asong1

Folks,

I tried searching the LC forum, but couldn't find anything, so I'm starting a new thread regarding the safety of longevity of AGMs when installed on LC 500. I know that certain Lexus models (GX 460) is NOT fully compatible with AGM due to non-modulating charging voltage. And only way to fully charge the AGMs on the GX was to connect it to a battery charger directly as the alternator's current was limited to sub-optimal voltage, which severely limits the life of the AGM batteries on the GX models.

I have a 2023 GX 460, and due to some 'jenky' device you had to install to trick the system to up the voltage, I decided to not take any chances and just jump straight to the lithium battery. In case you weren't aware, look here:

https://www.clublexus.com/forums/gx-...m-battery.html

Do the LCs have the same problem? I'm not asking what you believe or unverified opinions, but anyone specifically test this? Most modern vehicles have smart charging system that detects the AGM and modulates the voltage to make sure that the battery is getting a full charge. But on GX, this was a major issue for those who wanted to upgrade to the AGM. I couldn't find any threads regarding this on the LC side. If someone has tested this, please confirm. I am planning on upgrading the batteries very soon, and would like to know if I can go to a cheaper AGM route (if fully compatible).

If anyone here has already jumped to AGM without checking, I would recommend that you do check and verify that. At least on the GX, when the engine is running with the AGM installed, the alternator was only supply 13-ish volts, and NOT the 14-ish volts required for the AGMs to fully charge and maintain + prolong it's intended lifecycle.

flowrider

iTrader: (9)

I have run an Optima Yellow Top AGM in my LC since December of last year with no issues. See this thread:

https://www.clublexus.com/forums/lc-...attery-11.html

asong1

I read that thread. Doesn't have any definitive information. Most people say, "I use AGM with no issues". I am concerned about the longevity of the AGMs unless correct charging voltage is applied from the alternator. I was hoping someone here tested the charging voltage with the AGM installed as they did with the GX and confirmed that the alternator was not putting out the full voltage required for the AGMs. Even with the lower voltage charging, I'm sure the car will start up and run fine. I am more concerned about making sure the AGM actually lasts 5-7 years as intended.

With the external smart charger, it will correctly, and fully charge the battery. If LC's alternator is correctly charging the battery with the correct voltage, It's one less thing I'd have to wonder / worry about. On the GX side, people were doing all sorts of crazy things like installing a diode in place of a fuse to trick the bus system to output 14.4 volts (fire hazard), then someone productized it to make it relatively safe. I was really hoping that the Lexus has fixed this issue on the LC side.. I hope someone with the right knowledge and know-how will see this thread and do some testing for all of us to put this to rest.

flowrider

iTrader: (9)

^^^^I have gauges in my LC. I will be driving tomorrow and I'll check the voltage. But as I say, my AGM has been in for a year now with now issues. Allays starts strong.

asong1

Thank you! That would be great! Charging voltage while the car is running should be 14-ish volts.

flowrider

iTrader: (9)

My Voltmeter reads between 14.1 and 14.3, staying mostly at 14.2 volts on the LC. I also have a Silverado that came with an AGM battery stock. My Voltmeter reads between 14.0 and 14.9, but staying mostly at around 14.3 volts. This is the first time I really paid attention to those readings Hope it answers your question

asong1

It sure does! Thank you so much for putting this to rest! LC knows AGM! Awesome!