GS450h questions

Congrats on getting the GS450H. It’s an awesome car and fun to drive especially with a fully functional battery pack. I bought one few years back with a bad battery and I've been messing with it since then. I used resources from here and YouTube to get it fixed multiple times. My battery was in really bad shape the car wouldn’t even start or it shuts of after few miles. Here are few things that might help you with fixing yours;

1. MPG isn’t a great indicator of battery health on the Gs450h because the hybrid system on these cars is pretty much an acceleration booster. Your car might get much quicker once your battery is fixed but you won’t get more gas mileage than what you got now.
2. Use Dr Prius android app to get an idea about the health of the individual cells. I couldn’t find a better or easier tool for this car. The app recognizes the car and number of cells automatically and help you identify the bad cells.
3. The battery is extremely heavy. You’ll need 2-3 adults to get out of the car and help you with bolts and nuts especially with your shoulder situation.
4. Complete battery for this car is much more expensive than a Prius or a Camry battery. And don’t even think about a new battery from the dealer. So I think a DIY solution is worth it especially if you’re able to identify the bad cells. You might even have good cells but corrosion on connections and bus bars. You should at least try to fix it once before you drop thousands on a replacement.
5. If battery indicator goes to green a lot or runs out quickly it’s definitely a battery issue. No EV mode and it’s not designed to drive on electric only so I think it’s normal for the gasoline engine to kick after few blocks of cruising on electric.

You don’t have tons of miles on your battery and I don’t think it’s in a bad shape. Good luck fixing it.

 

It’s the hybrid battery it needs to be replaced

 

Battery replaced with brand new or remanufactured?

 

Park the car after the engine warms up fully and see if it shuts off after 5-10-15sec - it's the idle speed calibration (ISC). Also called MAF calibration, s3+ mode, etc. It just needs to "idle" without any sort of load or anything that might affect readings - I've managed to get it to shut down while literally crawling in traffic, but speeds that register on the speedo = 1k rpm idle. It will also run if you let it sit in S-mode and if it needs to raise the water temperature for cabin heat.

As for the expense - 40 6-cell modules vs 28 6-cell modules, so shouldn't be much more expensive. I refurbed mine for ~1750eur equivalent over here, gen4 ch-r modules off of crashed 2017 cars, 50eur per module, discount for getting 40. On that note - the 4th gen gs hybrid also uses 6-cell modules... yay - no need to worry like on an RX or LS. These do seem to eat batteries more than the other toyota hybrids, but the refurb isn't so difficult.

I do have the prolong deluxe kit - the relevant thread in the forum has all the info, mine didn't differ. In short - it works, but it's not a miracle. Read up

MPG - otto-cycle motor (the same 2GR-FSE that's in the IS350 and GS350), the next gen has an atkinson cycle configuration (2GR-FXE/2GR-FXS) and is waaaaaaaaaay better in this regard. It is slower, but that seems to be due to the changed rear diff - the US and JDM spec 3rd gen gs450h have a 3.769 diff, whereas all 4th gens + the EU 3rd gens use a 3.266... and the acceleration ratings didn't change in the EU

EU diff:

EU gs430 diff (3.6-something, not quite 3.769):

Diffs can be easily swapped.