I've had my 2004 Prius (Bought with 174k, now almost 178k miles) for a little over a month, and I think I may be coming up on a battery failure- The last tanks of gas went from 50 mpg, to 48, now down to barely 44, and the battery seems to drain rather quickly. I parked a few days ago with the A/C on and ran it for maybe 5 minutes, not paying attention to the charge level. Shut it off and went into a store, came out and it was at 2 purple bars. Powered it up and drove maybe a mile, the charge was still at 2 bars. Force charged it to 4 bars, went into another store. It never really seemed to recover. It isn't losing charge overnight and will stay at 6 bars on the highway, but seems to be discharging quicker now. The engine seems to be running more, and it won't go very far on electric only before the battery is discharged enough to start the engine. My question (s) are, 1. How long do I have? 2. Will it get me home once it lights up the dash (I am working 3 hours from home with a trip home every week or so)? How far can it be driven once that happens? 4. What are my options as far as replacement? And how much will it cost? I'd like to keep my Prius going for as long as possible, or at least until it's paid for! Is the replacement something my Dad and I can accomplish or is this a professional only job? My Dad is great with cars but has never worked on a Prius. Any advice is appreciated, thanks!
Recondition it, quick! It may be too late, but probably not: What causes hybrid batteries to degrade and fail? - Hybrid Automotive
You do not mention the dash lighting up with warning icons, so I assume no codes have occurred. One possible way for the 12 volt battery to fail is to short out internally. When it does this the car uses a great deal of power trying to charge a defective battery. Test the 12 volt battery in the morning before you start it, and if it is much under 12.4 volts no load it is bad. the Prius takes an odd battery (S46B24R) that will be about $150 but it has to vent to the outside of the car to protect your passengers.
I do not know its going to drain to purple pretty fast with A/C on. Some say a little warm up helps a lot with older batts, so in PARK let the engine cycle on and then cycle off when you start up. Maybe turn off A/C in this period. Now go...just takes a few minutes.
No warning lights yet. I usually try to let the engine cycle on and off before driving, if I don't, especially with the a/c on, I can go from 5-6 bars to 2 or 3 before I get to the first stop light (2 blocks from our house). Has anyone used the prolong charging system and would it actually benefit my (possibly) degraded battery? Is it worth the $400?
Here are some before and after testing done by a fellow PriusChat member: Quantitative Results of Grid Charge/Discharge | PriusChat We have sold close to 2,000 of our systems, many to Prius owners like yourself. Several are here on the forum, but in case it helps you can read some of our customer feedback here: Hybrid Automotive LLC
I would recommend this: Prolong™ Battery Reconditioning Package – Hybrid Automotive Works great, same a ton of money instead of buying a "junkyard" battery.
In the summer, the AC draws more power to cool the car. The A/C can drain forced-charged to full (80%) battery to two purple bars (40%) in as little as 10-15 minutes, less if the battery is aged. At full power, the AC can draw around 10 amps running the compressor. To save power, set the AC to the highest temperature you can tolerate. If you use AC Auto mode, try setting a higher temperature so that the compressor runs less and at a lower power, but then also setting a higher fan speed, so that you get more airflow on you to compensate for the warmer temperature. At a moderate temperature setting, the AC draws 3-5 amps instead of 10. I recommend reading this thread : How to test HV battery state of health on your Gen 2 (answer) | PriusChat and performing the test so that you can test your approximate battery state of health. If your battery is degraded, which it most likely is, given your mileage, a battery reconditioning will certainly help. I just reconditioned mine over Memorial Day weekend, and my 170k mile battery is acting the same way my mom's 2014 Prius' battery acts - Holding its SoC much longer, taking much more charge energy before it reaches full on long downhills. Just make sure to closely follow the directions and don't over discharge. But do keep in mind, even my freshly reconditioned battery drains fairly quickly when sitting parked with the AC running in this heat - Its been around 90+ degrees during the day down here in Alabama, and the AC takes its toll on your mileage when it runs non stop.
