The vents are on the vertical outside walls of the car and are fitted with a very simple flap to allow air out of the car only. They vent into the gap between the side metalwork of the car and the side parts of what we call the rear plastic bumper. (Sorry do not know you call it).
Isn't that the vent for the exhaust of the battery cooling fan? Is there more than one? If the above is true, I didn't want to use that vent. I wanted to keep the intake and exhaust away from each other. Then again I could route the hoses so they stay away from one another.
No they are just two extenal vents that most cars have and are fairly large suggest you take a look. The storage box is held in by a quick fit nut in the centre of it's base.
I spoke to my buddy who has a laser scanner and he said that he would be willing to scan any existing duct work intake or exhaust so we can manipulate it in a PC. Output from the PC could be used to make foam mold for us to make fiberglass prototype of the new ductwork. I should go visit a prius junkyard.
Why not use the ventilation fan for air intake? (See Hobbit's hack.) He estimated he needed ~1A for it to be effective. I have the same problem with car interior heating up. If you have to park in a large parking lot, shade is almost nonexistent. Using the front window shade (like the one from the PC shop) helps immensely, especially with windows cracked. But cracking windows can lead to problems on days when rain is possible.... I've always wanted to do Hobbit's vent fan hack to cool down the car interior, similar to the Gen3 solar option, but I worry about draining the OEM 12V battery.... Adding a 12V SLA battery could be a good option, especially for us PHEVers. We have to plug in our car every day anyway, adding a trickle charger on the incoming AC line would be pretty straightforward.... BTW, in cold winters (like we have here in MN), preheating the OEM battery would definitely be useful. I can have a sub-zero OEM battery temp in the cold months. MPG tanks (esp. with the PHEV).
I've made the battery fan variable and can run it at anywhere from 700mA to 5A. The one benefit to running the ventilation fan is that you are using positive pressure inside the car as opposed to a vacuum when using the battery fan. I have window visors so rain isn't a problem. I just tinted my windows and I've decided to use a sun shade and that seems to work well.
Just had another experience with a hot OEM battery today. It was 95F today and despite using the HV battery fan all day (only while driving), my battery got up to 127F (upper temp)! My CCL was down to 7A. With my Enginer PHEV injecting ~12A into the OEM battery, the Prius computer was doing some weird stuff (no codes, though, surprisingly). For instance, it was running the ICE even though my tachometer was at zero (???) -- I could hear the engine running. Not sure what was going on there. I turned off the PHEV, figuring it wasn't good to inject the 12A into the OEM if the computer only thought 7A was okay. The weird stuff went away then. After driving for a bit with the HV battery fan at full blast, the temp came down and all was well, but it just goes to show that running the fan only while driving is not good enough. Needless to say, my MPG sucked for the trip home (no EV mode, no PHEV, etc.) Let me know when you've finished adding bells and whistles, FirstFlight. I'll definitely be a customer!
Almost there. Another week or so and I'll be done. I do custom work so each board is customized to what the end user wants. In fact, if there's something that you want let me know and I'll see if I can add it. The additions I'm working on now are: 1. Using a 4X20 LCD. This is something really cool but isn't necessary. It's good because you know exactly what your fan speed and fan timer is set at. If you have the LCD option, I can also include: 1a. Monitoring the 12V battery1b. Temperature hack for the engine1.c Change all parameters and see what they are on the screen2. The other cool thing I'm doing is using the stereo buttons on the steering wheel to control my board. This is great because you don't need to install numerous buttons/switches to make everything work correctly. Having that OEMish feel to a mod is nice to have. 3. Instead of having the fan at off or run at max speed, my board will allow the user to select speeds that allow greater cooling but not annoy the hell out of the passenger sitting in the right rear seat. Of course running the fan after the car is off is the number one factor for having this board. Of all the features, this one is critical and my battery has run so much cooler since I've installed it. In addition, my CCL has never deviated from 125 Amps. 4. Not really looking to sell this option but.......have two-way communication with the Prius and where I live. I'm doing it now and it works good but I just don't see a market for it. It's just one of those cool things but it does allow me to see my battery temperature as my car is sitting outside. I guess it would be good for someone who wants to charge their prius but is nervous about the temperature increase. It can do other cool things like unlock/lock the doors, turn on lights, check battery voltage, etc.
How is your board getting the battery temp? Are you hooked into the CAN bus? Or do you have your own temp sensors? The LCD screen sounds pretty nice. I'm all for more information and control.... Do you think operating the ventilation fan is possible with your board? The other thing I always thought would be cool was a friction brake monitor. But not cool enough to warrant the circuitry needed to put it together. Maybe using a microcontroller would make it easier, though? What did you decide about the extra SLA battery? Overkill? If you can monitor the OEM 12V battery, you could have your board go into a suspend mode when it looks like the OEM battery is getting drained too much. That could be a compromise.... I assume your board is running off the OEM 12V. (although you said earlier it needs both +12V and -12V. Where are you getting the -12V from?) What is the parasitic load you are drawing from the battery to keep your board powered up?
Right now I'm using my own battery temp sensors and haven't tried to access the OEM ones. That will have to wait until I take my battery apart next month but that is my ultimate goal. Using the CAN would be good but I didn't do it for two reasons. The processor I'm using will not interface with the CAN. The other reason is that my board does some tasks when the car is off. I haven't looked at it completely but I think most, if not all, devices are powered down when the car is off so using the CAN during that time would be useless. Yup. Interesting hack by Hobbit. Yes, I can do this too. Maybe have the four wheels numbered on the LCD screen and then next to (or below) each wheel I can have the three stages Hobbit mentioned. Maybe in the end it would only be advantageous to use a two stage indication but it's something I will definitely experiment before releasing the first board. It's not overkill, it's just not necessary. The testing I did using the battery fan to cool the car pretty much did nothing other than provide a cooling effect while the fan was on. On a hot day, the car would get back up to temperature in a matter of minutes. I will, however, add a solar panel just to keep the OEM battery topped off. I have two of them so I might as well put them to good use. The only problem I'm going to have is to find a place to mount it. I tinted my windows this weekend (I can definitely tell someone what NOT to do when tinting windows) so I may need to cut a piece of tint out and glue the solar panel to the back window. Yes, that's what I was doing. That will be a permanent feature of the board. I get both directly from the battery. If you look at some of my pics or the Youtube videos, you can see the board is mounted approximately six to eight inches away from the battery. It depends on what version people order. The most basic version might draw 2-3 mA while the one with the LCD may draw 110mA. Most of the current that is used by the LCD version is due to the backlight of the LCD. I'll design it like most other electronic devices where it times out after a specified amount of seconds. Of course that would be adjustable just like the fan speeds or times are. One thing I forgot to mention is that not only will my board do the temperature hack, if you have the LCD version it will tell you what the real temperature is and what temperature the spoofing temperature is. This project originally started as something where Prius owners could get a practical device for a low price, which does some cool stuff but it also serves to protect one of the more expensive components on the car - the battery. It's also worthwhile to mention that this board does increase efficiency and it's proven that it will save you money. What do I mean by that? When your battery temp increases your CCL goes down. If your CCL goes down you cannot recoup as much energy during braking. Not only is that energy lost because it's not being stored in the battery, your engine also idles higher and longer and you also wear your brake pads down quicker. Since heat is one of the biggest factors in determining battery life, you're also saving on that too. I realize this isn't an everyday occurrence but if you add the numbers up over the course of years, the savings would have to be noticeable and the board would essentially pay for itself. At the same time, it would allow me to sell off some of the boards I'm stuck with and in a sense, I'd be "making lemonades out of lemons." The problem is, the system I originally designed the board for only needed three inputs and two outputs. Even with that I went higher and used a 12 I/O MCU. I have so many things I want to incorporate on the board that I really want to design a new board where it incorporates the CAN and has something like 40 I/O. That defeats my original intent and I don't know if I feel like spending a ton of time on it. Reworking the boards takes enough time as it is now. Anyhow, enough with my diatribe. Let me know if you have any more questions and I'll be happy to answer them. Once I complete the board and I'm ready to start distributing them, I'll make a new post and put another Youtube video up to show what it can do. I'm still not sure about the price point but I can't see it being more than $30 for the basic version and something like $100 for the LCD version.
