miscrms wrote:Have any Leaf owners tried switching to a good quality deep cycle AGM type battery? I went to an Optima Yellowtop on my 2005 Prius, which is also notorious for undercharging 12V batteries, and have had no issues for 5 yrs. Even in Phoenix, which also tends to also be tough on 12V battery life.
Several LEAF owners have done this. One issue is that the 13.1V float voltage used by the LEAF can actually be LOWER than the standing voltage for these batteries when fully charged. In other words, the LEAF charger may actually DISCHARGE the battery if fully charged rather than simply failing to charge it. At least one owner has installed a Li-ion 12V replacement battery.
miscrms wrote:It does seem surprising to me that the Leaf uses a flooded type battery, as well as a conservative charging routine. The only advantage of a 12V flooded I can think of is its tolerance to more aggressive charging.
They are also cheaper.
miscrms wrote:I guess the explanation is in the "reduces the electric power consumption from the Li-ion battery" statement, seems like they went a bit too far in the efficiency direction.
miscrms wrote:The Leaf does also use a 12V backup capacitor bank as someone else mentioned the Prius does.
That's true, but only for MY2011/2012. In MY2013 and later LEAFs, backup braking power is provided by a hydraulic acumulator.
miscrms wrote:So its a little surprising that it could still get into this sagging voltage failure mode if that is indeed the cause. Unless I guess the 12V voltage is just not sufficient to charge the cap bank sufficiently? But that voltage should come up quickly as soon as the DC/DC converter engages when going ready?
It seems that the ultracapacitor in the MY2011/2012s must be charged above a certain level before the brakes will work, even if the voltage in the car is fine. I know this because my dealership could not deliver the car to me after reprogramming the brakes due to the technician not knowing how to recharge the ultracapacitor. But it did eventually charge up on its own.
miscrms wrote:Still it doesn't seem like a total brake failure should be possible even if the electronic control system fails completely. According to the manuals (and my own experimentation) there is still manual hydraulic braking force available in the event of a complete system failure. In my case this was simulated by disconnecting all control and power connections to both the ABS and IBU/master cylinder. Without the boost pump I will say the braking is very heavy, and the pedal position quite low from what I recall. So if the brake boost motor cuts out it may well feel like you've lost the brakes, but a firm pressure on the pedal should still stop the car.
The technician who had the problem with my car said the pedal went straight to the floor..
miscrms wrote:Additionally its perhaps worth noting that the parking brake can (according to the manuals) be used while the vehicle is in motion to apply mechanical cable driven force to the rear brakes as long as the handle is pulled up. Of course this motor does depends on 12V power, but not sure how sensitive it is to voltage.
The electrical parking brake system was replaced with a mechanical one starting with MY2013.