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My solution ...attach quick connect to battery terminals ... - cable runs into edge of trunk and get a 12v charger to connect and use it every time after i completely recharge the big battery..
My solution ...attach quick connect to battery terminals ... - cable runs into edge of trunk and get a 12v charger to connect and use it every time after i completely recharge the big battery..
Yes, many folks have drilled holes into the car for their 12 V charging cable as well.
That approach doesn't work for me, because I only signed up for hybrid battery charging when I gave my money to Lexus. Not an additional charging/cable attachment daily for the 12 V battery charging chore. The latter is an unacceptable path for me, simply for the privilege of owning a Lexus. Hence if I have to use a band-aid, it would rather be an AGM battery or such eventually - assuming Lexus will never fix the charging algorithm at their end, despite wide, statistical prevalence of this problem as evident in this forum and on reddit forums.
Just a thought here but if changing type of battery away from oem like agm I would get Lexus dealer something in writing stating it would not void warranty. There is something strange that only Toyota knows how this charging system actually works. There is probably a delicate balance which in the end maximizes mpg.
Just a thought here but if changing type of battery away from oem like agm I would get Lexus dealer something in writing stating it would not void warranty.
They would never do that - because their "corporate script" is that they will only replace with the exact same battery (Ampere-hour, type), and will parrot that bureaucratic BS. SMartin has tried and failed already, as he reported. So he drilled a hole in the car for the 12 V charging cable, I think.
Originally Posted by alextv
There is something strange that only Toyota knows how this charging system actually works. There is probably a delicate balance which in the end maximizes mpg.
Yes, from a design perspective, you may have hit the nail there. They, by design or possibly "looking the other way", simply crippled the 12 V charging - because providing sufficient charging ability to the 12 V subsystem might have reduced their MPG ratings with EPA, and therefore affected their business plan ($$). Or it could have simply been an incompetent engineering of the 12 V charging subsystem design that was copied/pasted from the Rav4 Prime, without any regard to the enormous number of sensors, data telemetry and useless vanity frills ("illuminated door sills") that we we have in a Lexus. You see how the problem is worse in the 450H+ than the 350H (both in RX and NX lines), as the 450H+ are more loaded with sensors and factory-fit options like "illuminated door sills", irrespective of we want the latter or not.
You may want to look at the NOCO Genius 5 amp charger, as it is less costly and has float capability, as well. It will charge flooded, AGM and LiIon batteries and also has a desulfation mode, too.
Just a thought here but if changing type of battery away from oem like agm I would get Lexus dealer something in writing stating it would not void warranty. There is something strange that only Toyota knows how this charging system actually works. There is probably a delicate balance which in the end maximizes mpg.
As I understand it, a flooded lead-acid battery is charged at 13.8 to 14.4 volts and an AGM battery requires a charge of 14.4 to 14.9 volts. Charging an AGM battery at a lesser charge level will greatly shorten it's overall life. I am certainly not a battery expert but, I am not certain that I want to stick an AGM battery in either of my cars just yet. I am still going to wait until the mothership gets this resolved. Latest news may indicate that it is the DCM module causing the issues.
You may want to look at the NOCO Genius 5 amp charger, as it is less costly and has float capability, as well. It will charge flooded, AGM and LiIon batteries and also has a desulfation mode, too. https://www.amazon.com/NOCO-GENIUS5-...zcF9hdGY&psc=1
Thanks. I actually did ended up getting the Noco5 since it was a bit cheaper.
So given the chalice handed to us by Lexus - we have to pick our poison.
Either risk waking up or arriving at the airport parking lot encountering a dead battery, or mitigating that risk with an AGM, while heightening the out-of-pocket cost/risk of buying/replacing an AGM.
For what its worth, Odyssey lists its AGM as compatible with 2023 NX450H+. And more than one user by my surveying of NX/RX450H+ have derived benefits from using an AGM, which is of course a band-aid. Just as monitoring the 12 V continuously with a gizmo/app, and charging the 12 V every day/week/month is a band-aid. I do not have time or patience for this particular poison.
So my poison of choice will have to be an AGM, it seems.
AGM isn’t going to be a fix because it’s a current draw issue. Capacity is capacity. Additionally, the car won’t charge the AGM at the higher voltage that it should. It might be possible to set the car up to do it, I did with my VW, but I haven’t seen anyone mention that being possible.
AGM isn’t going to be a fix because it’s a current draw issue. Capacity is capacity. Additionally, the car won’t charge the AGM at the higher voltage that it should. It might be possible to set the car up to do it, I did with my VW, but I haven’t seen anyone mention that being possible.
Internal resistance of the battery also plays a part in the charging system and I have seen on other forums where mpg suffers when not putting similar type back in. The charging is all software controlled and it should be designed with a failsafe that if the battery capacity gets too low to shut off the DCM and resume when ready is on with charging initiated.
I think there may be more to it than just capacity increase.
The capacity increase of a OEM sized Odyssey battery is usually marginal, though anything helps.
I believe the lower internal resistance helps as well.
My observations of the charging behavior of the RX450h+ lead me to believe that it is time-based. It seems to have no concern for battery charge state. There is an initial 14v charging cycle while driving, but then it drops to a low float-voltage, around 12.8, at most times. The primary exception is when the vehicle is in Ready mode and in park. At that time, the voltage stays above 14.
I did observe the charging system stay above 14 volts for about 30 minutes, while driving. I believe this is a time-based maintenance cycle. In 3 weeks of driving, I've only seen it happen once. The battery was not at a low state of charge when it occurred.
Due to the lower resistance of the Odessy battery, I believe it can accept more charging current, so, if true, it would get to a higher charge state with the limited 14v charging times, than a conventional flooded lead acid battery. One could liken it to running the gas pump at low flow, vs high flow. More gas will go in the tank on high flow, per minute of time.
Another benefit of the low resistance is that it can supply more current at low voltage levels than a FLA battery, so that it might not register as "dead" at the same voltage where a FLA would not be able to power the vehicle.
I'm still leary of putting an Odessey battery in though, because a deep discharge can result in the need for a special( and expensive) high amperage charger to restore it to full capacity, and the random nature of the parasitic load which could see the battery deeply discharged in the span of several hours, regardless of battery type and capacity.
I now have several weeks of data from the voltage monitor. Below is a 2 week snapshot that shows where I fully charged it, and then what I consider normal parasitic loads took it down over the course of days. Drive cycles do not interrupt the steady drop. There is also one charge cycle, on June 3rd, which is followed by a dramatic discharge in about 8 hours. If I had not caught that, I'm convinced it would have completely discharged the battery by the next morning.
Due to the lower resistance of the Odessy battery, I believe it can accept more charging current, so, if true, it would get to a higher charge state with the limited 14v charging times, than a conventional flooded lead acid battery. One could liken it to running the gas pump at low flow, vs high flow. More gas will go in the tank on high flow, per minute of time.
Another benefit of the low resistance is that it can supply more current at low voltage levels than a FLA battery, so that it might not register as "dead" at the same voltage where a FLA would not be able to power the vehicle.
I'm still leary of putting an Odessey battery in though, because a deep discharge can result in the need for a special( and expensive) high amperage charger to restore it to full capacity, and the random nature of the parasitic load which could see the battery deeply discharged in the span of several hours, regardless of battery type and capacity.
I now have several weeks of data from the voltage monitor. Below is a 2 week snapshot that shows where I fully charged it, and then what I consider normal parasitic loads took it down over the course of days. Drive cycles do not interrupt the steady drop. There is also one charge cycle, on June 3rd, which is followed by a dramatic discharge in about 8 hours. If I had not caught that, I'm convinced it would have completely discharged the battery by the next morning.
Thanks for the data. That matches what I had found as data on my 20 minute trip to the store, posted above with my Bluedriver (that sources the data from the ECM (Engine Control Modlue) involving A/D conversions, and therefore noisy) - in terms voltage behavior.
As for the AGM, yes, AGMs drawing larger current and hence getting higher state of charge at a lower charging voltage seems to be the characteristics of AGMs I found in general (not just the Odyssey), as to be expected from the lower internal resistance and Ohm's Law. As is the ability to supply current at lower voltages you've noted. FWIW, my $ 25 charger states it can charge AGM batteries in the same "mode" as a Lead Acid, but has a separate mode for Lithium Phosphate ones that require higher voltages and voltage/current requirements.
I was initially settling on the AGM Walmart sells, because its cheap at $180 and also has 4 year replacement warranty serviceable at any Walmart. However, on looking closer I found that it has two "venting" ports that can release occasional gas from the chemistry - which makes that particular AGM a problem for the NX/RX batteries that are sitting in the passenger cabin. However, the Odyssey AGMs are fully sealed and do not have those vents.
As for any possible mpg hit with any AGM, yes, that is the poison package I already paid Lexus for, and now just have to swallow it.
06-06-24, 10:56 AM
