If I am not mistaken the idea is to leave all the elements of the bus connected in the circuit and sense a midpoint in all series branches. For example if a cell in the lower part of a given branch has shorted, the midpoint will sag about 10% to about 4/10 of the bus voltage instead of half (ie 5/10) of the bus voltage. Once the branch with a defective cell is determined automatically by periodic polling of voltages on the points marked with X with respect to ground and an alarm is activated, the operator could cut out the defective branch quickly before cells get overcharged and find the defective cell by measuring each cell in the branch manually and maybe repair the defective cell if possible. Very clever and practical idea.
Maybe a pair of 100k resistors in series with a 22k in the middle sets about +/- 5% window for the center point of the bus and each measurement of the points marked with X is compared to this window? Maybe connect a heavy load on one cell and measure the midpoint voltage to test the system and/or determine the optimum window. Too narrow a window is likely to results in false alarms and too wide a window will miss a failure. I would appreciate if Mark shared his findings after the project is finished.
Cheers
Ahmet
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From: "boat_works@yahoo.com [electricboats]" <electricboats@yahoogroups.com>
To: electricboats@yahoogroups.com
Sent: Friday, November 3, 2017 10:37 PM
Subject: [Electric Boats] Re: Battery monitor idea
Maybe I'm missing something here, but since you'll need to isolate the parallel connections to be able to check voltage on an individual series string, do you have an easy way to do that? Plug-in jumpers, maybe? Otherwise monitoring would seem pretty tedious....
-Tom
-Tom
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Posted by: sv8827 <sv8827@yahoo.com>
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