12 Volt Battery drain Gen5

There is no malfunction of the 12 volt battery BMS on generation 5, it is simply programmed to maximize the vehicle's economy by recharging the 12 volt battery for only 5 minutes after starting the vehicle if the temperature is above zero celcius.

As said by BISCO, accessory mode should be avoided because it consumes a lot of current from the 12 volt battery, but by putting a current clamp on the battery, we see that we have approximately the same consumption when the remote control is near the vehicle.

Now, the reason the dealer says a battery is still good while it is sulfated and damaged is because you need to charge the vehicle's battery to maximum capacity before testing.
It is not necessary to test the residual energy that the battery contains but its capacity to provide energy when full.
A dealer cannot replace the battery under warranty if their tester says it is still good.
If he performs the test without recharging, the battery will test good.
But if he recharges it before performing the test, the battery will test defective.
Many mechanics skip this step (recharging) to save time and we end up with a bad diagnosis.

For those who want to try to understand the principle, we can imagine that a new battery is like a cylinder filled with liquid, when we use the liquid, the level drops slowly and in this case, the level corresponds to the voltage in volts.
When a battery is sulfated, the cylinder becomes like a (beer) bottle with a neck.
If the bottle is half full and the liquid is used, the level will drop slowly and you will believe that the battery is good.
But if we repeat the test when the bottle is full, the level will drop much more quickly because of the neck and this will confirm that it is sulfated and damaged.
In reality, the level that drops corresponds to the voltage that drops quickly during the test.

Therefore, require the 12 volt battery to be recharged before testing at the dealership and there is a good chance that it will test defective and will be replaced.

 

Good grief, here we go again.

For some reason, @bisco always steps in to post misinformation on this particular issue whenever he sees a Gen 4/Gen 5 battery thread. With him, first it was because Gen 4/Gen 5 was badly designed, then a bad batch of factory batteries, and now it is the accessory mode.

No, the Gen 4/Gen 5 BMS software is definitely buggy, and it has been reported on this forum and others. Once something happens, and the SOC drops too low, the BMS may never charge the battery satisfactorily. Sure, the BMS will work fine, perhaps almost 99% of the time, but it doesn’t handle low-SOC scenarios, caused by such things as infrequent driving or not doing long trips, the car having sat too long at the dealer lot before being sold, forgetting the lights on, too much accessory use, etc., properly due to software bugs. That is what a computer bug is—things work fine until they crash. The point is that if your battery's SOC is low, you can no longer rely on the BMS to charge it satisfactorily due to software bugs, so you should hook up a Noco Genius.

Using the accessory mode is not recommended for any kind of car, except briefly, but it is not the root cause of the 12-V battery problems in Gen 4/Gen 5. If the BMS worked as it should, it would charge the battery just fine afterwards, even if you used the accessory mode.

I give up. You guys are on your own. LOL

 

we might be better off. it is accepted across priuschat that you should never sit listening to the radio and etc. in accessory mode. except by you, apparently