12V battery life

I found this older thread as I was wondering if my ~12 year old original (made in Japan) battery has to be replaced after I have put it on a smart charger recently after longer than usual ABS booster pump running time once the driver door opened in the morning. I took the battery to a local Canadian Tire shop to do a load test (Twice - two separate days and different mechanics ) and both times they told me the battery is fine. I think I am keeping it for now, no replacement for me yet.

QUESTION: Is it OK to not replace it this long, how much longer can this battery last, anyone with same experience?

I have a portable booster, just in case I or others need a boost.

 

You risk damaging the computer because they are not getting enough voltage or amperage.
12 years is really old. More than your money's worth.
Obviously they don't understant about a Prius battery, or what the computers NEED.
You're just keeping it on life support.

If you want to take the time to open the hood, attach your jumper, start the car, remove the jumper,
close the hood, finally drive off..... all the time, keep it.
You also risk having issues because all the power from the inverter will try to charge a dead battery.
You'll likely start getting error messages and code because of the dead battery...

Invest in a new Toyota 12 volt battery. And charge it at 4 amps or less for at least 8 hours before installing it.

 

I am not quite sure if my explanation was clear. There are no trouble codes or risk of low voltage damage to computers. This battery holds its nominal voltage for many days or weeks when I am not driving the car and then starting with no problem. I agree that 12 years is a long time for FLA battery to work normally, but this battery appears to work and charge normally, no issues, no trouble codes.

Do you mind sharing how do you tell if the battery is on "life support" apart from its manufactured date?
That is why I took it to the shop to do a load test and it passed that fine, how else it can be tested?

 

12 year old...... About twice the normal age.
You said you had to put it on a charger. They only reason to do that is you rarely
drive it so it doesn't get charged daily, or it's getting weak.

Would you wait until the engine oil completely breaks down before you'd change it?
If you did, you'd be replacing the engine too.

When the battery gets weak, the inverter works harder and longer to "TRY" to charge
the battery. Which could lower M'sPG. When you first start the car, the battery starts all the
computers, which MUST have a certain constant voltage. If they don't, they'll get hot quickly,
and try to draw more amperage trying to get enough voltage. HIGH risk of burning them out.

It's your car, if you wish to use a 12 year old 12v battery, go ahead.

 

12 years is a good life for an AGM battery. (It is much better than you can expect from a normal 12v car battery). It's definitely time to start shopping for a replacement. I don't agree that it will lower your MPGs or risk any damage to anything on board the car, but it will strand you one of these days, and Mr. Murphy will ensure it's the most inconvenient possible moment.

"I'm well acquainted with the good Mr. Murphy - I married one of his daughters, and sired several of his grandchildren." - Carroll Smith

 

Thanks for your comment. I see no MPG degradation at all as far as I can tell. I agree it is a good time start new battery shopping, in a meantime I am really curious about this battery real condition. The only reason I charged it was to check if the charging it will shorten ABS booster pump up time and it did, but not dramatically. Other than that the battery appears to work fine. I just checked the voltage in vehicle with my cheap voltmeter (not Fluke, of course) and it showed 12.35V which is ~70% SoC for AGM. Maybe I'll buy a battery analyzer (any recommendations?), as I am getting curious to learn more about the battery life now and what affects that. Note that the car lives in moderately cool climate, not a hot desert.

 

No, that was not the reason. I did not charge it because it was weak, it was about 60% SoC at that time. I did a full charge to test if it will shorten ABS booster pump up time.

 

"I have put it on a smart charger recently after longer than usual ABS booster pump running time once the driver door opened in the morning."

Yuo just wrote it was at 60% charge, that's weak. But also said it was at 70%, 12.35v is marginal
for a Prius 12v battery.

How long had it been sitting? Do you drive everyday? How long do you drive, on average?
You wrote it's the original 12 year old battery. That IS old, even for an agm battery, average for
Toyota's original, and replacement, battery has been 5-7 years.

And since the inverter will work harder, so to speak, to charge the battery it will use more power
from the hybrid battery, which will drain that battery, causing the engine to run more often and
for longer to charge the hybrid battery, thus effecting m'spg.

It's a 12v battery, nothing really excting about it, and it's really pretty simple.
Smarter to invest in a new Toyota Prius battery, and a 4 amp agm charger/maintainer and charge
the new battery for at least 8 hour. No place charges there batteries, they just sit on the shelve until sold.

 

The car is not driven every day, sitting outside in colder temps for a week or more. I am shopping for a new OEM battery now, thanks for all the help here, appreciate all valuable information provided.

UPDATE: I called my local Toyota Dealership, Service department and told them my story about the 12 year old battery and whether changing this battery is now in order. They told me they have seen Prius batteries last over 16 years in their shop, so if the load test is good they recommended just continue using the battery until there is an issue. The main reason batteries are dying sooner is the car not being driven often and getting a battery tender is a great idea if that is the case. Just passing on what I heard from Toyota Service today.

 

I just bought my 2010 Prius as a fixer upper, with 262k miles and a blown head gasket... AND the original battery. So yes, I believe the dealer. AGM batteries have more gradual failure characteristics than normal car batteries. Though I stand by my previous point: at that age it is not a question of if, but when is it going to strand you.

 

I agree. Thanks.

 

It's YOUR battery, do whateer you want with it.

 

There are probably enough good reasons for having a healthy 12 volt battery (not liking to be stranded, etc.) but this part seems more like scaremongering.

ECUs made for a car environment have a wide input voltage tolerance, from 15 volts or higher down to well under 11. The internal regulators that turn the arriving input voltage into the constant 5 volts or so the microprocessors demand can happily do that trick as long as they have even a few volts of headroom. The regulators draw higher average current at lower input voltage (the switched-ON pulse times are longer), but that only matters to heat dissipated in the regulator's input stage, where of course the higher average current goes hand-in-hand with a lower voltage drop.

Several of the ECUs in the car have trouble codes they will set if they've seen a low input voltage, so you can tell if that happened. Those codes are generally triggered at around 9.5 volts (which is very low for a nominal-12-volt system, but still plenty for the ECUs to do their jobs and log those codes for later review).

When the input voltage is too low for an ECU to operate, it typically just doesn't, and will reboot when the power is ok again.

 

I can tell you that a daily driver with an old agm battery can start with pretty low voltage, often as low as 10.5 vdc. Obviously the inverter assembly will quickly recharge the 12v battery.

You still get good load tests over and over again, especially with the newer electronic testers that don’t require a charged battery and do not have a large resistive load to perform an old school load test. Then one day you drive 20 minutes to a shopping center and park it. Thirty minutes later you get a no start due to a depleted battery. You pull out the lithium jump start and away you go. Unless it happens to your wife or kids.

Rinse and repeat over the next couple of weeks unless you replace the agm. Its kind of like tires, sure you can go another 10k after the wear bars are flush but does it make sense for safety and reliability?

 

I have two different chargers for my Prius. One is the Harbor Freight 4amp maintainer Viking charger. The other is the one I use almost all the time. It's a 10amp 7 stage quick charger that reconditions the battery and does quite a few things that a standard charger does not do. You would think 10amps is a good charge but it starts at 10amps and draws down to as little as 1amp when complete. Usually takes 2-4 hours to run through the conditioning cycle.

The Harbor Freight charger just does straight 4amp charger and when fully charged goes in to trickle charge mode. You can leave that charger on throughout the winter. The 7 stage charger, you select motorcycle battery mode for trickle charging.

I charge my 12amp one a week in the winter months and every other week to once a month in the summer.

I have the Astro TRMS 6000 count multimeter (Amazon) everybody knows the model. I bought some alligator clips for it and my Prius registers 12.44amps. It has not be driven for a couple of days.

I think that getting a good little charger that is at least 4amps will make your battery last a very long time in a Prius. I think once the battery hits 8 years of age. It's probably time to think about getting a new battery. If people live in very hot or cold climates, their battery may last 4 or 5 years. If they maintain it with a charger once a month. It would probably last a lot longer.

 

Anybody knows if AGM batteries manufactured by East Penn have good reputation?

I was told that Canadian Tire's Eliminator batteries are made by East Penn and they have the S46B24R Eliminator battery needed for Prius.
East Penn make Deka Intimidator AGM battery for Prius as well, looks exactly the same battery spec as Canadian Tire Eliminator.

Thanks in advance.

 

It is NOT good to use 10 amps to charge the Prius battery!
I believe it's like 4.5 amps max...

 

bump..

 

It's not like a bench 10amp charger. It charges at up to 10amps but for only a short period of time. By the time the battery is reconditioned, it's charging @ 1amp.

 

FWIW My 2015 Prius with over 150000 miles is still on the original battery - only one time I needed a boost: last year when we hit -30.