Dead battery problem

More like LARGE current drain… but have the new battery tested at the place purchased.

 

a lot of new batteries need a full charge before installation

 

most any brand has not been problematic. and yes, you want to keep the fob a good 20' away, otherwise, the car is always talking to it.

to me, it sounds like the battery came with a minimal charge, and her commute is enough to sustain it. then, on the weekend, it slips below minimum voltage needed to start.
prius does not charge well, more of a maintainer.
i would disconnect any devices, aftermarket or otherwise

 

Any possibility that it could it be the Brake Booster Pump / Actuator issue? Some early 2015's also were covered by the problem.

A leaking Actuator, combined with a key fob nearby could cause the Booster pump to run all weekend, draining the 12 volt battery. If the car has less than 150k, it should be covered. The dealer will pretend not to know anything about this recall.

 

Get this one,

https://www.batteriesplus.com/battery/car-and-truck/toyota/prius/2015/l4-1.8l-325cca-hybrid#finder-box-top

I got mine two years ago, and it is working fine. They installed it for FREE.

 

It is most likely (1) a very poor battery incapable of holding a charge longer than a day or (2) a big parasitic draw well over 50ma. A free load test at O'Reilly's can check the first item and a low cost meter can check the second.

There is nothing wrong with another O'Reilly's battery if they need to replace it again. It would be free and should be your first stop.

It is highly unlikely (99%) that she is not driving enough and its almost unheard of that a nearby fob could discharge it in less than two weeks, much less two days. Discount those theories. The brake booster won't keep cycling when shutdown. It simply pumps up when you open the driver's door if it needs it and more often while driving. That is not the issue.

Its either a bad battery or an excessive drain.

 

@rjparker I've studied EE just enough (dropped out of my school's EE CS program) to know that picture's got issues. Since I'm poor at downloading, editing, and uploading I'm afraid I'm gonna have to ask you to edit it please. As shown that is a parallel circuit....

(Sorry for the necro post as well...)

REVVL V+ 5G ?

 

The instruction is correct. The diagram is misleading because it shows the jumper cable still attached, but it says to #4 REMOVE JUMPER. After the jumper is removed, the ammeter is in series.

 

The whole purpose is to have it in parallel until step 4. By doing it this way you never disconnect the power to the vehicle and are able to avoid the computer reboot times prior to them going to sleep again.

 

Just installed O'Reily's brand Super Start Platinum AGM battery not on Prius but on our PathHy. The 8 years old OEM 12v battery on our PathHy was dying. At -26F temp, the car did not start. The battery was holding the voltage at 12.6v but just did not have enough CCA.

I did not need an AGM battery but @sam spade 2 always says AGM is better than regular flooded lead-acid. This car is not driven every day and tends to sit on our driveway for days sometimes weeks between use. The price difference was only $20-$50 compared to the cheaper regular batteries which were also in stock, so I decided to try my first AGM. Made sure to fully charge it before installing it.

 

What is a PathHy?

 

Pathfinder Hybrid

 

I see the light....

But:

"3. ADD AMMETER IN SERIES"

REVVL V+ 5G ?

 

@Salamander_King I like AGM better/much better than flooded lead acid. It may not be relevant where you live, but I find it a pain to remember to open up the caps and refill with distilled water. AGM avoids the problem completely, should last maybe double as long to boot.

I now like LiFePO4 even more. After a few months take a straight edge to the long side of that AGM battery, then tell me how you feel about them. That warpage is discomforting. Plus LiFePO4 is much lighter/easier on the back, and should last even longer...

Of course cost wise: LiFePO4>AGM>flooded lead acid

REVVL V+ 5G ?

 

Yeah, AGM may serve me well, but in my situation, probably a good old flooded lead-acid would have done fine. I did not do anything to maintain or service the OEM flooded lead-acid battery I just replaced, and it lasted 8 years. I already live in a region where the lead-acid battery life expectancy is the longest. Even if the AGM I just installed lasts longer, I am not likely to see its full-service life on this car. The car will not last another 8 years. Now, about the LiFePO4 battery. I am wondering without any thermal management, would it be OK in -30F temp? It is rare we get that cold, but the temp in winter is rarely above freezing in our region. I read that lithium chemistry needs to keep it above freezing temp in order to charge. If the temperature is below freezing, and try to charge it, it may damage the cells. Unlike the traction battery in the hybrid, the 12v battery has no thermal management. I don't like to spend more money on a Lithium battery only to find out that it dies during the first winter.

 

I recently have had the same issue with mu 2017 v. The battery died. I replaced the battery ($225) and I just got an alert it is critically low again. I had a Drone remote start installed and I believe that is the problem. The installer said they need to do a parasitic test on my car and will charge me if its not the drone. What else could it be. It’s been very cold and I do not drive it much. During 2021 I did not drive it at all and had no issues, however, did not have the Drone until 12/21. My son has my old 2014 with 187,000 miles and Never has replaced the battery. Any ideas?

 

@Salamander_King The cold weather performance/reliability of LiFePO4 is definitely a good question. The question does come down to the internal BMS that the seller/manufacturer provides, whether it does in fact have a thermostat or not. That I honestly don't know. I am in a warmer area and it very rarely gets much beyond freezing here. Some mornings within the last year I have noticed some snow/ice on the tops of cars/roofs, but the Prius sat unused through it. (It's my parents' car and they don't go out much nowadays).

On a similar note why would you spend a lot more for the lithium battery when you already suspect the AGM will outlast the car....

REVVL V+ 5G ?

 

Yeah, I have no intention of spending $$$ on lithium 12v batteries for my cars. I was just curious about LiFePO4 batteries in general. I am thinking of building an off-grid tiny house with solar panels. I started looking into battery power banks for this application. But a deep-cycle lead-acid vs LiFePO4 batteries question came up. Our area gets cold enough to -20F or lower occasionally, so wanted to know how LiFePO4 batteries behave in extreme cold.