12v Battery Is Discharging, Re-Charge Now !

Good work and testing.

I throw a charger on my Prime, 4Runner, and my wife's Camry Hybrid every two months or so. It keeps them all happy.

I still remember the sticker shock I got when I went to replace the bat in my 2010 Prius. $300+ Dang. The bat for her Camry was $380. Yes I shopped around a lot. The dealer price was very competitive.

 

Yeah, after reading many Gen4 and Prime threads on dead 12v prompted me to look into taking care of 12v battery. I sold my Gen3 less than 3 years old, so I never had to do anything with the AGM battery in the back of the car. For Gen4 and PRIME with a regular flooded lead-acid battery, even OEM battery is not as expensive as your 2010 Prius's AGM battery. I think they are now about $120 either OEM or aftermarket.

Still, I thought it would be a good investment to have an automatic charger, portable jump starter, battery tester, and a battery monitor. Well, I bought all of them last year but never used any of them on my now sold 2017 PRIME or on other cars in my household. COVID-19 stay-home order has prompted me to check on 12v battery recently. I am glad that now I have used 3 items (automatic charger, battery tester, and a battery monitor). I hope I never have to use the portable jump starter, but I have it if I ever need it.

BTW, my old battery charger (30+ years old) is a Schumacher manual 10A battery charger. It is a beast compared to a new automatic 4A charger I purchased last year. It was still working fine when I last used it in our ICE car several years ago, but I did not want to use it on our newer hybrids. I am still holding on to it just in case I need to charge a dead battery very quickly.

 

Interesting that the caps atop the 4th gen battery looked to be readily removable, and not covered by a sticker.

 

Are you talking about caps on each well? It supposed to be a "maintenance free". I never had to add any distilled water into any of my previous 12v batteries in our cars. Not sure if this battery allows the addition of H2O through a removed cap or it is just for checking the fluid level.

 

I used to add (distilled) water, sometimes. Considering batteries tend to last around 5 years, I've found it good to pull them out say around the third anniversary, clean the clamps and posts, shine a light through the case (hopefully semi-transparent) and top-up the cells. It's no big deal.

I think the way battery manufacturers say they're "maintenance-free" is somewhat akin to Toyota's "lifetime" fluid on the transaxle. With the batteries, putting a hard-to-remove sticker over the fill caps maybe seals them a little better, reduces evaporation, but more so, makes them "maintenance-thwarted", my 2 cents.

 

it would have been interesting to see how far i could have extended the life of my previous 3 batteries over the 7-10 years i got out of them by checking the water levels.

 

This is mostly applicable to conventional lead-acid batteries. I think.

 

Yeah, if I really want to prolong the 12v battery life, I should "maintain" and "care" for it. But if my past experience is any indication of how long the regular 12v battery lasts in our region under our use case, it last at least 6 years totally "maintenance free" and for HCH, the OEM battery lasted 10 years without any maintenance.

I checked my wife Pathfinder Hybrid 12v battery after working on my PRIME last week. Nissan made it so difficult to get to the 12v battery, it took me quite a bit of work just to access the battery posts. I only checked the battery health using the tester and charged it fully using an automatic charger, but I could not figure out how I can remove the battery. After this stay-home period is over, other than occasional charging if needed, I will not likely ever remove the 12v battery until it needs to be replaced. It is an OEM 12v battery in it, so it is already 6 years old, although I bought the car used 1 year ago, so I have no idea how it was cared for (or more likely not cared for).

 

I do have a lot of time on my hands, lol. And yeah, some cars, especially more recently, can be a royal pain for access.

 

My current charger is a Schumacher SC-10030A. I love it.

 

Yeah, 3 years old battery is likely to be different from an almost brand new battery in a bad way. That being said, I have read some threads here both on PRIME and Gen4 in which an almost brand new battery failed prematurely. I am relieved to report that the 12v battery in my 2020 PRIME is really stabilizing at ~12.6v. Currently, it is 12.61v 99%. This is up 0.03v from this morning 12.58V 95%. I don't think this is "false positive" but it is an actual increase in charge due to ambient temperature. The lowest voltage corresponds to our daily low in the early morning, and the highest voltage is at the day high temp in mid to late afternoon. Our temp has been mid-20s low and mid-40s high.

 

Yes, these caps unscrew. I used a toonie as a wrench. They're relatively tight, so be gentle.

 

Are you going to leave the traction battery fully charged for a long period of time? I have been stoping my weekly charge so that I have only 35-45% SOC left while the car sit.

 

Based on my recent issues and suggestions from you guys, I am going to start checking my 12V for the next 12 weeks. I'll edit this post as I update 12V readings.

Context:
2018 Prius 2, stock car. Bought car in 09/2018.
04/22/20: Dealership replaced my 12V after diagnosing a battery failure. This is my 3rd 12V.
04/23/20: Took it for a 2-hour drive

I just ordered a trickle charger so I can't top up from 100% 12V. Either way, I want to simulate normal use so I'm fine with this.

Commence Testing:
4/24: 12.46V @5:30pm. Current outside weather is 91F

 

Just finished a similar test on mine. 12v was at 12.42, traction battery at 31%. Charged traction battery to 100% and checked 12v, which was still only 12.45. I’m guessing the difference was probably with the margin of error for the tester, meaning the 12v was not charged during the charge of the traction battery, which conflicts with what is stated in the owner’s manual.

 

Had just unplugged it.