Prelude conversion project - some questions

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Re: Prelude conversion project - some questions

Post by jonescg » Sun, 15 Sep 2019, 09:20

Well I plugged the Type-2 connector from the OpenEVSE and looked at the charger: red-red-green-green...
I connected D and F and it briefly caused the pumps to change pitch (suggesting some fluctuation on the 12 V system) and the charger changed to red-red-red-red...
Before reverting to reg-green-red-green...

And of course nothing charges.

I disconnected D and F and measured the voltage between them - 13.5 V. I will now attempt to measure a voltage between E and the others, which I am doing via the CAN line which requires a ground (in this case, described as -12V on the TC manual). Unless one of the ends of the enable link touched chassis ground I can't say it had anything unusual happen to it.
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Re: Prelude conversion project - some questions

Post by jonescg » Sun, 15 Sep 2019, 09:59

OK some more diagnostics.

I put the sixth and final pin in the TC charger plug and ran it out for measurement.
A - CAN Lo
B - CAN Hi
C - CAN Ground (continuity with chassis)
D - 12 V+
E - 12 V-
F - Enable

I plugged the Type-2 plug into the charge port and started probing with the multimeter

I found -14 V (yes, that's a negative reading on the multimeter) between D and E. The assumption was that D was the positive and E was negative, but alas.
I found -13.5 V (again, negative) between F and and E, assuming E was the negative.

I found no voltages between any of these pins and the chassis.

When D and F are connected, the pumps raise in pitch, suggesting an increase in voltage before dropping back when disconnecting. Still no charge takes place.

I'll be sending this charger back before too long...
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Re: Prelude conversion project - some questions

Post by jonescg » Tue, 17 Sep 2019, 21:29

Okay I might have some insight into the charger problem.

I jury-rigged a solution using one of my 2 kW chargers I use to charge the race bike. These are designed for charging 84 cells in series, up to a Vmax of 350 V. So higher than that of the current Prelude battery at 72 cells, but not so far away. It began to charge giving a red-red-red flashing sequence, but at barely an amp. It was making very quiet static noises, as if it was struggling to maintain the right power. Before too long it gave the red-green-red-green error. So I think these chargers are very sensitive to starting voltage. The race bike charger Vmin would be about 250 V, so I was surprised that the 270 V of the Prelude battery was an issue with it.

Reassuringly, I connected the charger back up to the race bike and it charged happily at full power, indicating I hadn't permanently broken it. Perhaps the current 402 V max charger in the car isn't broken, it's just not happy.

What this does mean, is that I need to mount the other two modules in some way.

Pros - better performance, longer range, charger will work. I can pull the laggard module out at the same time and fix the honeycomb with 6 mm ali plate.
Cons - significantly more work, complicated cooling loop, more specific fabrication required, more rear axle weight, immobilised car for several weeks.
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Re: Prelude conversion project - some questions

Post by coulomb » Tue, 17 Sep 2019, 22:29

jonescg wrote:
Tue, 17 Sep 2019, 21:29
What this does mean, is that I need to mount the other two modules in some way.
Actually, I believe that the CAN version will have a very different minimum start voltage. It might well be fine with the battery voltage as it is. If it's the nominal 312 V @ 20 A model, it is rated for 110-440 VDC, and presumably the CAN model will happily operate anywhere in that range. Even the 540 V @ 12 A model can do 170 V to 650 VDC, so a battery at 270 V should be fine.

I'm almost (but not quite) tempted to suggest some sort of bad boy charger to get the car going again, until the CAN charger arrives (I assume it's on the way). By the sounds of it, you just need to get the battery voltage up a bit, and the present charger might well stop spitting the dummy and start a charge, as it has done before. But of course, those bad boys are frighteningly dangerous, so the point is moot.

[ Edit: 250 V → 270 V ]
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Re: Prelude conversion project - some questions

Post by jonescg » Wed, 18 Sep 2019, 08:43

Yes the new charger is being assembled while I wait. It will be good to be able to decrease the power to suit a 10 or 15 A socket, but as I've covered before, the extra voltage is worth adding if I can. It's just a bugger to fit.

If the new charger would get here sooner I'd install it and just get the car licensed, and deal with all the upgrades later, but since we're going to be waiting for a while anyway, I might as well go about fitting the last modules. The plumbing is going to be complicated. The best way to ensure even flow is to add one module to the current three in series, making 4 in series. However, this also means we need to do the same on the other side - so two inlets and two outlets...
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Re: Prelude conversion project - some questions

Post by jonescg » Wed, 18 Sep 2019, 09:47

I think this will be the least worst way of running coolant through the pack. The return line need not go back through the main battery pack, but it will be a bit neater. The gap between them is about 900 mm, and the axle and 4-wheel steering unit are right in between.
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Re: Prelude conversion project - some questions

Post by T1 Terry » Wed, 18 Sep 2019, 10:38

What if you flipped the cooler circuits over so they all met up in the centre. Then you could feed the cold in at the 3rd pack from the end and let it split both ways on each side. That way 2 packs on each loop from cold and all feeding into the hot return.

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Re: Prelude conversion project - some questions

Post by jonescg » Wed, 18 Sep 2019, 10:52

I can't do that because there will be a large, structural beam through the centre, along with all the buslinks :(
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Re: Prelude conversion project - some questions

Post by Jeff Owen » Wed, 18 Sep 2019, 16:05

I just tried my adaptor on a recently installed Schneider EVSE at the local Nissan dealer. It worked without the need to use the switch. A single diode and equivalent resistor is all that is required. Assuming the EVSE at Melville Renault is the same, you should be able to connect using the AVC2.

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Re: Prelude conversion project - some questions

Post by jonescg » Wed, 18 Sep 2019, 19:18

Hmmm, might need to swap the AVC2 then?
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Re: Prelude conversion project - some questions

Post by jonescg » Wed, 18 Sep 2019, 20:26

Good news @coulomb the CAN controlled charger should be here by next Friday. I'm torn now - do I get the car going on 6 modules so we can get it over the pits sooner? And risk the charger not working again, and DoT taking issue with the battery pack floor's occasional oscillations? Or do I hack the car apart again, fit the last two modules in the boot, remove the laggard module and install the solid aluminium floor, and risk the DoT taking issue with the even saggier rear end? I have a feeling a new set of springs and shocks are in order regardless.
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Re: Prelude conversion project - some questions

Post by jonescg » Fri, 20 Sep 2019, 22:31

The charger works now!
I wanted to move the car, so I got in, powered up, pressed the throttle and it dropped out. Repeat, same thing...

Aha! The master contactor isn't closing! The master precharge relay was closing, but it was trying to pass big voltages across a 200 R resistor inside the pack. No go.

Why was the master contactor not closing? The precharge delay timer I bought off Alibaba stopped working. Good thing I put it up the front so I can access it. Since nothing capacitive is being powered from the battery at this stage (A/C compressor will be a while off) I just omitted the precharge delay and turned both on at the same time. And it charges, drives, and works as it should!

That's a relief. Still going to drop the battery out tomorrow and build the aluminium plate floor instead of the Honeycomb. Should give about an extra 6 mm clearance. But the added 10 kg of mass might lower it about 6 mm :)
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Re: Prelude conversion project - some questions

Post by coulomb » Fri, 20 Sep 2019, 22:39

jonescg wrote:
Fri, 20 Sep 2019, 22:31
The charger works now!
Wonderful! Presumably, this is the CAN model that arrived, and you swapped out the fixed voltage model and replaced it with the CAN model. Otherwise, I think I missed a step.
it was trying to pass big voltages across a 200 R resistor inside the pack.
Ouch. You should check to see if it's still a 200 Ω resistor. Weber and I made a terrible stink when we did much the same thing early in the MX-5's development.
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Re: Prelude conversion project - some questions

Post by jonescg » Sat, 21 Sep 2019, 09:31

No, this is still with the original Enable-only charger. I have put a failsafe relay on the Enable line so it will disconnect the charger once a cell goes high, but this is only a stopgap until the new charger arrives. However my goal this weekend is to install the new battery floor with provision for the last two modules in the spare wheel well of the boot. It really does need more power, and the range boost will make it more useful too. ~24 kWh should see it achieve about 140 or 150 km around town.

And yes I will definitely inspect the resistor - I think it will be OK as both the charger and the controller struggled to do much before the sag caused it to drop out.
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Re: Prelude conversion project - some questions

Post by jonescg » Sat, 21 Sep 2019, 18:35

Now that the charger can charge the car, I decided to bypass the master precharge delay and charge the car fully. The Enable feature stopped the charge as soon as the first cell exceeded 4.2 V, which is good.

Since the car was driving so I figured, before I go and immobilise the thing for a few weeks while I put the new aluminium battery floor together and try to fit the extra modules in the spare wheel well, I might as well go for a drive. I put the Gopro in the corner of the dash so you can listen to me yammering on for 10 minutes or so. Took a drive to Bunnings to pick up some 19 mm aluminium channel and glue I'd been meaning to get for a while. I am uploading the video to Youtube, but it will take a few hours on this copper-dependent connection.

On my way home I went via @reecho's house. However, thanks to the 4-wheel steering on this car, every time you think you are turning a regular old corner, your rear wheels clip the kerb. So there was a bit of a sizeable bump. Thankfully, nothing on the body struck anything solid, and it drove just fine afterwards. However again, the Zeva screen was playing up in the heat of the cabin - seems anything over 30'C it seems to freeze on the menu screen and stop working. I have to take it off, let it cool and try again. It seemed to spaz out with this problem just around the corner from Richard's place. I parked up and had a neighbourly chat. However I noticed an isolation error when I turned the car back on. Bizarre. It normally only does that when I put a jumper between charge sense and ground to force-balance the battery (which is better, but module 5 might as well just get swapped out).

Upon attempting to leave, it would not engage the drive contactor. Again, it persisted with this isolation error... This sucks. Multi-meter time.

The master contactor was getting +12 V when asked to, but we had lost all HV from the rear pack. It was clear I'd blown a main fuse :x

Very strange as it only decided to fail in the last part of my drive to Richard's place, on flat ground at modest speeds. Either way, three tows in three weeks was not a good record :oops:

Back up in Kalamunda I pulled the battery pack out. Gotta love having a hoist!
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Clamp the hoses carrying coolant and pull them off. Remove the HV connector and the 18-pin LV connector. Lower the car onto the bench, undo all the M6 bolts, and lift the car up again. Battery out.
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Next, cut the Sikaflex and pry it open with a chisel. This stuff is proper tough - so I think it's the right choice. The battery was thankfully dry and had no signs of a dead short anywhere :?

However the fuse was indeed open circuit. That was no doubt giving the isolation error. But so strange it only decided to pop when rolling around a corner at 20 km/h!

Well now is the time to start building the new 6 mm aluminium plate as a battery floor. In order to create a useful battery with two extra modules in the boot, I need to run a pair of HV cables out through the top and into the boot space. Also, coolant lines will need to go from the last module of either side and into the two modules in the boot, and back out the same way (or something like it). I'll worry about that tomorrow. For now the plate is ready for stiffening with a section of 100 x 100 mm SHS aluminium. THat will hopfully eliminate a lot of the wobble when you hit the right span of bumps in the road.
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Re: Prelude conversion project - some questions

Post by coulomb » Sat, 21 Sep 2019, 19:09

jonescg wrote:
Sat, 21 Sep 2019, 18:35
However the fuse was indeed open circuit. That was no doubt giving the isolation error.
Forgive me, but how does a blown fuse cause an isolation error? To me, an isolation error is too much conductivity to chassis. By adding an open circuit, I don't see how you end up with more conductivity to anywhere, earth included.

Any idea what caused the fuse to blow? Perhaps you are assuming vibration, which the aluminium plate is hoped to address?
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Re: Prelude conversion project - some questions

Post by jonescg » Sat, 21 Sep 2019, 20:37

I don't know either - all I know is that the ZEVA wasn't giving an isolation error before it blew, and now it does.

I never saw the current exceed 180 amps, but it's possible that it had been 'singed' at some point driving up the hill and the big bump might have weakened it? But I still had power as I drove around the corner and parked up. The fuse didn't look like it had been blown under serious duress.
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The internals of the battery looked just fine.
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My short drive down the hill:
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Re: Prelude conversion project - some questions

Post by antiscab » Sat, 21 Sep 2019, 21:01

What size fuse are you using?

Semiconductor fuses do weaken over time if they're undersized (current goes above the continuous rating on the regular but doesn't exceed the I2t rating)
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Re: Prelude conversion project - some questions

Post by jonescg » Sat, 21 Sep 2019, 21:06

antiscab wrote:
Sat, 21 Sep 2019, 21:01
What size fuse are you using?

Semiconductor fuses do weaken over time if they're undersized (current goes above the continuous rating on the regular but doesn't exceed the I2t rating)
200 A Bussman. I have passed 230 A through it while testing but not for long. And its been driven another 50 km since then, but yeah, I think a 300 A fuse might be better.
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Re: Prelude conversion project - some questions

Post by jonescg » Sun, 22 Sep 2019, 21:13

Today I started to assemble the new battery floor from 6 mm plate aluminium and square hollow section. A total of 8 countersunk M8 high tensile bolts hold the central beam in place, while the front gets a single length of 19 mm SHS which serves as a bit of stiffening, but mainly a solid stop for the modules to sit up against to prevent any forward motion. The coupling nuts worked just fine, but I like the extra rigidity this adds. The total weight of the base plate and sections is about 13 kg, compared to the ~7 kg of the composite. But jeez this stuff is easier to work with.

The composite panel was light and strong, but it needed support in the middle. Also, if you ever damaged it on a kerb, it more or less disintegrates.


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Curiously, the low module didn't have anything obvious wrong with it, but the three modules on this side were blocked with precipitate in the coolant! It was running reasonably well with water, but it seems to have precipitated a bunch of gunk out. I'll have to flush them with a decent flow of DI water, and replace the whole lot with DI water when I reassemble. This same module appeared to be damp underneath the cooling plate, but there wasn't any obvious weak point. The idea is that a leaking module can only leak away from the cells, as opposed to filling the inside of the module with coolant. But anything is possible, and it might be creating a path to the aluminium below.

The challenge coming up will be trying to route the cables into the boot using the tank inspection covers. It won't be pretty but it will be more convenient than any other options I think. I can't have cable leaving this battery pack horizontally, as they won't clear the subframe.
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Re: Prelude conversion project - some questions

Post by jonescg » Mon, 23 Sep 2019, 11:19

Pondering what's going on with the popped fuse.

Is it possible that the DC/DC converter suffered an inrush current issue now that I'd removed the master precharge relay on the battery pack?

I would have thought that the 20 A HVDC fuse would have popped before the 200 A HVDC main fuse popped :?

I have also heard that DC/DC converters need a diode on the input to prevent backfeeding issues, which sometimes present as a popped fuse. Likely to be an issue here?

And should I just leave the DC/DC converter hooked up permanently to the battery pack? I'm not comfortable with that, but if it makes for a more stable system I guess I can live with it.

I just noticed on my drive on Saturday that the auxiliary voltage was very low - 11.5 V or so. As if the DC/DC converter wasn't working properly :/
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Re: Prelude conversion project - some questions

Post by coulomb » Mon, 23 Sep 2019, 11:44

jonescg wrote:
Mon, 23 Sep 2019, 11:19
Is it possible that the DC/DC converter suffered an inrush current issue now that I'd removed the master precharge relay on the battery pack?
...
I just noticed on my drive on Saturday that the auxiliary voltage was very low - 11.5 V or so. As if the DC/DC converter wasn't working properly :/
Lack of pre-charge would be my guess. The DC-DC should be easy enough to test.

Edit: but a 250 A fuse... it does seem unlikely.
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Re: Prelude conversion project - some questions

Post by jonescg » Mon, 23 Sep 2019, 11:52

coulomb wrote:
Mon, 23 Sep 2019, 11:44
jonescg wrote:
Mon, 23 Sep 2019, 11:19
Is it possible that the DC/DC converter suffered an inrush current issue now that I'd removed the master precharge relay on the battery pack?
...
I just noticed on my drive on Saturday that the auxiliary voltage was very low - 11.5 V or so. As if the DC/DC converter wasn't working properly :/
Lack of pre-charge would be my guess. The DC-DC should be easy enough to test.

Edit: but a 250 A fuse... it does seem unlikely.
They may be two unrelated issues... It's quite possible that the low auxiliary voltage was due to the DC/DC converter not being operational (hopefully not broken).
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Re: Prelude conversion project - some questions

Post by jonescg » Sat, 28 Sep 2019, 21:41

Some progress on the new battery floor.
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I'm in the process of putting the spare module in place of module 5 which was giving me grief. Should have it back together by tomorrow afternoon, but the car won't be moving until I get the last two modules in place. And that's going to call for modifications to the fibreglass enclosure.
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Re: Prelude conversion project - some questions

Post by jonescg » Sun, 29 Sep 2019, 21:17

The new battery floor is almost ready. I have swapped module 5 for the spare module I built first. It's balanced and all the cells seem to be behaving, only thing is the thermal epoxy coverage wasn't as good. At this stage a battery that works is good going, cooling is a bonus. The big lump of 100 mm SHS should supply the stiffness the previous battery pack didn't have, but it also adds about 10 kg of mass. I think we can live with it.

The modules are much tighter together, and are well secured by the aluminium channels on all sides. I didn't use the sheet of G10FR4 in the end. There shouldn't be anything conductive between the cells, the terminals and the chassis, so only time will tell how the isolation works out. There is a layer of non-slip mat under each module though, to take up any irregularities with protruding screw heads and the like. Isolation will be a tough gig here given the base of the pouch cells are a fraction of millimetre away from the aluminium cooling plate, but well supported in the epoxy. The isolation monitoring on the ZEVA will be good insurance.

Once I have finished all of the module wiring, I'll have to run a CAN Bus line out from module 6 to the rear two battery modules. The fibreglass cover will need to be modified to accommodate a couple of HVDC cables, and three coolant lines.

Speaking of coolant, I have ordered an EWP25 to replace the current EWP15 I have pumping battery coolant. There's simply no way it will move enough coolant, so the bigger pump ($250!) should be able to push coolant through four modules in series, and two of these loops in parallel as drawn earlier. Unfortunately the coolant pump is in a very inconvenient location underneath the controller/charger shelf. Good thing I have a new charger to replace, making it all (somewhat) worthwhile.
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