So my 2013 Lexus GX460 left me stranded today. Dead battery after just driving it normal for 20 minutes at freeway speeds and turning it off. Tried to restart about 20 minutes later. No battery. I got a jump then, when at home, I tested the 3 year old interstate battery with a load tester, tested ok, not great, very low end of OK. Also tested the DC Voltage at idle and revving. 13.6 at Idle, 13.75 at 3K revs. I talked to a Lexus tech who said the DCV supplied is low but maybe not ready for a replacement yet. To me, if it is not supplying 14.4V then it is not adequate.
Your opinion? (because I am on the fence for a $450 replacement unit)

 

The fact that you drove home after a jumping a dead battery suggests that the alternator is working.

The SM says voltage between 13.2V to 14.8V @ 2000 RPM is within spec. The fact that you drove home after a jumping a dead battery suggests that the alternator is working.

I would replace battery, it may be on its last leg.
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how did u load test the battery?

 

well you're interested battery is a very good brand known for its quality if it's only 3 years old I would assume it's still under warranty. Go back to where you bought it have him test it and go from there

 

i have a commercial load tester for the purpose.

 

yes. I have decided to replace the battery first then see how it goes.

 

I would check any parasitic draw if this continues

 

I would definitely check for a parasitic draw first. If it's within spec > 50ma, I would recommend upgrading your battery. Lexus has 710 CCA battery that fits perfectly. I live in the northeast. It definitely helped during the winter. Another test to try, don't raise the RPM'S, check battery voltage at idle with as many electrical systems turned on as you can. All the lights, radio, rear glass/mirrors, and blower motor on high. If you are at 12v your alternator is fine.