lsteadman

Lexus RX450h 2009

Looking to find what the draw should be for the car when left for a few days. I understand some power is required for alarm, immobilizer, central locking and approach lights etc. but I am trying to find out what that draw should be. The 12V battery is (i believe) 60Ah) but mine goes completely flat in 2-3 days.

Thanks!

Rosscoe83

I don't know the answer to your question but if your battery dies in 2-3 days, you have two options: 1. Get your battery tested and replace if needed or find where your unintended draw is coming from. 2. Get a new battery.
Even if you leave an interior light on, it should shut itself off after a certain time so that it doesn't drain your battery.

tempestv8

Have you got some electrical modification that could be drawing significant amounts of power? Perhaps a dash camera that is on all the time, and happens to be drawing too much power because it has developed a fault?

If not, then your battery needs to be replaced as it's lost a lot of amp hours capacity. Not surprising if it were the original battery - it'd be 9 years old by now!

lsteadman

Thanks for replies.

The battery was replaced two years ago - as that was the "solution" - typical bloody garage: "cure" symptoms and ignore cause. I don't have any modifications so I am just trying to work out how much extra amperage must be being drawn. As I understand it all cars will drain their 12V over time when not driven due to alarms, immobilizers, lights etc.

tempestv8

I'm curious now - what type of battery was used as a replacement? A standard flooded cell lead acid battery will fail very quickly with the RX450h. For the hybrids, the 12 volt battery needs to be an AGM battery, and even so, I personally believe that a battery maintainer (aka smart battery charger) would be necessary to keep the 12 volt battery fully charged every couple of months or so. Use this as a reference: https://static.nhtsa.gov/odi/tsbs/20...87543-5448.pdf

Re your original question, I found this comment in this thread: https://www.clublexus.com/forums/hyb...us-rx450h.html
Not sure if it answers your question but I found it interesting, nonetheless.

riredale

I haven't heard anything here at the Portland Lexus dealer about needing an AGM battery, and I think there are lots of folks on this board who have been able to use a regular battery successfully. My own understanding is the the primary advantage of an AGM battery is there's no need to check and replenish the liquid level. Also, there is less outgassing during charging.

kamie

Is this means that better keep 450h when garaged with unlocked doors and open some windows in order to avoid a faster discharge of 12V battery in storage? When read this topic discussion came to this conclusion, correct me please if I’m wrong in my understanding. Thanks

salimshah

Storage of 450H is a bad idea.

Concern for 12v battery is secondary issue, the major challenge is keeping the high voltage traction battery to minimum expected voltage. One needs this voltage to not only drive in reverse but more importantly spin the ICE (start of the internal combustion engine). This requires running the vehicle at least once a week. You can possibly extend it to 2weeks but pushing beyond that is a bad idea. When the high voltage battery runs below min, one has to flat bed to the dealer or EV shop to charge the high voltage battery above minimum.

Back to 12v battery:
The innards of 450H has various levels of battery use without any charging. The least amount of draw happens after the vehicle has been turned off and locked and armed [turn off and double lock] AND the key fob is taken out of the range. This puts the vehicle in sleep mode. [I don't know the exact time but if you walk away within 20 minutes the vehicle will go not sleep mode] When the key fob is within range the vehicle kind of wakes up.
Even in sleep mode certain functions still operate .... receiver is still searching, the brakes are always primed [see discussion on ABS pump leak] and certain other house keeping task.

In summary the demand on the 12v battery in 450H is fairly low and a good battery should last 5+ years. If it passes the load test, the battery is far above good enough state for 450H.

Salim

PS: My estimation of 2 weeks or more depends upon the charge state of the battery when it was last turned off. If was fully charge the time can be longer but if it was at the low end then it can be shorter. To my understanding the the high voltage battery does not support and device when turned off and the decay is purely due to leakage.

Roscol

I got to test this last year when I had a 3 week trip out of country.
I have previously gone away many times for a week or 2, and the 450h was none the less charged from what I recalled, but this time, for 3 weeks, I wanted to really test this out.
drove around the neighbourhood to stop and go to force charge the traction battery to absolute full as indicated on the dashboard, all solid bars to the top, then immediately parked it.
Returned exactly 23 days later, opened the door , pressed the start button, bingo!, still at full charge, no loss whatsoever.
I can now plan my month long trip now, lol

kamie

The answer of this question reflects my own experience with hybrid vehicle. In short if you did not get a new 12V battery in the last couple of years it’s a time to replace it with this symptoms, unless you have electrical problem with slow el. drainage which of course need to be checked if happens regularly. Good luck.