Twice today I had to jump start the vehicle. This time I was able to reproduce the issue.

• unlock vehicle
• open rear trunk
• fold down rear seat
• finish what I needed to do
• Attempt to start vehicle.. followed by click, click, click and no dash lights.

The draw just seems be too much for such simple tasks of unloading and loading of the vehicle. In the past 12 months I have had 2 calls to Lexus Roadside and the other times I had my battery booster on hand. The RX500h is driven daily, FOB is not even remotely close to the vehicle.

 

I use the ANCEL battery monitor and it often shows a low voltage and very low SoC, especially after trying to bring the voltage up. Does your formula also apply to the ANCEL for obtaining a more accurate SoC?

 

have you customized your ANCEL settings to match your battery?

 

With an Ancel, you can get an even more accurate measure of the battery state of charge.

Here, the battery starts at 12.6v and takes 2.4 hours to charge at 4 amps, so the battery state of charge was at about 83% SoC.


Here, it starts at 12.39v and took about 10 hours at 2 amps so the battery started at about 66% SoC

 

How do you do that?

Thanks

 

 

Great community of volunteer folks here supporting owners. Yes, to, @Lexuscome : The "formula" is very general to any charging - its essentially the analogous to the way one might back-calculate your gas-mileage, if they knew the gas-tank capacity, and then measured the gas they pumped in at the gas-station) .

I did not buy/attach a Ancel or other voltage monitor to the battery, so I never went this route and always used the back-calculation method I outlined above. I do have a visual monitor directly attached to the digital rear-view mirror power, which shows me the 12 V subsystem's "bus voltage". However, he correct translation is elegant if one is using a battery monitor.

Question for @Castrum : How did you find out the actual calibration/lookup table for your NX450H+ that you then put into the Ancel ?

 

Thank you

 

This is the SOC chart that I used to set up the ANCEL BM200. I used this chart when monitoring my sail boat and Airstream house batteries. You can use these values or others that you find on the internet, but I found these to be reasonable. They are easy to set up in the ANCEL software.



You can use a volt meter to monitor the 12 volt state of charge. Try not to let the battery get below 12.0-12.1 volts before charging.

When measuring the battery voltage it is really the "resting” voltage of the battery. (“rest" = no drain for several hours, the voltage at which the battery will stabilize.) that you want to measure — not after it has been recently charged. You will find that after charging the battery voltage will be higher than 12.6 volts, but after a period of rest it will drop closer to 12.6+ volts.

 

Yes, I've always maintained in this thread and in the NX thread that folks are unnecessarily getting worried about their "SoC" because their charger/monitor's "SoC from Voltage" lookup table was based on some historical ICE-based 12V subsystem/battery calibration, and not relevant directly for our Lexus (or any other modern) battery/design with a DC-DC converter and charging subsystem. As a result, people are furiously charging their 12 V battery even when when unnecessary and generally worrying more than necessary over a potentially dead battery situation. On reddit, I saw some self-professed expert lashing out based on their "that's how it always worked" outdated knowledge from ICE cars of 20 years past. So its great that you are helping bringing this realization to light for the community - that such a "lookup table" that needs to be customized in their battery monitor, to the exact battery and charging system of modern/hybrid/EV cars and charging subsystem.

 

Every source I can find indicates that a resting voltage below 12.4 results in sulfation.

I can fInd no source that indicates that there are lead-acid batteries designed to stay below 12.4v for long periods.

My theory is that the approximately monthly interval when the RX450h+ charging system reverts to a conventional >14v system for a while is to reduce battery degradation over time, perhaps eliminating much of the sulfation of the previous month.

Based on my charging of the RX450h+ battery, I do believe it actually has less than is rated capacity due to the reduced voltages it maintains. My guess is that is ok for most people, but still leaves the battery closer to being unable to start the vehicle than of it was maintained at a higher charge voltage.

 

Well, the battery is also not off-the-shelf, its sourced by Lexus from Panasonic, and its costs quite a bit more than Walmart batteries - unless that's just Lexus making money off its margin.

Even after I charge the Lexus stock/factory battery to full with external charger, the fact is, the system bus voltage NEVER goes above 12.3 V in resting state - as monitored through my digital rear-view mirror supply voltage on longer drives. When my external charger starts, it has a built-in de-sulfation routine - and it auto-exits that routine quite quickly in a matter of couple minutes, and starts regular charging.

So my money, based on my above observations, is that this is a subsystem designed for lower voltages than legacy off the shelf 12V batteries of ICE cars. Even if its not and my battery is constantly 100% of the time in sulfation but actually hasn't died in my ~2 years of ownership, I'm fine if I have to replace it in or out of warranty (will get an H6 AGM if its on my own dough) - personally, its just not worth my while to constantly worry about it and keep charging it. So long as I have Ionic Emergency Start, I'm guaranteed to never be stranded.

 

How does the OEM hybrid battery compare in price to the OEM ICE battery?

 

I don't know - but a few folks in this thread, who got their hybrid 12 V battery from the dealer, (under warranty) seem to have stated their dealer told them the hybrid one costs close to $280 - 300 if out of warranty, if my memory serves me right. This is obviously way higher than what you pay at Walmart for a 12 V battery.

 

Walmart replacement: EverStart Platinum AGM Battery, Group Size H5 680CCA for $179.84 with 4 year warranty