Rear battery fan

floggit · June 21, 2017

May have been running before but first time i really heard it this week. Took me a second while driving to realise what it was.

Finzky · June 22, 2017

Never heard this before, where it`s located? How it sounds like? Just to be prepared and don`t panic...

Britprius · June 22, 2017

On 6/21/2017 at 4:24 PM, floggit said:

May have been running before but first time i really heard it this week. Took me a second while driving to realise what it was.

Almost certain to be the hot weather that caused it to run. In the CT as with the Prius it is recommended that you run the AC with the windows shut so that the air intake for the Battery cooling draws cool air. Make sure the air intake is kept clear, and not covered by anything. If you carry dogs in the car check the air intake and fan for obstruction by hairs.

Heat is something that degrades the NiMh batteries.

John.

floggit · June 22, 2017

1 hour ago, Finzky said:

Never heard this before, where it`s located? How it sounds like? Just to be prepared and don`t panic...

Its located just inside the door by the seat bolster on the rear o/s . Just looks like a grille.

6 minutes ago, Britprius said:

Almost certain to be the hot weather that caused it to run. In the CT as with the Prius it is recommended that you run the AC with the windows shut so that the air intake for the battery cooling draws cool air. Make sure the air intake is kept clear, and not covered by anything. If you carry dogs in the car check the air intake and fan for obstruction by hairs.

Heat is something that degrades the NiMh batteries.

John.

Thanks john, yeah had about 3 rear seat passengers in 6 months and im not one for carrying junk so it will never be covered. Its was blisteringly hot with windows shut and a/c on high . That and the stop start journey kicked it in. May have run before but ive never noticed it. Good advice

McRattlehead · June 22, 2017

Funnily enough i had a look at the ducting on my car on monday,only a light coat of dust inside,the fan itself looked fine,gave them a wipe with a static duster.Got the idea from a recent article in car mechanics which featured a prius,which has a similar arrangement.

Britprius · June 22, 2017

The Battery cooling fan works on a number of speed steps dependent on temperature. Ar the lower speeds it is all but silent, but still acts as a vacuum cleaner for the air around the rear seats. It is not uncommon for the fan to become completely blocked with pet hairs where owners carry there pets either on or behind the rear seats.

The result unless cleared can be a failed Battery. Unfortunately there is no check or clean the fan in the service schedule even at 60,000/120,000 mile big services.

It can be a good idea to remove the intake grill, and fit a piece of vacuum cleaner filter cloth trapped behind it when re fitting. This can be seen and cleaned easily as it changes colour when becoming blocked.

John

NemesisUK · June 22, 2017

57 minutes ago, Britprius said:

It can be a good idea to remove the intake grill, and fit a piece of vacuum cleaner filter cloth trapped behind it when re fitting. This can be seen and cleaned easily as it changes colour when becoming blocked.

Even though the system was designed without such a filter? Would the airflow be restricted, enough to force the fan to run more quickly than otherwise required?

Verbout · June 22, 2017

Wouldn't it be best just to check and clean regularly?

Britprius · June 22, 2017

It is a bit of a pain to dismantle the rear trim of the car to get to the fan but that would be the best way. The vacuum filter cloth has very little resistance to air flow so is a reasonable alternative removing the need for disassembly of the rear trim, and cooling ducts.

The fan motor it's self is a three phase brushless motor, and is very efficient only drawing around 1.4 amps from the 12 volt DC supply at full speed

John

Verbout · June 22, 2017

It's worth trying.

McRattlehead · June 22, 2017

41 minutes ago, Britprius said:

It is a bit of a pain to dismantle the rear trim of the car to get to the fan but that would be the best way. The vacuum filter cloth has very little resistance to air flow so is a reasonable alternative removing the need for disassembly of the rear trim, and cooling ducts.

The fan motor it's self is a three phase brushless motor, and is very efficient only drawing around 1.4 amps from the 12 volt DC supply at full speed

John

Yes quite a fiddle removing various clips and bolts,not all are obvious,i managed to gain access without removing rear seats,took me just over an hour in total.

NemesisUK · June 22, 2017

2 hours ago, Britprius said:

The fan motor it's self is a three phase brushless motor, and is very efficient only drawing around 1.4 amps from the 12 volt DC supply at full speed

John

Doesn't it draw it's power from the traction Battery? The very Battery it needs to cool?

NemesisUK · June 22, 2017

1 hour ago, McRattlehead said:

Yes quite a fiddle removing various clips and bolts,not all are obvious,i managed to gain access without removing rear seats,took me just over an hour in total.

And what did you find? Masses of fluff?

McRattlehead · June 22, 2017

None at all,just a small coat of dust, as would normally occur on the dash etc.

On a few off shift days at the moment and sometimes perform maintenance tasks that are not included in a normal service plus i have a curiousity to know how things work.I have been known to dismantle tv`s hi fi`s cookers etc,my family just love this .Sometimes i even get them back together.

Britprius · June 23, 2017

12 hours ago, NemesisUK said:

Doesn't it draw it's power from the traction battery? The very battery it needs to cool?

Very indirectly it does. It is powered directly from the 12 volt Battery, and this in turn is charged through a DC to DC converter from the traction Battery. The motor is of the same type, "but smaller" used to drive the gearbox oil pump.

There would be a small efficiency gain if all the electrics were powered directly from the traction Battery, but that would mean having most of the wiring carrying 280 volts DC not conducive to safety.

John

NemesisUK · June 23, 2017

Must admit to thinking that all electrical consumers were supplied from the traction Battery, once the hybrid system was Ready. Sure I read that somewhere?

Britprius · June 23, 2017

8 hours ago, NemesisUK said:

Must admit to thinking that all electrical consumers were supplied from the traction battery, once the hybrid system was Ready. Sure I read that somewhere?

Technically correct. Although most items in the hybrids are run from the 12 volt Battery this still must be charged by some means. The Toyota/Lexus hybrids do not have an engine driven alternator that other vehicles have to serve this purpose.

The high voltage from the traction Battery is stepped down for charging the 12 volt Battery. The reasoning behind this is that at times the engine does not run even with the car moving so a conventional alternator would not work "same goes for the AC".

The traction Battery gets it's charge from either of the two motor generators in the gearbox as as long as the engine is running "with the car in any gear position but neutral" or the car is moving without the engine running one of the generators will be producing power to charge the traction Battery. In neutral this is not possible, and both batteries can become discharged if the car is left in ready mode, and neutral.

The AC is supplied directly from the traction Battery by it's own inverter. The power steering on the GS450H runs from another step down supply from the traction Battery running at 48 volts.

John

stormchaser · June 23, 2017

Heard mine very faintly going last night. First time since I've had I've noticed it.

Sent from my Iphone using Tapatalk

floggit · June 23, 2017

1 hour ago, Britprius said:

Technically correct. Although most items in the hybrids are run from the 12 volt battery this still must be charged by some means. The Toyota/Lexus hybrids do not have an engine driven alternator that other vehicles have to serve this purpose.

The high voltage from the traction battery is stepped down for charging the 12 volt battery. The reasoning behind this is that at times the engine does not run even with the car moving so a conventional alternator would not work "same goes for the AC".

The traction battery gets it's charge from either of the two motor generators in the gearbox as as long as the engine is running "with the car in any gear position but neutral" or the car is moving without the engine running one of the generators will be producing power to charge the traction battery. In neutral this is not possible, and both batteries can become discharged if the car is left in ready mode, and neutral.

The AC is supplied directly from the traction battery by it's own inverter. The power steering on the GS450H runs from another step down supply from the traction battery running at 48 volts.

John

Now ive indirectly learnt something here... if stationary for a period of time id shift to neutral to save the car holding in gear but i guess its better to stay in drive?

Verbout · June 23, 2017

37 minutes ago, floggit said:

Now ive indirectly learnt something here... if stationary for a period of time id shift to neutral to save the car holding in gear but i guess its better to stay in drive?

Britprius · June 24, 2017

19 hours ago, floggit said:

Now ive indirectly learnt something here... if stationary for a period of time id shift to neutral to save the car holding in gear but i guess its better to stay in drive?

Park will equally do. Neutral is the only "gear" that the car cannot look after it's self.

John.

smoneill · July 30, 2019

I service my car (2015 CT 200h) at a Toyota dealership as there isn't a Lexus nearby. The latest list of recommended services came back with a "hybrid Battery service" , when I pushed for info on this service they said it's cleaning the fan. I've not had any issues and only have 56,600km on the car. Work from home, no kids/super rare to have anyone in the back seat, and my dog doesn't shed a lot (bulldog) and is very rarely in the car. From what I can find this fn cleaning seems to be everywhere online related to the Prius, and the one Lexus document I found from 2014 recommended it for severe use vehicles only (taxis etc). Is this a service scam, or have others required this? The cost seemed ridiculous... Thanks!