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Discussion in 'Prius PHEV Plug-In Modifications' started by jdh2550, May 23, 2012.
Kokam have lipo cells that pass the puncture test. Others may have too.
DROID RAZR ? 2
3 CAN buses? Well I just started working with the charger this evening - and what do you know? I missed the fact that it's data rate is 250kbps whereas everything else on the car is 500 kbps.
1) I don't think different baud rates can exist on the same CAN bus - does anyone know any different?
2) I've sent an email asking the vendor if the charger has a 500kbps option - I'm guessing not.
3) So, I think I'll end up with 3 CAN buses... (1) Original master bus; (2) Secondary bus (with ICE ECU and repurposed Battery ECU; (3) Tertiary bus with just the charger on it.
Oh well - at least I know a lot about CAN now!
That is strange as the standard for Pins 6 and 14 on the OBD connector is J2284 - High-speed CAN (HSC) for vehicle applications at 500KBPS which could also be SAE J2284-125kbps, SAE J2284-250kbps on other makes and model cars.
You would probably get a better answer fom the CAN expert by posting your question on www.thebackshed.com
I am surprised the vendor did not ask which speed you needed.
Have you tried this yet ?
Have you tried this yet ? How well did it work ?
I'm about halfway through the conversion. I just need to get a "roundtuit" to finish everything up...
You can install a OOG (out of gas) switch which will disable the ICE so it will run on battery only. This method mimics the Prius running out of gas which is forced by a DTC. The drawback is that you need to come to a complete stop and cycle the power to enable the ICE again. Many users like me and FWD and others are using this method. If you send me an email I will send you details and photos if you are interested. My email address is in my signature.
The OOG method is more suited for a 40Ah kit.
By the way do you know why CAT temperatures display as 0 deg on Duino..CANview ?
Still working on that one.
The better option is to get the ECM board from PIS which can get near to EV performance but I have yet to hear of anybody who is using it. According to the PIS website it is selling for US$250 ea. You would have to send them an email for more details.
Unfortunately the trustworthiness of PIS is questionable. There are other PIS threads in this forum which goes into more detail about how trustworthy PIS is.
I like this concept (ICE ECU has own private CAN bus off a custom battery ECU), but it means that all-electric mode will be limited to the ~ 20 kW of the boost converter. This is around 27 HP (edit: was 15 HP), which is not a lot of power. Of course, the ICE can assist if you happen to need more power, but if it's not warmed up, it won't be ready to assist fully for around a minute. Plus, who wants to use the ICE if you can avoid it altogether.
One possible way around this is to reconfigure the 240 V 40 Ah pack to become a 480 V 20 Ah pack. But that means that when the booster isn't boosting (so it's basically straight through), like at low speed acceleration, you only have half the current available, so startup torque is halved. Plus, it's not clear (to me at least) whether the HV ECU will accept the motor DC bus staying at 480 V when it has commanded it back to 240 V. Finally, I'm not thrilled about connecting 500 VDC from the back of the car to the front, and you likely could not re-use the existing Prius contactors.
What might work is a second boost converter in parallel with the first. I'd make it about the same power, possibly using a boost inductor from a junked Prius inverter. It possibly only needs to be single directional, because 20 kW of regen might be enough (and might be all that your pack can typically handle). That means only one IGBT is needed. It is possible that you could even use the same PWM signal for both inverters (but if you made the second boost converter single directional, you'd have to be very careful to not drive the second one during regen). I say this because I think I read somewhere that the Prius inverter has raw PWM signals coming from the hybrid ECU, so it's possible that the boost converter would also have the raw PWM signal available.
So this would allow an additional 20 kW of power from the pack for EV-only, and also for combined ICE and battery power (so you could drag off other Prii at the lights, assuming you had the ICE warmed up ). Of course, this means you can't get away with the cheapest prismatic cells, unless you had a big pack, so possibly Headways or similar would make more sense. You also would need to find space for the added boost converter and its cooling system; you might be able to get away with fan forced air cooling. Since the output of this boost converter would be 200-500 VDC, it would need very careful attention to insulation, and it would me most sensible to have it near the main inverter. You would also need a waterproof, safe way to get at the 500 VDC bus, which normally stays tucked away inside the original Prius inverter. Oh, and the higher current draw likely means new contactors and cabling from the back of the car to the front, but you might have had to do the latter anyway. If the existing cabling is only 8 AWG, then it's only capable of 40/50/55 A continuous (depending on its insulation temperature rating, 60/75/90 °C) according to American wire gauge - Wikipedia, the free encyclopedia .
A boost converter is not a trivial thing, though the component count would be small; basically one IGBT, a freewheel diode (edit: was integral; that's wrong), the boost inductor, a bus capacitor or two, and a gate driver. You would need some circuitry, possibly including a small micro possibly with a CAN bus interface, to drive the gate driver. The layout would be tricky, since you would not be able to make low inductance connections to the rest of the Prius inverter, unless you were able to locate it inside the original inverter, and put something else (12 V dc/dc perhaps?) outside the main inverter box. Actually, I suspect that the 12 V dc/dc is integrated too tightly with the other logic (gate drivers, general housekeeping) to make enough room for another boost converter.
There is also the question of whether the hybrid ECU would need modification or spoofing of some sort to accept the higher boost converter capacity. So plenty of unknowns here.
Actually 20kW is about 27hp not 15.
Initially I shared your concerns about performance. However when I asked most folks said they found it acceptable for driving around town.
I plan on sticking with the approach I've outlined & I'll be happy to share performance numbers when I get them.
DROID RAZR ? 2
D'oh! Brain spasm; edited now. Thanks for the correction. We don't use horsepower much in Australia.
Great. No need for you to change course; if you do decide you'd prefer more power, and this idea turns out to be viable, I'd say it could be implemented after the rest of it is done.
Well, ok, that's assuming that your pack can handle the extra power.
Yeah - I was thinking the same thing. (a) that I could try this afterwards; (b) but my pack probably wouldn't stand for the increased power draw.
Maybe it would be possible to upgrade the original Booster, the hardware is about 10 years old, since that there are much better IGBTs available on the market, and with that, you don't have to think about space for a second Booster or something like that.
If you attempt to change the boost converter or augment it, you're faced with outright replacement of the HVECU and/or it's HUGE codebase! I don't see anyone ever doing this for that reason alone. I wouldn't even bother with the further thought exercises along these lines. (BTDT)
I agree. 20kw of power is all I need to commute to work in pure EV mode at max 85kph. I have been doing it for just over a year now. It does not sound silly to me.