Many of us with early 4th Gen GS450h (2012/3) are probably due for 12V back-up battery replacement. Mine just died last week.
Instead of spending $700 at the Lexus dealer, here is how I replaced mine.
1. From research, it seems its best to use an AGM (Absorbed Glass Matt) replacement battery.
Maybe it's OK to use a normal lead acid as the DC-DC converter keeps it at full capacity most of the time, anyhow I used an AGM, which can deep cycle and lasts longer.
2. In terms of what is readily available in the US, the most similar AGM I could find was a Delphi 47AGM.
Its readily available on Ebay/Amazon for about $170.
It's similar in capacity at 60AH, vs 58AH for the existing.
Most importantly the +- terminals are the correct way around for the wiring.
See the pictures below for comparison to the Panasonic battery that came in the car.
3. For the vent hole, I drilled out the minus size to fit & sealed off the plus side.
Then I inserted the vent hose with a little butyl to seal it.
4. It's a tight fit to the battery tray - it bends the base bracket a bit, but it basically fits & is a little higher.
The upper hold down bracket also just fits and bends slightly.
5. The Battery + terminal & connecting terminal need to sit at an angle, so loosen both nuts and adjust (see the picture).
I gave up on the Battery + cover and just took it off. The Battery - wire fits fine.
Instead of spending $700 at the Lexus dealer, here is how I replaced mine.
1. From research, it seems its best to use an AGM (Absorbed Glass Matt) replacement battery.
Maybe it's OK to use a normal lead acid as the DC-DC converter keeps it at full capacity most of the time, anyhow I used an AGM, which can deep cycle and lasts longer.
2. In terms of what is readily available in the US, the most similar AGM I could find was a Delphi 47AGM.
Its readily available on Ebay/Amazon for about $170.
It's similar in capacity at 60AH, vs 58AH for the existing.
Most importantly the +- terminals are the correct way around for the wiring.
See the pictures below for comparison to the Panasonic battery that came in the car.
3. For the vent hole, I drilled out the minus size to fit & sealed off the plus side.
Then I inserted the vent hose with a little butyl to seal it.
4. It's a tight fit to the battery tray - it bends the base bracket a bit, but it basically fits & is a little higher.
The upper hold down bracket also just fits and bends slightly.
5. The Battery + terminal & connecting terminal need to sit at an angle, so loosen both nuts and adjust (see the picture).
I gave up on the Battery + cover and just took it off. The Battery - wire fits fine.
