I can't find that this Prius has ever had its original 12v battery replaced. Any way to tell if it's original, or is it possible to test these? I have read that they normally only get about 4 years, and that would make this battery about 8.5 years old. Your thoughts?
The original equipment battery is made by GS Yuasa. If you remove the battery bracket over the battery, you can see the date code located near the middle of the top of the battery, in DDMMYY format. If you see that the battery is made by some manufacturer other than Yuasa, you will know that it had been replaced. Then look for a date code on the top of the battery. If you see that the battery is made by GS Yuasa but it has a more recent year date code than 2005, that will mean that the replacement battery was sold by a Toyota dealer. Many US battery manufacturers use a very simple date code consisting of one letter and one number, where the letter corresponds to a month while the number corresponds to the last digit of the year. For example, B4 would mean February, 2014 (or it could mean February, 2004, etc.) A simple way to assess 12V battery condition is to measure its voltage after it has rested overnight without being charged. That will give you an idea of its current state of charge but won't say much about the battery capacity. A new, fully-charged 12V AGM battery will measure ~12.9V.
You might want to check your battery using this test procedure. If it is original, then it has lasted well beyond its usual service life.
All I see on top of the battery is "S34B". Say's it a Toyota battery on a sticker on top without pulling it all the way out. I tested the battery and I got 12.55 Volts.
It sounds like you did not remove the battery bracket on top of the battery. S34B is the first four digits of the GS Yuasa battery size code. The full code is S34B20R. This is the smaller of the two 12V battery sizes for 2G. I assume that your car does not have the Smart Entry/Smart Start feature since it has this smaller battery installed. 12.55V is pretty good if the car had been sitting unused for 8 hours or more. That means the battery is at ~60% SOC.
yes, i did not remove that bracket all the way. Just unbolted one side to read what i could. And yes, i do not have the Smart Entry/Smart Start. So where would the date be? below the size code? The car had been sitting for about 22 hours when I tested the battery.
Can you get if off without disconnecting the battery? If I disconnect the battery will that cause any harm?
Well, since the positive battery terminal is attached to the battery bracket, it may be difficult to remove the bracket without first disconnecting the battery terminal. However as previously stated, you will lose the radio station presets. You will also lose the trip odometer and MFD mpg/miles driven counter, and will have to reset the driver's window auto up/down function. None of these are highly critical. Finally, the engine ECU keeps track of how long the car has been driven with the battery connected (for emissions testing purposes) and that counter will be reset when the battery is disconnected. All this means is that your car cannot be taken for an emissions test until you've driven some distance after reconnecting the battery, like 100 miles or so.
The only thing I can add to what Patrick has shared with you is that if in the future you ever decide to change that little battery there is a post here on Prius Chat that documents exactly how to do it. Look in my signature file below this post. You will see links there. Two of the links pertain to the 12 volt battery in question. One link will lead you to the onboard test. The other link will lead you to a post on how to change the battery. Refer to post #8 in that string for detailed info. It took me about an hour to change the little battery in the Gen II Prius I used to drive. You only need a small handful of tools. A list of all the tools I used as well as detailed step by step instructions are plainly written out in post #8. Please don't ask the dealer to change your battery for you. They will charge you a outrageous amount on a job that you can easily do yourself. Have a great day, and I hope this info helps you. Ron (dorunron)
