Cross-post from honda-hybrid yahoo group.
After reading a lot of reports that new 12V batteries fixed recals for some of us on the yahoo group, I went to watch the 12V system voltage more closely while driving. I thought, I'd share my observations:
While the DC-DC converter is operating, the 12V system is held very accurately at 13.85V (at least in my car). No matter what 12V load I'm drawing. (But then, I don't have a Wayland sub.)
During assist, the DC-DC tends to turn off, presumably to preserve current to be available for the IMA motor. This causes the 12V system voltage to drop, depending on what accessories are running. The little battery is now the only source of 12V power.
However, once the 12V system voltage drops below 12.29V, the DC-DC converter instantly turns back on, quickly restoring the voltage to 13.85V. This happens even under extended full assist.
As someone else had pointed out a while ago, the DC-DC converter may also turn off during cruising (no assist) if the 12V load is small (no accessories running). But it always comes back on once the voltage drops to 12.29V. The same is true during auto-idle-stop.
In summary, I still don't understand how the 12V battery can have an effect on the recals. Even with the most severely dead 12V battery, the DC-DC would still prevent a drop below 12.29V.
However, there was a recal for DC-DC's once. And one might assume that they can fail, too. A bad DC-DC combined with a bad 12V battery would certainly spell trouble!
After reading a lot of reports that new 12V batteries fixed recals for some of us on the yahoo group, I went to watch the 12V system voltage more closely while driving. I thought, I'd share my observations:
While the DC-DC converter is operating, the 12V system is held very accurately at 13.85V (at least in my car). No matter what 12V load I'm drawing. (But then, I don't have a Wayland sub.)
During assist, the DC-DC tends to turn off, presumably to preserve current to be available for the IMA motor. This causes the 12V system voltage to drop, depending on what accessories are running. The little battery is now the only source of 12V power.
However, once the 12V system voltage drops below 12.29V, the DC-DC converter instantly turns back on, quickly restoring the voltage to 13.85V. This happens even under extended full assist.
As someone else had pointed out a while ago, the DC-DC converter may also turn off during cruising (no assist) if the 12V load is small (no accessories running). But it always comes back on once the voltage drops to 12.29V. The same is true during auto-idle-stop.
In summary, I still don't understand how the 12V battery can have an effect on the recals. Even with the most severely dead 12V battery, the DC-DC would still prevent a drop below 12.29V.
However, there was a recal for DC-DC's once. And one might assume that they can fail, too. A bad DC-DC combined with a bad 12V battery would certainly spell trouble!
