EV mode not engaging and rear battery fan always on

Just guessing here, but if you are gently accelerating and cruising conservatively perhaps you are just using the electric motor. It follows that the HV battery will deplete and the engine will only come on to top it up. The Prius needs to be driven less conservatively occasionally and I find that keeps the SOC fluctuating. Incidentally, as long as the ICE stops the HV from discharging when too low, it's working as it should.

 

Never acted that way until the issue with the main battery cooling fan. Seems to be related to temperature as it was cooler the other day and the bars did not drop as fast. A/C compressor load draining the battery?
Dealer service manager admits something does not seem right.

P01M ?

 

I'm having the same issue with my 2010 prius. When I accelerate sometimes the battery fan kicks on. I have no warning lights or issues. Did the issue with your get resolved?

 

welcome!
it might be as simple as cleaning the fan and intake grille. hopefully nothing more serious.
how many miles on her?

 

I bought it at 115k miles it now has 138k as I drive for uber. Everything was going good until I got the air filer and second oil change. I took it back to the mechanic and we cleaned out the hv battery fan and the vent. It still kicks on after I drive for a while. I goes off but when it kicks on it's at a moderate rate. What could be causing this?

 

has the weather been warmer? the fan has 6 speeds, and if the battery needs more cooling, the sound gets louder.
it can also be a warning sign of the hybrid battery getting weak. hopefully not.

 

I think it automatically works it out - charging or discharging happens continually in a hybrid environment - and, both cause heat, which needs to be dispersed.

It could be that your older fan is a bit noisier than a brand-new one, but still working fine. Personally, I can't hear mine on my Gen4 unless I put my head near it - but that could be my hearing too.

Maybe someone knows how to check that it is working correctly?

 

I started when the weather was warmer. It's been cold here in the Bay Area and I've not heard it kick on as much. Also the battery was replaced at 115k before I bought it. I did just find out however it's a refurbished battery with a 5 year warranty.

 

that makes sense.

 

Still doesn't explain why it kicks on. It's never done this before.

 

This is the Gen 4 FORUM - I've reported your posts to the Moderator - hopefully he'll move them to the Gen 3 FORUM, where you'll get more relevant answers. There were considerable changes to the entire Hybrid Synergy Drive between Gen 3 and Gen 4.

 

It may be that there is some imbalance on the fan making it sound louder. See if you can access the fan itself and check if the blades are all clean and intact and see if there's anything obstructing the fan.

 

it may explain why it kicks on; 1) warmer weather 2) refurb battery.

 

Agree with @bisco. I expect that you'll soon be getting a big ol' red triangle on your display. Refurbished batteries don't last long. Are your HV battery level bars going up and down more quickly than they used to?

 

I can't speak for the Gen 4 (mine is a 2017 Prius 2 as well), but my 08' Gen II's HV battery fan would not turn on till the battery was above 98 deg. F. I've always used a ScanGauge to monitor various systems, being from an Engineering background. There still are no X-Gauge codes for the Gen 4 traction battery as I'd like to keep an eye on the temperature during warmer weather. I have not however heard the fan come on. There is an experiment you can perform that was useful for me with the 08'. Sometimes when something peculiar was occurring, I found that by disconnecting the 12v battery for a few minutes then reconnecting, which basically reboots all the computers, many times the problem would be fixed. No guarantee of course, but you never know. The bottom line however is finding out what the main battery temp actually is.

 

I think I found the issue. I'm going to get the actual fan replaced.

 

Hope that's all it takes.

 

all the best!