Deep cycle just means that it is designed to be able to be deeply discharged without much loss of capacity. A starter battery is not meant to be deeply discharged and will usually suffer loss of capacity from deep discharges much more rapidly than a deep cycle battery. A deep cycle battery will still suffer sulfation if left discharged for long.

Basically, a deep cycle 60A-H battery and a 60A-H starter battery have the same capacity. It's just that the starter battery isn't meant to use that full capacity often, while a deep-cycle battery is. They are also both meant to be kept fully charged most of the time for longest life.

A small clarification - that picture is from my RX450H+ - Lexuscome simply reposted my picture, since the question from Markfm was about the Ionic.

So this battery is not technically from a RX350H. Mentioning this since the 350H has a different drive-train than the 450H+ after all - so not sure what battery A-h and CCA is actually in the 350H, or if its the same. I remember vaguely that the 12 V batteries on NX350H and NX450H+ are somewhat different, so I suspect the RX350H 12 V battery may be different than in the picture. For the problem at hand (charging algorithm, not the battery), it may not matter.

Given I do not charge my 12 V externally to make up for Lexus' deficiency, I tried to get my Lexus dealer to do a capacity test with their tester at my 5K mile service - I simply got ignored. For my 10K mile service, they first charged the battery externally, then they took a picture of the tester screen that states "Good Battery", measured CCA as 550 (and its rating at 345), and measured volts at just above 13 V (since they just charged it - they probably still had the charger connected when taking the picture, and showing the charger's voltage!)

Pretty much any autoparts store up here will load test a battery. I might just do that for free.

The dealer sent me a video showing the battery test results. It was definitely bad and their tests showed only 1 minute to conclude that. They replaced my battery, washed her up and brought her back by the end of the day. All in all I am a little bit happier. I am curious though if the replacement battery is same specs as original or if they have gotten smart and changed it.

Sorry Wrinkle and my apologies to all. I posted the Wrinkles image by mistake. I had downloaded Wrinkle's to help me install mine. My old battery was 20H/563CCA/60AH and dealership replaced with 84 mo. 540CCA/100RC.

Doesn't show battery but stats are shown in reply.

100RC means the battery will drop to 10.5v in 100 minutes with a 25 amp load. One conversion factor i found gives me 42 A-H, but a conversion chart i found says 100RC is equivalent to 63 A-H. I believe the chart is closer to reality because the conversion factor doesn't take Peukert's Law into account.

Peukert's Law basically says that the higher the amp draw, the lower a battery's capacity will be. RC uses a straight 25 anp draw where A-H uses 3 amps in the case of a 60 A-H battery @ 20hr.

The 12V battery issue is not unique to Lexus. My last car, a '22 Subaru Outback has 100+ pages in the Subaru Forum of battery failure reports and Subaru launched a campaign to reimburse owners for the cost of a new battery if still under warranty.
I'd imagine that is is a value engineering decision from the manufacturer to save on build costs.

The issue for Lexus, in the vast majority of failures is NOT due to the battery, but instead the charging algorithm. As Smartin’s results conclusively shows, a larger capacity battery doesn't eliminate the problem - because the car doesn’t sufficiently charge even the 60 Ah battery.

And I posted about my experience with the dealer not because I’m too stupid to find a battery load tester - but to demonstrate the dealers’ attitude towards the problem, which is gaslighting.

Well, dealer called me. They said Lexus is not authorizing a battery replacement and corporate is telling them to just charge the battery and give the car back to me. I am not happy!

Ah, ok. I appreciate the Cliff Notes, I don't have the bandwidth to read-up through 68 pages of this.

The Subaru scenario were just cheap manufacturer spec'd batteries that failed in many models in the past 5 or so years. I didn't even bother waiting and went out and bought a new HD Odyssey for mine and when I traded it in for a Crosstrek for my son, put the original back in and swapped the Odyssey into his new Crosstrek. Odyssey is an excellent battery btw. I feel like I read an informative article that took a deep dive in to the manufacturer work of auto batteries and there are only a few actual manufacturers and a bunch are private labeled etc..

Man, I am so with you about dealers. I personally LOATHE car dealerships. And not just sales but parts and service the same. I keep it to a minimum and only visit for warranty related items. I have ALL of my service done my a private shop, aka dealer alternative (what the better examples call themselves these days). Current dealer labor rates are nearing $300/hr for labor these days which is obnoxious. I have obtained every one of my cars for the past decade via email/internet and had them shipped to me.

Smartin's latest post, 1/25, shows using a larger, AGM, Odyssey battery does help, if not a cure-all.

"...But I do think it helps. I used to use a trickle charger whenever the battery dropped to 50% state-of-charge; this required charging (on average) every 3.3 days regardless of how often I drove the vehicle...I think it’s manageable now without trickle charging..."

I do still see it as a combination problem, they simply missed the boat on the design point for needed electrical power: charging algorithm likely could be improved (charge the 12v to a higher SoC); unintended parasitic drains (or expected parasitic drains are higher than designed for) need SW updates; adjust the battery capacity/chemistry given the charging algorithm and actual parasitic drains. You can toss in some plain bad batteries (QA/QC, it happens), plus any sulfation from sitting in the dealer's lot without properly maintaining the battery (due to the parasitic drains).

I have to disagree - fundamentally the problem is only the charging algorithm, in the vast majority of cases. Even if you start the car's life with a perfect battery, but you will end up degrading that perfect battery unless you take pains to either externally trickle charge AND/OR let the car sit around Park/READY mode - because the charging algorithm is deficient. This is not how normal cars are supposed to work. The charging of the 12 V should be normally accomplished sufficiently during regular driving. There is plenty of data in this thread by multiple people, and even in the multiple videos by LSFT in Youtube, documenting this deficient charging algorithm.

Quoting below what SMartin noted after your quote ends: Instead of needing trickle charger + Car sitting in Park/READY to charge the battery, with the Odyssey, its only Car sitting in Park/Ready this is needed by SMartin, but sitting in Park/READY mode is still needed. This is because the root cause of the deficient charging algorithm DURING DRIVING is still present despite the larger capacity AGM battery installed by him.

"I do let the car recharge the 12 V battery a few times a week. When I pull into the garage, I let the car sit in READY mode and in PARK (in EV mode so no engine exhaust) for 10 - 15 minutes (while I check email on my phone). This lets the DC-to-DC converter charge the battery."

Lexus knows it - that is why they are refusing to replace the batteries especially if their tester is not showing problems. But they won't take ownership of the root cause, unless forced to by a Class Action or such means, because they already have our money.

Very close to what I got, conversion formula gives a 100 RC battery 41.67 Ah. Ironically the new battery the dealership installed is less Ah, CCA and RC than the origional, and lower than the manual's recommended for RX 350h (20HR/60Ah or greater & CCA563 or greater). Luckily, the new battery is holding despite the algorithm afflictions but I'm driving a lot and in Florida for a few months. I suspect if I was back up north? Still it charges too low most of the time using "basic voltage control". Occasionally it will charge higer for an extended period, when it reaches one of the "Constant Voltage Control" parameters (e.g.cold temp and low SOC). I think I witnessed constant charge around the "20 Hr of operation" parameter. All that makes me think Lexus could alter the algorithm, but possibly they're afraid the mpg would decrease. More ICE and traction battery used to charge the auxillary battery lowers overall mpg, beyond the already lower than quoted mpg I get. I'm grateful that I have a pretty good dealership, so far, as compared to other folks reports in the thread. Good luck and hang in there to those mistreated by a dealership. Also thanks to all the great info provided!

Thanks, now I understand.

I'm still curious about the little "wakeup" type activities shown from this older post, looks like they're happening every 30 minutes: https://www.clublexus.com/forums/rx-...l#post11780502

Again, thanks for your insights!

Yes, having lived through technically fascinating, but practically highly vexing experience with a brand-new Lexus - has been, well, quite interesting, to put things mildly. But I have been quite okay living with the problem since finding the Ionic.

So those, wake-up type activities can be definitely part of the problem - which is why we have to keep the car fobs within Faraday pouches or 20 feet away from the car, keep Bluetooth-pairing chargers/garage-door-openers and such stuff physically or electrically disconnected from the car, too. Because they make that fundamental problem even worse.

However, even if you manage to avoid those problems in order to have a dependable car - you still have the fundamental problem of the charging algorithm. And while you can take pains manage all those other problems, you can't fix the charging algorithm, only Lexus can - only if they were prepared to spend some dough for the sake of taking care of customers. Or it could very well be what Lexuscome noted - that fixing the charging algorithm problem would reduce the mpg ratings, so the problematic charging algorithm is actually a "feature" of Lexus, not a "bug".

Each day you run into a new failure-mode of the fundamental root-cause: Yesterday I saw a Rav4 Prime owner having a dead battery while plugged in. So its not just Lexus-wide, even in Toyotas, but to a significant lesser extent. And by the way, here's some very interesting measurements an NX450H+ owner made, for current drain from the 12 V battery, when the traction battery charger is plugged in - which is why we 450H+ owners can't afford to keep the EVSE plugged in for longer time than actually charging the traction battery.