36volt 2000 ezgo txt, voltage reducer question

[TBcart]

Hi Everyone I purchased my cart a year ago and the 12volt is being drawn from two batteries. I have noticed that my lights dim when I press the gas pedal and I feel the battery goes down super fast when the lights are on.
I was talking today to a fellow cart owner and he said I should have a voltage reducer that it will save my battery's and the lights shouldn't dim as much. Plus the cart might run alittle faster since I'm not killing two of my six batteries by always draining them faster than the others. Is there a recommended voltage reducer at a reasonable price maybe good for more then 52volts but will work with my current 36volts. I'm planning a 48volt lithium conversion in the next year and was told to make sure the voltage reducer can handle the 52volts since the 48volt is really around 52volts.
I see them on amazon from 29dollars to 130dollars on a golf cart website. Obviously you get what you pay for but is there one that's not 130dollars that works just fine. Thanks