Charging the 12V ancillary battery - step by step guide?

Maxz · January 29, 2020

Hi,

There are several other posts on this but nothing clear in regards to a guide. Does anyone have actual experience of charging the 12v Battery that powers the ancillaries on a IS300h?

I have a Ctek charger, so can I attach this without having to disconnect the Battery? If so what have others used as the grounding post in the boot area, with the live connected to the Battery?

OR

Has anyone actually disconnected it, charged, then reconnected? If so were there are reboot issues or settings/data lost when the Battery was reconnected? Remove the ground first then the live, reverse order to reconnect if doing this method?

Reason I ask is lots of stories of these failing. Aware life of these can be improved by keeping the charge topped up, not necessarily relying on the alternator to keep it at tip-top charge, especially at this time of year.

Thanks

Max

NemesisUK · January 29, 2020

First off, there is no alternator on a hybrid car. The 12v Battery is recharged using the traction Battery.

I've haven't used my CTEK on my RC but I see no issue with connecting directly to the Battery terminals as I did on my Mercs. Or you could use the jump start terminals in the engine bay as detailed in the handbook?

I personally wouldn't disconnect the 12v Battery to trickle charge it.

Herbie · January 29, 2020

1 hour ago, Maxz said:

I have a Ctek charger, so can I attach this without having to disconnect the battery? If so what have others used as the grounding post in the boot area, with the live connected to the battery?

Yes you can and basically any unpainted nut or bolt can be used to clamp the earth on to.

I believe that Ctek also sell something they call a 'comfort connector'. One end of it is permanently connected directly to the 12V Battery terminals and the other end can be positioned anywhere in the boot that's convenient, thereby eliminating the need to mess about getting to the Battery every time and you plug the charger in there.

matt8 · January 29, 2020

3 hours ago, Herbie said:

Yes you can and basically any unpainted nut or bolt can be used to clamp the earth on to.

In my CTEK manual it advises to connect black to negative and red to positive.

I thought the recommendation to ground the car to any unpainted nut or bolt was for jump starting cars (which I'd never do to my Lexus) rather than trickle charging.

There seems to be much conflicting evidence online about whether to jump start with a cable attached to each terminal, or whether to ground it to the chassis as you suggest.

3 hours ago, Herbie said:

Ctek also sell something they call a 'comfort connector'.

I use one of these and they work great. Highly recommended. Don't bother with the one that has flashing LEDs on, they are misrepresentative of the Battery state / charge level. I only got that one as it was cheaper than the one without the LEDs.

I leave the Battery connected to the car when trickle charging. Disconnecting it would cause you to lose settings.

200h · January 29, 2020

radio stations & clock that is all that needs to be reset after reconnecting the Battery.

just connect + to + & - to - on the Battery.

NemesisUK · January 30, 2020

No resync of the windows and sunroof one-touch operation?

Herbie · January 30, 2020

15 hours ago, Herbie said:

Yes you can and basically any unpainted nut or bolt can be used to clamp the earth on to.

11 hours ago, matt8 said:

In my CTEK manual it advises to connect black to negative and red to positive.

I thought the recommendation to ground the car to any unpainted nut or bolt was for jump starting cars (which I'd never do to my Lexus) rather than trickle charging.

Yes, sorry, my fault. Got myself confused there but it doesn't matter anyway, given that the Battery negative terminal is directly strapped to the car's metalwork.

By the way, the recommendation for using an unpainted nut/bolt/metalwork for jump starting applies to the recipient car, not the donor.

Maxz · January 30, 2020

Thanks all for your advice, especially interesting to learn no alternator, makes sense about the regenerative braking/energy system charging the Battery. 👍

I will check the model for my particular Ctek charger model but in summary, for trickle charging with one of these, appears I am safe to connect directly to the Battery terminals and whilst the Battery is still connected to the vehicle (and it's electronic systems).

Time for a top up!....

Herbie · January 30, 2020

32 minutes ago, Maxz said:

Thanks all for your advice, especially interesting to learn no alternator,

Because the petrol engine isn't operating all the time in a hybrid, anything normally driven by a belt from the engine such as the power steering pump, the aircon compressor etc., etc., is driven electrically instead. Oh, and there's no traditional starter motor either - I think it's MG1 that starts the engine if I remember correctly.

MONTIMAR · January 31, 2020

I have used a CTek charger for the past 3 years and always used the under bonnet connections as illustrated in the Lexus manual. During the winter months when I'm away in sunnier climes I leave it permanently connected and never have any problems.

John Mosey · January 31, 2020

Hi

The 12v Battery in my IS 300h has been causing me problems, I've called the AA three times this year.

I've decided to replace it. Went to the local Halfords, they cant help. We to two other dealers. One quoted 'about' £350.00, another said they could get one,but, it would have to be programmed at the factory, price unknown.

Now the good news. I rang Lexus,their technician said, the Battery in the boot is a conventional 12v Battery (£125.00)

A ctek mxs 5.0, or any trickle charger will be ok. Just connect the clips to the Battery first, then switch on and leave.

Hope this helps.

Maxz · February 3, 2020

Just hooked up my Ctek xs800 using the under bonnet connections, positive on the jump start terminal and negative connected to the chrome bar on the side of the engine block (thanks to Montimar for the guidance). All seems to be working fine with the amber charge indicator lit.

I have extra logistics at play because the car is parked outside on the driveway leading to some additional questions/thoughts:

1) To keep the car secure I used the button in the headlining light cluster to switch off the alarm sensor so I could leave the bonnet slightly open and still lock the doors and boot. This is because with a clamp secured to the positive jump start terminal, it is not possible to fully close and latch the bonnet.

2) I also opened the Battery compartment cover in the boot, put down a folding rear seat and left a window slightly ajar. Batteries can give off gas when charged or is this OTT overkill because during normal operation, doesn’t this Battery get charged in it’s confined compartment anyway?

And last one related to 1):

3) Is there a bonnet alarm switch/sensor? The idea being, if I leave the bonnet and window(s) slightly ajar, can I still arm the alarm for complete peace of mind when charging the car out on the driveway, without the bonnet (unlatched) triggering false alarms? Aware a fly could get in and set off a sensor but unlikely at this time of year so not concerned about that part.

Thanks all for your thoughts and tips as always!

royoftherovers · February 3, 2020

Well thought through Max, but wouldn`t one of these have been easier ?

https://www.audew.com/Audew-2000A-Peak-20000mAh-Car-Jump-Starter-for-Any-Gas-Engine-or-Up-To-8_5L-Diesel-Engine-with-LCD-Power-Display-p-100058.html?gmcCountry=GB&currency=GBP&cur_warehouse=fba_eu&ID=3498792&utm_source=google&utm_medium=cpc_gg_ssc&utm_campaign=will-20191118-uk-ssc-vehicle-CBN888-da&gclid=EAIaIQobChMIvv3BqKK15wIVhLTtCh0Z5gOHEAQYASABEgKZxfD_BwE

Herbie · February 3, 2020

Given your circumstances and security concerns Max, would it not have been easier/better to just take the Battery into the house/garage/shed to charge it there?

Maxz · February 3, 2020

7 hours ago, royoftherovers said:

Well thought through Max, but wouldn`t one of these have been easier ?

https://www.audew.com/Audew-2000A-Peak-20000mAh-Car-Jump-Starter-for-Any-Gas-Engine-or-Up-To-8_5L-Diesel-Engine-with-LCD-Power-Display-p-100058.html?gmcCountry=GB&currency=GBP&cur_warehouse=fba_eu&ID=3498792&utm_source=google&utm_medium=cpc_gg_ssc&utm_campaign=will-20191118-uk-ssc-vehicle-CBN888-da&gclid=EAIaIQobChMIvv3BqKK15wIVhLTtCh0Z5gOHEAQYASABEgKZxfD_BwE

Smart little gadget. I think the clamp could fit to the jump start point horizontally instead of vertically so the bonnet could be closed. Will look into one of these.

Next time around might also try the existing charger via the boot direct to the Battery instead, as the clamp cables should be thin enough to run between the boot rubbers whilst it is closed. So can charge and arm alarm at the same time 👍🏻

Maxz · April 1, 2020

If your IS is not getting as many miles due to the lockdown, don’t forget to keep the 12v ancillary topped up. Avoid any nasty surprises when you do happen to want to go out!

If you lay the clips out as in the image, you can still latch the bonnet and keep the alarm armed 👍🏻

Sandyman12345 · December 29, 2020

Can someone help,

I’ve got my brothers Lexus is300h in my drive as he’s working away,

the auxiliary Battery in the boot keeps discharging so I disconnected it took it inside and gave it a deep state charge.

when I reconnected it the alarm sounded, lights flashes and dash lights all flashing at random,

eventually got alarm to silence but all lights on dash flashing as if something needs reset,

When I press the start button it asks me to press the brake and press the start again, the hybrid system tries to fire up on the screen but won’t fire up nor the engine start, it reverts back to various dash lights, hazards flashing and horn low tooting

any idea how I reset things?

thank you Andrew

200h · December 29, 2020

nothing to reset

the random flashing lights on the dash and being asked to press the brake pedal

is a classic sign of a flat Battery

to prove it get another Battery and connect it to the Battery in the car

all your issues will go away and the car will start as normal

Sandyman12345 · December 29, 2020

Ok thanks will try this tomorrow presume can just put jump leads over from another

car even with its engine off

see my video I took earlier today hope it confirms your thoughts as I had over 11 volts once I charged it up

Herbie · December 29, 2020

Video not playing but 11V isn't brilliant:

royoftherovers · December 29, 2020

3 minutes ago, Herbie said:

Video not playing but 11V isn't brilliant:

Took 90 sec to download Herbie.

Has he tried to start it with ignition key in his hand or nearby ?

Herbie · December 29, 2020

25 minutes ago, royoftherovers said:

Took 90 sec to download Herbie.

Has he tried to start it with ignition key in his hand or nearby ?

You must be on a slow connection John. It had fully downloaded for me in 15 seconds and I can hear the indicator/hazards ticking away but just no video.

Not sure about the key, he doesn't mention that (or not that I've seen anyway) but like Mark above, I'd almost guarantee that the 12V Battery is too low.

royoftherovers · December 29, 2020

4 minutes ago, Herbie said:

You must be on a slow connection John. It had fully downloaded for me in 15 seconds and I can hear the indicator/hazards ticking away but just no video.

Not sure about the key, he doesn't mention that (or not that I've seen anyway) but like Mark above, I'd almost guarantee that the 12V battery is too low.

WE ARE IN deepest darkest South Wirral Herbie and we only found out yesterday, that Mafeking has been relieved and that Shergar hasn`t been found yet !

Mark is a good lad and will do his level best to assist. He`s from North Wirral Herb !

Finished that Bubble and Squeak yet old Pal ?

Herbie · December 29, 2020

2 hours ago, royoftherovers said:

Finished that Bubble and Squeak yet old Pal ?

Absolutely, and it was delicious 😊

Sandyman12345 · December 30, 2020

20 hours ago, Herbie said:

You must be on a slow connection John. It had fully downloaded for me in 15 seconds and I can hear the indicator/hazards ticking away but just no video.

Not sure about the key, he doesn't mention that (or not that I've seen anyway) but like Mark above, I'd almost guarantee that the 12V battery is too low.

Hi it started up ok when I connected to another car Battery left it running for over an hour and it’s still only holding 11.2 volts

no error messages but it’ll happen again as clearly the Battery is not holding a charge

thank you guys

Andrew