Prelude conversion project - some questions

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

Post by jonescg » Tue, 12 Jun 2018, 09:39

HV distribution rev 1.png
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R indicates a resistor across the main terminals of the contactor.
(edited to use the words closed and open, instead of off and on)
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Re: Prelude conversion project - some questions

Post by Richo » Tue, 12 Jun 2018, 12:44

Why not put the charger in the battery box before the main contactor?
Then you only have mains going in and HV coming out of the box.
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Re: Prelude conversion project - some questions

Post by jonescg » Tue, 12 Jun 2018, 13:55

I have some lower current HV connectors and 4 m of cable which can come directly from the battery pack. I just figured if I'm going to be putting a contactor in series with the charging leads, I might as well use the same one as the discharging leads. Anyway, the charger is the size of a small briefcase, so It probably wouldn't fit.
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Re: Prelude conversion project - some questions

Post by Richo » Wed, 13 Jun 2018, 12:35

With mains coming out of the box small 240V Relays can be used to isolate the mains and the car is HV safe while charging.
Unless the charger can go in the battery box its best to have the contactor(s) on the HV lines as you have drawn.
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Re: Prelude conversion project - some questions

Post by jonescg » Sat, 30 Jun 2018, 21:38

So the shopping list is nearly complete:

Motor - Greatland 60 kW peak liquid cooled PMAC
Inverter - Greatland liquid cooled drive; works well with said motor. Hopefully the adapter plate will be quick, and the protective shelf separating the motor from the inverter and other parts will be a smooth process too. We might skip the clutch as the motor seems to be powerful enough to spin tyres in third (based on Jamie Pardoe's Jumbuck).

Charger - TC Charger, 6.6 kW CAN capable, liquid cooled. I might use the same cooling loop as the inverter and motor.

EV-West AVC2 Modular EV Power control boards for the J1772 protocol on the charge inlet. Oh yeah I better find a charge inlet...

DC/DC converter - From TC also. 1.5 kW air cooled unit with 12 V digital enable signal as well

Hot water unit - 350 V DC 2 kW kettle type. Will set up with a pump and contactor, activated from a switch on the dash.

Air Conditioning compressor - 350 V DC powered, uses 12 V signal and PWM to vary speed. Might be just as easy to set it to full speed and switch it on or off from the dash. Wiring it is easy. Plumbing it and gassing it well that's another story.

Brake vacuum pump - OzDIY parts (thanks Graeme).

Power steering pump - From a Holden Astra. This is a 12 V high powered fluid recirculating type. Will need to set up to run whenever the drive contactor is engaged. I found a 150 A relay at Altronics which should be able to handle the load.

Battery - 25 kWh worth of high energy density lithium cobalt cells have arrived. PCBs and busbars are made and ready to assemble. Liquid cooling plates to be fabricated in the meantime. The battery will be a single unit which goes in place of the Prelude's fuel tank. Except there is a bloody 4-wheel-sterring rod in the way... It's not a show stopper, but it does complicate the battery construction. Construction hasn't started in earnest, but I think that will take quite some time. The battery will be thermally managed with coolant circulating through the plates and out to a large aluminium radiator (matches the original radiator). The coolant will go via a heat exchanger which allows refrigerant to pass through it, so on really hot days the AC compressor can help keep the battery cool.

BMS - ZEVA units and main control unit. The MCU can change the charger output currents and voltages as well.

Miscellaneous - this is the stuff that catches you out. Things that take 5 minutes to discover and 5 weeks to recover. Trying to make use of the car's original 12 V wiring and getting utterly lost... Contactors, fuses, relays, indicator lights, microswitches, weatherproof enclosures, conduits, lugs... the list goes on. I fully expect the car to take a solid 80 hours to convert, assuming all the parts are ready to go and there are zero surprises (and there have already been some).
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Re: Prelude conversion project - some questions

Post by brendon_m » Sun, 15 Jul 2018, 14:02

jonescg wrote:
Sat, 30 Jun 2018, 21:38

Air Conditioning compressor - 350 V DC powered, uses 12 V signal and PWM to vary speed. Might be just as easy to set it to full speed and switch it on or off from the dash. Wiring it is easy. Plumbing it and gassing it well that's another story.
I don't know where abouts in Perth you are but at my work we can make up custom a/c hoses and systems. Getting the fittings / ends can be tricky sometimes but we regularly cut old special fittings off pipes and weld them onto new ferrules and crimp on new rubber hose. Splices and Tees etc for split systems with lock off valves are all possible. One
other trauma you would have to be careful of is that I know production Ev's use a special a/con oil in their systems to help with high voltage isolation(I'd assume your pump would also have it). So you would want to make sure the original system parts get flushed right out to avoid contamination

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Re: Prelude conversion project - some questions

Post by jonescg » Sun, 15 Jul 2018, 14:11

Very good to know! Yes there will be a need for adapting the additional AC parts to the existing system, particularly crimping onto the heat exchanger after the evaporator/blower unit.
I'm in Willetton, but will be moving to Kalamunda soon.
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Re: Prelude conversion project - some questions

Post by brendon_m » Sun, 15 Jul 2018, 14:16

jonescg wrote:
Sat, 30 Jun 2018, 21:38
Power steering pump - From a Holden Astra
My experience with these is that they can suck a lot of power because the pump runs all the time You'll probably want to try to have it wired so it only runs when trying to steer (although they take a while to get up to speed) or something.
Alternatively has anybody used/adapted an electric assisted steering column out of another car(I know the hyundai i30 has them). Leave the factory rack in the prelude without the hydraulic lines connected and modify an i30 column (or part of it) into the car?

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Re: Prelude conversion project - some questions

Post by jonescg » Fri, 14 Sep 2018, 14:21

Been a while since I posted on this thread!
Never fear, progress has been made. All of the components are in, and all that's required now is assembly. The battery cooling plates are made and the battery module enclosures are next on the list of things to make.
Fabricated cooling plate1.jpg
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However I have just moved house (new shed is AWESOME) and the first thing I need to do is build some decent workbenches upon which I can begin to assemble battery modules. Then by about the end of October I should be ready to install a hoist for working on cars. Even the first oil change on the CRX will make it all worthwhile!

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Re: Prelude conversion project - some questions

Post by jonescg » Sun, 04 Nov 2018, 21:29

Well the Prelude project is ticking along - I have given myself till the end of the year to finish it, or at least have the car rolling on electric power.
The plan is to build these 12s10p battery modules in the meantime, before the hoist is installed in the shed and I can start taking the fuel tank out and measure up the battery pack placement.
Enclosure assembly2.jpg
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The modules are ~3.2 kWh each, and have a liquid cooling plate incorporated into the base. A thermal epoxy resin is used to form a non-electrically conductive path from the base of the cells to the cooling loop which is air cooled by the radiator on the front of the car, plus whatever the aircon can do via the heat exchanger.
Cooling plate adhesive on.jpg
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It's a bit of a process to do everything in exactly the right order, because there's a few points where there's no turning back. So that's why I'm making ten of them, instead of the 8 required for the car. One is to be set aside as a spare, and if I don't &#@& them up during construction, two are spares :)

Tolerances are very tight, so everything is done to keep things nice and square.
2s10p block assmbly.jpg
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The final terminations come out the same end as the cooling spigots, which are 3/8" hose fittings. They are bastards to get off, so I'll make sure they are ready to go before cutting any hose to length. I'll use stainless nuts and bolts to link modules with copper links.
Terminal placement.jpg
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Each module will get a 12s BMS unit (ZEVA) and two thermistors. One for the BMS and one for my own battery thermal management system. It will run from an Arduino Mega and operate independent of the BMS.
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Re: Prelude conversion project - some questions

Post by francisco.shi » Tue, 06 Nov 2018, 07:05

How much clamping force do you put on the pouches? As far as I understand you need to clamp them so they don't puff up during operation.

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Re: Prelude conversion project - some questions

Post by jonescg » Tue, 06 Nov 2018, 08:22

The pouches only need to be snug - enough to prevent them from swelling should they ever be pushed to that point. But the cells will only swell if they've been treated mean, and I hope to not do that.
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Re: Prelude conversion project - some questions

Post by francisco.shi » Tue, 06 Nov 2018, 11:42

I thought that they had to be under some pressure. I remember having seen something that said that if the cells are not constrained they will get bigger and loose capacity even if they are not mistreated.
Also the specified thickness is less than the measured value of the free cell.

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Re: Prelude conversion project - some questions

Post by jonescg » Tue, 06 Nov 2018, 11:52

Yes, some pressure to ensure they can't swell further than their originally manufactured thickness. The internal resistance will increase if the cell is allowed to expand considerably.
Over time they will soften up as the electrolyte is able to off-gas (generating CO2) but this is normally accelerated through excessive discharge and recharge currents, and being allowed to get hot. The cooling system I've incorporated here is for ensuring a long service live, which also means it should help prevent swelling in the long term.
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Re: Prelude conversion project - some questions

Post by francisco.shi » Tue, 06 Nov 2018, 13:01

Do you need much pressure to get good contact between the cells and the heatsink?

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Re: Prelude conversion project - some questions

Post by jonescg » Tue, 06 Nov 2018, 13:15

No - I'm filling that gap with a thermally conductive (electrically insulating) filled epoxy. There are silicon encapsulants out there too, but they are all in the 1.0 to 2.0 W/m.K range. Generous application is the key though, as you're aiming for a uniform temperature gradient from cell to sink.
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Re: Prelude conversion project - some questions

Post by francisco.shi » Tue, 06 Nov 2018, 13:32

So the epoxy will also I conduct the heat between the plates between the cells and the cooling base or are the cell plates attached to the cooling base?

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Re: Prelude conversion project - some questions

Post by jonescg » Wed, 07 Nov 2018, 08:43

The cells are standing on top of the flat cooling plate, and the thermal epoxy fills the air gaps between the base of the cells and the plate. Since the electrodes inside the pouch cells stand upright, most of the plates will have a short thermal path to the cooling plate. Sure, it goes via the polyethylene/foil outer packaging, but it's going to help with maintaining an overall lower temperature.
Hope to get some testing done after the conference.
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Re: Prelude conversion project - some questions

Post by francisco.shi » Wed, 07 Nov 2018, 10:28

Putty you are not in Brisbane. We could use the same test load. I worked out I need about 4m of packing steel belt to make my 35kw load. So i will just wind it in some wood former and inmerse it in a tank of flowing water.

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Re: Prelude conversion project - some questions

Post by jonescg » Fri, 16 Nov 2018, 16:16

As I put the battery together I started to map out the plumbing. Apologies in advance for the potato-camera.

As the battery modules will be in parallel for inlet and outlet I want to ensure they all get the same flow, so that means making sure the flow path for all 8 modules is the same length. Frustratingly, several parts involve hose diameter step-ups and downs. Main radiator is 32 mm, pumps are 19 mm, charger and water heater are 15.8 mm, heat exchanger is 12.5 mm, battery modules are 9.5 mm and the spigots on the small radiator are also 9.5 mm.
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Battery cooling gets the lions share of radiators since it's an investment worth protecting. A nice new aluminium radiator is ready to install, along with the Rube-Goldberg array of adaptors and reducers. The pumps and fans will be wired to go on at the same time when instructed to do so by the onboard thermal management system.

The water heater should be pretty straight forward, but I think I will need a small metal header tank. The heater has it's own thermostat making control rather easy.
20181116_155943.jpg
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The inverter, motor and charger will be serviced by a second radiator and pump. I want the charger to be liquid cooled, but I don't necessarily want the fans and pump going all the time. Might need to rig up a thermostat on that one too. This way the battery will be thermally managed at all times, and the charger will be able to activate the cooling system when it's plugged in for several hours.
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Re: Prelude conversion project - some questions

Post by 4Springs » Fri, 16 Nov 2018, 17:26

jonescg wrote:
Fri, 16 Nov 2018, 16:16
The water heater should be pretty straight forward, but I think I will need a small metal header tank.
Any ideas on what to use as a header tank?
A metal one will leak heat more than a plastic one.
I ended up using a garden hose T-piece with the T pointing up. To that I attached a small plastic juice bottle upside down (the mouth of the bottle happens to fit a piece of pipe very firmly, which in turn fits onto the T-piece). In the bottom of the bottle (now the top) I drilled a small hole - big enough to take a syringe tip so I can add water (antifreeze) if I need to, but small enough so that I don't get much evaporation. To my surprise I have not needed to top up the antifreeze in about 18 months since it was first commissioned.
My pump is in the sump - the lowest part of the water circuit. The header tank is just before it, also in the lowest part. The pump pumps fast enough that any air that collects at the top is easily taken around the whole circuit. The air naturally collects in the header tank since the T-piece points upwards.
jonescg wrote:
Fri, 16 Nov 2018, 16:16
The inverter, motor and charger will be serviced by a second radiator and pump. I want the charger to be liquid cooled, but I don't necessarily want the fans and pump going all the time. Might need to rig up a thermostat on that one too.
Nice little thermostats sold by Jaycar that I use on my chargers: https://www.jaycar.com.au/normally-open ... s/p/ST3831

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Re: Prelude conversion project - some questions

Post by 4Springs » Fri, 16 Nov 2018, 17:43

jonescg wrote:
Sat, 30 Jun 2018, 21:38
Air Conditioning compressor - 350 V DC powered, uses 12 V signal and PWM to vary speed. Might be just as easy to set it to full speed and switch it on or off from the dash.
I used an off-the-shelf controller for this, mine uses a 0-5V signal (from memory) to control the speed based on the temperature of the coolant. I find that it runs flat-out until the outlet gets too warm or the intake gets too cold. Then it slows down for a couple of seconds before switching off. So if yours works the same I think your strategy of a switch is fine. Just make sure you have cut-outs for if the upper or lower temperature limits of your compressor are reached.

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Re: Prelude conversion project - some questions

Post by jonescg » Fri, 16 Nov 2018, 18:26

Yeah I think I might leave the aircon set to 100% PWM and leave it as an on-off switch.
Those NO thermostats - you stick them to the base or side of the charger? I figure if you drive up a steep hill and park on a warm afternoon, the motor and inverter will still be rather warm, and the coolant in the loop could well be at about 65'C. If you were to plug in and start charging, the coolant would continue to circulate and hopefully come down to a more reasonable 40'C or something. There's a good chance the battery will still be trying to keep cool too. At least a 7 kW charger will only be generating ~600 W of heat at full tilt.
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Re: Prelude conversion project - some questions

Post by 4Springs » Sat, 17 Nov 2018, 07:43

jonescg wrote:
Fri, 16 Nov 2018, 18:26
Those NO thermostats - you stick them to the base or side of the charger?
Indeed. Find an appropriate spot that gets warm once you've hooked everything up and see how the coolant works. I have two chargers, and I've added fans to both. I think in both cases I used screws to attach a thermostat to the heatsink of the charger, but they could be glued instead. In my case they are controlling 12V fans directly. Once the charger is warmed up they are on continuously, but while warming up (or in cold weather) I hear the fans come on and off reasonably frequently (perhaps a 20 second cycle?). You may decide that you need more hysteresis than that, depending on what you decide to control.

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Re: Prelude conversion project - some questions

Post by jonescg » Sat, 17 Nov 2018, 18:54

Starting to put the battery modules together now. I reckon i can make two modules a week working only evenings and weekends...
Module assembly.jpg
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I picked up some thermostats too - might be worth using these to only turn the fan on, since the pumps should be fairly quiet by comparison.
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