Volts for Cranking Battery

[crappiechappy]

I now have 3 graphs hooked to my cranking battery. I won't be using more than 2 graphs at any one time. My question is this. What should a fully charged cranking battery read on a volt meter? Should it be right at 12 or like 12.5 to 13 like an auto? Also, how low can the volts get and still be able to safely crank the big motor? Thanks in advance for any help.

[Cane Pole]

I now have 3 graphs hooked to my cranking battery. I won't be using more than 2 graphs at any one time. My question is this. What should a fully charged cranking battery read on a volt meter? Should it be right at 12 or like 12.5 to 13 like an auto? Also, how low can the volts get and still be able to safely crank the big motor? Thanks in advance for any help.

10.5 volts equals "dead", no crank. I believe most books reference 11 volts as the dead zone for cranking. I believe full charge is 12.85 to 12.95 volts. I am trying to recall specifics but am drawing empty numbers, but
these numbers are close range.

[green80]

volts can read 13 or more on a just charged battery. I have seen batteries still start the engine at 11 volts or less.

[Barnacle Bill]

This is from a battery web site.
A reading of 12.66 volts indicates a fully charged battery; 12.45 volts is 75% charged, 12.24 volts is 50% charged, and 12.06 volts is 25% charged.

Yes you can see higher than that at times. Its considered a surface charge and will slowly go away on its own.

[Cane Pole]

This is from a battery web site.
A reading of 12.66 volts indicates a fully charged battery; 12.45 volts is 75% charged, 12.24 volts is 50% charged, and 12.06 volts is 25% charged.

Yes you can see higher than that at times. Its considered a surface charge and will slowly go away on its own.

12.7 rings the bell. I have read 12.9v with a digital vm but the battery was slowly discharging through the voltmeter (which has a hi Z input). Good to get refreshed once in a while.

[Barnacle Bill]

12.7 rings the bell. I have read 12.9v with a digital vm but the battery was slowly discharging through the voltmeter (which has a hi Z input). Good to get refreshed once in a while.

Your memory is better than mine Tom. I had to look it up.

[luvjign]

Crappiechappy, here's some pretty useful info on marine batteries that will help answer your question.

http://www.marine-electronics.net/te..._faq/b_faq.htm

[boat49]

10.5 volts equals "dead", no crank. I believe most books reference 11 volts as the dead zone for cranking. I believe full charge is 12.85 to 12.95 volts. I am trying to recall specifics but am drawing empty numbers, but
these numbers are close range.

From experience,(last Saturday), 10.3 wont budge my yamaha 150. Luckily I had 2 other fully charged batteries on board. This is what happens when you dont check to make sure everything is turned off when you arent the last one out of the boat!!!

[Cane Pole]

From experience,(last Saturday), 10.3 wont budge my yamaha 150. Luckily I had 2 other fully charged batteries on board. This is what happens when you dont check to make sure everything is turned off when you arent the last one out of the boat!!!

I think we have all been here. There is a device on the market that protects the battery from too low voltage. I can't remember where I read about it though. Brain cell seepage problem.