coulomb
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Location: Brisbane, Australia

Battery leakage detector (presumed)

Thu Sep 10, 2020 4:13 am

[ Edit: I neglected to mention that this detector resides inside the iMiEV battery enclosure. ]
I've seen this described as a "battery detector"; I'd say it's actually the battery leakage / insulation detector. Note the long plastic legs separating this device from the metalwork. (The mounting holes are cropped off in this photo, sorry).

Image

Here is the PCB from above:

Image

Two components stand out to me. The thing that looks like a battery (especially with code BAA3 on it), but it seems to be a zener diode, ZD8.

Image

And this rectangular thing, that initially I thought was a PCB relay, is a capacitor, C13, 1 μF, presumably with a very high DC voltage rating. It connects from the double insulated orange cable to "earth" (the large area under the PCB, connects to what I assume is pin 1 of the 5-pin connector).

Image

I count 6 8-pin chips, one (the smallest, marked LTTH e3) by Linear Technology, and three by Analog Devices (hence, quality and expensive). It seems like a lot of electronics just to measure insulation leakage. I'd love top know if this is way over-engineered, or just what it takes to make a reliable EV. [ Edit: the "e3" isn't a part number marking code, it's a code for the finishing of the leads. So that's no help. But see several posts down. ]

[ Edit: modified last paragraph to add "LTTH e3" and the mention of Analog Devices.
Changed subject insulation -> leakage. ]
Last edited by coulomb on Wed Sep 16, 2020 5:00 pm, edited 1 time in total.

kiev
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Re: Battery leakage detector (presumed)

Fri Sep 11, 2020 4:59 am

Nice pictures of the Main Battery Ground Fault Detector. It has a pre-check/self-check feature so maybe that's the reason for so many chips.

Found this in the FSM:
The main battery ground fault detector is installed in the main battery. The main battery ground fault detector has the ground fault detection circuit. When a ground fault occurs in the high voltage circuit, the main battery ground fault detector should output the voltage into the BMU. This allows the BMU to detect the ground fault occurring in the high voltage circuit. The main battery ground fault detector has a pre-check circuit. When the pre-check signal is input from the BMU, the main battery ground fault detector should be quasi-state of detecting the ground fault. The BMU detects this signal to check that the main battery ground fault detector normally operates.
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kiev
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Re: Battery leakage detector (presumed)

Tue Sep 15, 2020 4:37 am

i can't find anything on the "LTTH" chip; all the others are dual op-amps (AD8617) and a dual comparator (2903Q1).

Is there anything of interest on the back side?
kiev = kenny's innovative electric vehicle

coulomb
Posts: 223
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Location: Brisbane, Australia

Re: Battery leakage detector (presumed)

Wed Sep 16, 2020 4:50 pm

kiev wrote: Is there anything of interest on the back side?

No, no components, and only a handful of tracks.

coulomb
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Location: Brisbane, Australia

Re: Battery leakage detector (presumed)

Wed Sep 16, 2020 5:01 pm

kiev wrote:i can't find anything on the "LTTH" chip;

It seems to be a true RMS to DC converter. Why they want this I don't know. This definitely seems overkill to me.

Datasheet: https://datasheetspdf.com/pdf/635832/Li ... /LTC1966/1

kiev
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Re: Battery leakage detector (presumed)

Wed Sep 16, 2020 5:55 pm

Thanks for finding the datasheet, i used up all my google-foo, even searching the LT site for part marking codes...

Well that is a very unusual datasheet. It would likely make more sense to know why this chip was needed if we knew how the rest of the board functioned. It appears that the entire board was designed around this chip based upon it's location in the center of the board and the fat silk screen borders.
kiev = kenny's innovative electric vehicle

coulomb
Posts: 223
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Location: Brisbane, Australia

Re: Battery leakage detector (presumed)

Thu Sep 17, 2020 8:33 am

I believe that connector C-21, which connects to the battery leakage detector, is different between some models of iMiEV. C-21 looks the same in all the schematics that I've found (2011, 2012, and 2013), so I don't know any details. I wonder what might change that would require a different connector.

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