How do i know if my HV (hybrid) battery is dying??

usually, you start getting more rapid cycling of the battery meter and reduced mpg's.

 

As "bisco" states rapid charge and discharge on the colored bars display "going from full charge to full discharge and back in a few seconds" is often a sure sign.
You may get an extended life from the battery by having it balance charged. This can be done yourself if you are able to work on high voltage electrical systems, or there may be someone close to you that can carry out the work. This is best done before any fault codes and warning lights appear. Many threads on PC about this.
Buying a Mini VCI with Techstream software and using a laptop will enable you to check the general condition of the battery. This equipment is available on Ebay for around $25, and gives you dealer level of diagnostics on the Prius or any Toyota.

John (Britprius)

 

When the Big red triangle comes on , time to pull a code. I had one bad cell, then replaced it, then a month later I had two more, once they get a certain age, they start dropping like flies. I finally cycled , and load tested all 28 cells, and weeded out the lame ones.

 

The Prius battery uses 168 cells in a series chain. There are 6 cells built into a unit called a module, and there are 28 modules.
Over the working life of all these cells "for a number of reason I will not go into here" some cells will have less charge than others "out of balance". The capacity of the whole battery is the same as that of the cell that has the lowest charge, "weakest link in the chain".
Balance charging is done by slowly overcharging the battery. Any cells with a full charge will take no more charge and give the energy off as heat, but cells with a lower state of charge will continue to charge until they to are fully charged. This means that at the end of the process all the cells should have the same level of charge, "balanced". The Prius cannot do this in normal operation as it never charges the battery above 80% of capacity.
The simplest way to balance charge is with a grid charger linked below.
The above should only be done if you are confident working on voltages of around 250 volts DC that can be lethal. Being in the UK I cannot advise on local workshops capable of this service, but no doubt someone in the US will add this information to the thread.

The Mini VCI is a piece of diagnostic equipment that plugs into the OBD2 diagnostic port on the Prius and gives the ability with a laptop "preferably an old Windows XP or earlier" to look at the battery module voltages and resistance. This can give an indication of the state of the battery. The VCI can also clear fault codes and enable many service tasks that would normally require a trip to the dealer. This is a must if you intend to do most of the work on your car, and will more than pay for it's self if it saves one trip to the dealer.

Use the search feature to find many threads on battery balancing.

Traction Battery Preventative Maintenance - Hybrid Automotive Chargers

John (Britprius)

 

Coolride, just curious... how many "bad cells" did you need to weed out in the end?

 

Many people start out by just putting out fires (ie replacing only the obvious ones) but then after doing it a few times they understand why test all of them for both capacity and load is the smarter route and is alot less hassle in the long run. Congrats on your rebuilt battery.

 

I have the same question.

If the battery (that powers my car) is about to die, will the dashboard on my Prius C warn me? (Year of car: Circa 2013). When I had a Toyota YARIS, there was never really any official warning from the car that the battery was about to die. So one day I came back to my car and it was dead. (What was really frustrating is that I got regular oil changes, and regular inspections, and never once did they tell me my battery was about to die. I’m pretty sure a normal 3 point inspection doesn’t include looking at the life of the battery. Why the hell not? If the inspection place doesn’t tell you that, and your car/dashboard doesn’t tell you that, how can you have any advanced warning that you’re about to be marooned in a dangerous place? Or marooned in dangerous weather conditions?! THAT’S A SAFETY HAZARD TO ME!)


Now that I have a Prius, I need to know if the same lack-of-warning should be expected (like the Yaris incident), or I need to know if the dashboard will tell me that my battery is about to die. I realize there is a dashboard menu in my car that shows battery life, but I never switch to that menu. I'm always on the menu that shows the temperature outside. So if I'm not on the menu with the battery, will there be some kind of text that comes on to my dashboard to warn me that my battery is about to die?


Someone said I can lift up the hood and look for some eyeball red/green image on the battery? I suppose I could do that, but that’s kind of a terrible suggestion because months from now when I forget all about this subject, I won’t think to look at the battery under the hood. That’s why I want to know if the Prius will give a dashboard readout warning you if your battery is about to die.


(Side note, My question has NOTHING to do with the Toyota people telling me or not telling that my battery is going to die soon). The question is very simple. Will my Prius C (circa 2013) tell me on the dashboard ‘your car battery is going to die soon’??? I’ve googled this question until I’m blue in the face and all the results that seem to come up are results like ‘preparing for prius hybrid failure’, ‘what are the warning signs’, or ‘what to do when your battery dies’. (WHEN it dies? That’s not helpful, I don’t want to know what happens after death, I want a warning BEFORE death!) I read the articles and they don’t even address my question. Not sure why I can’t find the direct answer to my question through an internet search, so I’m guessing that that hints towards the answer of ‘no, your prius will not tell you/warn you verbatim on your dashboard that your battery is about to die soon’.

 

again, no.

 

The prius 12v is a deep cell battery, it can die and be charged again, somewhat.
IT's also really small and leaving the car in accessory mode will drain it in about 15 minutes, the yaris has a regular, larger, 12v battery, it won't die in 15 minutes, both batteries last 4 or 5 years, the traction battery is good for 5 or 6 years, balancing it is good, replacing it with a factory new battery is the way to go, 2500$ and another 5 or 6 years of good mpg's.
No, there's no idiot light to tell you either is dying.
Do the math

 

Instead of waiting for the unexpected surprise battery failure, perform preventative maintenance to make sure does not happen in the first place:
What causes hybrid batteries to degrade and fail? - Hybrid Automotive

 

You can pay Toyota $99 and they'll check it for you ... Do the install yourself though ... Get a Dorman battery, and watch youtube on how to do it. I just successfully replaced mine - 2006 with 153K on there. I got the red triangle of death ... that's how I found out.

 

It's been quite a few years. I was wondering if other batteries went after you weeded out the lame ones as you put it. We have a 2005 with 120,000 miles and are trying to determine if we get rid of this car or our other one. Don't need two cars anymore. Thanks in advance.

 

This decides it. If still on the original battery, your 2005 WILL fail sooner rather than later. When exactly? No one can tell you for sure but it will happen. Since you say you no longer need two cars and if the prius is not getting used much, that can quickly kill an already weak battery. BTDT.

 

welcome!

they all go eventually, get rid of this one before the headaches start.