Yeah if your 12V battery is only showing 10 volts it is most likely toast. You can put it onto a charger and see if it comes back. It's a 50/50 shot that it will but being that low it will never be 100% again. Check the water level in it also it may be very low affecting the charge rate and Voltage it will keep. That battery is 4 years old now that is the avg life span for a deep cycle 12V. I've had some last a good 8 years and others that have only lasted a season. I have had the worst luck with Interstate batteries and the best with the Duracells from Sam's club over the last 22 years