Electrical problem {boat}JANICHOLSON or any other

James Williams

Well-known Member
My co-worker has a bass boat that after a week something is draining his starting battery.I always thought I could un-hook one of the cables and read voltage,or voltage loss.With a full battery Im measuring 12.7,when I measure with one cable off im reading 12.3 a difference of .4 voltsI also am measuring continuinty from the hot terminal of the starter to the ground or frame,I didn't think this was right butI checked his lawnmower and got the same reading,any help would be appreciated

jimmy
 
(quoted from post at 09:35:49 07/28/14) My co-worker has a bass boat that after a week something is draining his starting battery.I always thought I could un-hook one of the cables and read voltage,or voltage loss.With a full battery Im measuring 12.7,when I measure with one cable off im reading 12.3 a difference of .4 voltsI also am measuring continuinty from the hot terminal of the starter to the ground or frame,I didn't think this was right butI checked his lawnmower and got the same reading,any help would be appreciated

jimmy

Yes , but no. You need to check for an amperage draw. Instead of typing it all out this is a decent site for that.

http://www.flashoffroad.com/electrical/Batteries/BatteryDrain.html
If you determine there is a draw start taking out fuses and when the draw goes away you have found your suspect circuit. From there either start looking for the short or replace the defective part.
 
The .4 volts found as described in your post, between the terminals at the battery should be taken between the battery post and the terminal that was removed from it. This will give you the voltage loss. If you put an amp meter in that position (from the naked battery post to the removed terminal) you will be reading the amps (or milliamps) being drained.
100 or so milliamps will drain a battery in a few weeks or a month. If every accessory (like depth finders etc.) are for sure off, the alternator in the power unit might be the cupret. Once the meter is in place, the process is to disconnect things while watching the reading. (reattach those that show no change to avoid radical issues putting it back the way it was.
Starter motors are so low in resistance that they can be considered a dead short. They usually have less than .25 ohms. Jim
 
Jim, Did not know that IH made boats ?

Sorry, only kidding ! Could not resist. I know, I know, I need more to do.

Looks like you got good advice.

Bill
 
I would start with a new one of those. They sure can become internally shorted to ground. Solid state materials are not perfect. Jim
 

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