Solution to 12V issues? Disconnect 12v negative terminal sensor plug

I know that disconnecting the battery can prevent parasitic drain,
but it's such a pain to reset everything afterwards.

 

I read the OP as suggesting to unplug the connector that wires the battery state sensor assembly back to the ECU, thus leaving the ECU in the dark as to the battery's actual state. I didn't read it as suggesting to disconnect the battery.

 

I might try this to see if it'll keep my battery at a higher state of charge; now that it's no longer a daily driver.

 

I would naïvely assume some trouble code is raised

 

Well the article stated that it didn't trigger a CEL; so well see. It'll probably place a code in the error logs; but as long as the CEL remains off; I'll be happy with that.

 

They make a knob that you turn to disconnect the battery on some camper vans... That'd be the easiest way to do it. And I bet you could put some aux power on the radio to at least save those settings, but window roll down and trip meter, probably not so much...

 

Again, that would be doing something other than what this thread's about.

 

I haven’t had a problem with my 12 volt battery yet but this fix looks very promising. I disconnected a similar sensor on my F150 truck years ago after the first battery failed prematurely. On the F150 charging was minimized to slightly improve fuel economy - every little bit helps.

I have been monitoring the voltage when driving and I have noticed that in the winter my car has been charging at 14.2 volts more often.

Also, I have noticed that just testing the battery while connected in the car doesn’t give a true resting voltage because there is a significant parasitic load all the time. With the car closed, locked, and no remote within 100 feet - test leads fed out under the hatch still indicated a lower voltage (12.45 volts) than when I then disconnected the battery from the car (12.75 volts).

Also, temperature must be considered since the battery state of charge versus voltage charts are all based on room temperature.

 

Interesting, I didn’t know it was possible to bypass the 12-V battery-management system (BMS) and have the DC–DC converter produce 14.1 V at all times.

I wouldn't do it myself, but it would certainly solve the battery issues for some.

The drawbacks: (1) The battery would be slightly overcharged. (2) The fuel economy would slightly suffer.

 

No, they are telling to rig the 12-V battery-management system (BMS) by disconnecting the connector of the sensor on the negative terminal, not the negative terminal itself. What it does is that the battery is always charged at 14.1 V when the car is in the READY mode. Normally, it is kept at 12.89 V at most times when in the READY mode. This could actually help you, as your battery is always draining.

 

For sure. LOL

 

No, there shouldn't be that much parasitic drain. It takes about two minutes for the car to go to deep sleep if the key is not within ten feet and everything is closed. Perhaps with the hood open, it doesn’t go to deep sleep. Get the BM2 battery monitor on Amazon that plots the voltage vs. time. It is much better than poking around with a DMM.

 

Interesting.

 

Here are a couple of pics from my 2026.
Looks like the negative lead would have to be removed to get a peak at the numbers.

 

It seems to be called a battery current sensor, part number 28850-K0010

https://toyota.oempartsonline.com/oem-parts/toyota-battery-current-sensor-28850k0010

 

For what it's worth:
Toyota Prius - Battery Current Sensor - M20a-fxs (battery / Charging)

 

Apparently P1550.

Not sure if that would be in the ECM or something else, ie, BodyCM.

 

I saw a video just know where the guy mentioned putting the car in Ready for an hour if not driving.
If the car was parked outside, you could do the triple tap thing, but I'm not sure how long it would remain-probably times out earlier, I would imagine.