salimshah

Hybrid [450H] does not use the 12v battery, so the 12v system should not experience voltage spikes during start. Has any one checked the switched source on the hybrid to see if the 12v is switched off during "push to start" on 450H.

Curiosity is killing me.

Salim

tempestv8

I'm not sure how one could go about doing a check on the switched source? I don't know what this "switched source" is that you're referring to..... And why would the 12 volt switched source go off when the engine is cranked?

The only easy/practical way that I could come up with to test what I think you might be asking is that if I were to turn on the halogen fog lamps and observe them to see if they dim like a conventional engine when the ECU decides to crank over the engine. Would this might be a valid test?

tus

On many cars, when you turn the key to the crank position may things that are running off of the battery get turned off since all you really care about is the starter and ECU. I suppose the theory is you would want to use all the power available to start the car so listening to the radio or the dashboard lights are things you can live without for a few seconds.

I was thinking he could put the RX in accessory mode by pushing the start without the brake pedal down. Then push the pedal down, and hit the start again and see if the radio cuts out while starting. Given that the thing starts and stops all the time without having the radio cut out I'd guess the 12v system is going to stay on (which does bring up the question on if you are draining the 12v when the thing is moving under the power of the traction battery alone, and does the regen braking charge the 12v and traction battery?)

Htony

12V aux. battery is keeping the brain alive, if it is so, how vehicle could start? 12V DC charging source is tapped off from propulsion/starting battery (~220V) . I believe there is a Youtube tutorial put up by a college about Toyota hybrid system. This college officially train hybrid technicians for Toyota. I used to own 450h,went back to regular vehicle realizing not much fuel saving in extreme cold, constant worrying of 12V battery going, poor performance in heavy snow. 450h was the only vehicle made me stuck going out to my cabin in the Rockies. BMW M5, Acura MDX, Audi SQ5, MB GLC had no problem even plowing thru EOD snow berm. Think 450h has poor front to back weight balance making it weak in deep snow. Our cabin is at 1090 meter altitude in the Rockies. Snow fall is heavy in the winter. Toyota 4 Runner or ,FJ has no problem.

Droid13

My thought is "No", the 12V system stays active. As far as I can tell, the only difference going to Ready mode is the 12V "charging" system in energized. I have seen on the built in diagnostic screen, which displays the 12V system voltage as one of its functions, that when switching from accessory mode to ready mode the voltage simply rose to about 14V on the display. All the computers, radio, lights, etc stay operational before, during, and after transition to Ready state. I often, in fact, turn accessory mode on first if I'm waiting for my wife to get in the car, just so the computer can boot up so I can be looking at the rear camera instead of the Lexus logo on the screen after I startup and go into reverse.

tempestv8

I concur with Ando, In my personal assessment, when the engine is started by the ECU, various 12 volt items like headlights/fog lights, dome lights, radio, etc. remain on. As a matter of fact, there is not the usual voltage drop when the starter motor engages, because the power to crank the engine is not coming from the 12 volt battery at all. So the overall 12 v voltage stability is far better in the hybrid compared to the RX350/RX270 voltage scenario.

Htony

Electrical/Electronics part of hybrid system is by NEC/Denso. Actually Toyota has a stake in Denso. Even in non-hybrid German cars some has two batteries. One is called auxiliary battery.