battery voltage

Matt85cs

Cadet
Joined
Jun 12, 2010
Messages
14
should a new battery read 12 volts when the boat is not running or not? when i turn the key it reads only 10 volts but i was wondering if that was right or if the gauge is not working, the new battery is fine.
 

Matt85cs

Cadet
Joined
Jun 12, 2010
Messages
14
Re: battery voltage

Lets just say it should read 12 volts and the gauge is working, where should i go from there to find out why it is not getting proper voltage?
 

cr2k

Captain
Joined
Mar 19, 2009
Messages
3,730
Re: battery voltage

If you don't have one get a cheap volt meter form Harbor Freight like $4

Test across the battery as it is and then disconnect one terminal and test across your battery. Then test from the battery to the disconnected current.

Then test your battery hooked up and the engine running.

If the batt volts are the same hooked up and unhooked it is your battery or alternator.
If not there is a draw and the batt to cable voltage can help lead you to it.
If no change then +change with engine running its battery
if no change with engine running, bad alternator.

This should take you all of 15 minutes.
Get back with the results and we can help narrow it down.
 

JimS123

Fleet Admiral
Joined
Jul 27, 2007
Messages
7,952
Re: battery voltage

If you don't have one get a cheap volt meter form Harbor Freight like $4

Test across the battery as it is and then disconnect one terminal and test across your battery. Then test from the battery to the disconnected current.

Then test your battery hooked up and the engine running.

If the batt volts are the same hooked up and unhooked it is your battery or alternator.
If not there is a draw and the batt to cable voltage can help lead you to it.
If no change then +change with engine running its battery
if no change with engine running, bad alternator.

This should take you all of 15 minutes.
Get back with the results and we can help narrow it down.


Thats the proper procedure....just to add some numbers to the tests:

A fully charged lead acid battery should read about 12.6 volts. AGM or Gel maybe a little higher. Any less than about 12 volts and the starter won't engage. With the motor running, and alternator charging properly, the voltage should be about 13.8 to 14.2.

Be cautious about the cheepie Harbor Freight $2.95 on sale volt meters. I have three of them and they vary by about 0.5 volts from one to another.
 

asm_

Petty Officer 1st Class
Joined
Apr 11, 2010
Messages
245
Re: battery voltage

Actually, a fully charger Pb flood pack is 12.6v ~ 12.8v. 11.8v ~ 12.0v is considered fully discharged. All voltage measured assume no load and 78 degree.

Like others have said, get a voltage meter. Even the Harbor Freight cheapo is more accurate then the dash mounted unit.

B
 

5150abf

Vice Admiral
Joined
Aug 12, 2007
Messages
5,808
Re: battery voltage

I just got 2 new batteries for mine and they read 12.8 fully charged, 12 is actually discharged a bit.

New batteries can be bad too, take it back where you got it and have them test it.
 
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