Keeping RX400h charged during Covid 19

sando63 · March 21, 2020

Usually after 10 days my car Battery goes flat, is it safe to run a trickle charge to the car without disconnecting the Battery ? I don't like disconnecting the Battery because the start up procedure is a pain resetting everything, thanks Dave.

rich1068 · March 21, 2020

Nothing wrong with going for a drive Dave. Just about the only thing keeping me sane at the moment.

Gliderpilot · March 21, 2020

If tou are going to stay in for a long period, the AA and others sell a small solar panel that you can plug into the OBD socket which connects directly to your Battery. That will trickle charge it even during none sunny days.

007M · March 21, 2020

I would go for a drive to charge it up. I do this sometimes myself when I have left the car for 3 days+ without driving in the winter period.

NemesisUK · March 21, 2020

3 hours ago, sando63 said:

Usually after 10 days my car battery goes flat, is it safe to run a trickle charge to the car without disconnecting the battery ? I don't like disconnecting the battery because the start up procedure is a pain resetting everything, thanks Dave.

Presuming we are talking of the 12 volt Battery, not the traction Battery?

Perfectly safe to use a conditioner such as the CTEK without having to disconnect the Battery. CTEK sell leads designed to fit to the Battery, with a quick connector for the charger. I had such permanently installed in my Mercedes.

Delphius1 · March 21, 2020

I got a 5 watt solar panel and an obd plug and wired them together so the solar panel delivers 12v to the 12v Battery. I use on both the Wife's and my car if we leave them for any length of time.

I just prop the panel up on the dash and plug it into the obd socket.

Passerby · March 27, 2020

It shouldn't go flat in 10 days.. either sort out what is taking the power or it is knackered and needs replacing

Illogan · March 27, 2020

When we will be away, (hopefully) on a boat and without the car, for sometimes three or four weeks at a time - I realise I'd need a charging system to look after the Battery

I've read this thread, and have just bought myself one of these: https://www.ukb4c.co.uk/products/aa-essentials-12v-solar-powered-car-battery-charger-solar-panel-obd-version?_pos=1&_sid=22302d684&_ss=r

(I'm sure other brands are available! - )

(And I have not received any benefits in either cash, kind or favours for posting this link!)

Barry14UK · April 1, 2020

A number of us are not likely to use our cars for quite some time due to tightening restrictions. A have a 5amp CTEK smart charger which I have used by just connecting the grip connectors to the Battery terminals in the boot of my BMW without problem. I have in mind to use this on my RX450h in the same way but the Lexus Manual says that if the Battery is charged in the car the ground should be disconnected. Like the OP I don't want to do lose settings by doing this. Why would Lexus say the ground should be removed and is this really necessary using a smart charger?

OldTrout · April 1, 2020

On 3/27/2020 at 10:22 PM, Illogan said:

I've read this thread, and have just bought myself one of these: https://www.ukb4c.co.uk/products/aa-essentials-12v-solar-powered-car-battery-charger-solar-panel-obd-version?_pos=1&_sid=22302d684&_ss=r

Just sending mine back as it does not provide enough current to maintain the Battery. At least in the ad above it says 2.4W which the ad I bought from did not.

Go for at least 10W but the ads for these things are a minefield of misleading information. e.g. I found oner ad with 25W on the photo, 20W in the title, and depending how you interpreted the data in the description perhaps 15W there. I asked for clarification. Nothing yet.

John

Herbie · April 1, 2020

7 hours ago, Barry14UK said:

I have in mind to use this on my RX450h in the same way but the Lexus Manual says that if the battery is charged in the car the ground should be disconnected. Like the OP I don't want to do lose settings by doing this. Why would Lexus say the ground should be removed and is this really necessary using a smart charger?

I have no idea why they say that in the manual but, as a time-served electrician, then telephone engineer on BT, licenced radio ham, and now self-employed doing computer repairs - in other words, someone who's been around the electrical/electronics fields for the last forty-odd years - I can say that it's just not necessary.

Even if there was some form of voltage spike, the Battery itself would act as a huge smoothing capacitor and stop that.

Although you do it at your own risk and if something bad does happen then I can't be held responsible, if it were my own car I would have no hesitation in doing it myself as I just cannot see any reason whatsoever to disconnect the Battery. After all, you don't disconnect the Battery to give the car a jump start and it's the same scenario, ie, supplementing one dodgy 12V source by piggybacking a good 12V source onto it.

Barry14UK · April 1, 2020

Thank you for your prompt and always helpful reply Herbs. I understand your logic in this and would not have hesitated had it not been for the fact that for some inexplicable reason Lexus specifically says to ground the Battery connection where Battery is charged on car and I know hybrid electrics are different in some respects. I can only think that perhaps it might be because some owners might connect a very high powered charger to the electrical system but then again as you point out, the car can be jump started from the location under the hood, very strange! Understand your disclaimer and will connect direct to Battery as I have done with non hybrid cars.

I don't envisage a problem but should there be one I will post so others may be aware.

GS300h2014 · April 1, 2020

Herbie argues that 'Even if there was some form of voltage spike, the Battery itself would act as a huge smoothing capacitor and stop that'

I agree with this; but I think it would only apply if the charger was directly attached to the Battery terminals in the boot. This would not be the case if one connected the charger via the terminal connection in the fuse box under the bonnet. This because of possible inductance in the cabling to the Battery in the boot.

However it would be ok to follow Lexus' advice to use the connection in the fuse box to jump start the Lexus as the donor car's Battery (supplying the power) would prevent a voltage spike.

GS300h2014 · April 1, 2020

Further info from Yarso in today's Toyota Yaris forum:

'If you haven't already done so, it would be worth disconnecting the Battery, leaving it for a few minutes and then reconnecting - if the voltage has been brought up slowly from dead flat you may find that some control modules activate before others and things then may not work properly.

Unfortunately it's not unknown for control modules to fail completely during Battery discharge and recharging - but hopefully that's not the case here.'

Barry14UK · April 1, 2020

Thank you for your post on this John. I hope that by trickle charging occasionally I will be able to avoid the 12v Battery going flat. I am aware that once flattened they are not always recoverable and even if they are this can drastically reduce their efficiency/life.

Illogan · April 2, 2020

On 4/1/2020 at 11:06 AM, OldTrout said:

Just sending mine back as it does not provide enough current to maintain the battery. At least in the ad above it says 2.4W which the ad I bought from did not.

Go for at least 10W but the ads for these things are a minefield of misleading information. e.g. I found oner ad with 25W on the photo, 20W in the title, and depending how you interpreted the data in the description perhaps 15W there. I asked for clarification. Nothing yet.

John

Hmm - - thanks John.

Have to admit that I'm not an electrical engineer, and made the assumption that being an AA branded panel designed to trickle charge car batteries that it should have stood a fighting chance to achieve that function.

I have conected my panel this morning - and will now keep an eye on it - - thanks for your heads-up on this issue John

Chappy2121 · April 2, 2020

Just had a scan through this thread regarding grounding the Battery. Is that the main Battery or the one for the hybrid side of things? I'm in no means an electrical expert but working in the refrigeration industry for the past 10 years we have some very complex electronics on supermarket pack systems. I.e. invertor driven comps, and rule of thumb thinking doesn't always work so to speak. I would do as lexus say then at least you have a fallback if something goes off with it. I've had issues where the slightest wrong voltage has caused major issues with controllers ect that were designed for a specific voltage ect. Do they not do specific hybrid trickle chargers?

Illogan · April 2, 2020

Ash - the Battery the OP, Dave, is speaking of, is the 12v Battery that runs the alarms/door locks etc - not the propulsion/hybrid Battery, which is why a trickle charger, either wired or solar, should resolve the issue

06_400_h_se · April 19, 2020

I use the AA solar charger via OBD also. It works fine.

Extiffy · April 25, 2020

I've just charged my 12volt Battery in rear of 2009 RX 450h . Disconnect the negative terminal as stated in the owners handbook before connecting the charger. When recharged reconnect the negative terminal and power up the hybrid system . Settings will be restored automatically. Initialise the rear door as in handbook. WARNING don't close the rear door as you will to crawl into the boot via the rear seat to manually release the catch. Just follow handbook, then no problem. Mike