How do the batteries get charged

The hybrid battery charges from running the gas engine; it only does that if it gets to around 1 or 2 purple bars on the battery display. If you have the heat on, the gas engine will run to heat up the cabin. As for the 12v battery, I'm not sure - I've never heard of anyone having problems with it, unless they left their Prius in storage for several months, so I wouldn't worry about it.

Don't bother turning off the Prius, leave it on. Just keep in mind that having the heat on will gradually reduce your overall fuel economy.

 

You should not worry about the batteries in general, just drive your Prius.

The Traction battery (200v, 6.5 AH) is maintained between 40% and 80% charged under computer control as long as your car is in READY mode and either in Park, Drive, "B" (seldom used) or reverse (Neutral is bad as the battery cannot be charged while in neutral).

Your little 12v battery is always under a slow (note the word slow, it take a while for a Prius to recharge a depleted 12v battery) charge (constant voltage charging at about 14v that comes from the main battery via a DC converter) whenever your car is in READY mode. In ACC mode or when the car is off you can easily deplete the 12v battery as it does not have much capacity. Just a small number of full discharges can kill a lead acid battery so make sure that you close all doors when leaving you car.

JeffD

 

Further to what Jeff said above, note that the headlamps can stay on if you shut off the car and just sit inside. They won't go out unless you actually turn them off or open the drivers door and close it again. This has caused several owners to fully discharge the tiny 12V battery, which is pretty much a motorcycle battery. For example, shut off the car while waiting for the wife to come out of work, and sit with the radio or CD playing. The headlamps can be ON!

I warn of this because many owners in the US leave the headlamp switch on, as when you leave the car they will shut off automatically when you open the -drivers- door.

In Canada we have the automatic headlamp option and DRLs. When the car is shut off the DRLs can stay on until the drivers door is opened. Ditto for the headlamps (only difference is "headlamps on" is full brightness and DRL is somewhat less). If you get into the car and the parking brake is applied, the DRLs will not come on until you release the parking brake. But if you stop and apply the parking brake the DRLs don't go off. They do in some cars but not the Prius.
I haven't quite figured out what is happening, but sometimes the lights go off when you shut off the car, though usually they don't until you open the drivers door.

Warning - Warning - Warning - if you exit from the passenger side you -could- be leaving the headlamps on!

 

I usually shut the car off (and turn off the headlights!) if I anticipate a wait of more than 5 minutes or so. For a long freight train I just put it in Park, so I don't have to keep my foot on the brake.

As noted above, the engine will charge the big battery as needed, as well as providing cabin heat as needed, any time the car is in Ready mode. The big battery charges the 12-v battery, also whenever the car is in Ready mode. Headlights don't draw a lot of power, so it's not really necessary to shut them off unless you shut the car off. Air conditioning, however, will draw the big battery down and cause the engine to come on sooner. So for a long wait (e.g. when someone else is shopping and you're sitting in the car) I'd recommend shutting everything down with the windows open, rather than sitting in the car with the A/C running. Just my opinion.

 

Daniel shuts the car off to save gas, which is admirable, but there is no need whatsoever to shut the car off for battery charge management. The car takes care of that entirely by itself whenever the car is ON ("Ready") and not shifted into Neutral. Run the headlights, radio, A/C all you want, and the car will be fine until it runs out of gas. If you get tired of holding the brake pedal the easy alternative is to shift to Park and set the parking brake.

 

I shut off the car to save gas, not for battery management, if I'm going to be stopped for a long time. Why burn gas for five minutes if I'm not going anywhere? A full battery has about a mile and a half in it. If I allow the car to sit until the battery goes down so far the engine has to kick in, I've burned a mile and a half of gas. What's the point? I also turn off lights when I leave a room.

The car does all the battery management just fine.

 

"Why burn gas for five minutes if I'm not going anywhere?" Well in Florida during the summer, that would be "so I don't arrive at my destination drenched in sweat" but I understand that's probably not an issue in Washington I'm going to have to look up that Zap Xebra in your sig. I'm wanting an Aptera, but losing faith that they will be widely available soon.

 

I understand that there are reasons to keep the car running. I was just saying that I shut it off to save gas if it's going to be a while.

Zap has a web site, but it's not a particularly good one. A better site is Grants Pass Electric Vehicles, which is the dealer in Oregon where I got mine. He also sells other electric vehicles. The Xebra goes 35 mph, is licensed as a three-wheel motorcycle, so in some states you have to take a trike test to drive it, and with the stock batteries goes about 20 miles on a charge on level ground. I have an aftermarket battery pack good for 40 miles. The car is available as a 4-passenger sedan and as a 2-passenger pickup truck.

The Aptera is clearly going to be a much better car. But it's not available yet, and will only be sold in CA at first, with no guess on when it will be available elsewhere. It would not surprise me if Nissan has an electric family sedan on the road before the Aptera is available, and almost certainly will before the Aptera is sold outside CA.

I believe the Aptera official waiting list is already a couple of thousand, and those will have to be supplied before anyone not already on the list gets one. So "widely available soon" it will not be.

My Xebra will be for sale when and if my electric Porsche arrives. Best guess is March. Feel free to PM me with questions.

 

If I've got my math right here, 50 miles/gallon Prius, which is about 13 miles per liter; works out to about 198mL of gasoline used in that mile and a half. Thats 4.5 shot glasses worth of gas. If you turn your car off, it probably uses something similar to heat up the coolant again. Do you really think its worth it to shut off the car?

Besides, unless you've got the A/C running, the battery probably wouldn't deplete itself in five minutes unless it was at 2 bars or less.

 

Something not adding up here. I read somewhere that the available battery power was equivalent to 4.5 tablespoons of petrol, that is just over 66 ml. It seems that it is probably my figure of 4.5 tablespoons as 1.5 miles doesn't seem unreasonable.

OK, its got me now. Is 13 miles per litre not 115 ml / 1.5 miles? Why can't you colonials use a real, 4.55 litre gallon instead of making your own up. It still doesn't add up though

 

The battery's nominal capacity is 1.3kWh, but only about half this range is used. One watt is one joule per second, so the useable battery capacity is 600 x 3600 = 2.16MJ.

Gasoline has an energy value of around 34.8MJ/litre, so yes, the equivalent of the battery's energy is about 62ml of petrol. However, the car, at idle revs, can only use about 25% of this so in practice you'd have to burn nearly 250ml.

On the EU fuel economy test the car gets 4.3L/100km. (This is 65.7 miles per Imperial gallon.) If you achieved this, you could go about 5.8km, 3.6 miles. In practice I get around 5.0L/100km (56.5mpg), so 5km, about 3.1 miles. At 104g/km CO2 on the fuel economy test, you'd emit around 600g of CO2. At 85.9 pence per litre (i.e. £0.859) it costs around 21p.

Hobbit states that the electronics base load when the car is on is 300-400W. The 600Wh battery should therefore be good for about one and a half to two hours, assuming no losses in the DC/DC converter.

The aux battery is 28Ah, which means it can supply 28A for one hour, if fully charged. At 33A, assuming a linear conversion (and it generally isn't), it would manage 50 minutes, which is why you shouldn't leave the car IG-ON. With the car off or accessories only, the current draw is much lower. Hobbit says 10-14mA with the car 'off', although this is higher with SKS present and enabled. (Presumably also higher with the alarm armed.)

 

I did a VERY rough calculation there, forgive me. The 50 miles/gallon figure is what I typically get on the highway in my Prius - nobody here is talking about driving on the highway, so already I'm being optimistic.

Google says that there are 3.78 litres in a US gallon. From that, and the 50 mpg figure, I went 50/3.78 to get 13.22 miles/litre.

Then I took that 13.22 miles/litre figure, divided the 13.22 by 100; which gave .1322; multiplied that by 1.5 to get the consumption over 1.5 miles, and got .198. So therefore, 198mL for 1.5 miles of driving.

If nothing else, I know that using the highway mpg figure will lead to inaccuracies because the highway mpg is when the ICE is running at its most efficient; but as I said, it was a rough calculation

Mjolinor, is 4.55 litres/gallon per UK gallon?? edit- google says it is. Hmph.

 

I generally have to wait a while at the border crossing when I return to the U.S. from Canada. While I don't remember the actual time, it seemed to me that the engine will come on if the car is in park for 5 or 10 minutes. No, it's not a lot of gas. But if I don't need the A/C or the heat, why burn any gas at all? And I don't like the way a car vibrates when the engine is running.

All I'm saying is that if it's going to be more than 5 minutes or so, I shut the car off. At the border, when I have to advance a car length every 3 or 4 minutes, I start it in EV mode, creep forward, and shut it off again.

 

I'd agree the ICE runs far more often than Mike's calculations would suggest. I've run the car for 30 minutes a couple of times to keep the 12v battery charged. When parked my 2008/9 Prius seems to want to keep the battery SOC somewhere between all the blue bars and just going into green (I've never seen the battery SOC go purple).

 

I was stuck in start/stop trafic in my 2008 Prius the other day for nearly 45 minutes. Being a sub zero night, the heater and headlights were on, and the battery hovered between one and two bars. When traffic moved, ICE would kick in, and as soon as ICE started, the traffic would stop. Within a second or two of ICE stopping, the traffic would inch another few steps, and the cycle would repeat. I nervously kept watching the battery bars, as ICE kept starting and stopping a million times, seemingly, without giving the battery a chance to recharge. It left me wishing Toyota had provided a manual override button to force ICE to charge the battery to it's optimal capacity. Has anyone encountered such a situation ? I must say, I entertained thoughts of shifting to park and revving ICE to keep it running, but was not sure a) if it would charge battery in park, b) if I'd damage anything in the process and c) ICE would still ignore my anxiety and shut off anyway

 

That's normal behavior. I wouldn't worry about the battery in cases like this. The car's control systems manage it very well for the varying conditions it encounters. It won't let it discharge below about 40%.

You can't charge the battery in Park by the method you describe. You can "force charge" it, as it's called, in D by stepping on the brake and go-pedal simultaneously. But I wouldn't do that for ordinary driving. The only time I've done it is for testing or fuel economy competition. Again, just let the car manage it and enjoy the ride.

 

Thank you Jim. I will enjoy the ride and learn to let the car's control systems do the worrying.

 

Remember that even "empty" on the battery gauge is still around 40% of battery charge, and "full" on the battery gauge is around 80% charge.

The Prius is very good at keeping the battery within a narrow range for optimum life

 

You should just enjoy yourself and turn on the A/C, because even with everything off, the battery drains eventually, so the engine will have to come on anyway. Either way its up to you, but I don't mind burning a tiny amount of gasoline to keep myself cool.