Prelude conversion project - some questions

Technical discussion on converting internal combustion to electric
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Re: Prelude conversion project - some questions

Post by brendon_m » Tue, 02 Apr 2019, 12:40

That will work but the a/c will only work with the key on. If you want it to cool while charging etc it will have to change. Also the system will trip out on low temp really quickly if the blower fan isn't going (evaporator will turn to a block of ice) and you won't get good cooling on your pack. Maybe have the battery system feed in after the thermostat?

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Re: Prelude conversion project - some questions

Post by jonescg » Tue, 02 Apr 2019, 13:47

The +12 V supply from the TMS is supplied by an OR gate which is powered when the charger is plugged in, so it will work without the key on:
Charge control box2.png
Charge control box2.png (65.35 KiB) Viewed 592 times
(edited to include DPDT relay for interlock and pump output)

* Edit - Ah yes I can see what you mean. Will work on the circuit a bit longer...

But yeah, not sure whether the heat exchanger should go before or after the evaporator inside the blower...
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Re: Prelude conversion project - some questions

Post by brendon_m » Tue, 02 Apr 2019, 15:58

I would say parallel would be best, or after if you really have to be in series. I think that once the refrigerant has gone through the heat exchanger it won't have anything left to give for the poor people in the car.
The compressor/condenser should cope fine with the extra load from a parallel system and you can use lockout solenoids to isolate each part of the system for maximum cooling where you want it.

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Re: Prelude conversion project - some questions

Post by jonescg » Wed, 03 Apr 2019, 12:08

Just found another error on the new A/C wiring diagram - the diode as placed initially would prevent the fans from turning on.

So the right place to put it is just before fuse 18 and 17.
new Aircon wiring2.png
new Aircon wiring2.png (293.29 KiB) Viewed 591 times
However the blower motor will need to be able to work when the vehicle is charging with the AC on, so I also need to put a jumper between the junction of inputs to fuses 17 and 18, and to the blower motor supply from IG2B:
Dash fusebox changes.JPG
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Re: Prelude conversion project - some questions

Post by jonescg » Thu, 04 Apr 2019, 11:44

I managed to buy an automotive grade DPDT relay (30 A rated) for the interlock. Why have two relays when one will do?
DPDT relay.jpg
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I also realised that everything will be operational through the OR gate, including pumps, fans, relays etc. So that calls for a fairly hefty pair of diodes.
So this one seems legit:
30 A diode pair.jpg
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I also picked up a few 10 A diodes, so I should be able to solder a few in parallel to satisfy the currents we'll see coming from the blower/AC/fans/pumps etc too.
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Re: Prelude conversion project - some questions

Post by francisco.shi » Thu, 04 Apr 2019, 12:33

2 10A diodes in parallel do not give you 20A capacity.
Diodes have a negative temperature coefficient. This means that as the diode gets hotter the forward voltage drop gets less. This means that of the two diodes takes slightly more current than the other which causes it to heat up more. This causes a lower forward voltage drop which causes the hotter diode to take a bigger share.
To avoid this you can put some series resistors on the diodes which reduces this effect.

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Re: Prelude conversion project - some questions

Post by brendon_m » Thu, 04 Apr 2019, 12:36

What he said^

But that being said the diodes really shouldn't be carrying any real load, they should only be used as logic control for relays/contactors etc

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Re: Prelude conversion project - some questions

Post by jonescg » Thu, 04 Apr 2019, 12:40

Well I don't expect them to take a huge amount of current, but the compact nature of the diodes is convenient.
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Re: Prelude conversion project - some questions

Post by Richo » Fri, 05 Apr 2019, 12:58

francisco.shi wrote:
Thu, 04 Apr 2019, 12:33
2 10A diodes in parallel do not give you 20A capacity.
I'm still trying to get my head around why the diodes are wanted in the first place.
5A=5W
10A=10W
Are they for an in-dash auxiliary heater

I'm just saying...
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Re: Prelude conversion project - some questions

Post by jonescg » Fri, 05 Apr 2019, 13:14

Richo wrote:
Fri, 05 Apr 2019, 12:58
francisco.shi wrote:
Thu, 04 Apr 2019, 12:33
2 10A diodes in parallel do not give you 20A capacity.
I'm still trying to get my head around why the diodes are wanted in the first place.
5A=5W
10A=10W
Are they for an in-dash auxiliary heater

I'm just saying...
It's the blower motor which drove the decision for a high current diode. If I am supplying power to the auxiliaries when the car is charging, it needs to have enough power to run relay coils etc as brendon mentioned. But the blower motor is not powered by a relay - it's powered directly from it's source (IG2B). I watched it add a cool 15 amps to the 12 V load by turning it up to 4 on the dash. So the diode will be wearing this load as well as the various relay coils.
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Re: Prelude conversion project - some questions

Post by T1 Terry » Fri, 05 Apr 2019, 14:11

I'm guessing the diode pr are Schottky diodes. We use these quite a bit running around 40 amps through them and they do require the heatsink to dissipate the waste heat. We use a tunnel heatsink with a fan and 2 thermostats to keep 2 x 100 amp DC solid state relays cool and happy so we already had the heatsink available. This could be mounted in the air stream from the blower motor, much like they do with the resistors for the different fan motor speeds.

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Re: Prelude conversion project - some questions

Post by jonescg » Mon, 08 Apr 2019, 20:56

Well that clears that up then. The CanEV adaptor plate definitely won't work.
20190408_202354.jpg
20190408_202354.jpg (135.83 KiB) Viewed 531 times
The Prelude has the B20A6 engine and the matching manual gearbox (left) was completely unique. A more common B series engine (right) has the starter motor in the rear and a completely different dowel spacing.

Time to design the custom plate myself...
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Re: Prelude conversion project - some questions

Post by Richo » Tue, 09 Apr 2019, 13:04

jonescg wrote:
Thu, 04 Apr 2019, 11:44
... everything will be operational through the OR gate, including pumps, fans, relays etc. So that calls for a fairly hefty PAIR of diodes.
T1 Terry wrote:
Fri, 05 Apr 2019, 14:11
We use a tunnel heatsink with a fan and 2 thermostats to keep 2 x 100 amp DC solid state relays cool
A solid state relay is overkill in this case as bidirectional isolation isn't required.
And a diode is simple but makes a lot of heat.

Can I suggest an LM5050MK-2/NOPB and N-channel Mosfet?
Even with a 10mR Fet this would keep it under a few watts of heat.
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Re: Prelude conversion project - some questions

Post by T1 Terry » Tue, 09 Apr 2019, 15:55

Richo wrote:
Tue, 09 Apr 2019, 13:04
jonescg wrote:
Thu, 04 Apr 2019, 11:44
... everything will be operational through the OR gate, including pumps, fans, relays etc. So that calls for a fairly hefty PAIR of diodes.
T1 Terry wrote:
Fri, 05 Apr 2019, 14:11
We use a tunnel heatsink with a fan and 2 thermostats to keep 2 x 100 amp DC solid state relays cool
A solid state relay is overkill in this case as bidirectional isolation isn't required.
And a diode is simple but makes a lot of heat.

Can I suggest an LM5050MK-2/NOPB and N-channel Mosfet?
Even with a 10mR Fet this would keep it under a few watts of heat.
Only mentioned the solid state relays and heat sink we used for cooling because we already use them in our battery management systems, they are for solar control and sometimes mains or DC to DC control if there is not another available method such as voltage control of the piece of equipment being used.

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Re: Prelude conversion project - some questions

Post by jonescg » Wed, 10 Apr 2019, 21:22

Spent some time designing the PCB for the charge control box and drive interlock. Turns out I can fit the thermal management system in there too.
The Zeva BMS main unit will have to mount in another box, along with a few other bits and pieces. PCB design makes these tasks so much neater.

This afternoon I traces out the shape of the gearbox adaptor plate and will try and get this shaped up before the weekend. All the accurate measurements can come later.
Plate1.jpg
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Plate2.jpg
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Plan is to cut the basic shape out, then using this start to clock the dowels and the shaft. I should be able to come up with some fairly reliable numbers this way.
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Re: Prelude conversion project - some questions

Post by jonescg » Sun, 14 Apr 2019, 20:11

I've ordered a slab of 40 mm thick aluminium, big enough to make three adaptor plates (minimum purchase was 1200 mm x 600 mm). So if anyone wants some let me know.
The goal is to machine it out as a single part with motor PCD on one side and gearbox bell housing on the other. I have the dowels and centre shaft properly measured now so it should all start to come together. So while that's all underway I finally got a chance to get back to the air conditioning wiring.

The first goal is to have the aircon come on when you press the button on the dash. It never worked before so just getting it to work would be an achievement. Part B of this goal is to make sure the diode I installed on ignition yellow allows the thermal management system to have the aircon kick in while charging on a hot day without the keys in the ignition. But first things first - remove that compressor control box and replace it with a relay. Seriously, it's an on off situation, why Honda needed a 50x60 mm PCB with an IC and a million diodes and resistors I don't know...
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Re: Prelude conversion project - some questions

Post by jonescg » Sun, 14 Apr 2019, 21:55

Nailed it :)
After finding the diode I would work out which wire was supposed to supply the A/C system with power from the compressor control unit. Turns out it was a red and blue wire, which was nowhere to be seen on the compressor control unit, but I figured since it's being replaced with a relay anyway, I might as well recycle one of the other wires going back to the unit. I took the yellow wire which was redundant anyway and spliced it back onto the RHS input to the diode. Back under the glove box I put the other end of the yellow wire onto the ground end of the relay coil, and fed the +12 end of the coil with a supply from Yel-Blk. The NO contact was wired into Red-Yel to activate the coil of the original A/C system Relay A from the original diagram is now redundant. Time for an updated diagram I think...
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Re: Prelude conversion project - some questions

Post by jonescg » Mon, 15 Apr 2019, 10:07

So the final wiring for the A/C looks like this:
new Aircon wiring3.png
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The Arduino will switch a relay should it read a temperature greater than 26'C or something. This will provide unswitched +12 V power to the Aircon control relay in the glove box, which runs the compressor. All of the safety and thermal control features remain in use, but as before, it relies on the blower being set to 1 or 2 to prevent it from icing up. It should only run for a little while, until the battery is at or below 26'C.
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Re: Prelude conversion project - some questions

Post by jonescg » Wed, 17 Apr 2019, 09:37

Hehe, well as always you find errors as you go along. I wired up the A/C system as drawn here with much discomfort (soldering painfully short wires upside down in a car footwell is awful) but when I turned the ignition to ON, the system fired up. That's not supposed to happen...

Then I realised what's wrong. The second relay which is designed to switch the A/C system to ground and power it up is also being powered by the ignition +12 V supply. I still need to take the +12 V supply from the Arduino thermal management system and use it to power the grounding relay so that all of the thermal protection sensors are in series.

I believe the solution is to add a blocking diode. Provided the current doesn't exceed 10 A...
new Aircon wiring5.png
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Re: Prelude conversion project - some questions

Post by jonescg » Thu, 18 Apr 2019, 09:38

Added the diode and it works a treat :) As I mentioned earlier, it means the power of the blower motor is being drawn through this diode when the vehicle is being charged, but on the lowest setting it's about 6 amps - well within the ratings of the silicon (10 A).

So now we move onto the adaptor plate in earnest...
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Re: Prelude conversion project - some questions

Post by jonescg » Fri, 19 Apr 2019, 17:21

The chap who bought the old engine let me go up and take some measurements, and it was a good chance to offload the fuel tank and a few other bits and pieces. I came back none the wiser though, as the engine face plate was difficult to take measurements from. I later went past Mike's place and picked up the gearbox for a couple of reasons - I can use it to trace out a plan for the adaptor plate aluminium, and so I can mount it back in the car, without the motor for an indication of how much depth I have to work with for things like the inverter, charger, vacuum pump, DC/DC converter and two battery modules.

I ended up taking better measurements from the gearbox anyway. I think a combination of transfer punches, accurate measurements and a bit of good fortune will make the plate work.
Flywheel hub and adaptor plate 2d.jpg
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The motor side will look like this - the critical measurement was 21.4 mm - the distance from the mating face of the flywheel to the flange of the engine block. Everything else was worked around this measure. So as a single block, I can machine it out from 40 mm thick plate aluminium. Not cheap, but single parts are always more elegant and better aligned than two or more. I ordered the aluminium from Capral and I expect to see it on Tuesday or Wednesday. The main reason for it to be this thick is the flywheel has a good 37 mm depth to it, and I can't be bothered machining it down. At least with this mass if should wind down pretty similar to the ICE engine :)

The hub can be bought from CanEV, but between the time zone differences and the lack of reply emails, I have decided it's easier to just make one here. Simple design really - 63 mm PCD for the threaded bolt holes, 39 mm long, 80 mm at the flange, standard 28.5 mm inner diameter and 6.3 mm keyway.
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Re: Prelude conversion project - some questions

Post by jonescg » Sun, 21 Apr 2019, 19:16

I lowered the gearbox into place so I can work out how much room I have available for mounting all the other components. Looks like there's a fair bit of space, but without the motor attached I'm still sort of guessing. I will try and mount the aircon compressor somewhere close to the original A/C compressor - lower front LHS. At least this way the plumbing is pretty close.
20190420_113559.jpg
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The other thing I realised is that the engine mounts are going to be a bit of a headache - only the RHS transmission mount and rear diff mount are still attached to the gearbox, while the other two main mounts were fixed to the block. I can devise something for the LHS engine mount to come from the rear of the motor easy enough - I'm going to have to since the intermediate shaft needs it's bearing block to be fixed to something. Likewise the front block mount will need some kind of attachment points on the adaptor plate.
20190420_113539.jpg
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Re: Prelude conversion project - some questions

Post by jonescg » Mon, 22 Apr 2019, 17:37

Easter Monday and nothing is open, so I spent the afternoon working on the heater plumbing since it's a bit more straight forward than the battery plumbing.

Well, until you realise that without some specific U-turns and 90 degree bends, it's starting to look a bit comical. I might try and find some elbows and car-specific rubber hose fittings. Lest it start to look like a pretzel.
20190422_163132.jpg
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Preferably 5/8" hose because that still fits the heater without too much slop, but 3/4" is way to big. As usual, the pumps are 3/4", the heater is 1/2" and the Prelude heater core is 5/8". A T-piece will be needed so I can take it up to a header/surge tank.
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Re: Prelude conversion project - some questions

Post by T1 Terry » Tue, 23 Apr 2019, 13:48

The hose fittings were all available from an engineering mob is outer western Sydney back when I was doing engine transplants in various vehicles. They could make up any combination of pipe sizes, angles and 2, 3 or 4 way fittings, all machined out of brass and not very expensive. No idea if the mob still exists because this was back in the late '90's but the fact they could make them up means just about anyone good with a lathe could do the same. Each pipe fitting was silver soldered into the base block and the block size depended on just how many connection had to come out of it.

As far as the drive coupling, I'm guessing you will attach the flywheel to the motor shaft, but do you plan to use a clutch plate and pressure plate? I saw the clutch fork and bearing in the gearbox so I'm guessing you are. Don't forget about the spigot bearing required to support the gearbox input shaft, you need the space machined into the flywheel mounting boss to hold the roller or ball bearing.

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Re: Prelude conversion project - some questions

Post by jonescg » Tue, 23 Apr 2019, 17:51

I found some Holden heater and bypass hoses, seems to work reasonably well. Not 100% comfortable with the heater unit inlet, as the hose clamp was done up pretty tight to stop it from sliding around, but I can't do much else but make sure it doesn't leak. I will find a surge tank and test it tomorrow.
New plumbing.jpg
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Terry- yes the plan is to mount the original flywheel to a new hub which is fitted to the motor shaft. Clutch, pressure plate and everything else should all remain in place.
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