2020 Lexus RX350 purchased in Dec 2019.
Below, all voltages measured 30min after doing anything with the car, with the remote being far away. Clamp current meter (which is *highly* inaccurate) shows current around 60-70mA).
Question upshot -- can there be large *intermittent* battery drain even though measured draw is reasonable (35mA)? If so, how can this be verified?
Due to COVID, driving it only 5-10 miles per week. Realized early on that battery drain may well be a problem. Got the Scotty-recommended Topdon AB101 battery tester. Expected battery charge to remain above 25% charge (above 12.15V) for at least three weeks. However, noticed much faster drain. Complained to dealer in June 2020. Dealer replaced the battery and claimed they measured the parasitic draw to be around 35mA (which is very reasonable). However, the problem persisted, with the battery voltage going down to 12.37V (61% charge) after only *4* days.
Went to the dealer again in October -- they claimed everything was fine (35mA parasitic draw, battery tests out in perfect condition). The technician told me that with the driving I do I should only need to charge the battery every *couple of months*.
Now, if I charge it fully with a battery tender or by driving on the freeway for 30min, the measured voltage is 12.66V (reasonable). It goes down to 12.30V (50% charge) in just *3* days.
It seems to me that either the dealer's technician was lying about the measured parasitic draw or there is some intermittent large draw. Is it possible for there to be a large interimittent draw? How can this be verified?
Thanks!
Anything is possible. The only way I can think of to detect this directly is to hook up some kind of logging device. Or something that wakes up and alerts you when current rises over a threshold
I've heard of things like underhood lights coming on by themselves.
Are you leaving any phone/gps chargers plugged in? I've head of kids leaving things plugged into back seat sockets. Any aftermarket electronics? Remotes/alarms/stereos/cameras?
I've also been reading from other members here, that certain Japanese vehicles do some kind of funny EVAP business while parked. Sounds like motors coming on something. I wonder if that has something to do with it.
Disconnect the negative battery terminal. Connect a test light from the battery negative terminal and the disconnected cable. If their is a draw, the light will be on. Start pulling fuses, one at a time until the light goes out. You have found the circuit where the draw is occurring. Check all components on the circuit for ground, bare wires or corrosion in the connectors.
he said he only measured 35mA of standby which is normal. So something is happening after he walks away.
I would like to have some more concrete data the next time I go to the dealer. Does anybody have experience with the rate of battery drain in a parked Lexus? Any information would be greatly appreciated.
I don't have anything plugged in. No third party anything installed on the car. As far as I can tell, there is no under hood light on the 2020 Lexus RX350.
I have also read somewhere about some periodic activity (possibly related to EVAP) when a car is parked. However, I don't know whether this applies to the Lexus RX350 and I haven't heard any noise from the car when it's parked.
The draw of 35mA is what the dealer's technician claimed to have measured. Perhaps he did not do it correctly.
I haven't seen any concrete data.
Battery self discharge depends a lot on chemistry and temperature etc. But is usually around 5% per month.
Standby current for the electronics in modern cars also varies depending on the number of computer modules etc. but definitely should be less than 100mA.
The underhood light was just an example. Some cars light up when you lift the door handle, open the trunk etc.
I did look carefully all over the car at night to see if there were any lights visible -- didn't see anything.
I also did a calculation that should be relevant. My battery has a listed reserve capacity of 133. Reserve capacity is the number of minutes a fully charged battery at 80°F will discharge 25 amps until the battery drops below 10.5 volts. We can translate this to Amp-Hours:
133 * 25 / 60 = 55.42 AH
Once the battery drains to about 20% of its capacity, it will not likely have enough capacity to start the car Hence, what you have is 55.42 * 0.8 = 44.3 AH to "spend".
The dealer claimed that the draw is 35mA. I am in Los Angeles so it doesn't get very cold.
If the draw is 40mA, in 24 hours it draws 0.96 AH, which is 2.17% of the available battery capacity. How long should the battery last?
44.3 / 0.04 = 1107 hours = 46 days
I would be very happy if the draw was actually this slow.
Your math is correct. If standby current were 35mA, there wouldn't be an issue. Your own measurements confirm that the resting current was very low.
The only possibilities for the low voltage you observe I can think of are:
- something "waking up" when you're not there and using up the power.
- a defective battery that self discharges.
- a faulty meter
- some exotic battery chemistry with cell voltage different from vanilla lead-acid.
Which makes me wonder ... have you actually experienced any issues starting the car with the new battery?
I have used two different meters to measure my battery's voltage. These measurements are consistent. The current draw was measured by at the dealer so I am not sure about that.
I have not experienced issues starting the car since I monitor the battery voltage and charge it if it gets low. I would like to avoid getting stuck somewhere with a dead battery...
I purchased a new car, specifically a Lexus, because I was hoping to avoid hassles with my car -(
Well I looked up the battery part number you provided, and the search came up with some forum discussions. It sounds like a LOT of people have this problem.
If I were you, I would go make an account at clublexus.com and ask the guys there.
I am wondering is your Lexus battery made by Panasonic?
How can you tell who is the real manufacturer? The battery is a replacement installed by the dealer in June 2020. The only brand on the battery is "Lexus".
The model number is 00544-MF24F-630, the date on the battery is 06/20
The specs written on the battery are 630 CCA, 133 RC, 84-month.
Is the information above sufficient to determine the real manufacturer?
Also, is Panasonic-made good or bad?