The Insight battery packs can be safely charged to the 100% SOC, and held there so the weaker subpacks get a full charge, and therefore giving all cells a full charge.
The HV at constant current made this charger difficult to buy off the shelf. By combining isolated constant voltage switching power supplies with an isolated constant current led power supply, we can assemble the supplies to build a charger to safely charge the HV pack of any hybrid car.
I built the charger with off the shelf low cost switching supplies from the Meanwell company. The last supply in the series string is a 350MA constant current supply that can swing from about 3V to 48V while maintaining a constant 350MA. The three 48 V constant voltage supplies that are in series to raise the voltage are adjustable from 42 to 54V.These supplies can adjust the max voltage we can reach once the CC supply reaches it's max voltage. 42V*3 + the CC 3V to 48V will allow the constant current to be maintained from 129V to 174V if the CV supplies are all adjusted to 42V each, and from 162 to 210V if they are all adjusted to 54V.
If the constant voltage power supplies are chosen and adjusted to 48V less than the max voltage we want to see once the charge is complete, the charge will rapidly drop from the 350ma to a lesser value.
I would recommend that the the three CV supplies are all adjusted to their minimum, so the charge will taper off after the terminal voltage reaches 174V, which is an average of 1.45V per cell.

Schematic of grid charger/balancer

I started charging the pack at about noon,at an initial voltage of 152.3V. I turned the charger off at 1AM with 170.7V This pack had been sitting in the shop unused for at least 6 months.This morning the pack voltage settled back to 163.4V. The voltage rate of change during the charging was about .1V per 3 minutes, but I did not record the details. A definite slowing of the voltage rise began to be noticed about 11PM and 169V, and I saw the voltage start to dip by .1V at about 169.7.
*********WARNING THE POWER SUPPLY AND BATTERY CAN KILL YOU. DO NOT ATTEMPT THIS IF YOU ARE NOT PROPERLY TRAINED TO WORK ON HV SYSTEMS****************

*******WHEN CONNECTING THE CHARGER TO THE PACK, THE hv SWITCH MUST BE OFF.*********************

*************** THE NEGATIVE TERMINAL OF THE CHARGER CONNECTS TO THE NEGATIVE HV TERMINAL, BUT THE POSITIVE CHARGER CONNECTS DOWN ON THE SIDE OF THE PACK AT THE PRECHARGE RESISTOR/PRECHARGE RELAY CONNECTION POINT AS SHOWN,NOT AT THE TOP TERMINAL***********************************