The best solution is a heavy duty voltage reducer.  Voltage reducers come in many different configurations, capacities and prices.  This is a complex subject and you need some experience in 12VDC systems.  For the sake of simplicity I will speak of voltage in terms rounded to the nearest full volt.  (So if an 6V battery reads 6.14 volts its simply an 6V battery)

Golf car light kits and universal light kits are 12 volts.  12V from a 36V battery pack is obtained using one of two methods.  Use two batteries in series or install a heavy duty voltage reducer.  Also keep in mind you must use a heavy duty voltage reducer on 36V golf cars.  Economy reducers are not suitable or relevant for making 12V power in a 36V electric system. 

We sell heavy duty voltage reducers in our eBay store.  Here is a link to what is available right now!

You may not even need a voltage reducer for your golf car.  The advantages to installing a heavy duty voltage reducer are many and include:

• even battery wear, all six batteries discharge equally
• longer overall battery life
• longer running cycles, car travels longer distances on a single charge
  
• consistent electric power supply for radios and CD/MP3 players
  

When deciding if you need a reducer you need to consider what accessories you wish to power.

1. 12V lights only
2. 12V lights and an accessory port for your cell phone charger
3. 12V lights, accessory port, horn
4. All of the above and a radio

Options one through three do not require a reducer, simply use two batteries in series for 12V.  Option four requires a six battery voltage reducer with a high amp output. A six battery voltage reducer uses all batteries in series to drop 36V down to 12V.  Radios require the full battery pack reducer because radios require a constant 12V input.  A two battery reducer will have its output interrupted every time you step on the "go" pedal of your cart.  In other words with the radio on the cart standing still you start the cart forward and your radio cuts out using only two batteries for 12V power.

Shown is a Yamaha G14 model golf car's battery compartment.  Remove the front seat cushion bottom.  Standing in the bag well looking over the rear seats will look as follows.

This is a lengthy topic that could fill several pages with dozens of photos.  See my guides in the near future for more exacting details and how to instructions with illustrations for all of the various accessories.