Air flow around Hybrid battery pack.

Knowledge and acknowledgment are 2 separate things.

 

Goku,

I appreciate you taking the time to provide input. I am well aware that the upper and lower charge limit and the upper and lower discharge limit are variable. I am well aware that temperatures affect battery performance. I have removed one or two Gen 3 batteries. I understand the flow paths and I understand what affects them.

 

The next HV battery fan should use this technology, blade-less fan.

 

Or maybe they know better - planned obsolescence.

Pixel XL ?

 

Yes, you may have a better handle of the nomenclature of thermodynamics (buyancy vs pressure) and, yet, compared to Old Wrench, fail to grasp the electrical or chemical nature of the charging system.

First, a 10 degree or so increase in temperature of a battery module produces accelerated aging of that module because of the electrochemical nature of NiMH batteries. This means it loses capacity faster than the cooler battery modules/cells. Over time this leads to an increased unbalance across the battery modules.

Second and third, an increase in temperature of a battery module causes it to accept charge differently and to increase its leakage current (heating up even more). This also leads to an unbalanced battery pack. It's why Toyota shuts off the electric part of the hybrid when the battery exceeds a temperature threshold for the reasons of better performance and preventing thermal runaway

Fourth, the Prius does not have a charge balancer unlike other more expensive electric cars. Unbalanced battery packs cause an increase in fuel consumption. The Prius battery pack is only as good as its weakest module (lowest capacity module) - the main reason to use Hybrid Automotive's battery balancing system (charger and discharger).

 

it is said that parking in the hot sun all day in warmer climates is the biggest role. you would need a fan on constantly.

i don't believe toyota plans obsolescence, but i do believe they engineer their cars over time to get the majority past warranty.

 

O...M...G.................I appreciate you trying to explain this to me as if I'm a 4 year old, but your interpretation of my 'grasp'
is so far out in left field you may not even be able to see the stadium.

'First': I can mention it for the third time I suppose...I am well aware how temperature affects battery performance. How much more do I need to explain? Although I am nowhere near the level of someone like @2k1Toaster, neither am I a virgin in the area of batteries or battery charging. Granted, NiMH is a bit different than 100 ton lead acid batteries, but in the big picture, a battery is a battery.

As for 'second and third'? Please see previous statement.

And 'Fourth'? I never realized that...co'mon..really? I have approximately 1.5 TONS of batteries/modules sitting in my shop. Although I'm a firm believer in learning something new every day, I don't know that there's a whole lot of new info to throw my way about a Prius battery, unless it's lithium. Geez, I even have the 'deluxe' Prolong charger/discharger in my shop. You know what I use it for? To run my cooling fan when I'm testing individual modules. Other than that, it spends its time as a $700 paper weight in case I ever have a need for it, which isn't likely.

All this BS because I stated a few degrees difference in battery temperature would not account for an 8% increase in MPG or what ever? I continue to stand by my assessment, but the heck with it (much better term than I originally wrote), I surrender...............this conversation reminds me of the one with the guy who never checked his oil between 10k mile changes and was upset the engine ran low on oil. I surrendered on that one, too. On to better topics....Peace ..out..........

 

Not meant for a 4 year old. Just countering your drivel systematically...

Pixel XL ?

 

I am planning on doing this mod today, does anyone perhaps have a suggestion as to a convenient spot I can wire a 12v fan into that is somewhat near the left side of the HV battery?

also, the only tubing I've been able to score for this task is 1" bilge tubing from home depot, planned to wrap the side that is within the battery pack in electrical tape... is 1" tubing going to have clearance?

 

Like Raytheeagle said at the onset if the cars software was even the slightest bit unhappy with the temp it would increase the speed of the fan.

There is a very good reason the Toyota engineers put the vents where they did. I'm sure they did exhaustive testing and found there's a reason to put the vents there. Airflow cooling dynamics through a packed box full of hot things can be tricky.

Just do some common sense stuff like don't ride around with the car windows down. The battery cooling system is using the cabin air to cool the battery. The op says when he uses the ac the car gets hot. Dont know what that means.

Cover the battery area with insulation. I have a insulated aluminium board laying on the extended fabric hatch cover to keep direct sun off that back battery area. That really helps. And I have a very good tint job.

And the first thing I did when i bought my G2 is buy a WeatherTech window shield. Huge cross section of windshield on a prius.
If you let your Prius sit in the sun all day with no shield the cabin will get extremely hot and cook the battery all day.
Monitor the battery temps in the beginning of the hot sun event.

I see the op has a some delta going on with his packs. Battery is getting a little tired. Just about right its 8 years old.