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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 »

Drive it to work today in stop-start traffic. No trouble whatsoever. Will keep driving it until it faults though, if at all.
I suspect a larger reservoir might help, but if it's possible she's pressing both pedals at once by accident, it would certainly feel like there's insufficient brakes.
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Re: Prelude conversion project - some questions

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OK it faulted on me three times this afternoon. No assistance on the brake pedal. Good news is that you can still stop, you just need to really wail on the pedal.

Yes it seems the vacuum pump is not operating regularly. I don't know if it's the vacuum sensor which is staying off once a vacuum is achieved, or if the pump itself is not functioning correctly. I have a few options to check this with jumpers etc, but I hope it's the sensor and not the pump. The pump is nearly impossible to remove without trained hamsters...
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Re: Prelude conversion project - some questions

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Drove the car to work this morning - no problems with the brakes at all.

I'm wondering if this is a temperature thing... It was a warm night last night, and the brake pump failed several times. This morning it worked like a treat. If it fails again this afternoon (forecast maximum of 35'C) I suspect it's a heat thing. Now the lousy solution is to somehow duct airflow past the pump, but considering we had several 41'C days in the past and the pump worked fine, makes me think the pump may be failing prematurely.

If it stops working again this evening, I will put a jumper across the sensor and see if that makes it fire up again. That would confirm the sensor is letting me down. If it still doesn't fire up, the pump is at fault, and I'll be getting some hamsters in...
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Re: Prelude conversion project - some questions

Post by brendon_m »

Have you worked out if you are losing power? Or is it the pump?

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Re: Prelude conversion project - some questions

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I've been waiting for it to fail again. 300 km later, nothing...

I had the A/C running, and in lots of stop-start traffic figured a bit of heat would be starting to build up in the engine bay, but so far it's kept on working. I did notice the sound of the pump being a little more squeaky than before while it was hot, but it's kind of hard to hear it over all the other sounds (power steering pump, battery coolant pump, motor-inverter-charger pump, and a couple of small PC fans).
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Re: Prelude conversion project - some questions

Post by antiscab »

intermittent faults are the worst

given accessibility of the wiring, it probably couldn't hurt to have the vac pump run when either the brake lights are on, or the pressure sensor says so.

you won't know if it's fixed unless it stops working again :(

I also wonder if the vac pump has a high temp cut out?
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Re: Prelude conversion project - some questions

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antiscab wrote:
Fri, 27 Mar 2020, 11:16

I also wonder if the vac pump has a high temp cut out?
I have written to the Chinese vendor who stocks them asking for a wiring diagram, or an instruction manual, but nothing yet.
If heat is an issue, it's unlikely to be a problem again until December...
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Re: Prelude conversion project - some questions

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The pump has been failing again, this time on a mild day. So I think it's time to replace it.

I wonder if the internals of the pump were damaged by the vapours from the PVC glue I used on the reservoir?
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Re: Prelude conversion project - some questions

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Today I picked up the Prelude and drove it carefully back to my workshop. The brakes worked for the first 5 km or so, but soon stopped working. Provided I kept my distance and was ready to stomp on it, I could still stop.

With the pump not working, now was the time to test the vacuum sensor versus the pump. The pump ran just fine when supplied with a 12 V source.
Must the be the sensor then. I took the sensor out and set it up on the bench with a known good pump and reservoir. It fired up, reached vacuum, and stopped. I let air in, the pump fired up again...

So it's not the pump and it's not the vacuum sensor. Is the power source in the car poor? I checked it, 13.5 V. Hmm, seems legit. Connected it all again, pump briefly worked, then stopped.
I went back to the fuse and checked it - no problems there, and +13.5 V coming from the other side. The wire leading to the vacuum pump sensor had good conductivity... I hooked it up again and double checked at the pump after it ran for a bit. 7 volts. Hello!

I pulled the fuse out and it was kind of hot to touch. Despite the pump never drawing more than about 3 or 4 amps, the 5 amp fuse was heating up and causing voltage drop. Which explains the thermal correlation. The only spare I had was a 15 A or a 30 A. I popped the 15 A fuse in and it worked beautifully even after a dozen pump-brake cycles. Drove it back to Francess' place no trouble at all.

So there you go - size your fuses appropriately!
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Re: Prelude conversion project - some questions

Post by T1 Terry »

The age old blade fuse voltage drop. Just for those less experienced but read all these threads to improve their knowledge and understanding I'll add the following rant.
Better to not use blade fuses at all if you can avoid it, they are a constant source of voltage drop problems and forget about anything bigger than 25 amps unless it is in one of those cheap Chinese chargers or inverters, then 50 amps is the go because they some how think the fuses will load share equally, and they never do resulting in the whole mess melting.
As far as fuse size, it is there to protect the cable so rate it to suit that job, not the expected load, the fuse will never save the smoke coming out of the appliance anyway so no point in using a smaller rated fuse thinking it will protect the appliance. If the load is likely to be more than 15 amps, use midi fuses rather than blade fuses or even maxi blade fuses and certainly mini ANL fuses. Speaking from bad experience, these mongrel things loosen the grip contact between the holder and fuse, this creates heat and voltage drop, melt the holder and the fuse and the whole circuit fails. The midi and Mega fuses are actually clamped to the cable terminal by the retaining nut ensuring a good contact between the 2 current carriers and avoiding the current actually passing through the stud itself.
As an example, the Holden VL Commodore melted the fuse box if the headlight globes were upgraded to 100w halogen high beam because the 30 amp fuse would get hot and melt anything close by. We have a few ice cream containers full of melted fuse holders and burnt wires into terminals and MC4 connectors that we take for "show and tell" when we do any of the talks at the RV get togethers to help highlight the things to avoid.

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Re: Prelude conversion project - some questions

Post by Rusdy »

jonescg wrote:
Sat, 18 Apr 2020, 13:59
...
I hooked it up again and double checked at the pump after it ran for a bit. 7 volts. Hello!

I pulled the fuse out and it was kind of hot to touch. Despite the pump never drawing more than about 3 or 4 amps, the 5 amp fuse was heating up and causing voltage drop. Which explains the thermal correlation. The only spare I had was a 15 A or a 30 A. I popped the 15 A fuse in and it worked beautifully even after a dozen pump-brake cycles. Drove it back to Francess' place no trouble at all.

So there you go - size your fuses appropriately!
Ok, this does my head in. This must be nothing to do with the fuse size though, as 1V drop per Amp equates to 1-ohm resistance. Even bad conductivity wouldn't have that high resistance (unless it's really, really, really, really bad).

Was the blade fuse corroded or something??

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Re: Prelude conversion project - some questions

Post by jonescg »

I wondered the same thing too. The wiring from the fuse block to the pump is only rated to 4.5 A continuous, so there's a drop there. I also noticed that the blade connected I had crimped onto the wire which lead from the fuse block was a bit dicky - I could wriggle it a bit and get the pump to run in fits and spurts. But even when I'd really squished it and pushed it on, it still seemed to struggle. It was only after pulling the fuse out and feeling how hot it was did I suspect it was experiencing drop. I suspect it may have also been a poor connection on the fuse block itself. It's one of these:
Image
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Re: Prelude conversion project - some questions

Post by brendon_m »

T1 Terry wrote:
Sun, 19 Apr 2020, 11:59
As an example, the Holden VL Commodore melted the fuse box if the headlight globes were upgraded to 100w halogen high beam because the 30 amp fuse would get hot and melt anything close by.
T1 Terry
Even without upgrading the lights I've seen them melted.

But you are right, blade fuses are crap however in this use case it should have held up fine.
My guess is the terminals in the fuse box weren't tensioned together so the fuse was loose causing a poor connection which caused heat and then an even worse connection which caused more heat etc etc etc

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Re: Prelude conversion project - some questions

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Aye, the old fuse slid in and out a little too easily for my liking.
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Re: Prelude conversion project - some questions

Post by jonescg »

That roadside phone call you dread...
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Re: Prelude conversion project - some questions

Post by brendon_m »

Oh dear

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Re: Prelude conversion project - some questions

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Yeah, will be a hoist / pack out job to bypass the cell. Which is the least worst solution.
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Re: Prelude conversion project - some questions

Post by brendon_m »

Any theories as to why a cell would have dropped?
Just a Bad cell? Damaged somehow?

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Re: Prelude conversion project - some questions

Post by francisco.shi »

Can you replace the cell instead of bypassing it?

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Re: Prelude conversion project - some questions

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No it's in there good. Bypassing it would be the easiest approach. But I want to know why it just dropped like that. How does a cell lose 30 Ah just sitting around?
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Re: Prelude conversion project - some questions

Post by antiscab »

check the 12 cell module attached to it - the shunt may have failed on (0.1A * 300 hrs)
it's probably not, but easy to check when you first crack the battery open.
would also mean you could just charge the cell group back up instead of bypass
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Re: Prelude conversion project - some questions

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Yeah I will make sure draining and bypassing is the last option. The temperature sensor on Module 3 is also whacked... Ranging between -4'C and 5'C!
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Re: Prelude conversion project - some questions

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It's currently being charged at a low rate, just enough for me to drive it 10 km to the workshop. There's definitely something wrong with that module, either the BMS or the cells group. Either way, it's not good. I need to remove the redundant contactor and precharge relay in the tank-space pack anyway, so this is as good a time as any.
I am mostly concerned that there's coolant leaking around the battery pack, which if it is, I'll just drain it and keep it air cooled.
Man, building a robust battery for an EV is hard.
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Re: Prelude conversion project - some questions

Post by francisco.shi »

Any chance it is just the BMS reading incorrectly?

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Re: Prelude conversion project - some questions

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It's a possibility, particularly given the thermistor is also giving weird results:
IMG_20200526_135620_3[1].jpg
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