasa.co.uk/batteries/automotive/yuasa-auxiliary-backup-specialist-batteries/hj-s46b24r-553.html

and have the spec sheet. 

Look forward to your response to my email below, 

Regards 

................................... 

REPLY

Note, car usage is intermittent with long motorway journeys.

Last week I had charged Battery fully and Friday did 130 miles then parked. By Monday morning the volts were 12.4V which flashes red on the Ctek LED Comfort indicator. This has three led’s red, amber, green.

By this performance the Ctek LED indicator is useless as the lowest is the red LED, ideally it should have more led’s which can indicate lower voltages!

I’ve charged Battery again and it measured 13.0V as I disconnected charger. I guess this relates to the surface charge you mention.

Lexus tell me 12.5V is what to expect when running car regularly. They also say the car will never charge the Battery as high as the Ctek will.

As the Battery will be around 12.5V, 60-65% state of charge by your info, will this be ok. Lexus state the charge should achieve 80%  and 12.5v with regular use which is contradictory to your information, who is correct?

Is a minimum of 12.4v on install the voltage of the Battery as fitted by Lexus dealer? It was this.

The Ah rating is 45Ah but this is I assume from full charge. What will be the Ah capacity if it is charged to 12.5v, 60-65% is it proportional ie 60-65% of 45Ah? Eg 45x60/100 = 27Ah which is poor to me even though the 12v Battery does not crank the engine at start up. As I understand it, as Battery voltage drops the internal resistance increases so I’m sure this will impact the available capacity at 60% charge as the internal resistance is in series with the load.

Maybe you could send me a specification sheet for my Battery which indicates all the info I need.

FYI. This is from the Lexus owners online manual:

The Lexus manual page 584 9-1 Specifications Electrical system states:

12.5 V or higher: Fully charged

11.0 – 12.4 V : Half charged

10.9 – or lower; Discharged

(Check the voltage 20minutes after the hybrid system and all lights are turned off)

Kind Regards

..................................................

REPLY

Subject: FW: Contact Form

Good Morning,

Thank you for your enquiry.

We recommend a minimum of 12.4v on install (wrost case 12.3v).  At 12.5 the Battery is classed as 60-65% state of charge.  The CTek charger will be fine and should take the Battery to 100% state of charge of around 12.8v. Please be aware that when you take it off charge you will see a surface charge which will be higher.

Kind Regards ,
     
GS Yuasa Battery Sales UK Ltd
Unit 13, Hunts Rise, South Marston Park, Swindon, Wiltshire, SN3 4TG
 
 ................................................
REPLY

Comment: Hi,  my lexus IS300h has just had a new 12v Battery fitted by Lexus. Lexus tell me it will normally test at 12.5v which is 80% of Battery of Battery charge. The Battery is pt no. S46B24L with Toyota label and ref also. Will this 12. 5v be detrimental to life of Battery and what will be the Ah capacity at this voltage. My CTek smart charger MSA5. 0 charges the Battery to a higher voltage than 12.5v Is this all ok?................."

.........................................................

Just checked the Battery it's 12.2 volts, car not driven for two weeks just started to move it around driveway, on charge now for remainder of the day.

Happy motoring

[mikejt]

More from Yuasa

 

"....Good Afternoon Mike,

 

40% to 80% range is approximately 12.1v to 12.6v which will vary depending on specific gravity reading and manufacturer.

 

 

 

Kind Regards,

 

Michael Davis | Automotive Technical Support Engineer

T:  +44 (0) 1793 833547 |  M:   E:   | W: www.yuasa.com | www.gs-battery.com

 

GS Yuasa Battery Sales UK Ltd Unit 13, Hunts Rise, South Marston Park, Swindon, Wiltshire, SN3 4TG

[Thackeray]

19 hours ago, mikejt said:

The micro hybrid battery profile is different to a starter battery as it operates within the 40%-80% partial state of charge range compared to a starter battery which typically operates between 85%-100%. 

The below state of charge reference is very simplistic, and I would be cautious to use it.

12.5 V or higher: Fully charged

11.0 – 12.4 V : Half charged

10.9 – or lower; Discharged

Interesting to read these comments from Yuasa about the difference between a starter Battery and a "micro hybrid" Battery.

Certainly, the high voltage Battery operates in a range from 40-80%, which shows as one to eight bars on the dashboard, and which Lexus Customer Relations seems to have mixed up initially with the 12v Battery.

But it seems from what you've been told that the car computer also aims to charge the 12v Battery to no more than 80%. It's certainly been my experience that you can start the car to the Ready state with the 12v Battery at around 11.5v, which is in line with the Yuasa chart.

[westo3]

Very interesting and informative post Mike. Thanks. I also have a traffic light indicator and was concerned at the short time it took for the red light to start flashing especially when my Battery was less than a year old. I keep my Ctek on all the time now as the car is sometimes standing for more than a week. 
I am assuming that will not damage the Battery even though it is charging it higher than the hybrid Battery would?

[Superduner]

I've posted a few times on this subject, and broadly speaking agree with everything above (including the red traffic light issue).

I've driven a few hundred km and then out of interest put the Ctek on to see what happens.  It took another 4 hours to bring it up to what the charger classed as full.  This on a new Battery.

FYI, I've had no trouble starting the car when the 12v was at 11.6v.  I have a voltage read out in my power plug and even if the Battery is at 12.3-5, as the "ignition switch" is turned, it drops down to about 11.6v just before the ready light comes on.

I also have a Bluetooth Battery monitor fitted.  It's extremely interesting (but I'm a sad person who doesn't go out much) to see Battery voltages over time.