I apologize. I don't know why I put a decimal point in front of the 5. I meant 5v. That's what everybody uses, but it's technically incorrect. It should be a 6 volt. The reason for that is 6v will make the gauges show half way and that's a good point for calibration. It's also half the total voltage of the battery, of course.
I'm sure you'll never see a 1v difference, but it's still not quite right. LOL I've used ona before and it worked well, but I have a glass jar full of the 6v ones and heat sinks. I caught on sale "somewhere" a while back. lol