Engine revving transmission slipping?

This was happening to my '09 about 2 months after I got it and it turned out it wasn't really the transmission slipping I don't know if that's even really possible It was the hybrid battery going a far as soon as the hybrid battery was changed the slipping nonsense was gone now I'm not sure I haven't tried it I'll do it today I'm getting ready to get in the car I don't think I can make it slip like I could before the hybrid battery replacement before the hybrid battery replacement I could get on the gas and the ribs would go up just like a clutch is slipping just like a manual car now I do not believe that that will happen I've gotten on it a few times and pretty much nothing but solid acceleration no slipping nothing. I'd look into that pretty quickly check your hybrid battery real good hell maybe tomorrow all the lights will come on because as soon as I notice the slipping. Lights were on within a week all of them and the hybrid battery was flat on its face I was running on the ice engine 37 mi to the gallon pretty much no hybrid happening at all.

 

It's a relatively common experience for when the battery reaches a low state of charge. A similar thing would happen if you sat in a parking lot with the AC on and then tried to drive away when the battery was at 2 or 1 purple bars. The car would seem like a dog. The car always keeps a charge limit and discharge limit on the HV battery. These limits vary based on the current state of charge, battery temperature, etc. When everything is relatively normal, these limits are about 25kw. I've seen as low as 7.5kw (?) on an extremely cold morning. Once your battery got to a low state of charge on that incline, the discharge limit likely dropped way down and now it's all on the engine. That low state of charge may be due to your engine not being able to make enough power at that elevation to maintain your desired speed, so the battery had to provide some assist, eventually depleting itself until the safeties kicked in.

 

As mentioned, your experience is "normal" for a Prius driven up an extended incline. Under most conditions the car uses the engine and electric motors together to provide locomotion. How much gas vs electric is a constantly changing balance that the hybrid control ecu figures out on the fly.

If you try and accelerate (or maintain speed uphill) when the HV battery is at a low state of charge, the ecu will limit motor function. Then "all" you have to move the (heavy for its size) car is a detuned 1.5L engine- which has to spin at 5000 rpm.

I wouldn't do this over the Rocky Mountains, but you're not hurting the trans. Some people pull over on the highway (if possible) when the battery goes down to 1 bar then "force charge" it up to 8.

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The above explanations are correct, there are no torque converters or clutches to slip like in a conventional transmission. But loss of battery capacity especially on a long uphill run will force the continuously variable transaxle to change the gear ratios, similar to shifting down in a manual transmission. This causes the engine to rev up.

It is very possible your hybrid battery has limited capacity left after years of use. Even when the bars are high, limited capacity means the battery will discharge much faster than when it was new. These batteries were not very big to begin with. Reduced capacity may not be an issue with normal highway driving which allows some engine and regen charging. On relatively level highways, the gas engine has enough power to keep the hv battery charged and still maintain speed. However going up mountain passes allows little room for concurrent charging, overall power needed is very high and regen is mostly nonexistent. The charge it does have it can deplete early if the battery has reduced capacity due to age.

The gen3 and gen4 engines have more power and rarely have these issues.

 

I once let my sister drive my Gen 1 and she was holding it around a steady 80 MPH going up Afton Mountain, which required a constant contribution from the battery the whole way, and I was just watching the state of charge on the ScanGauge counting down toward 40%. I knew at 39% she was going to immediately lose electrical assist and discover that a 71 HP gasoline engine by itself does not push you up a mountain at 80 MPH. But our exit came just as it was hitting 40%.

My Gen 3, with the larger 98 HP engine, is able to take the same grade and even slightly charge the battery. With me driving, anyway, and I'm usually not pushing it to make 80 MPH uphill. It still definitely isn't loafing though.

A gauge showing you your battery state of charge is useful in the mountains. If you have a long climb and you notice that your state of charge is steadily declining toward 40%, you can move into a slower lane and ideally find a speed where your energy output is sustainable. That way, you will not be surprised by the sudden loss of go when you cross the 40% mark.

 

Even in all gas cars all motor cars . Big engines cars . In the mountains I never really pushed vehicles Hard to generally conserve fore twas popular. And who wants all that downshifting etc noise . Kids and hot rodders. Maybe someone else paying etc. I've always been wary and aware of using what I'm paying for especially things like gas ,Av gas etc . Fuel oil all that it's costly . Why make it more so?

 

Yeah that's probably right but usually after the long uphill there's a long downhill so it should charge right back up or what have you and as your battery gets older and older this kind of taxing will get shorter and shorter to reach the near dead state or whatever we're saying here so when you get a new battery newer battery this will drastically improve for probably a long time if your batteries 10 12 years old or something

 

If you have a scan tool (or something like a ScanGauge II dash display) that can show you both the battery state of charge and the current that's being drawn from the battery, you can get a pretty good idea where you stand.

Even a brand-spanking-new Prius battery is only a 6.5 amp-hour affair.

On top of that, the car usually tries to keep it right around 60%. It will not normally give you any battery assist below 40%, and will not regenerate into it above 80%. So you have a maximum of 2.6 amp-hours to blow on your ascent, if your battery is brand spanking new, and if you're starting out at 80% (which would only be if you just came down a longish downhill). If you start the uphill at the more normal 60%, you've got 1.3 amp-hours available.

So if you are going uphill and you see that amps are being used to help you, there's a quick calculation you can do. For example, if you see around 13 amps being steadily drawn out of the battery, you could do that for a tenth of an hour (six minutes), or 12 minutes if you were at 80% when you started. If more amps are being drawn, the time is less. If you were using 26 amps, you'd be down to 3 minutes (starting at 60%) or 6 minutes (starting at 80%).

So if you're on a long ascent, it's pretty easy to use your available battery charge, even if the battery's brand new. If it's older, you can use the amps and the time you get to estimate how much its capacity is reduced.

Ideally, on a long ascent, you can slow down to a speed where you see no amps steadily being drawn, or even a small negative value (charging).