[brian_]

Based on your Post Title and the question, I'm guessing you replaced a battery pack with NiMH packs that yield lower max voltage. Since you can series batteries, why did you stop at 75 volts when the application calls for 150 volts? Maybe your solution is to simply rewire your batteries.

Possibly, but most hybrids use NiMH cells in series, none in parallel. This installation probably went from 120 cells to 60 cells, both entirely in series... although I don't know why anyone would do that.

From Honda's 2012 Emergency Response Guide For Hybrid Vehicles :

The electric motors in all Honda hybrid models except the 2012 Civic hybrid are powered by a nickel-metal-hydride (NiMH) battery module. This type of battery contains groups, or “sticks,” of 1.2-volt cells, each about the size of a D-cell battery. The number of cells varies by vehicle model, and total voltages range from 100-160 volts.

Similar guides for later years are all model-specific, and I didn't see one for the Civic.

 

[brian_]

I bought a hybrid battery-pack from Honda was going to use in ev conversion did not want to run 150 volts so thought if I made into parallel would give me more amp hrs but have changed my mind after realizing that I can not safely charge this pack have decide to use lead acid safer but heavier thanks for reply

If this is a pure battery-electric vehicle, the energy capacity of a NiMH pack from a non-plug-in hybrid will be too low to be useful... assuming it's not something small like a child's toy car. Typical capacity is only from 0.6 to 1.8 kWh; the lowest capacity currently available in a normal battery-electric car is probably more than 24 kWh. If this isn't for a car, perhaps there would be enough capacity.

Changing the configuration of the cells can double the amp-hour capacity, but since the voltage is cut in half the energy content is unchanged... of course. As long as the pack voltage is within the allowed input voltage range of the controller. I see no advantage to configuring the pack for lower voltage. I think sometimes people forget that the motor current is not the same as the current from the battery.