I did some testing yesterday to see if I could throw some fault codes. I cut into the PTC connections going into the BCM, and added a potentiometer. According to Mikes site:
PTC strips should be at 1 ohm each at room temp, this is easy to verify, or 20 ohms per pack, mine sits at about 18 ohms.
at 130F each strip should be 2 ohms, or 40 ohms per pack
at 160F each strip should be 4 ohms, or 80 ohms per pack
Well, I ran the total up to 85 ohms which should simulate a 160F + battery pack and nothing happened. No fans, no fault codes .... Everything still operated like normal.
Does anyone have a battery or PTC strip outside a case that would be willing to verify these values? My Civic case with Insight subpacks is fully assembled and I don't want to pull it apart again I would heat up the whole pack, but I don't even have a simple hairdryer in the house.
My intention was to determine if the BCM uses the PTC strips for determining faults, so if these numbers are correct the answer looks like no. My other thought is that the BCM might use them for determining a peak charge, and nothing else?
Next I will test at 100 ohms plus, but this might be a dead end.
I did some testing yesterday to see if I could throw some fault codes. I cut into the PTC connections going into the BCM, and added a potentiometer. According to Mikes site:
PTC strips should be at 1 ohm each at room temp, this is easy to verify, or 20 ohms per pack, mine sits at about 18 ohms.
at 130F each strip should be 2 ohms, or 40 ohms per pack
at 160F each strip should be 4 ohms, or 80 ohms per pack
Well, I ran the total up to 85 ohms which should simulate a 160F + battery pack and nothing happened. No fans, no fault codes .... Everything still operated like normal.
Does anyone have a battery or PTC strip outside a case that would be willing to verify these values? My Civic case with Insight subpacks is fully assembled and I don't want to pull it apart again I would heat up the whole pack, but I don't even have a simple hairdryer in the house.
My intention was to determine if the BCM uses the PTC strips for determining faults, so if these numbers are correct the answer looks like no. My other thought is that the BCM might use them for determining a peak charge, and nothing else?
Next I will test at 100 ohms plus, but this might be a dead end.
The Question becomes how does the BCM use the PTC strip data?
It also has access to additional other temperature probe data at the same time.... what does the BCM do when different temperature probes tell it different things??
The other question is. Even when it sees a overly high temperature, at what point does it do what?
Fans at what point? current limiting at what point? ....etc....
At 85 ohms I still had full assist / regen via mima, the fans never came on plus no codes. Later this week I will try again and go with a higher resistance. Most likely with a 1k pot just to make sure.
Right where they go into the BCM. There is a single bundle of wires coming from the battery pack, with the 4 temp probes. The ones with red sheaths are for the PTC strips. You can see these once removing the black electrical tape, and removing the black rubber sheath. The wires themselves are black and red on the Insight pack, and blue with yellow tracer and red on the Civic pack (both are in the red sheaths). They also sit on the passengers side of that particular connector and are on the front side of the BCM. resistance can be verified, mine is 18 ohms at room temp (both packs). The voltage inputs from the battery are on the back rearward side of the BCM.
Ok, I finally got the system to give me repeatable codes. It took 390 ohms + the 18 ohms of the PTC strips (in series).
I repeated this a few times to make sure it was cutting at the same point. When hitting 390 ohms on the pot the HV relay shuts off leaving 53 volts at the HV relay terminals. I assume this is from the DC - DC system which is still connected through the precharge circuit. The IMA light and check engine ligts come on, the error is a P1449 code (IMA battery failure or Battery Module Overheating). Can someone verify which this code is? I have searched for P1449 and get both.
The cooling fan never comes on, so it must be governed by the other temp sensors. I also noticed what appeared to be a pulse (voltage drop) across the potentiometer. It seemed to pulse at 1 hz, and had a low of 0.5 volts and a high of 1.8volts when the fault triggered. I'm guessing the system checks the PTC voltage drop every second to determine if a battery pack is overheating. The cuts were instant down to the second while turning the trim pot slowly. I used a 15 turn 1k ohm trim pot.
Now to get some accurate PTC strip resistance / temperature data.
I did this test by putting a single ptc strip in a pot of water on the stove with the PTC ends sticking out from under a glass lid. The temp probe was in the water and updated every 30 secs. I recorded until the temp probe maxed out. The strip's resistance climbed exponentially and was well over 20k ohms when I pulled it out; the water hadn't even started boiling.
edit: I tested another strip. There is a chance I had overheated the first one before doing the test in water. The first has a resistance of ~2 ohms at room temp, the second is at ~ 1ohm. I also tried taking a sample of submerging one segment; one of the 6 'bumps' on the PTC strips. I added it also.
Or when a single cell / subpack goes critical. The chart doesn't show the quick jump to 1k ohms, then 10k ohms, then 500k ohms, then 5 meg ohms, within a matter of another 20 or so degrees. I'm guessing on this value as I only recorded for the range of the thermometer I was using. My thinking is to use this with the parallel pack configuration. Run two PTC strip strings in series, and also add a trim pot to add even more inline resistance. Setting a safety shutoff of approx 130F for the whole pack should give a pretty safe margin. The trim pot would also allow to adjust this value up or down depending on any other unknown variables. I'll post more in the other thread when I get the parallel safeties all together.
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PTC Strips
I would heat up the whole pack, but I don't even have a simple hairdryer in the house.
