Replacing Original Traction battery with Nexcell LiFePO

Just purely on the basis of this test, I wouldn't say it proved anything one way or the other. The Prius is a gas car with electric assist and is not designed to be used as an EV. It is quite normal for it to go not very far before running right down if forced to use only the electric motors. It will then charge up quite quickly over the course of 3-5 miles.

That is not to detract from the fact that you have an old (most likely original) battery and your observation quoted below:

is more telling. Personally, I wouldn't jump to any conclusions until you have driven it a bit more. I would also ensure to drive it regularly as well.

Having said that I have an older car (2007) with the original battery and it is still running perfectly well for its age.

 

Welcome to PriusChat!!

Please tell us more. Were you watching the center screen (MFD) for changes in the HV battery state of charge (SOC)?

Normal for the engine to run when heating or AC'ing.

FYI : you're moderated until you've posted 5 times.

 

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if you were able to drive 2 miles on the battery alone, that's like brand new

 

It is not an absolute voltage that is important but the voltages under load i. e. when accelerating (Amps out of the battery) and deceleration (Amps into the battery) relative to each other. Any block that was 1.2 V higher (decelerating) or lower (accelerating) may be suspect.

You need to see all the blocks. Having blocks in isolation is almost meaningless.

FWIW, in your tablet image, I don't see any of the blocks with alarming voltages. But, there again, in that image, you are only drawing 1.3 Amps.

I only see a 4.3 ºF difference and it is normal for the second temp gauge to read higher than the other two. that gauge reads the middle of the pack and it is quite normal for it to be higher there. Have you checked your cooling fan (situated behind the right rear panel above and in front of the 12 V Battery) to see if that has any significant crud bogging it down?

Other than addressing those specific points I don't see anything that is overly concerning.

I haven't used it myself but there is another phone app called Hybrid Assistant that can run analytics and give you stats to help determine the health of your hybrid vehicle (HV) battery. If you can get the paid version and run its test (or tests) and there are other members here who can help interpret the results.

Really though, get over the tunnel vision (new owner syndrome) focused on the HV battery.

Run three or four tanks of gas with you at the helm and tell us what MPG you get. That would be a better benchmark.

If anything you are probably affected by a battery with a lower capacity. The only thing you could do about that would be to wake it up a bit with a round of grid charge/discharge cycling. However, at the age of your battery, I don't think investing in the gear would be worthwhile. Seeing if you could borrow or rent might be a better option though.

At the end of the day if the battery/hybrid vehicle ECUs are happy there is nothing wrong with your battery. When those ECUs see anything that troubles them, they will let you know with relevant codes.

 

You are over complicating the H out of this. The car is smarter than you, and me, and every other swinging D on this forum. Let it do its job. The car is completely happy with the condition of the battery and you're trying to find a problem where one doesn't currently exist.

If you want to buy a new battery then do it, but you're doing it because you want to, not because you need to.

as I was sitting in my car - in Ready, engine off, not even the radio on. I timed it and lost 0.5% charge every 65 seconds, or 1% every 2:10 mins. This seemed odd to me, so I made a note and then began driving.

Looking at your photo the HV battery had a current draw of 1.3 amps and has a rating (when NEW) of 6500 mAH. So one must ask.....how does that relate to your numbers.

A new battery with a 6500 mAH rating is being drawn down at 1.3 amps so in a perfect world, it should be able to handle that for.....5 hours ish

Lets assume your 1% every 130 seconds is accurate. 100% would be 13000 seconds....or 3.6 hours.

But overall, that's a lot of simplification and assumption

 

@JasonMRC I not sure why no one has recommended the Dr Prius app, but I really think you should consider getting it. There is a free version that gives some very good info, if you are familiar enough with Prius batteries and their characteristics. But the real value comes from spending (about $20) for the in-app purchase that gives you some tests to determine the condition of your HV pack. It will guide you through several very simple steps and calculate a percentage of how your pack is performing compared to a new pack. You don't need to know anything about batteries, but you'll learn a lot. This app has always been regarded as one of the core apps that all Prius drivers with battery questions should have. I know when I purchased my first Prius in 2020 this was highly recommended by users here at PC.

There is nothing wrong with the Torque app. It is a very comprehensive app with the only drawback being you the user knowing how to interpret the data. It also allows for data collection that can be graphed, charted, and exported to Excel if you wish which can be a huge help with emissions and other problems. So, by all means keep the app since it will serve you well for other purposes at some point I'm sure. But for the uninitiated to Prius batteries (like I was just a couple of years ago), the Dr Prius app was exactly what I needed with my low experience level. The simple tests showed my battery at around 60% of usable life and after repeating the test several times over several days it was very consistent with the results. The real value of this app is you don't need to know anything about how Prius batteries work to get a pretty accurate indication of your battery's health. This puts you in the driver's seat (no pun intended) in regard to if you need or want to change out the pack or you have enough life left in the pack to let it go for a while and maybe re-run the test once in a while to reassess. You will find many Dr Prius data discussions with screenshots on PC if you want to see what it's all about.

Good Luck!

 

I'm going to mildly disagree here. When I was new to Prius, I was very concerned over how good my HV pack was and how long I might be able to keep driving on the pack that came with an '07 at 126K miles. I mean I was glued to the MFD watching the battery bars without a clue what I was watching and if it all fell within a reasonable range for a decent battery. I just didn't have a clue. My first Prius was a pretty steep learning curve and a totally alien concept to every ICE vehicle I've owned in the past.

But you are correct to say that the Prius will let you know when a problem occurs, because it will happily do so. The only problem for me is I'd rather not wait for the Prius to chime in with an RTOD to let me know that a critical problem has occurred if I could know in advance and plan for that. I'm not really disagreeing with you as much as wanting a better way for me to handle a potential problem and take corrective action before it happens. I think this might apply to other users with a new but used Prius.

 

if you have readings from the original it would help to compare to the lifepo.

anyways the temperature differential is normal, the temperature sensors are at different positions in the battery compartment and get different airflow.

I have some data collection runs from my 2007 running NIMH battery cells from NewPriusBatteries, here: https://treecricket.com/vehiviz and its normal for the HVBattery temperature sensors to differ by a few degrees. Here is some temperature data from a run i did in August 2020.
(the website lets you checkmark different sensors to make graphs like this)


best of luck to you

If you have Torque setup properly and set it to save logs, i could actually load some of your data into the website if you want and make graphs like this for your car, it can display voltage, temps, O2 , current, anything Torque can store basically.

 

I'm not sure if i understand which of your screenshots go with what description. Normally the HV battery current is small and positive when idling, then the ICE kicks in and starts charging it so the current goes negative.

Normal amps with 0 speed , 0 ICE revolutions per minute, should be small and positive. This plot below is a typical ride, just get in, wait a few minutes, start accelerating, the amps go up, the ICE kicks in the amps go negative.



Here's another run, showing how Regen makes the Battery current go negative (its charging). Red is regen torque, green is HV battery current.

 

Another thing is... my SOC doesn't change that much. Like i would have to deliberately try to make it move more than a few percent. Most of my graphs show it around 60, very occasionally about 40

here is one where it did hit up towards 70. if you zoom in on the website you can see a huge spike in Regen combined with a slowdown in speed, probably going down a hill and braking possibly plaing with the "B" mode on the shifter.

 

You were on the right track there when you included "whatever base system the car uses when in Ready". That's been reported as around 400 watts minimum, and more depending on what accessories, lights, HVAC, etc. are doing.

So quite a bit more than you might be thinking just for radio listening.

 

400 watts with just the radio? That is 33A at 12V, so it doesn't sound right for "nothing much going on". A car radio at a reasonable volume is maybe 25W. No lights on. No AC. No motor. No cabin fan? That pretty much only leaves the various computers, and that is a lot of power for running little tiny computers, most of which should only be a few watts. (Remember, these have no graphics, no sound, little memory, and no rotating storage.) That leaves what, charging the 12V battery maybe? 400 watts at ~12V would be 33A, which seems like a possible value if the battery was depleted.

 

That was not what was said.

It was more like in addition to the radio the base energy use is something like 400 W.

 

400 watts at 200+ volts is like 2 amps.

which is not too far off the data i have collected. Torque can measure the current

The Prius computers were likely made before 2004 so maybe not as energy efficient as modern stuff. The coolant pump might be running intermittently, the MFD might be on, the vacuum fluorescent display for the speedometer takes energy, dome lights and door lights if you have the doors / trunk open, etc etc.

 

Sounds like your battery is nearing its end. But you now have some warning and a bit more time to make plans for how you want to resolve this whether new, reman, whack-a-mole, or sell the car and get something else. If you take it fairly easy while driving, now that you know the pack is a bit weak, you might get a few months or more use out of the pack to make a decision on how to resolve this. I wouldn't think you'll start getting codes really soon, just don't push the pack too hard.

The fact you haven't gotten codes yet is good because even in a weakened state your battery is still serviceable for now which is why it wasn't a test failure at this point. Just headed that direction. The life expectancy test is usually pretty accurate, so I would tend to believe it and plan accordingly. I'm glad you did the test. Having a good idea what you're looking at without seeing RTOD or codes is preferrable to surprises.