The diodes do mean that you cannot measure the pack on the connector, but will be able to measure the charger side which will be about 1.2V higher than the pack.
The pack voltage that represents full charge is when it no longer rises with the 350MA applied rather than a specific voltage. Part of the problem with using voltage to determine SOC on a hybrid car is that the widely varying current into and out of the pack with the associated lag in settling to a specific voltage, makes it nearly useless.
On a constant current charge with no thermal issues to add a variable, we will see a trend in the rate of rise in voltage that is pretty linear when the pack is in the under 90% SOC range, and almost stops rising when all cells are at 100%.
So the bottom line is that you dont need to measure the pack, only where the charger voltage is and the rate of change.
If you want to read the battery volts at start, the diodes present a problem.
Maybe put a 10K resistor across each diode? This would allow a 15meg DVM to measure the voltage but would limit max current back out of the pack to about 20ma?
Those computer cables look safe enough, except that they will dangle and could eventually break?
Were you planing to support them?
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