Pre-heating the Prius Transaxle and Engine for better fuel economy

[orange4boy]

Thermal cycles can lead to issues with dissimilar metals having different expansion rates. If the plug and fitting are both ferrous, no problem, any thoughts?

Good point. I've never used brazed parts in a thermally active location so perhaps a welded steel one will follow. I just need a steel elbow with the right OD or I could also just mitre a tube. Hmm. Good think I have spare drain plugs.

That loop also handles cooling the inverter, which is at the top of the coolant column.

This is one slight wrinkle that requires some thinking. I was hoping the hot fluid would bypass the upper loop, but If I leave it all like it is, the heat travels into the radiator before making it to the inverter and then back down. So it's been cooled a bit by the time it gets there but it's a waste of energy.

If I clamp off the return hose before it flows back into the transparent reservoir, then the heat flows through the loop I created by tapping the drain and stays in the transaxle. To solve this I bought a valve to install in the upper hose but then I have to open and close it all the time. What I need is a 12V valve that is wired to open when the IG is on.

The Graham scanner can report inverter temperatures and I would be interested in the final temperature after say 4-6 hours.

The transaxle heats up to over 50˚C within an hour and a half. If I then unclamp the top hose so the hot coolant can enter the inverter, the radiator fans come on even if the car is off. Built in safety. Is that an Easter egg?

I have a Kill-A-Watt on loan from the local library. I will hook it up to see what it costs for a heat up. My local rate is .085/kwh on tier 2. I'm not that interested in the financial aspect because all our power is clean hydro, I'm happy to pay more to not burn gas but I'm curious anyhow.

[orange4boy]

Got some more heater hose today and re positioned the engine tank heater so it's vertical. I had to mod the mounting bracket to work in the new position but it's a much cleaner install now and a shorter run. I just have to stabilize the hoses, insulate them, and I can fire it up. Will take some new pics tomorrow.

Almost done.

[orange4boy]

Stage 4 at start up !!!

Engine circulation tank heater is installed and working. Coolant temp is now showing 75˚C. Took about an hour to get there. I'll have to do a proper timed test and a Kwh reading so it can be graphed.

[bwilson4web]

Originally Posted by orange4boy

Stage 4 at start up !!!

Engine circulation tank heater is installed and working. Coolant temp is now showing 75˚C. Took about an hour to get there. I'll have to do a proper timed test and a Kwh reading so it can be graphed.

MOST excellent!

Electrical load? We typically have 15A service outlets and via extension cord, some limit there.

Bob Wilson

[rmay635703]

Originally Posted by bwilson4web

Just a couple of quick adds, more details later:

The failure occurs at the junction with the power cord and pad. It may be possible to rig up more support for the power cable and avoid the failure but that area also gets a lot of road water. Perhaps using the adhesive to anchor the power cable to the pan. Mostly I think it is 'cheezy.'

Chat at you later,
Bob Wilson

Copper + motion + vibration = eventual failure

Any electric cord that can flex will eventually fail if it flexes even a small amount repeatedly, the failure of all of mine (some have been on the car 3 years) is always just the cord itself, usually near the end, I have been locking the ends in place cause they keep fraying and have to be re-wired.

But needless to say for me its just a nuisance putting an end on a cord or splicing two together isn't much effort, just annoying.

And to prevent failures "elsewhere" you need to find a way to tiestrap or anchor the cord so it does sway or blow in the breeze or yes it will start breaking.

Cheers
Ryan

[orange4boy]

A 1500 watt load should be fine with a short 16 or 14 gauge cord on a 15 amp outlet. Most space heaters are 1500 watts. You could also get away with lower watt heater on for longer. I got the 1500 watt one because I also want to heat up the interior a bit as well. The ladies like that.

I'm almost finished the install. While I was at it I also installed a disconnection relay in the 12V supply from the DC-DC converter so I can kick it on when the battery pack gets low.

[bwilson4web]

Originally Posted by orange4boy

. . .
I'm almost finished the install. While I was at it I also installed a disconnection relay in the 12V supply from the DC-DC converter so I can kick it on when the battery pack gets low.

Do you have an automatic, voltage control for the relay? Something that doesn't require the driver to monitor the deep-discharge voltage.

Bob Wilson

[orange4boy]

No. For now it's manual but that would be a plan for later. Do you know of something readymade?

[bwilson4web]

Originally Posted by orange4boy

No. For now it's manual but that would be a plan for later. Do you know of something readymade?

Uh, no, I would build one from my 'junk box.'

Specifications:

• zener reference voltage
• setable "cut out" voltage - trim resistor adjusts the cut out, once set, the battery is disconnected
• setable "engage" voltage - second trim resistor adjusts the higher, enable voltage so the battery voltage rise from no load won't trigger oscillation.
• enable line - tied to ignition, it enables the deep storage battery. Breaking enable line, disconnects the deep storage relay.
• diode protected relay engage drive - (old school), optional MOSFETs

Actually it would be more fun to build an integrated system that includes the charger and a buck regulator to . . . <GACK> stop NOW!

Bob Wilson

[bgd73]

this thread set off a thought about my old sube...

it needs no heater, the axles are right behind the pipes and heads.

the contrast in cold climate can be a problem, the heater for the prius is a great idea.
Steel is a mysterious thing...my locale is torture like that. I could say with my own past, the heater is for more than fuel mileage, it will aid in longevity.