Odd Electrical, Six 6 Volt Batteries

I've never tried, and I hope there's a possibility that I can still do this.

I have a golf cart. The electrical system is 36V, and it is six, 6-volt batteries wired in series. This wiring allows me access to voltage taps at 6V, 12V, 18V, 24V, 30V, and 36V. Now, if I were to simply tap the array at 12V for my amplifier, I would load those two batteries more than the remaining 4, causing them to age more dramatically. What I want to know is this:

CAN I, tap that array at 3 points, say, with diode isolation, and have a 12V power source, that loads and ages the batteries the same, or do I HAVE to spend the cheddar to purchase a 36V to 12V converter, a la:

https://www.amazon.com/s/ref=nb_sb_ss_i_1_9?url=search-alias%3Daps&field-keywords=36v+to+12v+converter+for+golf+cart&sprefix=36V+to+12%2Caps%2C1185&crid=1UHSCI7HBRSPH

Let me know... anyone?

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

The batteries will be loaded incorrectly, as stated. A converter of some type is required. Diodes won't help in this case.