New to this website as we just bought a 2018 Rav4 Hybrid for the wife, which she loves. I've been driving a Lexus RX450H though for many years; very similar design under the hood, just beefier with the 3.5 V6.
(1) Everyone freaks out about the 12v battery. It's just a generic 12v battery, with AGM preferred because it's zero maintenance. Just measure the dimensions and go to Costco or somewhere else. Because the Lexus battery is in the rear but inside the cabin, the battery needs a vent to the outside. Many batteries have a small vent hole in the side for that purpose. The existing rubber hose goes into that hole, or find some adapter that you can use. Frankly, with an AGM battery there's very little outgassing anyway, but I think the regulations insist a battery be vented outside regardless.
Dealer wanted $400 for an "official" battery. Costco one was $250. Perfect fit.
(2) Buy one of those tiny battery packs for jump-starting if/when the old battery dies. Under $100 and about the size of a paperback book. They deliver an amazing amount of current for 5 minutes, which is all that cars need to start. In fact, with a hybrid there's very little current draw, since the 12v system is just for powering the computers, lights, and radio--the 250v traction battery gets its voltage doubled through the inverter and cranks the built-in motor/generator bolted inside the engine. That's why the ICE starts in a quarter-second.
(3) If you need to jump start, no need to get the rear hatch opened. Do what the manual says: Open the hood, remove the driver side fusebox cover, flip the red plastic cover up, and connect the +12v clamp to the metal bracket inside. Then the -12v clamp to any beefy metal part of the engine block, and you're in business.
(4) If you have the new battery ready and the tie-down removed, you can do a battery swap in just a few minutes. I didn't lose any settings on the radio or anywhre else.
That's ridiculous pricing, that's almost the price of a lifetime warranted Toyota hybrid battery ($1800-2500 USD) from Green Bean in the US.
