High Altitude Battery Life

Sorry but you are wrong. Your engine has 60,000 more miles than your sons car. Not the first 60,000 miles either but the 4th 60,000 miles. That’s a lot of wear, blowby, valve wear, cam wear. When is the last time you adjusted the valves? A battery does not care what altitude it’s at (within reason), however the engine does. Your engine could not keep up the speed you were driving and recharge the battery also. Your engine is just too worn.

 

In outer space (talk about high altitude!!), they don't use internal combustion engines. I wonder why. LOL! Nope. They use ....
BATTERIES.

As @Skibob said, engines lose power the higher you go. Hence the super chargers on WWII bomber engines. At sea level, a new Gen 2 ICE is rated at 76 HP. The online calculator I used said that at 8,000 feet (rough elevation of Angel Fire, it would lose 18.24 HP giving you only 57.76 HP on a perfect engine. That's really going to work the battery. The older the engine, the more it'll work the battery and the older the battery, the less work it can do. At 10,000' the ICE loses 22.8 HP, so the passes make it even tougher on a hybrid. The rule of thumb I used to hear was a loss of 30% at 10,000 feet.

So it can't be that the altitude hurts the battery or else batteries would not work in a vacuum. Altitude definitely hurts combustion, though.

 

And thats a brand new engine, not an engine with 240,000 miles on it. That extra 60,000 miles is a lot of extra miles.

 

My individual understanding* is:
Batteries do not care about altitude
Engines do. WWII fighter planes all had some form of supercharging to increase HP at high altitude)



More and more I am convinced heat degrades our High Voltage batteries, not time, not mileage, not number of charges; Heat. (the others can't help)
So descending long hills, use B so you do not charge too fast and over heat. Use sunshades where it might get over 100 F

* I have no authoritative source for any of this

 

I have noticed the same thing for many years in my old 2005 Prius. It seems the target SOC (state of charge) is actually dependent on altitude. It sort of makes sense that if you are at sea level, you might as well charge to nearly full BECAUSE THERE IS NO SIGNIFICANT DOWNHILL that you can go down to REGEN a lot of energy to capture. You can't drive down into the ocean!!! So why then leave a large amount of empty capacity in the battery? On the other hand, the higher the altitude you are at, especially if you are at 14,000 ft. in the USA, it is highly unlikely that you have any where to go BUT DOWN, in which case it's best to have as much empty capacity to capture REGEN from downhill braking as possible. It could be that this general algorithm maximizes fuel efficiency on the average, though it may guess wrong when, for example, you are in a high plateau at 8,000 ft. in Colorado, and it picks a low SOC because of the altitude, and you need to go over a pass at 12,000 ft.

 

There is no altitude related algorithm. That would screw up the whole works. Beside, it's unnecessary. Simple physics takes care of it naturally. When you're going up hill at 500 feet above sea level, the engine needs help from the battery because you're asking it to do more than it can do alone. When you're going up the same angle at the same speed at 12,000 feet, the engine needs more help because you're asking it to do even more than it can alone because now it's oxygen starved.

In either case, once the battery SOC gets low enough, it tells the engine, "Sorry buddy, I'm tapped out." Then the car goes slower because it lost about 40 HP when the battery ECU called time-out.

The only thing elevation has to do with it is how much help the engine needs in getting you up the hill.

 

Exactly. The engine produces less power at higher altitudes so it needs more help from the battery and it takes more time to recharge as the reduced power of the engine has less excess capacity to charge the battery.
One thing I have noticed about going downhill is the car kind of puts itself into B mode when the battery is as full as it can get. The arrows will stop pointing to the battery and the engine will speed up
Another factor to consider is a car traveling at the same speed on level ground will need more power at sea level than it will at 10,000 ft. The air is thinner at 10,000 ft so there is less air resistance.

 

Correct as per ICE airplane “mpg” (gallons per air mile flown) when I cruised at different altitudes. Similar effect noticed with Prius driving across the inter-range plateau area out west where we were at 9,00-10,000 feet MSL for most of the day, and managed 65 mpg at 65 mph over a 3-hour stint. Decreased air resistance plus a tailwind (we were driving west to east) made a remarkable difference.

 

While the ICE will speed up, it isn't true B mode. I've posted figures elsewhere, from a hill where real B mode produces over twice the engine RPM of 'B-like' D mode. And real B mode actually holds the car to approximately the posted speed limit (on that particular road and slope, in my larger-engined Gen3), where 'B-like' D mode has considerably less braking power so allows the speed to creep up far beyond PSL.

So while the style of actions are similar, the degrees are very different.