What charges the battery?

Both statements are true. The first holds for pre-production demo vehicles. The second is for the production version.

In 2014 Plug-in there is a single 4.4kWh Li-ion battery pack, charged either by external power or regenerative braking.

 

On thing that might have caused confusion for the first salesman is that the SOC display on the Plug-in acts as if there are two batteries. It starts with the "logical" EV battery that goes down to "zero" when down to 1/2 to 1 mile of EV remaining and then goes back to "full" on the "logical" HV battery. You can tell which is which in that the HV battery shows the SOC in stripes and the EV battery is solid.

 

See the difference...

 

To better depict what's available before & after depletion.

Otherwise, the gauge would be worthless at times.

It's pretty obvious when you actually observe it firsthand.

 

Or the ICE when the EV miles run out or any other time of HV operation.

 

Just to clarify for the OP: When the traction battery is depleted, the ICE will only charge the battery within a narrow range to support hybrid vehicle (HV) behavior. It behaves essentially like a non-plugin Prius in this case. The two different kinds of displays are for the purpose of illustrating how the system is currently managing things: as an EV or an HV.

All production models of the PiP have only had the one 4.4KW lithium-ion traction battery (plus the little 12V lead-acid battery to power the accessories and the control computers).

 

In what different ways is the lead acid battery charged?
1) When ICE is running (of course)
2) When PiP is plugged in?
3) Regen?
4) Directly from Lion Traction battery under any circumstances?

Since a normal car's lead acid battery is known to be low on charge (or getting old and not holding as much/enough of a charge) by the car's engine turning over slowly, solenoid clicking, etc, how do we know when our PiP's lead acid battery's capacity has declined significantly?

 

The 12v battery is charged from the traction battery via a DC-DC converter whenever the car is in READY mode or when the car is charging from the plug. The gasoline engine is not in the picture. If the traction battery charge gets too low, the ICE may kick in, driving a motor-generator to build up the charge in the traction battery, but that is a secondary effect.

The ICE is connected to the power split device, and pretty much the only other thing it drives is an oil pump (and water pump, I think... at least it is on my Highlander hybrid, based on a $3000 repair). The air conditioning, power steering, power brakes, etc. are all electric, since they have to operate when the ICE is not on.

 

The car has no way to tell you that there is a problem with the 12v battery...but then I don't know of any car that does, directly. Indirectly, in a conventional car you know there is a 12v battery problem because you can hear the starter not starting well, or maybe not doing anything.

I know first hand what happens when you unexpectedly have a bad 12v battery. Just happened last week to me. The car doesn't start right away on the first button press, other things in the display go screwy...for example my full charge miles on the display got cut (about) in half...even though the car, once started, drove normally for a few days with the expected EV range as the computer struggled to make sense of the estimated EV miles compared to what I was actually getting. The only reliable indicator I had was I measured the battery voltage when the car was off and it was way low at 11v.

Technically, what happens is that when the car is "on" the 12v battery gets charged from the traction battery. But if the 12v battery is bad (won't hold a charge well) then I think what happens is this (based on my experience last week): When charging the traction battery from the wall the 12v battery is drained a little because some charging circuits have to be energized. If/when the car gets started then the 12v battery gets charged and may stay charged enough to restart the car many times...until you plug in and charge again...the 90 - 150 minutes it takes to do a charge, again slightly drains the 12v battery and it may or may not have enough charge to properly start the car...but will have enough voltage to operate the smart key, radio, windows, etc. I don't know what will happen when you go lower than 11v...at some point nothing will work at all and you'll need to use the mechanical key to get into the car, pop the hood and do a jump start.

The symptoms could easily vary from the above.

Mike

 

Kind of a bummer we find out almost when it's too late, as opposed to getting hints earlier in a regular car. I wonder if the electric windows ran a little bit slower when your 12v battery was weaker?

When the Prius is "on", is the ICE started by the traction battery or the 12V battery?

I wonder if most previous drivers are taken by surprise by the 12 V battery just giving out when it's at the end of its life, without warning.

 

All Gen III Prii have an electric water pump.

 

The ICE is started by being spun up by MG1 using the traction battery. Unlike a regular car, MG1 is able to spin the engine fast enough to build oil pressure in starting the engine.

 

...which is why the startup process is so smooth. It also contribute to longer engine life from that significant reduction in the first moment of combustion.

 

Very interesting and good to understand. Thank you.

So when the ICE needs to start, does MG1 spin it enough revolutions for the oil pump actually disperse oil to bearings, etc. before gas and spark are introduced to the ICE?

 

yes

 

Assuming the PIP has the "jump start terminals" in the engine compartment that I've seen mentioned, you can check the accessory battery health by testing the voltage at those terminals (or at the battery itself, if you can access it) with the engine off, at least 5 minutes after it's been run. Anything above 12.5 volts is fine, 12.3- 12.5 is marginal, and below 12.3 is poor. Since it could also be just an insufficiently charged battery if the reading is low, try to test it after driving with the 12 volt accessories off. A common aftermarket upgrade is replacing the accessory battery with a Deka Optima 12 volt "yellow top" semi-deep cycle battery. This battery and similar aftermarket units give more runtime for accessories and are longer-lived.

 

Is there a way to replace the battery without losing all the HSI data?

 

Interesting idea! Has anyone tried to connect a backup 12V battery to jump start terminals while replacing the on-board 12V battery? I know, I know... There is a significant risk of frying anything if you touch the ground with positive battery connector, but this way the computer's power would not get interrupted.