450h in garage for 3 months, trickle charger or not?

[WilliamOrbit]

Hello,

 

I plan to leave my 450h sitting in the garage for 3 months. A quick email to Lexus asking if a trickle charger on the 12v Battery was ok, got the response that I could just leave the negative terminal disconnected. They also said a trickle charger was ok, but don't leave it for too long! Howling is too long?

 

Anybody have experience or advise?

 

Many thanks

 

William

 

[ChrisKaye]

Hi,

If you have a Battery charger already, why not purchase a timer and have it come on for 30-60mins a day? :)

[Zotto]

Modern chargers have a maintenance current  controlled by Battery voltage, if you use one of these no problem to leave them connected ; of course not the same if you use a traditional Battery charger.

[rayaans]

Probably just disconnect the negative terminal, its easier than faffing about with chargers.

[Britprius]

A tricle charger will do only good to the 12 volt Battery. It would also be a good idea to make sure the HV Battery is in a high state of charge when the car is turned off. If not force charge it till it has high blue or all green bars on the display. Do this by leaving the car in park and in ready mode, and putting you foot on the accelerator forcing the engine to run. This may also be done in drive with your left foot firmly on the brake. 

[Gliderpilot]

A float (trickle) charger can be left connected indefinitely, most modern chargers have a maintenance charge state when the Battery has been charged.
Here is a clip from Wikipedia.

"Float voltage is the voltage at which a Battery is maintained after being fully charged to maintain that capacity by compensating for self-discharge of the Battery. The voltage could be held constant for the entire duration of the cell's operation (such as in an automotive battery) or could be held for a particular phase of charging by the charger. The appropriate float voltage varies significantly with the chemistry and construction of the Battery, and ambient temperature.

With the appropriate voltage for the Battery type and with proper temperature compensation, a float charger may be kept connected indefinitely without damaging the Battery."

[Anthonyshybrid]

Modern trickle chargers are good so there is never a too long. But to reduce the possibility of flat spotting your tyres you should overinflated them by 10 lbs/sqin, remember to deflate them when you put it back on the road.

[WilliamOrbit]

Thanks for all the helpful replies guys.

In the end I decided to run with the advise from Lexus and disconnect the negative terminal on the Battery. A word of warning here. When you have disconnect the Battery, do not allow the tailgate to close fully. If you do, it will catch/lock. It's a pity that the Lexus tech didn't mention this to me before I followed his advise. Anyway, when I get back, I will have to put the seats down and scramble inside to pull off a small cover and use a screw drive to push a special unlock catch you allow the tailgate to open again. Annoying, but at least there is a solution. I will probably invest in one of those neg terminal switches in future. To be clear, I refrained from simply putting a trickle charger on, because this is my first hybrid, and naturally one is concerned about potential voltage issues with such a huge second Battery system in the vehicle. So I checked with my Lexus service department and the answer I got back was to disconnect the negative terminal rather than use a trickle charger, so I did.

I am sure many here use TC's on their rx400,450's however, if Lexus is being cautious on this, then I guess I will have to be too. I can just imagine the conversation if an electric fire started whilst a TC was connected for 9 weeks! "We did tell you sir, to disconnect the negative terminal.........

As time passes and more feedback from members occurs, I expect the use of TC's on Lexus hybrids will become standard practice as with all non hybrids.

 

best

William

[rynd2it]

If you disconnect the Battery (by whatever means) you'll have to reprogram various bits & pieces - mainly the tailgate and side windows. A bit of a pain.

 

 

[WilliamOrbit]

When you say "reprogram" you mean "reset" using button controls as normal? Or is there something more complicated involved?

[rynd2it]

There are some functions which are owner set and some dealer set -if you disconnect the Battery they revert to factory default. You can reset the owner ones yourself using the buttons but the dealer ones will require you paying money and usually lots of it.