Trickle charge or disconnect?

Tom Wenzel · April 14, 2020

I store my LC 500 in a hot (Arizona summer) for six months. Is it better to hook up to trickle charger or remove Battery and store in air conditioned room?

malcolmw · April 15, 2020

It is always better to use a trickle charger as this preserves the Battery and prevents sulphation of the plates. Battery disconnection can cause all sorts of random issues!

steve2006 · April 15, 2020

Invest in a decent quality “smart” charger and charge the Battery whilst still connected to the car, these things will monitor both charge and discharge and top up as required.

Kevin Williams · September 28, 2020

Is it best to connect a trickle charger to the points in the engine compartment, as shown in the owner's manual.

Or direct onto the Battery in the boot...?

I am buying a UK LC 500. I think the points in the engine compartment, are on the passenger side...?

ColinBarber · September 28, 2020

I don't think it really matters. The engine compartment points are there in case the Battery is flat and you need power to open the electrical lock on the boot. But it is easier to put cables into the engine bay than in the boot where the trailing wires will press against the boot seal and potentially damage it.

malcolmw · September 28, 2020

When I have used a trickle charger on my LC500 I used the underbonnet points which, as noted above, are in the passenger side fusebox. The positive pole is a direct connection to the Battery in the boot. You can connect the negative to any bare metal point on the chassis. Beware to get the polarity correct!

AJ500 · January 19, 2021

Can anyone confirm if the Battery in the boot of the LC500 V8 is an AGM.

My dealer advises that it is.

I want to connect my Ctek charger as the car is getting little use at present for obvious reason.

Thanks,

A J.

ColinBarber · January 20, 2021

17 hours ago, AJ500 said:

Can anyone confirm if the battery in the boot of the LC500 V8 is an AGM.

My dealer advises that it is.

I want to connect my Ctek charger as the car is getting little use at present for obvious reason.

Thanks,

A J.

It possibly is, but if there are no marking on it to indicate it is an AGM then just use your Ctek in standard mode as that is suitable for most AGM batteries and won't put the voltage too high in case it is a standard Battery.

AJ500 · January 20, 2021

There is no indication on the Battery label to state AGM although the dealer believes it is.

I have just ordered a new Ctek as my newest one is throwing weird lights and I have resorted to a previous model to get up to 100% charged.

As suggested ,I will use the standard mode.

A J.

Boosh. · January 20, 2021

As far as I can tell (input to the contrary welcome!), if the 12 volt Battery is inside the car passenger compartment or boot, then it is fitted with an AGM Battery from the factory (to minimize acid spill risk in the event of an accident etc.).

So far, that 'rule' follows for the hybrid models of CT200h, Auris, Yaris, Prius, Corolla, C-HR and from what I've spotted, cars on this forum too. The latest Prius, hybrid Corolla and C-HR, for example, now have their batteries under the bonnet (a physically smaller inverter allows space for this), and don't have AGM batteries. I can't see why the Lexus models would need to be different here.

With regards the subject of this thread and disconnecting the Battery when charging, I notice that when in 'reconditioning mode' the CTEK chargers use a 15.8 volt spike to rejuvenate the Battery, and I think I've seen 16.5 volts quoted on other makes of chargers in the same mode.

This particular mode will only rarely used, hopefully. But what will the vehicle's electronics make of that voltage? Probably nothing at all, I think.

Anyone else have any opinions on that?

malcolmw · January 20, 2021

The CTEK chargers are very good. However, do not use the "rejuvenating mode" with the Battery connected to the car in case of overvoltage.

The CTEK units typically charge at constant current (whatever the model used can generate) until the Battery reaches typically 14.7V. This is the bulk charge phase. They then hold this voltage on the Battery until the charge current drops to about 10% of the charger rating. This is the balancing phase. They then switch to typically 13.8V to maintain the Battery fully charged for extended periods without gassing it. This works for both wet and AGM batteries and will be fine. The dedicated AGM mode typically uses a slightly lower maintenance voltage but has marginal effect on Battery life.

LenT · January 24, 2021

On 9/28/2020 at 3:15 PM, malcolmw said:

When I have used a trickle charger on my LC500 I used the underbonnet points which, as noted above, are in the passenger side fusebox. The positive pole is a direct connection to the battery in the boot. You can connect the negative to any bare metal point on the chassis. Beware to get the polarity correct!

I don’t know if it might be different for a hybrid, but with my CTEK I also ordered the accessory connection leads - two, in fact.

These had terminals that connected directly to both Battery posts, with positive and negative clearly marked. The leads then combine to end in a socket. The lead from the CTEK plugs into this socket. This allows me to switch the trickle charger between our two cars without having to worry about polarity, sparking or poor connection.

I hope this helps.

eome · February 10, 2021

Hi,

I recently got a CTEK MXS 5 trickle charger to maintain the Battery in my LC500 during lockdown.

I am a bit confused as to how it should be connected. Firstly there is the question of whether it should be connected directly to the Battery or to the connections under the bonnet? Looking at some of the posts above it seems like either is fine. Have I understood this correctly?

Also where should the black negative clamp be connected? I read somewhere that in modern cars it should not be connected to the negative terminal of the Battery. Is this true?

And finally the owners manual says something about disconnecting the ground cable before recharging the Battery. Is this really something that's necessary for a trickle charger?

As this isn't something I've done before are there any dos and donts I should be aware of? I know not to have the ignition on and that the polarity should be correct but is there anything else important that I should now about?

Thanks for any advice.

AJ500 · February 10, 2021

I have the same CTEK charger and have been connecting it to both the Battery directly,in the boot,using positive and negative connections to the Battery and then sometimes using the special fuse box connector under the red flip panel.I attach the negative clip to the large bolt holding the brace bar which is easy to reach in front of the fuse box.Either method has brought my Battery up to 80% in about 15 mins so far and then maybe another 2 hours to get to the green light meaning 100%.

Despite being told the Battery is AGM,I cannot see any mention of this on the Battery labels so I have been using the normal mode on the CTEK which I was told was safe and may take a little longer to charge.

Up to this icy week the car has been used about 2/3 times per week but not long runs,hence keeping the Battery charged.Need to get out of lockdown to give it a cross country run!

Which LC500 did you buy?

A J.

eome · February 10, 2021

Hi AJ.

Thanks for the reply, that was very useful.

Mine is the base LC500, it's a 2019 model (delivered May 2019).

AJ500 · February 10, 2021

Be interested to know if your Battery states AGM.

What colour did you go for,mines the F Sport White with black leather.

A J.

Herbie · February 10, 2021

Battery labels may not explicitly state whether it's AGM or not but there should at least be a model number somewhere which will then enable you to either go to the manufacturers website to download the spec sheet or to just do a general search via Google to get the info.

As for where to connect chargers and/or jump leads - it doesn't matter.

All you're doing is piggybacking one 12V source in parallel with another 12V source. All the car/the battery/the electronics will 'see' is just 12 incoming volts and it doesn't matter a jot where it's coming from.

The only caveat regarding chargers is that you must be using a modern 'intelligent' charger with a regulated and clean output, not some rusty old transformer-based thing that's been in the garage for the last 40 years.

AJ500 · February 10, 2021

Hopefully my CTEK is ok as I ordered it last month!

Herbie · February 10, 2021

58 minutes ago, AJ500 said:

Hopefully my CTEK is ok as I ordered it last month!

It'll be great, no doubt whatsoever.

eome · February 10, 2021

I don't see AGM stated anywhere on the Battery (at least not on the bits that are visible when mounted in the car)

Mine is red with tan interior (when I was trying to decide I thought maybe there was too much tan with no darker colours to break it up but in the end I was happy with my decision, goes well with the red).

Herbie, thanks for the advice with regards to where to connect. That makes sense. I just wanted to double check before doing something I might regret.

ColinBarber · February 10, 2021

The LC500 and LC500h both uses a standard flooded battery:

An EN (European Norm: European Standards)-compliant and open type Battery is used, and it is installed under the luggage compartment.
A Battery hose is provided to effectively direct gas generated by Battery electrolysis out of the vehicle.

LC500 is 80 Ah and the 500h is 70 Ah (both at 20HR rating)

AJ500 · February 10, 2021

Thankyou Colin.

Dallas Johnson · February 19, 2021

How do you open the fuse box on a 2018 LC 500 not an H. ??? Tks

malcolmw · February 19, 2021

The fuse box you need for trickle charging is the one on the nearside (on RHD cars). There are 4 clips which are released by pressing them inwards and then pulling the fuse box lid off. The positive Battery connector is under a red cover which is also retained by a plastic clip. This is all very simple once you have done it at first.

The fusebox cover clips can be a bit tricky as you need to press the center parts of the clips to release them.

I hope this helps.