Yes, I know the old setup works wonderfully. My RX450h was traded in with a 14 yr old 12V still onboard, never let me down. But even with "dumb" charging there is still regulators to prevent over charging. I just don't know with these new ones exactly what role the battery sensor fully plays. Is there still another part of the system that will prevent overcharging or will it be a case of full on high amp charging all the time. The proper way to charge a battery is perhaps some high amps when the battery is low but as the battery comes up in charge the amps need to be reduced to practically nothing as the battery nears 100% charge. Perhaps it might even be a case of these new cars not even be able to produce enough amps after the rest of the car's electrical needs are taken care of for it to be a worry, but that's my ponderings...

I still recall a cheap battery operated tool I had with a "dumb" charger (that's what I get for buying a cheapo tool). Instructions say "charge for 3 yrs, do not leave on charger". Well, I put it on and forgot it. Next day I went to get it, battery was too hot to touch and basically ruined, no useful charge. Now I buy all my battery tools based mostly on making sure it comes with a quality smart charger.

 

The unknown risk is not to the battery, but to the DC-DC converter that powers the charging current together with the ALL other subsystems in the car. Reliability of the DC-DC converter is fundamentally physics-limited based on current drawn by the 12 V subsystem due to power-MOSFET and electrolytic capacitor lifetime physics limits, across the entire industry not limited to Lexus/Toyota. This is the likely reason why Lexus/Toyota designed the voltage-sensor and time-based (under-)charging, to begin with, which cost them money to design and implement. So I did my own research and chose not to go down this path.

 

I would bet my right hand that the only reason for this completely idiotic charging system is to comply with emissions regulations. Here in Europe Lexus decided to reduce the engine power in NX350h from 240HP to 200HP this year because they coulnd't meet emission limits
So they were desperately looking for every single gram of CO2 they could reduce, undercharging the battery might help with that, while another solution is decreasing engine power.

 

I read that too! Talking about 'just giving up!' that probably cost them nothing, they just changed the fuel mapping for the engine to provide less fuel. Didn't want to try maybe a slightly more thorough catalytic converter system, no might cut into corporate profits, owners won't know or care.

 

I thought this was 'discussed' in this recent thread and pointed out a study that had been done:
https://www.clublexus.com/forums/nx-...choices-3.html

Here's the studies link:
https://docs.google.com/document/d/1...h.t75rusbfgz8u

Wouldn't this indicate that the 12 volt battery doesn't seem to get overcharged while continually in 'dumb mode' with the connector disconnected? As you can read starting on page 25 Starting with:

Battery Resting Voltage After Sensor Disconnection

Actually as I'm writing this the paper is being edited by the author, adding in more details.
The article's author has (currently) been tracking their 12 volt battery for over 13 months with no visible sign of abuse to the 12 volt battery.

Please NOTE the annotation at end of the article:
Reminder: Any recommendations followed from this document are done so at your own risk. The author accepts no responsibility for any loss or damage incurred as a result.

 

I have mine unplugged for about 4 months now. I figure with all the people having problems with theirs on the Toyota/Lexus charging algorithm, Why not put in the dumb mode that has worked fine in throughout the 1900s. Obviously Toyota got this wrong so we shall see. If I have a battery problem, I will simply plug it back in and I won't be the first to complain to Lexus that I have a battery problem with my NXh.

 

So I had mine in for the reprogramming and door handles replacement. They also load tested the battery. It was defective somehow, they replaced it. This is the 2nd battery in the 35 months of ownership. Let's hope this one lasts a bit longer than the first 2

 

One way to help solve the problem is when ever at a red light put it in park. Its amazing at how it will increase state charge

 

I find it difficult to understand how this would ever be the case. Toyota hybrids do not use typical drivetrains, no old fashion transmissions no rear differentials powered by driveshafts from the engine/transmission. They are powered by motor generators - electric DC motors essentially. And as such when you come to a stop there is absolutely nothing that has any drag effect on the powertrain to drain or impede it of electrically stored battery power. The electric motors simply stop and don't receive any electricity to drive the wheels. Putting the car in park only prohibits the car from moving forward if you were to press on the gas peddle nothing more. There is no perceivable benefit in putting it in park other than you're waisting time in getting moving again when the light turns green and possibly someone rear ending you. Battery Regeneration while the car is moving and the internal combustion engine are the only 2 things that provide any recharging of the traction battery. At the point when you lift your foot off the brake when fully stopped a very small amount of battery power is used to provide the familiar creep you get with a gas engine and it's typical drivetrain to act as most drivers are familiar with, that's about it.

 

Well that is not true. When the car is in park the battery will be charged at 14.4 volts and when put in drive it will drop to 12.8 volts. Most of us who have driven a manual transmission are very used to putting the stick in nutral and clutch out while sitting at a light. On another note today i drove untill the traction battery ran out and after the car went in to hybrid mode the 12 volt battery went from 40% state of charge to 100%. It stayed at 14.4 volts for the better part of an hour while driving

 

nothing to see here

 

I just tested on my ES hybrid and with a voltmeter.
In both park and drive: 14.5V.
[edit] with ICE running.

 

What is the outside temperature at that time? When is below 0°C it will charge more frequently even when driving.

 

75

 

I have seen this behavior before as well, but it's not very consistent.