Going on a camping trip and Prius is overloaded 900lbs. Is this going to be a problem?

Add extra air to your young, deeply-treaded and recently/carefully inspected tires. They'll see the worst effects of the overload so pay attention there.

Remember to use B mode early & often on the hill descents.

Honestly if it were me the only thing I might do differently is buying the food and water when I'm most of the way there.

Good luck!

 

Brake early, accelerate slowly. Good luck!

 

Should be fine (famous last words). Once carried 12 (or was it 13) buckets of paint up the 101 into norcal, with a solid core rear sway installed the car handled the corners "ok". Will be interesting to see if those coil boosters hold up, how long have they been installed now?

Without mentioning the partially obscured rear license plate, I'd be more worried about cooking the trans when hill climbing or if heavy footed and under load. Here is an older @edthefox5 reply to my question "How does a low HV battery cook a trans?" (transmission, transaxle) when embracing a long / steep hill climb or otherwise : Transaxle Failure | Page 12 | PriusChat

 

That Ed reply starts with some information that lots of people learned in the old days and that really was true for the kinds of motors that used to be used in simple home appliances and industrial equipment and such. The plain induction motor that's just wired across the line voltage with a switch to turn it on, and if the line voltage drops much, the motor bogs down under its load, and the current it consumes goes way up (even to several times its normal running current) and the windings may overheat and burn out. That's why we were all taught brownouts of the electrical grid can be so destructive to appliances.

That was all true (and still is, about those kinds of equipment), but there are several ways the Prius powertrain is different.

The motors in the Prius are actively commutated. They both have resolvers that report their exact rotor positions back to the controlling ECU to a 4096th of a revolution, there are current sensors on the windings, and the ECU is doing pulse-width modulation in real time to shape the exact voltage and current waveform it wants each winding to be getting. This is nothing like clamping a familiar appliance motor across a voltage supply and letting it draw whatever current it draws.

Starting with Gen 2, there's even another layer of distance between the motor and the battery voltage; the inverter now contains a booster circuit to raise the voltage from the battery up to a maximum of 500 V (limit raised to 650 V in Gen 3). That allows the motors to be built lighter for the same or better power output. Just like the MG waveform shaping, the boost circuit is under the ECU's control. If the ECU has decided it wants 437½ volts right now to shape into the motor drive waveforms, that's what the booster will produce, independently of the battery voltage.

As for the total power being handled through the powertrain, the specs for a Gen 2 are that the engine can produce 76 HP but the combined system net power is given as 110 HP, which involves counting on the battery to chip in 34 HP on top of full output from the engine. 34 HP from the battery at nominal voltage is right at the 125 amp rating of the battery's fuse, so yes, that's a practical outside limit.

A full-capacity new battery could give you that for a shade longer than three minutes, but the car only uses the 40% of capacity between 40 and 80 percent charge. So you can get 110 system combined horsepower, but only for about a minute and a half—less than that with a tired battery.

So let's say you start your heavy-laden Prius at the bottom of a hill, and you want to climb this hill at the maximum speed 110 HP can take you. So you mash the go pedal, and the battery will chip in 125 amps, and the engine will go to full output at 5000 rpm. (Whether 5000 rpm sounds like 'screaming' will depend on how much you've been around actual screaming engines.) There you are, going up the hill with 110 HP worth of speed.

You'll get, at the outside, a minute and half of that, with a spanking new strong battery.

What happens next is very simple (and if you have something like a ScanGauge or a phone app displaying the battery state of charge, you can watch it happen).

The instant that state of charge crosses the 40% mark, the HV ECU says "that's it, no more from the battery" and you will instantly feel that you are in a 76 HP car. The engine was already at full output at 5000 rpm and it will stay there, but now that is all the power you've got, and your road speed will quickly drop to what 76 HP can haul up that grade. That is what the rest of your ascent will be like, if you still want to complete it as fast as you can.

With respect to heating of the tranny, notice that the total power it is handling has not gone up at this point. It has dropped. For that first minute or so, it was handling the full 76 HP from the engine and 34 HP from the battery. From now to the top of the hill, it won't be handling any more than the 76 HP from the engine.

How much of that is carried through the motors will depend on road speed. There's a magical speed where all of the power through the tranny is going mechanically and effectively none through the motors; at 5000 engine rpm and 825 rev/mile tires, that's about 123 mph. At any speed lower than that, some of the 76 HP will be going mechanically through the gearing and the rest flowing as electricity from MG1, through the inverter, and reused by MG2. At 61½ mph, the power will be evenly split, 38 HP flowing electrically and 38 mechanically.

At still lower speeds, the motors will carry still more of the engine's power output, with the limits of the smaller MG1 coming into play first; that's why the published System Performance Curve drops below 76 HP as road speeds decrease.

So for lower-speed travel, there is a way to see an effect like Ed described, though the reason is different.

Suppose you're on such a steep grade with your heavy-laden Prius that 40 mph is the fastest 76 HP can haul you.

If your battery isn't depleted, the HV ECU has options for how to give you 76 HP. For example, it could opt to give you 50 HP from the engine and 26 from the battery. The engine for 50 HP will be turning maybe 3400 rpm. The magic road speed for 3400 engine rpm is about 83 mph; 40 mph is about half that, so the engine power is taking an equal split, 25 HP through the gears and 25 through the electrics. The battery's 26 HP contribution is joining in at MG2, which is the larger motor and rated 68 HP, so 51 there isn't a problem.

Even a strong battery starting at 80% SoC would reach 40% that way in under two minutes, and then the HV ECU runs out of options. Now the only way it can give you 76 HP is by running the engine flat out at 5000 rpm, where as we've seen the magic road speed is 123 mph, so 40 is a third of that, so the engine power is splitting 25 HP through the gears and 50 through the electrics (MG1 and MG2). That's a lot of power through the smaller MG1 (and probably more than the HV ECU would allow; Toyota hasn't published MG1's power rating, but the ECU surely knows it).

In any event, the main thing is to be aware of when you're running the machine near its design limits; those are the especially good times to have something like a ScanGauge or phone app set up and be watching the engine coolant, MG1, MG2, and MG1/MG2 inverter temperatures.

 

We did a 7500 mile trip in our '04 back in '07. Two adults, two early teens, all the camping gear, roof rack. Not sure of the e
weight, but very likely over 800 pounds. No problems.

 

What are you carrying thats 900lbs? Initial estimates I thought I was at 900 but after weighing on truck scale my calculations were off.

I did install new springs, actually i tested out 3 different sets with different spring configurations for each. I know I'm a Gen 3 but Gen 2 and 4 springs are avaliable. I'll post my results shortly if interested.