When to Replace 12V Battery

I think it depends on your usage pattern TBH.

If you only use the car occasionally, the battery is likely to cycle deeper and last a shorter time.

It it's a daily driver, just carry a battery booster pack or jumper cables and drive it until it fails!

 

But unless you have a discount code, not much cheaper than the OEM one -- and with a much shorter warranty

 

They give out discount code all the time. Just sign in, put the items in the cart and next day, they'll send you a code. Diehard used to be really good.

 

Would like to hear from real world experience on agm Barrett life. I have a 2012 Prius with 460k kms and original agm battery. Did the voltage level check thru the dash shows 12.5 and have never had issues with the battery. In one post a gentleman stated he has several vehicles with agm batteries and their life is at least 16 years. Mine is 10+ now and thinking of just let it go to end of life whatever that maybe. Anyone else have an agm with over 10 years?

 

"Excluded from discounts except Speed Perks rewards"

 

mine lasted 8 years. one day it was 12.7v static, and the next day i was stranded 4 miles from home after a 10 minute drive.
the only caveat is that the car sits a couple months every winter while we're in florida

 

That sounds good. Still, that's a lotta years. Dealership (for a fee) or battery retailer (say Canadian Tire) can hook it up to an electronic load tester, let you know the battery's "health". I'd seriously doubt it'll last much longer, and swap before next fall.

A few months back I emailed SaskBattery, they'll ship for free the OEM Yuasa, for $229 CDN. If you're not in Saskatchewan they only charge GST, no provinical tax.

There's prosumer level testers available: I'm using a Clore Solar BA5, current itteration is BA9, and Ancel makes several testers.

 

I'm sure that there are. And they probably live in a "cold" climate.
My guess is that most people pay no attention to their battery until it does fail completely.

Would I keep a 10 year old battery in my car ?
NO. But I don't think that is automatically a bad thing to do either.
To each his own.

 

I would say you are on borrowed time. As other's have stated, it could fail at anytime, and
there's a 99% chance it will be at the WORST time.
Engine oil is changed at X amount of miles, BEFORE it fails. Some go longer than others
between changes. But, like the battery, sooner or later it breaks down, and fails.

Question is, do you feel lucky, do ya?

 

10 years is possible especially if the car is regularly driven and kept in garage or not in hot weather. Offcourse it degrades slowly but as long as it is always kept above 12.5V and exclusively charged by the car, 8 years is very plausible.
One time left discharged below 11V, the battery is permanently damaged and may be less than 50% original capacity. So, if you leave it more than 2 month, smart charger like Noco, ctek will keep it charged without overcharging.
Check it under load like headlights on, if it is stable above 11V, it is still decent and plenty of life.

 

I have a 2012 Prius gen 3 & still have the original 12 volt battery installed, no problems up to this point.

For checking the 12 volt without a meter, you can check it through your radio maintenance menu. Go to YouTube & search PRIUS GEN3 12 VOLT BATTERY SELF TEST.

 

There is no reason to change batteries just because they are old. Many factors on battery life and always use OEM/original type battery/AGM for safety reasons. We can check the battery voltage in Prius without a voltmeter. The most important thing is the voltage under heavy load like turning the headlight on for 1 minute, it should be above 11V all the time. If it does, the battery is still good and usable although not perfect anymore.

Mine is 11.7 V in ACC mode and 11.3V with headlights on for 2 minutes. It has been like that since 2 years ago and it is already 7 years old. Do I have to change it now? NO, I won't because it never fails to start the car. I bought a $40 jump starter battery pack for emergencies that we always need anyway even when the battery is new. Delinquent happens. Prius only need 60Amp to start the computer, we do not need a stupid expensive big battery.

 

Everyone knows you are on borrowed time. They do not last forever.
You can keep a jump pack in the car, but that might not work to get the car going,
depending on how the battery fails. The battery may try to use all the energy the pack has
and there will be none for the electronics for the car.
Plus, electronics don't do well when the voltage and amperage are below the minimum they need
to operate, which could cause them to fail. Big money to replace.

How do you know it's the original battery? Are you the original owner? Just wondering.
If you have the money, replace the battery. For your peace of mind. Just remember to put a
4 amp charger on it overnight because it probably isn't fully charged from sitting on the shelve.

The risk is yours to take. Just because one or two people have been lucky, doesn't mean you will be.
The battery will fail at the worst time, and you could be left stranded, in the pouring down rain, trying
to jump the car....

 

I am the original owner and the date on the battery is also only about 3 months older than when I got the car. Prius only needs 60 Amp to start and after that, the DC to DC converter takes over the 12V lines. There is no reason to worry when the battery still can hold voltage and can supply enough current to start the computer. For 5 minutes with headlights on, my batter still holds above 11.7 volts. When my 06 Prius 12V failed, it will not hold the charge on any load. 12.3V open voltage, 10.5V in ACC, and below 10V when the headlights are ON. That's a very obvious sign of failure because basically one of the cells cannot hold any load.
I never use any charger because I drive it regularly at least twice a week. I only started to charge it this year and it does not make any difference. NOCO5 so far is the best charger on the market with proper cooling, 4 optocouplers instead of 1 like n blazing hot CTEK.
I come to the conclusion that the 12V battery is indeed really reliable when it is used regularly and parked in the garage. The degradation over time still happens but very slowly.

 

That can be a good argument for being extra obsessive about keeping your jump pack fully charged, if you feel you are near the end of your battery's lifespan. Sometimes my jump pack sits in the glove box for months without me thinking to charge it.

Also, when jumping a Prius, it is possible to unhook the Prius's battery (unplugging the cable at the battery terminal in Gen 1 or 2, or the fat white cable in the glove box in Gen 3, don't know about Gen 4) before jumping at the jump terminal up front. That eliminates the risk of the battery slurping up all the juice in your jump pack. Once the car is READY, you plug the battery back in.

If you're in a really dicey situation (not sure how charged the jump pack is, zombies approaching, must get car started now), you might even do that and remove the fuses or relays for the brake pressure pump, make sure all the headlights, seat heaters, etc., are turned off, and so on. Then you put the fuses/relays back once in READY mode. Some trouble codes about the brake pump may result, but you don't get your brains eaten.

 

As I stated: The risk is yours to take.

 

Agreed . I have a folding camper parked in my garage with a leisure battery that has only started to degrade after 5 years. I know that is not the same as the Prius 12v but in both my gen2 I changed the battery after 3 years. See my sig for their mileages.

 

I think the warranty is 1.5 years new replacement and 5 years prorated in Toyota batteries. I prefer any battery with the longest warranty. It is true that we should not leave the car more than 1 month or at least unplug the A/C Cut fuse to disable body and accesories modules including remote system. The open voltage of the battery should never lower than 11.8V to avoid sulphation or permanent damage. Besides that, the big HV battery also need to be cycled regularly by running it at least for 30 minutes every month if it is not driven at all for more than a month, which is bad.

 

I think the warranty is 1.5 years new replacement and 5 years prorated in Toyota batteries. I prefer any battery with the longest warranty. It is true that we should not leave the car more than 1 month or at least unplug the A/C Cut fuse to disable body and accesories modules including remote system. The open voltage of the battery should never lower than 11.8V to avoid sulphation or permanent damage. Besides that, the big HV battery also need to be cycled regularly by running it at least for 30 minutes every month if it is not driven at all for more than a month, which is bad.

 

Our 2010 Prius (175,000miles) original battery was finally replaced in Jan 2021. It had been sitting around (not driven every 2 days at min) and someone chose the coldest day of the winter to try to start the engine. It was an extra car (4 cars, 3 drivers). We have AAA and it couldn't be jumped (probably because it had died a 5-9 days earlier).

Our 2011 (150,000 miles) and 2012 (140,000 miles) is still on the original battery. I live in New England, near Boston.

At $330+ to replace, we will take our chances. Esp since we have spare cars.

 

I don't understand why it could not be jumped. It is probably your HV Battery is way too undercharged and cannot power the dc to dc converter. I remove the 12V battery completely and it still can start with the jumper battery pack. But it is still important to have any 12V battery hooked up so the DC to DC converter has voltage feedback to adjust the current rate.
You can buy Yuasa battery for about $200 online. Either from Toyota dealer or Yuasa directly.