Hi everyone, Long time viewer. First time poster. Please forgive me if I posted this in the wrong message group. I tried to post in the Gen 3 forum but it seems that I am not allowed to create a new thread as a new member unless I have made 4 posts. I thought I'd post it here as I am having the similar issue. I bought a new 2016 Toyota Prius 3 Hybrid just over a month ago. I had it installed with a remote starter and a dashcam (Blackvue dr650gw-2ch with Power Magic Pro). The power magic pro is set to cut off once the battery reaches 11.8V. The dashcam runs when the car is turned on and goes into "parking mode" when the car is turned off (it periodically records when it detects motion e.g. when someone hits on car that is parked in a shopping center). When I come back home from work, my car's 12V battery is about 12.3V. I am unsure but this seems like a low voltage to me. In the mornings, the car voltage is about 12V or 11.8V. My car has refused to start twice. When I checked, the battery voltage was about 9V when it refused to start (I checked it using the remote starter remote control). I took it to the Toyota service dealer and they blamed the dashcam and me driving short distances (my workplace is not far from my home), even though the camera is suppose to cut off at 11.8V. I turned the "parking mode" off so that the camera is completely turned off when the car is turned off. I also bought a volt meter that plugs into the cigarette lighter socket to do some further testing (I am aware that its not the most accurate testing device). I found that the car voltage in the mornings is about 12.2V. I have tried leaving the car on about 40 - 50 minutes to charge the 12V battery. I have seen it as high as 12.5V after leaving the car on for 40 minutes. But in the morning, its still about 12.2 - 12.3V (this is with the dashcam's "parking mode" turned off). Again, to me, that seems low. I left the volt meter in the car while driving and noticed something peculiar. I would see it at about 14.1V when the car is in "ready" mode. But after driving for a short while, I would see the voltage reading drop to about 12.5V. This is with the lights and AC turned off. When I put the car into neutral or park, the voltage will rise back to 14.1V. Only in drive or reverse will I see this voltage drop. Turning on the AC or lights makes no difference. I know the traction battery delivers about 14V to charge the 12V battery and I also understand (based on the info I found in this forum) that it drops the voltage after a while to prevent overcharging the 12V battery, but a drop to 12.5V is something I have not seen mentioned here. I also noticed that when my battery's charge is low (e.g. 12V as opposed to 12.3V), the car takes noticeably longer to drop from 14.1V to 12.5V i.e. it stays longer at 14.1V. Anybody have any ideas or any experience with this? Anybody tried checking their voltage of their 2016 Toyota Prius? Would love some feedback. Thanks.
You'd need to check the specs with TOYOTA. The voltage can vary by make/model of car - last I remember checking (about 10 yrs ago), was about 12.5 or maybe 12.8 cold, and in the high 13s while the engine was running. The other alternative would be to disconect the DashCam for a few days/weeks and get some baseline figures.
I am not familiar with the capacity of the gen 4 battery. No previous generation had a 12 volt battery large enough to support any drain when not in READY.
It sounds like the dash cam is the culprit for your battery drain, have you had any problems since disabling the parking mode on your dash cam?
That's way too low. I'd concur with the dealership: there should be nothing drawing current when the car's off. At this point I would either disconnect the camera, or rewire so when the car's off it's off. Then try charging your battery with a smart charger, and get it assessed with a digital load tester, to see if it's still viable.
When the car is in "ready" the voltage you see is the output of the charger built into the inverter, so that reading tells you nothing about battery health. If it's hot the voltage should be lower, if it's cold the voltage should be higher, though I'm not certain the Prius makes that adjustment. You have fully discharged your 12V battery several times. Its current health is therefore questionable, as each time it is fully discharged it suffers damage, and that damage is cumulative. I concur with the others above. The dashcam's "parking mode" is the culprit.
Thanks a lot for the reply everyone. Really appreciate the great input. To answer some of the follow up queries in the replies: alanclarkeau - I did turn off the "parking mode" for a few days to assess the battery drain (see paragraph 4 of my initial post). I should clarify that when I say leaving the car on, I mean leaving it on in "ready" mode. IMkenNY - since I disabled the parking mode on my dashcam, I did not have the battery die on me. But I still have the battery giving me about 12.2 V in the morning before I go to work. And that's with me leaving the car on for 50 minutes in "ready" mode to charge the battery. Mendel Leisk - is charging the 12 V battery with a smart charger better than leaving the car in "ready" mode and allowing the car itself to charge the battery? I thought that was the best way to get the 12 V battery charged. I am no expert on this topic though but appreciate your opinion or anyone else who is knowledgeable on the topic. I am still interested to know about the voltage drop phenomenon i.e. from 14.1 V to 12.5 V. I looked around the forum and saw some posts about voltage drop but that's to about 13.5 to 13.8 V. Has anyone else seen a voltage drop that is that low? Again, thanks to all that took the time to reply. Appreciate the opinions.
The car is designed to maintain charge of a 12 volt battery in decent condition. But for a seriously depleted battery, you really need to intervene with a charger. I took a quick look look through the 2016 Owners Manual, looking for max charging amperage, without success. I'd suggest sticking with 3rd gen limit to be safe: use a charger around 4 amp max. It should be a "smart" charger, ie: runs a charging regimen with stages, tapering off as the battery comes back, and able to be left on indefinitely if needed.
Thanks for the reply. I flipped through my manual and it says that 5A is the maximum. Thanks again for the input. Do you have an idea about the voltage drop? Does your car have the same thing?
In my v, when in READY, the inverter maintains a 14.4 volt charge on the battery. (In my gen 2, 13.8 volt) This is not the voltages the battery can maintain, it is the voltage of the inverter. When not in READY, it shows 12.8 volts, which is the battery voltage.
Thanks for the reply. I understand that. The traction battery provides the 14.4V to the 12V battery when the car is in READY mode. My question is why is there a drop to about 12.5V when I have the car in N or D gear, but when I place the car back in P, it goes back up to 14.4V? By the way, without the dashcam turned on, I am getting a parasitic draw of 250 mA. This is with all the doors closed, and waiting for about 5 minutes for all the computer / fuel pump stuff to turn off. My understanding is that it is too much of a draw.
You're right. I tested ours a year or two back. Disconnected the negative battery cable from the body, connected a wire to that cable, another wire to the body, ran both wires out through the hatch threshold, closed the hatch, and waited about 20 minutes. Hooking up those wires to my multi meter in milliamp mode, I got readings around 16~18, with occasional spikes to around 40. Not sure what the spikes were, maybe the security icon that blinks on the dash? But they didn't seem to sync, so not sure.
This is a good find for me, as my 2018 Prius Prime is doing the same thing and I'm trying to determine if this is normal or an indicator of a future issue. Did someone get any answers to this from Toyota?
This is probably intentional. I have seen similar algorithms described for other cars (not necessarily hybrids). The voltage will be raised to charge the battery after it has been discharged then reduced to 12.5-12.8V to put the battery into float operation. In the case of a GM car I was reading about it had more aggressive charging for the first 500 miles of the car's life to condition the battery. Doing this minimizes gassing and corrosion of the battery plates as well as consuming less energy. The reduction of gassing is especially important for low-maintenance batteries. kevin
I tend to feel that's the normal behaviour of the Prius's charging system , you might find below video useful as it explains how the 12V charging system in the Prius works .
