Heanorboy

Flat Battery on NX Hybrid 2016

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Having just come back from a month away with the NX sitting in the garage big surprise was that the Battery was so flat even the door locks would not work.

So had to call the AA (Lexus assist) who managed to get into it and then jump started with a high power unit. purpose of this note is he told me that it is quite common for the Hybrid to go flat quite quickly he has one couple not far from me with a car less than two years old that they find goes flat in as little as 2 weeks.

Has anybody else had this problem or even better know a way of preventing it happening again as the guy from the AA said it was not a good idea to put any hybrid on a charger even the smart charger that I had as it could cause serious damage to the Electronics 

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1 hour ago, Heanorboy said:

Having just come back from a month away with the NX sitting in the garage big surprise was that the battery was so flat even the door locks would not work.

So had to call the AA (Lexus assist) who managed to get into it and then jump started with a high power unit. purpose of this note is he told me that it is quite common for the Hybrid to go flat quite quickly he has one couple not far from me with a car less than two years old that they find goes flat in as little as 2 weeks.

Has anybody else had this problem or even better know a way of preventing it happening again as the guy from the AA said it was not a good idea to put any hybrid on a charger even the smart charger that I had as it could cause serious damage to the Electronics 

I connect a Solar Charger to my GS450h twice a year for 3 months each time. Have done so for 5 years without a problem..

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I went away this year for close on 3 week's with my NX 65plate, turned over first time. I did try to make sure that the hybrid Battery was pretty much as full as I could get it within reason

Sent from my Mi MIX 2S using Tapatalk

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It's not the traction Battery that goes flat, it's the small 12V "hotel" load Battery and it is this that operates the door locks etc.

You only need a Battery which can supply a jump start of about 60A to get a hybrid going as this is what the fuel and brake system pumps take to get going. The engine starts from the traction Battery. The 12V Battery is charged via a dc/dc converter from the traction Battery when the ignition is on.

If you have power in your garage you can connect a small trickle charger to the car to keep the 12V Battery full.  Refer to the manual for where to connect it (same as jump starting).

I have been looking after another NX for 6 months now and try to run it every 2 weeks to keep everything OK.

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2 hours ago, Heanorboy said:

the guy from the AA said it was not a good idea to put any hybrid on a charger even the smart charger that I had as it could cause serious damage to the Electronics 

The man from the AA, he know nothing.

And I don't mean that in a nasty way but he is talking rubbish. There are no problems whatsoever in using a Battery charger on a hybrid, and while we're at it I'll also say that there are no problems with giving a hybrid a jump start if needed. However, you should never use a hybrid to provide a jump start to something else.

In normal cars the Battery is only used to power the starter motor, which will draw 300A or more, to start the engine. When the engine is running and the alternator is spinning, it's the alternator that provides the energy to the car and also keeps the Battery charged. When dealing with normal cars the procedure is to attach the jump leads then start the engine of the donor car before attempting to start the engine of the recipient car. This is done just in case the donor Battery isn't up to scratch and to make sure it doesn't flatten itself while trying to get the other one going - the recipient car draws mainly from the donor alternator, not the donor Battery.

Hybrids don't have alternators; their 12V batteries are charged from the 288V Battery via a DC/DC converter. They don't have starter motors either, and you'll see from the photo below that my RX450h only draws a current of 15.32A to get the car into the READY state. Given that it takes 300A or more to operate a starter motor but less than 20A to 'start' a hybrid, the DC/DC converter of a hybrid is not designed to provide 300A or more to the dead car and if you were to try it, you'll almost certainly find that the very expensive magic smoke inside the converter that makes it work will start to escape into the atmosphere and it'll cost a fortune to get some more put back in.


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The real question is "why", and the answer is that you left probably your keyless remote nearby your NX: if so the remote receiver stays in ready mode draining current from 12V Battery faster than if remote was far away. For long periods without using car the suggestion to keep 12 V Battery with an automatic charge keeper is  a valid alternative.

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The biggest danger with using a trickle charger is remembering to disconnect it before driving off..

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32 minutes ago, Zotto said:

The real question is "why", and the answer is that you left probably your keyless remote nearby your NX: if so the remote receiver stays in ready mode draining current from 12V battery faster than if remote was far away. For long periods without using car the suggestion to keep 12 V battery with an automatic charge keeper is  a valid alternative.

Yes I would love to know "why"  it is definitely not due to the remotes being near the NX. The NX was in a brick garage which is detached from the house by min 6 mts and both keys inside blocking key pouches inside separate steel filing cabinets.  

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36 minutes ago, C Mclean said:

The biggest danger with using a trickle charger is remembering to disconnect it before driving off..

Been there, done that...Wondered why my IS was a bit clunky to reverse out, and then drove off with the charger wires dangling.

My IS300H used regularly to run out of charge on the auxiliary Battery when I left it for a week or more. So I started keeping one of those RAC Battery things in the boot to save calling Lexus/AA out. Then I bought a Ctek charger and left its connector wired up permanently in the boot. The connector has little LED indicators indicating the state of the Battery.

I removed the CTek connector before I sold the IS300H, and one of the first things I did to the new NX was add it back. It gets low on auxiliary Battery charge after about 5 days non use. This is with both the standard key fobs switched off and the card key way over on the other side of the house  where it cannot possibly be received by the car. 'Blocking' key pouches aren't necessary with the current cars since the buttoned fobs can be switched off and the card key has a very short range. Try it and see!

Having to regularly charge it is one of the things I've  got used to, given my intermittent use of the car!

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12 minutes ago, Heanorboy said:

Yes I would love to know "why"  it is definitely not due to the remotes being near the NX. The NX was in a brick garage which is detached from the house by min 6 mts and both keys inside blocking key pouches inside separate steel filing cabinets.  

It's keeping all its keyfob sensor stuff active.All just to get the lights to glow as you get to a couple of metres of the car... I think the NX  also keeps its wifi running because I seem to be able to use 'Mylexus' on the PC to download routes to the car even when it's parked out in front of the house but within wifi range.

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1 hour ago, Zotto said:

you left probably your keyless remote nearby your NX: if so the remote receiver stays in ready mode draining current from 12V battery faster than if remote was far away.

I'm afraid it makes no difference whether keys are near or far away Luigi. The car will always be active looking for a signal from the key no matter where it is.

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After some time (4 days?) the car goes in a waiting state reducing Battery draining; reducing but not deleting, as some services are always on in all modern cars.

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There will always be confusion and misunderstanding as long as the term " Jump starting" is used when applied  to hybrids. The manual for my MY17 CT says the engine of the donor car should be started? May have to talk to somebody at Lexus who knows  about  these things.

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14 hours ago, Charlie Alder said:

There will always be confusion and misunderstanding as long as the term " Jump starting" is used when applied  to hybrids. The manual for my MY17 CT says the engine of the donor car should be started? May have to talk to somebody at Lexus who knows  about  these things.

There should be no confusion at all.

All you're doing is supplimenting a dodgy 12V supply by piggy-backing a good 12V supply on it. Nothing complicated, nothing mysterious, and nothing dangerous.

The reason for having the donor engine running is as I explained above and if a hybrid is the recipient then it absolutely, categorically, does not need the donor engine to be running.

I'll own up straight away and say that I'm not a qualified auto electrician, but I am a time-served, qualified electrician by trade and learned my trade in a factory. When the factory closed down I got a job on BT and the vast majority of my working life has been spent as a telephone engineer with BT. After a back injury saw me retired early on ill-health grounds, I'm now self-employed doing computer repairs/builds and one of my hobbies means that I'm a fully-licenced radio ham.

I'm not trying to be obnoxious or big-headed or anything, I'm just saying that almost my whole life has been spent in or around the electrical/electronics fields and, although I obviously don't know everything, nor would I ever claim to know everything, I'm confident in this particular topic.

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Another reason for having the donor engine running is that who wants two cars with flat batteries, although this is really only for conventional engines.

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1 hour ago, C Mclean said:

Another reason for having the donor engine running is that who wants two cars with flat batteries, although this is really only for conventional engines.

Exactly :thumbsup:

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