Plug in option with no batter mods

I don't believe such measure would help very much. The ICE is running for the first few minutes of your commute just to warm up the engine--not only to charge the batteries. I suspect that if you had an EV switch, that would probably help more, assuming the switch would prevent the ICE from starting up (which could be an incorrect assumption).

I've been considering installing an EV switch for just this reason. Although my average has been 47.1 MPG over the first 10,000 miles, my mileage to and from work (about a mile each way) is relatively abysmal, at about 40 (my highway mileage is generally about 51 MPG). And, yes, I know I really ought to walk to and from work, and I confess my laziness.

 

Like DanP said, the engine is working to heat itself up and not just charge the battery. In fact, Toyota has purposefully designed this battery to never be fully charged nor fully discharged. This is done to lengthen the life span of the battery. So if you overrode that feature by charging off the gird, you would cause the battery to die prematurely.

One of the major advantages of the Prius is the nearly zero pollution. And you only get that nearly zero pollution when the engine is fully warmed up, especially the catalytic converter.

The EV (Electric Vehicle) switch is a switch that is available in Europe and I believe in Canada, but is not available in the USA. However, it can be added in the USA, but no one is quite sure if it will violate the warranty in the US. (I think the consensus is that it will.) That switch helps to force the car to stay in electric only mode longer. However, it will only work for a mile or so, and under 40 mph or so. So it won't really help with MPG for that drive.

The plug in batteries/system is not yet commercially available ( I think) and is expected to be a $12,000 add on. If I were independently wealthy, I'd buy it in a flash simply to help push the technology along, but as it is, it's also not practical. But I'm willing to bet it will be less than $3000 in 5 years – with an EV only range of 150 miles.

I'm afraid the only way to get better mileage is to move farther from your job. But you can take solace in the fact that you are contributing to near zero pollution, and helping the entire world see that hybrids really do make sense.

I suspect that the Prius has done more to facilitate REAL EV research than anything else in history. And IMHO, the EV is the way to go to get the oil monkey off our back. And every Prius owner is a part of that.

 

OK, EV facts (which are available in posts elsewhere.

1. EV if engaged soon enough will prevent (defer) ICE warmup.
2. car will only stay in EV under 35MPH, limited acceleration, and battery SOC above 2 bars. Battery temp also seems to affect EV mode.

So EV can be strategically used to defer warmup for your next trip, if the first trip is extremely short. That one mile trip might be a good candidate.

One thing that hasn't been calculated is conversion of miles per gallon to miles per KWH of battery power. We would need this to find out if grid power is more financially economical than ICE power.

It is agreed that grid charging of the OEM Prius battery should be limited to 80% absolute SOC, as the Prius does itself. Otherwise, a separate battery should be used for auxillary power so that you don't risk shortening the life of the OEM battery. But in either case, that WOULD definitely void the warranty.

The consensus on the EV switch and its voiding the warranty is split. Toyota might try to use that to avoid its responsibility, but all we are doing is adding a momentary grounding switch to activate a feature Toyota themselves designed, and provided in every country but US AND Canada. They COULD say they won't honor emissions warranty if the car is found to not pass EPA emissions tests, but I don't see that happening, other than finding the car has reduced fuel economy due to unwise use of the EV switch. In the long run, using the EV switch could actually give you LESS fuel economy, when the ICE has to recoup the energy back to the battery that you used up.

 

So here is a question. Would installing and engine block heater, which is primarily used in northern climates help? would that heat the engine up quicker so that gas milage improves? Just a thought.

Cosmo

 

Helps me a lot. I calculated with my expensive electricity I can save 60 cents for a cost of 5 cents each day approximately. The big question is what temp to start using it, but looks like it would help even at like 50 degrees at least some. For sure the savings would be there at under 20 degrees.
In between I'm not sure yet.

I figurered my electricity at 14 cents a kwh.
gasoline at $3.

heater plugged in 1-2 hours or less, forget exactly. This to handle temps down to -10 degrees F on the worst days. I fugured even 30 min use would help for the warmer days.

These are just estimatesfor now, since this will be my first winter with the heater.

Your savings may vary, both due to different electric costs and temperatures, but also due to different commute conditions: I have slower warm ups than most, due to lights etc. Typically takes me 10-15 min for car to reach 170 degrees F if it even does!

 

At the very least, it will provide faster cabin heat.

 

I've been investigating ways to add a system to grid charge to ~ 80% for short trips + potentially solar power.

The factory battery size is small and the delta between "full" and "empty" is smaller still so it is not alot of energy to top off the system. I believe the current packs are ~273 volts and 6.5 Ah for a total of ~ 1.7 kWh. However, given 80% is top and 40% is low charge, then only ~ 700 Wh is available before the enigne starts running. This is enough for ~ 1-2 miles at <25 mph. Perhaps more if temp, road, level, no stops, tailwind, etc.

700 Wh is less than 10 cents worth of electrical power and perhaps 40 to 50 cents worth of gasoline (assuming 0.15 gal/hr for 900 W [ref Honda EU-1000i gen]

An 80 watt solar panel could replace ~1/2 of this on sunny summer day by the end of the workday. At ~ 400 bucks you would need 12 years to breakeven vs grid power but only 2-3 years at current fuel prices... Battery coulometric charging efficiency is ~ 66% and conversion efficiency 12 V to 270 V is <100%.

Assuming you have power available at both ends of a commute and < 35 mph driving for ~ 3 miles of the commute then a grid based system would be at least a 20% savings in gas on trips less than 12 miles - even if 9 of those miles are at highway speeds. This is roughly another 12 mpg.

In summary, there is an opprotunity for further savings using the existing battery. Estimated cost for a system is << 12,000 dollars.

The addition of an external solar system would likely be a net loss at highway speeds due to drag. At low speeds, it could provide almost a charge over a day's worth of sun. In stop an go traffic, power would be enough for car systems other than A/C.

I think an engine block heater is a good idea. Battery warmer might be useful too.

Eric

 

This is another reason to post your location! If you are uncomfortable be vague. A block heater may help. In the temperate climate of the costal PNW (Pacific Northwest) the block heater is a benefit if combined with a timer. Your location helps folks answer questions.

 

Hydragas, I am in Portland, OR. Can you quantify the benefit in MPG for the first 5 minutes with/without a block heater? I'm surprised you would see an upside at mild temps of 50 deg F. I would think two weeks of data would give you a decent statistical sample.

Initial Battery SOC would be a variable but MPG for the first 5 minutes seems dominated by engine warm up. I saw some where that max power for charging the batteries is ~ 4.5 to 6 kW (no regenative braking). This is ~ 8 HP and ~ 0.6 gal hr = 0.05 gal over 5 min - should be less than 5 mpg impact at 30 to 50 mph speeds.

My post was primarly regarding the topic of this thread, "Plug in option with no battery mods".

Thanks,

Eric

 

Interior preheat? I grew up in northern Michigan (a town called Charlevoix), where we had nasty winters. To make matters worse, I drove a 73 VW beetle, and did not have a garage. During the really cold weather, I would run a heater (OK, a 1000 watt hair dryer) inside the car for about 20 minutes before I left. This would pre-heat the inside and make things tolerable.

Getting to the point - assuming 1) the Prius heating system will command the ICE on if it senses you need heat and/or defrost, and 2) you have pre-heated the inside, would the engine run (idle) less and save fuel? Secondly, would the fuel savings make up for the electricty cost of the interior pre-heat?

 

I don't think pre-heating the interior would reduce gas consumption as most of the intitial heating is for emissions related heating of the cat converters and getting the water hot enough so that the mixture can be leaned out.

One exercise would be to fool the temp sensor into reading "at temp". My guess is redundant sensors would detect the fault. This would also defeat the emmision system and would likely be illegal in some states. CA for sure.

I was thinking of pre-heating the battery as you can extract more power from a warm battery.

Does anyone know how the prius system measures SOC? Is is voltage based, or does it keep track of current in/out?

Eric

 

Hi.
Greetz from Germany.
Battery SOC is definitively not simply measured via battery voltage as it's done for the 12V batteries. The exact modus of calculating the SOC is currently unknown to me, for my resources are not accessible temporarily. I'll provide it as soon as I have access again.
The SOC band for the battery is between 25% low and 75% high. The the car is set up to aim for a value between 50% and 60%, look at it as steady state balance. Above 60% the car makes further use of battery power, below 50% the ICE is more often used to reload the battery.
The european EV-Button only works, according to Toyota's reference manual, if the ICE is not in preheating mode at the begin of a ride, or above 30mp/h, or SOC below 40%, or if via throttle an acceleration is requested which exceeds the torque of the e-motor.

Best results concerning fuel consumption and emission reduction are achieved by (I don't know the correct english word) "Standheizung", which is one step above a block heater.(edit: found the word 'auxiliary heating system') It heats up the complete coolant while circulating it through the entire system so both engine and interior are preheated. This heating is run either by fuel (not so good becaus it can burn down your car) or by 12V car power (best option and tested working well in german forums) or grid plug and controlled via a remote or a timer.It can run independent from the ICE while parked, with the 12V option even if parked where no grid plug is accessible. A company providing these is WEBASTO. Cost in Germany about 1600 Euros. Best place to mount is front left under the bumper.

But why are you concerned about preheating? I have information that Toyota offers an option in the states called CHS (coolanf heat strorage) which is able to keep a coolant temerature above 120 degrees F for three days while parked via a system of valves, a pump and an insulated reservoir.
This is the one option I would like to put into my car, for it is passive and produces no emissions at all while reducing fuel consumption and prolonging engine life.
Sorryly not equippable in the european Prius.

 

One more to go:

Toyota preferred comfort over fuel consumption. If you branch off coolant to warm up the interior of the car you will cause the ICE to run for longer periods of time or more often .
Because a hybrid system has a better efficiency than combustion only, it produces less waste energy in the form of heat (seen in total). Therefore, if you take away heat energy to warm up the interior, the engine has to run to produce enough heat to maintain running temerature for itself and the catalytic converter, thus increasing fuel consumption in reversed proportion to exterior temperature.

 

The answer to the question "Is it cheaper to run a Prius on grid juice than gas juice?" is definitely YES if the car has a appropriately sized battery. Info from a C-SPAN brief from a CEO of a think tank type of company, the equivalent cost of grid energy is 15-40 cents per gallon of gas. The range is due to many variables such as cost of electricity. If its cost effective (reasonable pay back period) depends on the cost of the plug-in mod. I predict unbelievable profits for the company that bring the battery to market. The oil monkey would be replaced by the coal monkey. However, the coal would be American made!!!

 

Rather than using a solar cell to charge the NiMH battery have you considered using one to charge the 12V battery? If everything you draw from the 12V side reduces your mileage, wouldn’t reducing the 12V load increase your mileage?

There's a few decent wattage panels that would fit in the back window and charging a 12V battery would be easier but I don’t know if it would void your warrantee. One problem would be a regulator that accepts a solar panel and the dc/dc converter input. I doubt if you could simply wire in a panel w/o problems (generally, it’s not good to connect two outputs together).

Of course I’m the guy that’s still considering a JetHot coating on my exhaust pipe for better winter mileage so consider the source. You may want to think this through.

 

Would work if the 12 volt battery was heavily discharged in operation. Unfortunately, the current to/from it is minimal and you would be fighting against the internal inverter.

Solar power would be mostly for show unless you made short trips and car sat in the sun. It might be possible to drive not only the main bat via DC/DC converter but also interior fan for summer cooling.

Solar cells inside might be a problem as partial shading can drop power output by 50% or more.

I think a 12Volt solar panel on the dash would work well for keeping the 12V battery topped off during extended non-use. However, I don't think there is a connection to the battery when the car is off. Coastal has a mod for this.

 

I see no reason why charging the 12V battery would not work quite well... good insurance against a dead battery. I'm not sure if the 12V is lead acid.. but if it is, it doesn't like being discharged and left there.... long times in storage would really help the battery stay healthy.... a trickle charge.. only at daytime.

a small zener diode in line would stop any reverse voltage, and you would not fight the inverter because if the voltage from the inverter is higher than the solar, then nothing would happen.. but if the car is off.. then the battery voltage would be kept up to the level the solar panels allowed.

I don't see you have anything to loose.
For that matter, enough solars panels in series could get slightly above 201 volts and charge the NiMH battery!... but unless you had serious panels like say in your yard and ran the wires to your parked car, I see the power gained negligable compared to the 10Kw and 50Kw chargers from the prius.

It would be nice to take advantage of the front windshild as well as the hatchback area inside to gain solar electric energy while parked at work all day for 10 hours?

In the future I hope they put panels into the roof and hood.. basically make the whole top of the car solar!

But right now, americans are even afraid of the inconvient "plug in" idea and unless the possibly strange looks of solar panels on the top of your car in place of a paint job appears to become popular, I don't think it will get too far....
Toyota knows that hybrid in americal will not do well at this time if the car looks like a freak show.... but that may change too.. once hybrid gets more fashionable!

 

Battery capacity is 1.7 kW and voltage is ~ 273.6 volts comprised of 38 NiMH modules in series with a 6.5 Ah capacity = 1.78 kWhr total.

I've decided to go ahead and build a plug-in charger system for the existing prius battery. It would be designed to charge battery to 80% and stop. I'll let everyone know if it works out.

 

YOu must have the pre 2003 model?..

I believe the ones now are 201.6 volts.... they can ramp to 500 volts within the charging system.. but the batteries are 201.... at least with the specs I've gotten my hands on.

But at any rate.. I believe that voltage is right for the older ones.....I bet you can do it.... you could start a nice little business for yourself?