My HV battery replacement experience - Australia.

Overall it was fairly positive. The original HV battery (2005 pruis) lasted 13 years and 314000 km before finally throwing all the warning lights a few weeks back. It finally died on a long descent near home, but it had been showing signs of weakness (reduced capacity) for quite a while. I had been expecting it's imminent failure for some time, so it definitely wasn't a shock or anything.

Not a very large number of Prius here in Australia, so I couldn't locate any low mileage donor cars to even consider a secondhand battery. And I definitely didn't want a rebuilt battery, given some of the issues that I've seen people on the forums here report with them.

A new battery from Toyota cost less than I was expecting, $2430 AUD (about $1865 USD) from my local dealer without any shopping around. I should have fitted it myself but was short on time so the dealer did it and the total price was $2890 AUD ($2196 USD) all up. I dropped off the car to them in the morning (it was still driveable but only just) and it was ready for pick up just after lunch time. The guys also did the steering recall while they had it.

Picked it up that afternoon and it hasn't driven this nicely since it was new. I immediately noticed much more stable SOC levels than I've seen for a long time (mostly staying at 6 blue bars) and much longer "glide" distances. I can definietly notice more power, with the electric motors much more willing to "put in". It also seems quieter and drives more smoothly, probably because the petrol engine is doing less peak work.

TBH, I probably should have got a new battery a year or two ago and not even waited for the old one to "officially die". It's a much nicer car to drive like this.

 

Now that it's got the new battery I'll definitely keep it for a few more years. There were no other problems with the car and it's been amazingly reliable.

I know that a lot of people think it's not worth spending anything on a car this old, but I do all the maintenance and I really know its history, so fixing it seemed a much safer bet than say buying a cheap one second hand where everything is an unknown.

With the price of petrol here and the amount of kms I drive, it will pay for the battery in under 20 months.

 

Hi Jamie. Yeah I've been interested to see how that goes too. I've been monitoring it and was going to update this thread with that info as soon as I'd run a couple of tanks through it.

Yes there's definitely been an improvement. Hard to say exactly how much (so many other variables and my wife drives it more than me), but at this stage I'd say around 5% (possibly even a bit more) from what I've seen so far.

 

Those figures align pretty well with my improvements in fuel economy too Jamie.

Up until this last week my wife had been on holidays, so I've been driving the Prius more than normal (she is the usual driver). And that's made it hard to judge the improvements because I usually get about 10% better fuel economy than her anyway. Last week however she averaged 4.0 whereas she would normally average about 4.3 (L/100k), so not too dissimilar to what you have noticed. It's about a 7 to 8 percent improvement.

There is one other improvement that was totally unexpected however, and that is the engine oil consumption seems to have drastically reduced since the new battery has been installed. It has used almost no oil (maybe 100 to 150 mL) over the past 4000 km whereas previously it would have used about 500 to 600 mL over that distance. So oil consumption seems to have reduced by about 75%, which is totally crazy as nothing has even been touched in the engine.

This one has me really scratching my head because I can't see why it should have any effect, and TBH I've been reluctant to even mention it here until I have more data. As I noted above, the driving pattern has been a little different over the past month or so, and that might be all that it is. It might also be due to it doing a lot less engine braking (as it does when the battery is full) since it's had the new battery.

Anyway, now that my wife is back to using it in her usual driving pattern I should be able to get some more solid data on this apparent reduction in oil consumption over the next few weeks. It does a lot more big hills (small mountains) in her normal commute and I think that was causing a huge amount of engine braking. I'll see how the oil consumption is holding up after a few weeks of her normal driving and update my findings here.

 

Well the engine probably runs about 10 percent less around town (but not so much on the open road). So that's nowhere near enough to account for the 75 to 80 percent reduction that I've noticed in oil consumption. There is definitely something else going on here as well. I'm just not totally sure what it is yet.

 

Yes engine load is generally less with the new battery, as is the percentage of the time that the engine runs (due to spending a bit more time in full EV mode, especially around town) as noted by Prodigyplace above. I'm sure that's at least part of the story.

I've got some suspicions that when the HSD spins the engine to dump charge (like in B mode or when descending a big hill with the SOC maxed out) that it's doing so at high RPM and under fairly high vacuum, and that this causes a disproportionate amount oil consumption compared to normal driving (probably through the valve guide seals).

I noticed this once before a few years ago when holidaying in the mountains and doing heaps of engine braking (B mode) on big descents to save stressing the battery. My oil consumption was quite a bit more than normal at the time, almost double as I recall. I actually thought I might have damaged the engine or something, but as soon as I went back to driving in my usual terrain then the oil consumption went back to normal. I mentioned it here and several other members told me that they'd had exactly the same experience - significantly increased oil consumption when driving in terrain that causes a lot of engine braking. So I think that this might be the main factor at play here. So far with the new battery it has hardly ever been maxed out, so none or very little engine braking or charge dumping.