Realistically, I don't think that there will be much to be gained from this. On my two 450h+ models, the fobs are religiously, either turned off or kept in a Faraday box which is over thirty feet from the cars. Still, the SOC declines dramatically overnight, typically going from 99 to 100% down to 68 to 70% within 24 hours. Every three to five days, depending upon usage of both vehicles, I just put them in READY mode for 45 to 60 minutes to keep the SOC to a decent level.
The app that I have on my iPhone, from my Quicklynks battery monitors ($29), gives me a heads-up when they drop to a low level. While I would be the first to admit that this is a bit of a PITA but, it is better than the alternative.....that being a croaked battery. I've only had that occur one time, which prompted the battery monitors. So far, this is a good workaround until Lexus moves this &%#*@! issue to the top of their fix-it agenda. With battery failures occurring, I have to assume that they are looking into it. You are, aren't you Lexus?

 

The dealer tech wrote a book on why the key fob communication with the vehicle if it's 9 ft or less while measuring the amp draw. It's up to those to believe or test themself. Just sharing my experience from what was shared from the dealer experience.

 

I'm thinking that the stock battery (Panasonic, not dealer provided) is designed to be different in that its resting voltage and SoC are designed to be "normally" lower than run-of-the-mill 12 V flooded lead-acid batteries - given that everyone finds the voltage lower than normal, and CCA is about 335 A despite it is 60 A-h (in my RX450H+). Panasonic may have designed it for this kind of high-drain but no-starter-motor CCA kind of cars. If that is the case, the SoC shown by the battery monitor may be overly pessimistic in its warnings, because it assumes a run-of-the-mill 12 V battery, not the Panasonic one. Just mentioning this theory, in case you want to try lessen your PITA by ignoring until the SoC drops further than what triggers alarms from the monitor.

I specifically did not get the battery replaced at the dealer at 5 K mile service, because I wanted to retain the Panasonic battery now, rather than have it replaced with a run-of-the-mill lead acid by the dealer. I have not been charging the 12 V proactively more frequently than 1 month+ intervals, and have not experienced a dead car other than on two days in winter.

 

My new-to-me 2023 350h hasn’t had any battery problems yet, but I’m planning on replacing the 12v with a Lifepo4 battery if I have any problems with it. My previous non-hybrid cars I’ve always wanted to buy needing high CCA for a starter meant an AGM battery usually was more cost effective, but I think a Lifepo4 batt would be perfect for the drainage issues I’m reading about here.

like this one, but with automotive battery posts:
https://www.canbat.com/product/12v-5...thium-battery/

anyone else try something similar yet?

 

Not a winter battery which is my use case
Discharge Temperature

-20 to 60 oC ( -4 to 140 o F )

Charge Temperature*

0 to 45 oC ( 32 to 113 o F )

Recommended Storage Temperature

-5 to 35 oC ( 23 to 95 o F )

 

That was just the cheapest option I'd found. Something like this might be better
https://no.co/nlxu1

 

Does anybody know where to get spec sheet for this 12V battery from 2T2* vin nx350h 2025? Like is it AGM or EFB or something else? No refill vents visible, only ..LN2-MF marking under the hold-down bracket. I have read plenty of speculation online but nothing specific.
I got 12V battery monitor as the car tells nothing about the state of charge and may die silently for that matter. But the mapping between voltage and SOC is slightly different for different types of batteries.

 

OK.....lets try to de-mystify this thing with some hands on testing rather than hear-say. My 3 week old car also this morning experienced what I think is a low voltage event, which resulted in the car refusing to go to READY and needing a "jump" start from my booster battery pack. Car behaved normally afterwards.

The battery in my 2023 NX 350h has part number 375LN2-MF. You'll see that model number after removing the battery hold down bracket. It appears to be the common battery used in several Toyota/Lexus hybrids.
There's a similar 380LN3-MF battery used in other Toyotas. None of these 3XXLNX-MF batteries are AGM or anything special, they're just SLA batteries. This can be further verified by the "DO NOT TIP OR OPEN" warnings on the battery typical of SLA batteries. So I believe Toyota/Lexus is only using plain SLA batteries and nothing particularly special.

SLA batteries should have a "fully charged" voltage of 12.6v. That's what your multimeter should read when connected across the battery while the car is off. On a car with an alternator, running the same test with the car running should read around 14v. On mine in READY mode with the Dc-DC converter it reads 14.4v.

An SLA battery that reads under 12.2 volts is under 25% charged, which means in a car with a starter motor it'd likely have trouble starting the car, and your mechanic would probably recommend replacing it.

I happen to have a NEW SLA battery, as well as an older AGM battery that was just replaced as a comparison point. the SLA read 12.6v, and the AGM read 12.4v with the car off.

My NX battery, after a full day of driving and then parking in the garage for 2 hours, read only 12.1v. That's pretty critically low. It still is high enough to close the relays for the traction battery and go to READY mode; however I worry that by the morning it will have dropped below that critical level. I have currently hooked up a trickle charger to it, charging at 4A, and will check the voltage again in a couple hours.

I will be asking my dealership about this and see what they say; the car is used but new to me, but shouldn't be having battery problems already.
I will also be looking to do additional research on deep cycle or LiFePO4 batts to see if there's a better replacement. It clearly doesn't need a lot of amps to connect the hybrid battery and start the car, but there are batteries with better deep drain characteristics that the current one.

when I have time later this week, I’ll do a parasitic load test and see just how many amps are being pulled while the car is “off”

edit: after 2hrs of charging, the charger dropped the charge rate to approx 1.5A, and the battery read 12.2v. I may just leave it to charge overnight.

 

the 375LN2-MF battery is used in a lot of Toyotas. See https://www.paulstravelpictures.com/...acement-Guide/

I'd always used AGM batteries in my previous cars whenever the stock battery died and never had problems, so I'd never looked into the voltage differences until now. But I don't see any concern with using AGM instead of SLA batteries in our hybrids.

AGM batteries have a slightly lifted voltage curve than SLA.

State SLA volts AGM volts
100% 12.6 13.0
80% 12.4 12.5
60% 12.2 12.12
40% 11.9 11.95
20% 11.58 11.81
0% 10.5 10.5

So if anything, it just means an AGM battery might never get to 100% charge. Which I don't see a problem with, since it'll still be at about 90%. It also maintains higher voltages at lower charge levels, which might help with ensuring the traction battery relays can still close and allow the car to start.

 

Yes 375LN2-MF battery is used in a lot of Toyotas and it can mean anything. SLA/VRLA, EFB, AGM, some hybrid tech in between - 100% SOC voltages would be all over place for these depending on specific battery, hence the question for the manufacturer specification.
I definitely see it doesn't look as classic flooded battery as it doesn't have service openings to refill water - it should be under pressure and doing some hydrogen/oxygen recombination. The Japan made cars have different batteries with service ports and indicator.
The only other certain way to say it's AGM or not would be to take it out and move sideways to hear sound of liquid inside, or disassemble it. Otherwise you don't know. Too often people just throw random "Trust Me Bro! [TM]" claims on forums, it's not worth much without telling how do you know. Obviously I don't want to take out my battery just for fun.

I have seen voltages on my Ancel BM300 Pro battery monitor like 12.6, 12.8V when the car is off. Probably still with some surface charge left - but no car would do full saturated charge for a day to reach 100% either. Surprisingly the monitor voltage reading matched my cheap not calibrated voltmeter within 0.01 V.

Just like most current cars it doesn't charge at some 14.2V when driving all the time. But it always at 13.6-14.2V when car is in Park with hybrid system on in Ready. So you can just leave the car running in Park, or start it remotely if you are concerned about 12V battery. I don't see the issue myself yet.

 

In the interest of contributing some data to this thread, here's the Japan-made RX450H+ battery I have. Its even lower 345 CCA and marked as 360LN2-MF. It underwent two dead-car incidents in April when temperature minimums dropped to 4 C in California for a couple days, although this was after the car was parked 26 days, followed by 7 days of use. So essentially the 26 days of parking depleted the charge in it, and the charging algorithm didn't charge it enough in the subsequent 7 days of driving (my car is relatively free from any excessive parasitic drain, I think, since it survived the 26 day parked state). For those interested, the deficient charging-while-driving and charging-only-when-parked-READY phenomenon is well documented in the RX hybrid forums as well, and I'm also interested in a replacement battery for better robustness and less dead-car risk - so I appreciate the findings by Naito and others. There's at least one person in these NX forums who reported less dead car with the Odyssey AGM.

 

I don't believe any (especially recent) car charging system would revive fully discharged lead-acid battery unfortunately. You can get some life out of it if you charge it with a wall charger for a day at once. Or not if it was left for weeks dead. Or if it had plates damaged internally from impact. You would need to do full capacity measurement to see how the battery can hold charge after such adventures, but it's a hassle by itself.
Then 450h+ reportedly has plugin specific bug of draining 12V battery after charging traction battery from wall charger. Which can't be 350h issue.

It's sad that recent cars have trouble to manage ancient 12 V batteries in 2024. Hyundai showed the way how to do it in 2017 - reserve section of traction battery for 12V, add jump start button. At least show a warning just like you show for low tire pressure. But no, the industry didn't follow.
https://www.caranddriver.com/news/a1...arter-battery/

 

Yes, so this battery didn't go to zero charge/voltage - just low enough charge/voltage to not be able to close the relay/SMPS that is needed to switch to READY mode and receive power from the traction battery. I had charged the battery fully with an external charger at 5 Amp current for 8-9 Hours after the dead-car incidents. The dealer tested the 12 V battery (pictured above) and it came out fine at the 5 K mile service, and I have been running the car fine since then with no problem. Which leads me to believe that this is not a run-of-the-mill SLA, but a Toyota-specified and Panasonic made one for hybrids that is especially deeper-discharge capable than a run-of-the-mill SLA - and also survive any meaningful damage from reaching low-voltages.

Fully agreed on Toyota/Lexus fully dropping the ball on a robust BMS in their flagship luxury line-up. They may have just copied/pasted their Rav4 Prime assumptions into the Lexus lineup, without budgeting for the power draw from the much higher set of sensors in the Lexi, aside from those "illuminated door sills" vanity frills

 

People on forums complain about RAV4 12V battery too. Even about Prius. There is class action lawsuit about it, but in Georgia only, and for RAV4. Sure you may expect the BMS is the same for all TMC cars.
People complain about 12V battery on other cars too, like CR-V. Fuel economy mandates pushing to squeeze every bit of energy while driving may be one issue. Too many gadgets with dubious software quality on the same 60 Ah is another. Like you go next to the keyless entry car with a key, the car tries to wake up, and it takes significant energy every time.

 

@rch I took a closer look at both my new Motomaster SLA battery and the NX battery. The Motomaster definitely has the service openings, but they're covered by the sticker label. Feeling around on the NX battery leads me to believe the same is being done on the 375NL2-MF, the service openings are there but hidden underneath the label. Since the same battery is used in all the other lower-end Toyotas too, I very much doubt it's anything but a plain SLA battery. Deep-cycle batts tend to have less CCA which would probably cause more complaints about cold weather starting, and I think they'd be more appropriate in the hybrids but not currently being used.

My goal of trying to determine what the battery type was because there seems to be some discussions about whether AGM or LiFePO4 batts would be overcharged/damaged by the built-in charger if it was designed of something "special", so mainly I'm trying to verify that there is nothing special, it's still designed as a plain SLA charger so the standard replacement options are fully compatible.

After leaving the charger hooked up overnight, I'm still only at 12.2v. The charging rate had dropped to just 1A though when I peeked at the display prior to waking up the car and opening the rear hatch to detach the charger, I'm not entirely sure what to make of that yet.

Either way I'll give my service centre a call later and see what they say. I don't plan to replace the stock battery or anything until the warranty is out anyway. Unexpected drain Issues like this is what the warranty is for right??