PSA: Change your 12 volt battery every 4 years

The Optima I have tends to settle down to around 12.7, especially after the car's sat idle a day or two. If you measured that 13.1 directly after charging, that's due to "surface charging". Beyond the term I'm clueless, but basically: the car will read falsely high immediately after charging. Give it a day or two with some use, and check again.

All said, it's still a good idea to periodically recharge. An automatic "smart charger", rated no more than 4 amp max, is good for that.

 

Not for a week, either.

 

every battery i've ever had, of any kind, slowly loses voltage until it's too low to operate properly.
the reason to charge them initially, is in case they've been sitting awhile, because it takes a lot of driving to do it otherwise.

 

guess that's the 'nature' of a battery//

 

Why do you say this?

I check my battery voltage about monthly and it has held at 12.8V since installed about a year ago. As long as the charging system is working properly and before the battery begins to decay why shouldn't it maintain the proper voltage.

 

you check it monthly WITHOUT driving the car in between?
if not, the battery gets charged & for sure the voltage is 12.8 every time you measure it.... //

 

I've still got the OEM battery, that I pulled out and replaced with an Optima. It sits under a work bench, reads about 12.58 volts. A week, or two, a month or three: it'll still read 12.58. There are limits, eventually it does drop a bit, but I keep on it, charge it not too infrequently. From a suggestion here, I decided to hang onto it for a while, as a back up, just in case.

On the other hand, the voltage on the battery in the car slowly but inexorably declines if the car sits idle, due to the low but persistent "phantom drain", in the vicinity of 15~20 milliamps.

 

Where on the world did you read that?? I drive the car daily.

 

obviously you can't check then how good it holds a charge/

 

My original battery is still in use, and it's dated 150609W. I test weekly with fluke and usually tests 12.6 at rest. 13.3 in ACC with headlights and 14.4 with 2010 in READY. However, the traction battery seems to drop 2-3 bars after cruising into town (after just 2-3 miles using battery) directly after a 45 min drive, over hilly terrain at 65 mph. Upon entering the town, the traction battery is up to full. (Getting 50ish MPG and running A/C) The traction battery just seems to drop the bars at once (or in two sequences back to back) as if to burn off charge down to lowest 2, then charges right back up with ICE and/or REGEN. I thought maybe the 12 volt was causing a drain on inverter/traction battery but my thought may be wrong? What says you guys? Could traction battery have seen its better days after just 160k later? how reliable is a simple ELM and phone app to monitor remaining SOC and battery module charges while driving?

 

it's possible the battery is going south, wouldn't be that unusual. i think you need tech stream to watch the modules while driving.

 

I thought of that too but the rate of satisfaction is all over the board. Any recommendations of who to purchase from with out getting JIPPED with an unusable imitation?

 

no, you'd have to search the threads. i don't recall anyone mentioning a specific supplier, but there may be something in there.

 

I notice you have engine link are you using it with the ELM? if so how are the results?

 

Why would I want to know how it holds a charge without driving it? As long as it holds at about 12.8V with daily driving I am satisfied.

Yes. It works great with the iPhone or iPad.

 

Just recieved ELM tday. "Battery life remaining" states 69%. SOC 74%
Does EOBD read remaining traction battery that well?

 

I replaced mine two months ago as it was the original factory battery that lasted since the car was manufactured. It lasted a very long time but after putting the MFD into diagnostic mode to view the voltage of the battery and it was about that time needing replacement. I bought the same Duracel battery half the price that you paid for from the same store.

Posted via the PriusChat mobile app.

 

I have no idea how accurate the Battery Life Remaining parameter is.

The battery control module tries to maintain the SOC (State of Charge) at 60% on level ground and between 40% and 80% overall.

There are 14 HV Battery module pairs. The voltage for these modules are listed as V01 - V14 and the resistance is listed as R01 - R14. If you can read these and list them on here, there are some battery experts on here that can give you their opinion on the relative health of your battery.

HV Battery failures for a 2010 is very rare on here though.

How many miles do you have on your car? (I just re-read your thread and see 160k miles, which is higher than most 2010's I have seen on here.)

 

There are two "topics" here.

The 12V battery is pretty much like any other car's. It will self discharge over many months, but when connected to the Prius it will be slowly discharged by the "parasitic load" the computers put on it at around 15 to 20 mA (as already posted). If ANY interior light is on that's a much larger load, between 0.5 A and 2 A, depending on which light(s) (some work in pairs - door lights for example).
The charging system for the 12V battery is not an "alternator/regulator", but rather an electronic charger that is part of the inverter. It only operates when the car is in "ready", and it draws its' power from the "traction battery", which is charged by MG1, and the traction battery only charges when the car is in "ready".

At any rate, with any car, to fully charge the 12V battery, especially if it has been drained more than a bit, it takes an hour or two of driving, maybe more. The Prius is no different. Short trips of 10-30 min. won't fully charge the 12V battery. So if you only drive for, say, 20 minutes per day, and park the car for several days, you WILL have problems with the 12V battery, eventually.
Solutions include occasional charging, from the boost point is easiest. Another good practice if the car is used in the way just listed above, is to use a battery maintainer when the car is going to be left for several days. Again, it can be connected to the boost point under the hood. This is how Pearl S spends most of the winter.

The second topic is the high voltage or "traction" battery. Remember, even though this battery may look large, it is not as an EV battery. It's 6.5 A-Hr at 200V. It can be discharged from indicated "full" to indicated "empty" in just a few minutes if powering the car. Each generation of Prius seems to use this battery more and more. Probably due to improvements to the battery and probably due to the engineers becoming more comfortable programming each generation to use it more (for better fuel economy and smoother operation). So don't be alarmed if you see this battery state of charge indicator moving up and down a lot. The system (HSD) is designed to operate this way.

 

Thanks, found all those PIDs and looking like all resistances are alike either. 02ohms or. 03
The voltages vary with the difference in min/max running .20-.40 (delta? )
Min modules run between #6,8,9...
Max modules vary between 1,14 etc.
The prius HV Battery SOC keeps level on the road but I'm guessing the HV control module takes the first chance to discharge for its own reasons...?