Fried my Precharge Resistors  [SOLVED]

Nissan Leaf/e-NV200 drive stack topics
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Alibro
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Fried my Precharge Resistors

Post by Alibro »

Hi guys
I'm looking some advice please. I have everything from a 2011 Nissan Leaf except the battery pack and am trying to connect the HV components to my egolf battery pack. I've added two more 4S modules so I have the correct number of cells in series and the BMS is connected without releasing any smoke so I'm hopeful this is OK.
I tried connecting the Leaf PDM through a 100W 50R resistor and it immediately popped so I didn't get to the point of connecting the HV directly.
I then tried a 30R 100W resistor but used a slightly different sequence to connect it and it popped immediately too.
So to see what would happen today I tried 6 x 4R 60W resistors in series but before I could get the direct connection plugged in they overheated and popped too.
I have a 10A fuse on the pack which didn't blow so I don't think it was drawing big current from the pack but it was too much for my resistors.
At this stage I don't have the inverter connected to the PDM as I was trying to minimise any damage should things go horribly wrong.

Can anyone advise where I'm going wrong please.
Do I need a precharge resistor between the battery pack and the PDM?
Should the PDM be drawing current as soon as it is connected to the pack?
I have the 12V battery connected so is it trying to charge the battery?
Are my resistors too weedy or the wrong type?
Should they only be connected for a fraction of a second before the direct connection?

I'm negotiating with m.a.r.t.y to buy a Gen1 battery junction box atm (The unit inside the battery pack with contactors) but I'm concerned if I connect the pack through it I might have the same problem.

Thanks in advance guys.
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Re: Fried my Precharge Resistors

Post by ZooKeeper »

The stock Leaf PC resistor is 40W 30ohm based on the one I removed that failed under similar conditions. If the DC-DC is active or the inverter is "ON" during PC, this can cause an overload. Also, if the voltage setting for PC is too high, the PC system can remain on for too long and overheat the resistor to failure.
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Re: Fried my Precharge Resistors

Post by Alibro »

ZooKeeper wrote: Sat Feb 19, 2022 5:20 pm The stock Leaf PC resistor is 40W 30ohm based on the one I removed that failed under similar conditions. If the DC-DC is active or the inverter is "ON" during PC, this can cause an overload. Also, if the voltage setting for PC is too high, the PC system can remain on for too long and overheat the resistor to failure.
It may have been the DC-DC as the 12V battery was connected at the time but the inverter was disconnected.
I also had the AC pump and HVAC heater connected.
But all these would all be connected in the Leaf too so either my timing was too slow (I was plugging them in by hand) or I'm missing something.

The resistors I used worked OK with the inverter for testing but this is the first time I've tried connecting the PDM
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Re: Fried my Precharge Resistors

Post by Cookie6000 »

I have had similar issues in the past with mine. When DCDC is already active, I have found the precharge never completed as the DCDC takes all the juice so the inverter never reaches HV preset. In this situation, I never blew the resistors. I did blow them when I had the DCDC polarity the wrong way around. 2 seconds after I closed the contactors, the PCR went pop. Once I fixed the human error, all good.

Here is my setup from when I got things set up first for ref. I would check that all your Leaf PDM wiring follows the layout
Screenshot 2022-02-19 182343.png
Are you connecting this with the service disconnect out? That should be the last thing you put in place. I cant see why it is going 'live' at the point you are doing up the final HV fixings and the PCR is going pop. Something very wrong there. Are you using Damiens Leaf VCU? When it comes to timing as you mentioned, timing should only come into place with the settings you have in the VCU (Damiens or Johannes') and you trigger the Neg and Precharge contactors followed by the Pos main after you reach HV preset
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Re: Fried my Precharge Resistors

Post by johu »

+1 for reversed polarity. Resistors don't go pop from a bit of overload
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Re: Fried my Precharge Resistors

Post by Alibro »

I was pretty confident I had it the right way round but will check again.
Thanks guys.
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Re: Fried my Precharge Resistors

Post by Alibro »

Guys thank you sooo much, you are 100% right. I just did some more research and discovered I was connecting the pack with the polarity reversed. :o
It is such a relief Cookie that you said you did it too. Not so much because it means someone else is as silly as me (but that helps) but because your system still worked afterwards.

I had been watching this video.


At 1:52:32 he talks about the polarity. Had I listened and watched a little more carefully for a little longer I'd have realised he was talking about the battery connection side of the junction block and the other end of it was the bit I needed to know about. He then mentions this a few seconds later but I had already thought I had the answer and turned off.
Thankfully I never got to making the main connection so only the 100W resistors were in circuit so hopefully when my new resistors arrive all will be well.
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Re: Fried my Precharge Resistors  [SOLVED]

Post by Jack Bauer »

Annnndd that folks is the reason to use a filament lamp for testing your hv systems. I learned that the very hard way also:)
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Re: Fried my Precharge Resistors

Post by Alibro »

In fairness when I used a string of 4R resistors they kinda lit up like a filament lamp.
Or at least got hot enough to melt the polystyrene they were sitting on. :?

Just to confirm, Are you saying it's best to use a filament lamp between the main direct connection and the battery pack AS WELL as using a precharge resistor or in line with the precharge resistor or both?

Am I right to say the light should NOT come on if all is well (either through a precharge resistor or not) and if it does come on something is badly wrong.

Sorry for the newbie questions but until I've done it correctly I don't know what to expect.
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Re: Fried my Precharge Resistors

Post by Jack Bauer »

Let me reverse the question : how would you think it should work? :)
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Re: Fried my Precharge Resistors

Post by Alibro »

Jack Bauer wrote: Tue Feb 22, 2022 10:57 am Let me reverse the question : how would you think it should work? :)
Ah Damien you're hard!
OK, at the risk of looking like an idiot here's what I think.
I think the light should only come on if a bad thing happened and we have the pos and neg reversed with the bulb in the middle. Whether the resistor is in line or not.
But only if the bulb is a 240V one or preferably two 240V bulbs in series.

If I were to have misunderstood and used a 12V bulb then in the case of that bad thing happening the bulb would pop and wouldn't come on.
If I had the polarity correct I'm not sure what would happen where I to use a 12V bulb but I won't do that.

Do I get a gold star or is the Dunce hat still on? :lol:
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Re: Fried my Precharge Resistors

Post by Alibro »

OK guys so I couldn't find a filament lamp in the house so after swapping the polarity and triple checking I just went for it and reconnected through a new 50R 100W resistor and nothing bad happened. In fact nothing happened at all so either I fried something (hopefully not) or I need to close a contact or send a signal.
I suspect the master isolator sensor switch needs closed but I need to confirm the correct connector before going any further.
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Re: Fried my Precharge Resistors

Post by hugow93 »

Alibro wrote: Mon Feb 28, 2022 9:48 pm OK guys so I couldn't find a filament lamp in the house so after swapping the polarity and triple checking I just went for it and reconnected through a new 50R 100W resistor and nothing bad happened. In fact nothing happened at all so either I fried something (hopefully not) or I need to close a contact or send a signal.
I suspect the master isolator sensor switch needs closed but I need to confirm the correct connector before going any further.
Check out this video if you haven't already!

It's the FOC tuning vid that Damien and Johannes did a couple of years back.
The content is largely on the tuning process, but if you watch the first half it's demonstrated how to safely apply HV to your inverter for the first time.

At about 6mins30s Damien starts explaining the bench set up. I know you're not doing a Prius build, but stick with the video and you should get what you're looking for.
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Re: Fried my Precharge Resistors

Post by Alibro »

hugow93 wrote: Mon Mar 07, 2022 10:10 pm
At about 6mins30s Damien starts explaining the bench set up. I know you're not doing a Prius build, but stick with the video and you should get what you're looking for.
I knew I'd seen this somewhere but couldn't remember where :? . Thanks for finding it so I could have a refresher.
For the lazy out there:-
The 12V lamp demonstration starts at 7:20
And the HV lamp demonstration starts at 21:06

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Re: Fried my Precharge Resistors

Post by johu »

And I also blew a precharge resistor because I though "I'm a trained professional, I don't need that lightbulb rubbish!".

Worked on the Prius charging using my 60V lab supply. When I turned off the inverter the power supply went into over voltage protection and the precharge resistor was dead. The 6A fuse (I'm not spinning motors yet!) was still good
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