Gen 2 HV battery failures in mountains?

Yes Eric I also think there is a relationship. There's always a lot of random variation in battery life, but I do think you're increasing the probability of early failure with lots of mountain driving.

The lifetime of a NiMH is clearly related to the number and depth of charge/discharge cycles, and mountain driving certainly cycles the charge much more then flatland driving.

 

Agreed. I am in this category, as I live on a mountain and have a few thousand feet worth of vertical drop between my house and the main town. The battery is full/80% 1/3 to 1/4 of the way down, and empties within a minute of going up.

I have been experimenting with speed, at I can make it from 7 bars at the bottom to 4 bars at the top, if I keep the car between 43 and 50mph steady with little variation in acceleration. The problem is that these roads have a speed limit of 25mph which dumps the charge almost instantly, not to mention bagillions of mule deer that like to jump in the road.

 

The traction battery failed on my 2001 Prius at ~61K miles and 2006 HiHy at ~26K miles. At that time I lived in south Orange County, CA at 1,200 ft elevation and commuted to sea level daily.

The 2004 Prius now has logged 110K miles and I am a bit surprised that its traction battery has not failed yet. However I can easily get the SOC gauge to 8 green bars or 1 red bar via driving on hilly terrain as you related above.

 

My details wont be too helpful yet, as it is an 06 that I purchased with ~62k in February of this year. It now has ~73k-ish, and I have noticed no abnormal behaviour or diminished pack charge capacity over the time I have had it.

However some interesting things to note is the university I went to had Prius patrol cars for campus and I know of at least two of them that park around me at night time. So that is 4+ years of 12hrs+ on time low speed (EV intensive) as well as idling for long periods just draining the battery for whatever reason, and then a few thousand feet vertical every day. Now I dont know if their batteries have failed and been replaced, but considering most are staunch anti-Prius people I am sure news of the batteries failing would have trickled through the grapevine at some point. Students as well as the campus police use them, so there are numerous students that would know all the nitty gritty, and I never heard anything bad about them. But obviously that doesnt prove the other.

 

I know this is an old thread, but just in case some of you in Denver still get notices on it, I'd like to talk with some who drive I70 to/from Denver. I had what seemed to be odd occurance where it almost seemed like my '07 would "auto-shift" to like the "B" mode, and not come out of it, even though my shifter was never in "B". I was going east into Denver and of course the tough Mt. passes, up and down, but at a point I got off for gas/food and noticed my usually great Prius coasting was gone; releasing the pedal resulted in strong slowdown, and no "coast" or "feathering stealth" was even possible, regardless of if I was on a down slope little city street or what.
The battery was not depleated, nor max-green bars, no seeming overheating, etc.)

I was worried and tried stopping the car altogether, going in to reverse, back to drive, etc. but no change. Finally when I stopped and ate for over half hour, then came back and my Prius started up and drove as usual. And I never saw this condition again. I have driven it many times on the Mt. passes to and from LA, CA (clearly not the same severity of Mts, but still it swings the HV battery all the way from depleated to full-green strongly) and that situation NEVER happens, not before or since.

So I really just wondered from those Denver PriusII owners if you have ever had something like that happen to you?

 

If the batteries are really hot, the charge in and out of them will be minimized, which might cause what you are saying but I haven't heard of it before. That would do what B mode tries to do and spin off the excess in the MG's and not charge the battery.

 

Yes, B mode allow the driver to anticipate conditions that will force the car into engine braking. Even if you do not choose B, the car will use engine braking once the HV Battery 'fills' and no more regenerative braking can be done.

Here is my best post on this:
B under the D in the Drive gears? | PriusChat

 

Hills are the Prius achilles heal. Under powered car and most people drive it like its a normal car demanding good climb and speed.

The engine and mg2 is doing all it can to meet your foot demand and that provides little power left over to charge the hybrid battery. Quickly depleted. This is exacerbated if you begin your climb with a battery on low charge to begin with and a hot day.

Many posts here in the last 5 years of owners who were left on the side of the road with severely overheated cars trying to climb big mountains with 4 people in the car and driving it like its regular car. I would be very curious to see the coolant/Inverter case change pre mountain vs getting to the top.

A simple $20 IR Thermometer from Home Depot would suffice lacking an Android scan gauge.

If you climb mountains frequently with your Prius make sure you keep fresh coolant in the Inverter loop and keep up with trans fluid changes.

 

I agree with the others about temperature of the battery, and I have experienced something similar where the car seemed to go into "no coast" mode. One of the reasons I like to run Prii-Dash software is to monitor the battery temps. You may have had elevated temps, but unless the battery cooling fan comes on full speed, it is hard to hear unless you put your ear next to the vent.

My MG2 temps go up to 60C-65C on the steep areas. Not bad, but higher than most drivers see, I suspect. It spikes up to 80C when I am at the top of my driveway on a hot day. Battery temp is never more than 50C.

But I also think that sometimes I might be fooling myself with respect to level and downhill. When driving uphill for a long time, level can look like downhill, and slightly uphill looks level.

 

Only time I have seen my car down to a bar or two was when we went up to Mount Rushmore a few weekends back. That area isn't extremely mountainous by any means, but there are a number of hills to ascend and descend. I live in the surrounding area, but that trip seemed to really drain the battery....

 

We've seen a few premature (@120-130k) Hybrid battery failures from people that live in Evergreen (or similar) and drive to Denver each day. The 3000+ ft elevation change hammers the battery.

Once in a while mountain driving is ok, but if you do it every day the battery probably won't last along as someone who drives flattish terrain. If you live in Evergreen and commute to Denver buy a Prius from California to get the 150k battery warranty.

 

Thank you all for the varied viewpoint inputs. I take it easy up the hills and was not heavily loaded, and it was not just the regen braking cutting off after full-green HV bat.....but I think it most likely it was hot HV bat situation, since I had been quite a while between stops and I have no "modding" gauges or way to tell the HV temp. I don't do frequent mountain drives, but I do have the CA Pri so I'll have the better battery warrenty! And I don't think it's the feet in DROP that is the issue, as the Vegas--CA have 3000 feet and a LOT higher air temps, but what they don't have is the long time of the Mt. stretches, and I'm not driving them after a long day of driving like when I'm going cross country.

I'll be doing that same drive again this summer, so this time I'll try making a longer stop in the middle of the pre-Denver Rockies; get the HV totally cooled down rather than driving the whole Rockies with no break. See if I can prevent it happening that way.

 

Yes, this resonates with me as well. I seemed to notice something like that in my Denver/Rockies passes also. But I've seen that also on a very small patch out of Hollywood north on 101 before 170; you'd swear it was downhill, but it just does not coast.

 

Our east coast mountains are more rolling / gentle than those young mountains you have on the west coast. I drive in what I'd call "foothills" of the Appalachian mountains on a daily basis but someone from the flatter parts of the world might call them mountains.

Whatever you call them the roads here tend to go up and down and back up and back down so much that you don't generally hit low bars but you often hit high bars.

The only way I ever see one or two bars is if it is below 32F (driving in the cold running the heat, lights, radio, wipers, defroster will drain the battery pretty good) or if I sit in a parking lot running the radio.

So unless you are doing one of those drives where you go straight up the mountain it isn't much of an issue, driving along the mountains isn't that bad.

 

I've heard the issue of draining battery while driving uphill was fixed in gen 3. Can anyone confirm (or deny)?

 

So far as I know it was fixed between Gen 1 and Gen 2. ( I never had issues in the Ozarks or the Smokeys)

 

The biggest problem causing issues with the battery is heat. In my area I have had three customers which batteries failed due to clogged battery cooling fan(dog fur) two drivers under warranty and one driver I had to replaced the battery.

 

Thanks Ovni. Are you a DYI mechanic, or you work at Toyota, or you are an independent, Pro mechanic and just get a lot of Prius customers? What area of the country are you in?