slow cranking battery issue

[charlesson]

Two new batteries installed last year by the PO. They are both deep discharge marine batteries (albeit a "off" brand"). All was OK last season and the batteries were stored indoors for the winter. B4 launch I checked the cells with a hydrometer and got a acceptable reading but not great. the reading was in the white between the green and red. Testing with a volt meter while not under load, I get a 12.2 volt reading on each battery. Under load w/o the engine running a generally get between 11.6 anf 12 volts.

Yesterday, I was barely able to restart my engine after I motored out of the harbor for about ten minutes and used the auto pilot and nav/com instruments for about an hour under sail. Auto pilot was only on for 5 - 10 minutes.

I have not added electrlyte. Is this likely to make a difference or do my symptoms suggest, it may be time for replacement batteries?

Thanks in advance,

Ken Heyman
c34
"Wholesailor"
Chicago, Ill

[Ted Pounds]

Ken,

What kind of charger do you have?

Ted

[PAUL T.]

KEN...... What year is your boat? What size and type batteries? Are you trying to start the engine with the batteries on both? Are you trying to start the boat with the glow plugs engaged, I made that mistake when I first got my boat. Are you using the glow plugs? Were your batteries fully charged when you first got down to the boat?  Just some thoughts......PAUL

[reedbr]

Ken-

This is based purely from my car tinkering experience, but if you're not reading 13-15 volts with the engine running a little above idle, I don't think your charging system is charging.  If you had a gas engine without a functional charging system, it would eventually die just by powering the spark plugs.  Since it is a diesel, you are just seeing your deep cycle batteries slowly loose charge with accessory loads and occasional starting.  I would first check the alternator and regulator.  I would also charge the batteries back up with a shore power charger before they drop too low. *** I just re-read your post.  I'm not sure you gave us a voltage with the engine running, have you? ***

I would expect batteries in storage all winter without a trickle charger to read 11.5-12.5 volts until they are charged back up again.  In my mind that wouldn't be a sign of a weak battery.

Lastly, there are probably only 3 or 4 major manufacturers of batteries supplying the US, even though hundreds of companies slap their labels on them.  I wouldn't say that your off-brand is much of a factor for that new of a bettery.  I think the major players are Johnson Controls, Excide, and Interstate.  This site has some label/manufaturer cross references.

Of course I am guessing on the initial alternator/regulator diagnosis.  Certainly I'm wrong about the battery if one cell reads a lot lower than the others.  You should also make sure to fill the cells with distilled water until the plates are covered.  If you feed us some more facts as you investigate, we can help further.  Good luck.

[Stu Jackson]

Ken

It's unclear from your description if you charged them or not before you put them in and used them.

Did you?

Stu

[Jim Price]

Ken, you may also want to look at all the threads and projects on installing a solenoid in the starter circuit like many have done.  Makes a world of difference in putting the "heat" / voltage straight to the glow plugs and reducing the effort to start.  I agree you still have some recharging / battery issues but this step would save your tail when your batteries are low.  Think of being able to start a cold engine on one fully charged battery with 10 seconds pre-heat and starting with engine turning over only once.  Happens all the time now.

[Stu Jackson]

This is the link to the solenoid project:

http://c34.org/projects/projects-glowplugs.html

Stu