Just bought 05 Prius. Low bat, noise from ICE, is this safe??

Hybrid battery on its last legs. That has nothing to do with the 12 volt battery.

The fast fluctuation of hybrid power levels is classic sign of hybrid battery failure,
Next will be every dash light comes on with the triangle of death and car will go into limp mode have no power at all. It’s the hybrid battery’s way of saying I’m done.

Be aware when that battery is on its last legs it is not supplying hardly any power so all power then comes from the little 90 horsepower engine so your basicly flooring it on every hill and there’s going to be a noise all right. Very very hard on the engine especially if it has to deal with hills. Engine oil level is very low right now I bet.

Most of the power comes from a healthy hybrid battery.

people sell there G2s for mainly 2 reasons the hybrid battery has failed and or the engine is a little oil eating monster because the oil has been poorly maintained. Many have both.

Repair and replace of the hybrid battery is most common post on here now.

Go on YouTube lookup Prius Battery. Hundreds of repair replace videos.

Use search forum link up top search. Hybrid Battery. For hundreds of posts about rebuilds and installations of new battery’s,

 

With those symptoms it sounds like both the hybrid and 12v batteries are ready for replacement.

I hate to say it but I think you picked a very tired car.

 

If all you need is a HV and a 12v battery, I wouldn’t fret. A titred car is not a dead car, necessarily. With the prices of used cars and gasoline skyrocketing, the Prius with its track record of longevity even in taxi service is typically a good bargain.

Find a reputable and honest shop and despite what others routinely post here even some Toyota dealers fall into that category, and get the fluids changed, batteries serviced and move on. Often Toyota shops have service specials on fluid changes and cheap conventional oil changes to keep their technicians busy.

The Price for a used Gen 2 Prius has increased 30% or more in the past six to eight months based on my observations. If excessive oil consumption rears its ugly head, then that is a cause for concern but that does not appear to be your problem. Maybe delay HV battery work until you rule that out. A 12v battery replacement expense is peanuts.

 

I think Ed's both overestimating and underestimating the engine here.

90 HP is an overestimate ... a Gen 2 engine is 76 HP, when it's brand new, shiny, and tight.

So when you're going up a steep grade, once you've used up the temporary boost you can get from the battery, then yes, you will be limited to whatever speed the laws of physics say 76 HP can give you going up that grade.

At the same time, I wouldn't go as far as saying "very very hard on the engine". At full output it will be loud, and you can learn what that sounds like and recognize "oh yes, that's the sound of my engine at full output."

The engine control module knows where full output is, and it knows the safe RPM at full output, and it doesn't allow either to be exceeded, so the engine can keep that up as long as is needed. If the weather is also hot, you might want a ScanGauge or something to watch the coolant temp and make sure the cooling is keeping up (otherwise, there is a red idiot light, but it comes on rather late; heed it if it does). And it is worth checking the oil dipstick conscientiously, as oil will be used a bit faster at higher RPMs. If you're already in the habit of checking at every fillup, you should avoid any surprises.

 

Listen to ChapmanF, that is very good advice. Beyond that, get the oil changed like today! Then check the oil level every day for a while until you can judge how much oil the car is using, this is really important. If the car is a serious oil burner you will have to decide whether to keep the car or get rid of it. It probably won't use much if the previous owner took good care of the car and did regular oil changes, but you won't know until you have monitored the oil consumption daily for a while. The car only holds 4Qt. of oil, so maintaining the oil level is pretty important and unfortunately the dash warning light for low oil doesn't come on early enough to rely on that to let you know you need to add some oil before it starts to potentially do damage to the engine. Low oil warnings can not be ignored in this car... it is a serious warning.

If the car isn't burning much oil it will be a simple choice of getting a new HV battery pack or a reconditioned pack, and yes you need one or the other right now. You can try reconditioning yourself if you are handy and can spend the time, but I suspect by your description of the fast state of charge changes (battery bars) you will be better off with a new or reconditioned pack... new being the best choice for reliable long term service.

Seriously consider getting an OBDII BT adapter from Amazon and the Dr Prius app (or other apps) so you can test your current HV battery and see if any other codes exist that need to be addressed. This is something that will be useful to have for any future issues you will see on the car (or any car you buy that is MY 2000 or greater). Only the codes generated with an issue can tell you exactly what the issue is. Guesses are not really useful for a car like this. Fortunately there are many low cost OBDII adapters, so that won't cost very much... under $40. You can also go to a dealer and pay for a diagnostic to see the battery health and if any other codes exist, but that can get expensive so you're better off getting an OBDII adapter. Don't be tempted to dump too much money into the car before you have had a chance to determine it's condition whether it's from an OBDII BT reader or a shop. Once you know what's going on with the car you will be in a better position to make a decision on what to do next. For example: If the codes show both battery issues and catalytic converter issues you might want to flip the car instead of fixing because those items together will exceed the purchase price you paid.

Hopefully it's just an HV pack issue and if you replace it with a new pack you will likely have a great running car for a long time.

Good luck and let us know how things go for you.

 

As an aside, in the Prius I think the small 76 hp itself is not the issue, I used to drive a a fiat 127 in Europe, which weighed about what the Prius does, that had merely 68hp and it cruised up and around the alps and hills with ease. But it had a five speed manual. In the Prius I think the issue is the Atkinson cycle and the CVT.

 

My quick Google search for fiat 127 curb weight pulled up 688 kg (1517 lb), or roughly half of a Prius.

 

Could be. It was otherwise a POS car that served its purpose though.

 

Anyway, fizzicks says 76 HP will haul a Prius up a mountain around half as fast as it could have hauled a 127 (if the grade is steep enough for that to be the holdup).

 

LOL, the 127 only had at best 68hp. On a flat straightaway it would get up to about 140km/hr after a minute or two with the manual transmission, but the whole box was shaking and you hoped there were no potholes.

 

it may not be too late for reconditioning, or just throw in a new battery for 1600 plus labor.

keep in mind, at 16 years, your going to be having one expensive issue after another, and don't forget the cat problem, that's reason enough to get rid of it now

 

First of all, any "hybrid specialist" that can't tell you your battery condition (even if he charges a small diagnostic fee) isn't a specialist. There are tools that can tell you that and it can even tell you which modules are failing or failed. You can do this yourself for about $40.00 for the OBD BT adapter and app for your phone. Get the BT adapter and find out yourself so you know.

Second, I purchased an 07 last year and had the same experience as you. No codes, no lights, the car ran fine, but when going up steep long grades was challenging and usually left me with 2 bars at the top. When the weather got warmer and the A/C running it was way worse with the engine RPM running higher and lack of power. But still no codes or lights and when driving flat areas no problem, but long grades would get it down to 1 to 2 bars and the car would lack power with the engine RPM much higher than normal. I didn't want to go the summer running up the mountain with no A/C, so I got a new pack, installed it and everything is running perfect with A/C on max whether uphill or not. I guess it is a pretty harsh case for an OK but aging battery. But putting a brand new pack in has made the car perfect for me.

Test your HV battery and let us know what you find. Probably the easiest app to use to find the general state of health for your battery is the Dr Prius app (there are Android and iOS versions). Easy to use and gives a very good indication of health. Good luck!

 

If you're really a first-time Prius owner, it might not be a bad idea to set up something like a ScanGauge II (or a smartphone with an app like Torque), and set it up to show you some things while you're driving, like the (real) battery state of charge and the engine RPM. Then you can go through some of your usual uphill driving and make sure your expectations are matched to the car. What's the grade you're going up, and how long is it, and what speed do you expect to hold on the way up?

If you are watching the real state of charge and see it drop past 40%, the next thing that will happen is you'll hear the engine at full output and your car will slow down to the corresponding speed. Won't really hurt anything, but means you overspent your battery charge budget on the way up.

If you try the same run again (letting the battery be recharged to its usual happy 60% first), and try to take the climb a little slower, you might find the speed that lets you get to the top (or your turnoff) before the battery is sucked all the way down to 40%. You'll probably find that more satisfying.

Now, it's certainly possible your battery is old and tired, and you would be able to find a higher sustainable speed with a new one, and that would make you happier. But even the new one will have its limits, which you can use the same technique to find, so you don't end up overtaxing it. So paying a little attention to the car's capability this way will let you get the best you can get out of what you've got, whether you replace the battery or not.

 

i am surprised you don't have a triangle based on your description, but it is programmed to come on when one or more cells falls out of the design parameters. you would need tech stream or dr. prius or other to read the cell voltages under load.

the cat problem is that they are being stolen and sold for the precious metals at an alarming rate, especially in cali, and it is a $2000. replacement.
if you don't have emissions testing, you can get away with a cheapo for a couple hundred bucks. in fact, some sell their oem and replace it for a tidy profit.

 

What are you getting for gas millage? Poor millage is a sign the battery is going.

 

a new toyota oem?