Dead 12v battery Incident (merged threads)
#256
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I'm now going to use the battery charger/maintainer with 12 V & 5 Amps or 2 Amps max current, tomorrow. The instruction pamphlet suggests for maximum safety to disconnect the battery from the car's connection. Is such disconnection really necessary ? I see from many posters that they have made permanent connection to the battery to regularly charge from the outside (even drilling holes to pass wires, which I'm not going to do) - which is why I was thinking of doing, by not disconnecting from the car everytime - if that's reasonable.
Am I missing something ?
Am I missing something ?
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wrinkle (04-14-24)
#257
Advanced
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I'm getting an excellent education on car batteries (technically very interesting, however annoyed at Lexus I might be). One follow-up question: What is the definition or characteristics of a "fully depleted battery" ? Is that something measurable or understood without a full-fledged battery tester (i.e. with a multimeter ?). Thanks.
Does having to jump start at least once (I had to do on 2 consecutive cold day mornings at 4-5 C, but not afterwards), imply a fully depleted battery ?
Does having to jump start at least once (I had to do on 2 consecutive cold day mornings at 4-5 C, but not afterwards), imply a fully depleted battery ?
I used this on my vehicles . I will tell you however, that for the my hybrid 12v battery, I found that the capacity of CCA of the battery measures more than that of the factory specifications. On my non hybrid cars, it reads CCA inline with what the car battery indicates on the battery.
I have NOT disconnected my 12v battery post cables to measure CCA .
MOTOPOWER MP0515A
The best place to measure is at the battery posts, not up front in the engine compartment...at least not for my hybrid.
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wrinkle (04-14-24)
#258
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Tested my RX450h+ OEM battery, 6 months after testing it new to establish a baseline. It shows only slight degradation. Keep in mind that I fully charge it about once a month.
Readings are baseline then 6 months later;
540 / 521 CCA (345 claimed CCA)
189 / 183 MHO internal conductance
5.27 / 5.46 m ohms internal resistance
The MHO reading is the main one I'm looking at. 70% of baseline is considered end of life. I'm at 97% of baseline at 6 months.
Readings are baseline then 6 months later;
540 / 521 CCA (345 claimed CCA)
189 / 183 MHO internal conductance
5.27 / 5.46 m ohms internal resistance
The MHO reading is the main one I'm looking at. 70% of baseline is considered end of life. I'm at 97% of baseline at 6 months.
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neilsarkar (04-16-24),
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#259
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wrinkle (04-14-24)
#260
Intermediate
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The time it takes for a battery to charge depends on how deeply discharged the battery is, and how much current the charger provides.
A very conservative rule of thumb is to charge the battery at no more than 10% of it's amp-hour rating, or 6 amps in the case of the RX450h+ oem battery.
The last time I charged my RX450h+ battery, it was still charging at 8 amps (a slightly less conservative 13% rate), 3 hours later. 8 amps for 3 hours is roughly 24 amp-hours. When I looked at the charger again, at the 4 hour mark, it was in float mode, or at least 95% charged. I figure that the battery had been at about 50% state of charge, based on resting voltage and charging time.
It is extremely important that a fully depleted battery be fully charged as soon as possible after being jumped or its lifespan will be considerably reduced. A vehicle charging system will not fully charge the battery.
A very conservative rule of thumb is to charge the battery at no more than 10% of it's amp-hour rating, or 6 amps in the case of the RX450h+ oem battery.
The last time I charged my RX450h+ battery, it was still charging at 8 amps (a slightly less conservative 13% rate), 3 hours later. 8 amps for 3 hours is roughly 24 amp-hours. When I looked at the charger again, at the 4 hour mark, it was in float mode, or at least 95% charged. I figure that the battery had been at about 50% state of charge, based on resting voltage and charging time.
It is extremely important that a fully depleted battery be fully charged as soon as possible after being jumped or its lifespan will be considerably reduced. A vehicle charging system will not fully charge the battery.
The charger I got has the built-in test for the battery at the beginning and end of charging. The end of charging part I was particularly interested in, to confirm if the battery can actually hold charge after the torture from Lexus' charging subsystem. It seems to have passed, as the charger reached the final "FUL" state of 100 % charge. In my 6 month/5K service, I will still ask the dealer to replace the battery under warranty, since it has already needed 2 jump starts (and we all know how bad the 12 V charging system, all on Lexus. At least I'm doing Lexus a favor and not trying to trigger Lemon Law).
Now the next question is: Given all that we know, how frequently do I have to nanny the 12 V battery with the external charger - is about once a month sufficient ?
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#261
Instructor
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My Lexus dealer service dept told me that a vigorous documented printed out test has to be submitted with battery warranty that they have to follow and cannot just replace the battery. If they charge it and it passes tests they will not replace.
#262
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No disagreements that bigger AGM battery would be a band-aid fix - and the real fix needs to come from Lexus. That noted, what can we owners of $70K+ bricked Lexi do, when we are now loaded with a turd of a design by "ultra-reliable" Lexus - other than apply a band-aid fix and go about our lives, until and unless Lexus releases a TSB or recall notice to dealers ?
FWIW, I had the digital key disabled in-car and still had the problem. Don't have any other security system or theft cameras installed, no aftermarket accessories like dash-cam. So yes, its all on Lexus - and we are just trying to find a way of going about lives with band-aid fixes like trickle-chargers and AGM batteries.
There's at least one person in the RX hybrid forum who might ask for proceeding with Lemon law, since he had this problem right on the first week of a RX450H+ delivered.
FWIW, I had the digital key disabled in-car and still had the problem. Don't have any other security system or theft cameras installed, no aftermarket accessories like dash-cam. So yes, its all on Lexus - and we are just trying to find a way of going about lives with band-aid fixes like trickle-chargers and AGM batteries.
There's at least one person in the RX hybrid forum who might ask for proceeding with Lemon law, since he had this problem right on the first week of a RX450H+ delivered.
The local Lexus dealer has had the vehicle for ten days now, diagnosing and running tests. I'm told a (regional ?) Lexus engineer has visited the dealership during the process, providing guidance, probably asking questions. I don't have any real concrete answers, "aha" moments, or practical info on tests run, solutions found. What I am told - Thurs last week - is that they have observed the 12v battery (sitting in one of their garage bays this whole time) drop daily down to 11.8v. I'm being told this could be 'normal'. Doubt that, as my understanding is 11.8v on most 12v car batteries is a rather deep discharge.
I don't believe a brand-new $70k+ Lexus should have to have a trickle charger added daily to prevent a 'dead battery' situation with the vehicle, so yes: if this isn't resolved, we'll pursue the Lemon Law process.
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Sallywelsh (06-27-24)
#263
Instructor
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In there tests can they tell amount of parasitic draw over a time period like 24 hrs? That would be smoothing out the ups and down of the draw and give an accurate total and that is what needs to be looked at to see if it is excessive. There entire lineup is facing similar problems just seems to be more severe in some like yours. For yours to be depleted within 1 week is not normal. If they think that is normal then a salesman when demonstrating a car on the lot would have to charge the battery just to test drive. As for the lemon law especially here in NC it is almost impossible to do but in other states I have heard all you have to do is hand the keys back over with no repercussion.
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neilsarkar (04-16-24)
#264
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Any lemon law buyback is done by Lexus and not the dealership. Lexus will tell you when and how to return the car they are buying back.
#265
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#266
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It depends. VW and Audis go into a deep sleep with the car after 7 days to avoid this. Ford does it as well I believe.
Last edited by Urlik; 04-16-24 at 01:27 PM.
#267
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An update on the 12v battery parasitic draw for the new 2024 RX 450h+, where the vehicle 12v battery was 'dead' twice first week of ownership.
The local Lexus dealer has had the vehicle for ten days now, diagnosing and running tests. I'm told a (regional ?) Lexus engineer has visited the dealership during the process, providing guidance, probably asking questions. I don't have any real concrete answers, "aha" moments, or practical info on tests run, solutions found. What I am told - Thurs last week - is that they have observed the 12v battery (sitting in one of their garage bays this whole time) drop daily down to 11.8v. I'm being told this could be 'normal'. Doubt that, as my understanding is 11.8v on most 12v car batteries is a rather deep discharge.
I don't believe a brand-new $70k+ Lexus should have to have a trickle charger added daily to prevent a 'dead battery' situation with the vehicle, so yes: if this isn't resolved, we'll pursue the Lemon Law process.
The local Lexus dealer has had the vehicle for ten days now, diagnosing and running tests. I'm told a (regional ?) Lexus engineer has visited the dealership during the process, providing guidance, probably asking questions. I don't have any real concrete answers, "aha" moments, or practical info on tests run, solutions found. What I am told - Thurs last week - is that they have observed the 12v battery (sitting in one of their garage bays this whole time) drop daily down to 11.8v. I'm being told this could be 'normal'. Doubt that, as my understanding is 11.8v on most 12v car batteries is a rather deep discharge.
I don't believe a brand-new $70k+ Lexus should have to have a trickle charger added daily to prevent a 'dead battery' situation with the vehicle, so yes: if this isn't resolved, we'll pursue the Lemon Law process.
#268
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...And therefore they didn't bother dealing with the vigorous document and sent you home?
#269
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Mine 450h+ has been sitting in the dealership for 12 days. New battery did not do the trick. Today they declared they found the source of battery drain. It is a DCM that is bad. They replaced it. I have not gotten the car back yet but you may want to share this with your dealer. Since we are not the only unfortunate ones who had this kind of issue. My car is 1 month old. I am ready to turn it back to Lexus.
#270
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So it's been sitting there for 10 days. It would be interesting to see whether they can restart it after 14 days...2 weeks. if so, then that seems like a typical modern car to me? Many sites suggest anything more than 14 days standing is iffy for 12V batteries, and that has always been my understanding too.
This is just **** poor battery management system that Lexus has.
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