DC System "grounds" check

Liberty44140

I have digital displays and they just started cycling off then on real quick at engine start up. I have checked a couple sources and it seems this is not normal for my set up and there is likely some low voltage issue, hopefully a simple one. Batteries are new and exceed the min CCA. So I have been told to make sure the grounding is good. 

After some online research in to what checking ground really means, it looks like for DC "check your ground" really means make sure all is good and clean with the black wire battery connection at the battery. Make sure zero volts between the post and connection. Then chase that to check the same on the starter, but that battery connection is really important

Sound right? 

LaRea

You also need to find your ground terminal block and make sure all the wires connected there are solid.  That means (1) give each wire a firm pull to make sure it's tight in the crimp terminal, and (2) make sure the crimp terminal is securely connected to the terminal block.  

Most Rinkers have a single ground terminal block and the wires are not labeled, but your boat might be different.

Liberty44140

Very helpful, Thanks. While my positive cables are red, my black cables on the batteries are actually all yellow and from what I can tell they all come together to one spot like you mention. Here is a pic of where they all come together just under one of the battery chargers. Makes sense this is the main central spot to check?

Grahamu

Yellow cables is now the color for negative cables. If you have a house bank try switching the positive feed to your electronics. My last boat had this problem and I would start the engines first before switching on the electronics.

LaRea

Yup, that's the main ground block.  From the large size of those wires, I'm guessing you might have other secondary ground blocks elsewhere in the boat, like maybe one at the helm.  

Liberty44140

Thanks Gang!

Gramu to your point, the electronics are on house batteries so they don't restart at start. This is just my 4" Volvo digital displays that restart. I turn the key to "on" and the displays come on, show 0 RPM, wait 5 sec, then when I turn to "start" and starters engage the displays go off then back on real quick. Used to always stay on.

I will check all of the connections in the pic and on the batteries. Also LaRae it is pretty easy for me to get in to the helm to check for an additional block there. 

Batteries are brand new but I may run them to Auto Zone for a load test anyway to be sure. 

Open to any other thoughts, thanks! 

Dream_Inn

I think you are well on your way.  If you still have problems after that, you can check resistance to the helmet and electronics.  The issue can also be on positive side as well, just don't forget that.

LaRea

This is unlikely, but I'll mention it:  If something is causing the starter motor to draw more current than before, that might have the effect you're describing.  Loose connections, dying starter motor, etc.  Are you seeing the same thing on both sides?

Grahamu

Understand now miss read the first post. I would say a voltage drop is the cause and probably as LaRea is where to start checking. Can you put a voltmeter on the start battery and check when starting the engine.

Liberty44140

I only noticed this on the port side but I always start port first and when I turn the port key on both displays power up… and both have the cycle problem when I start the port. Pretty sure that when I go to start the starboard this does not happen as port is running.

yes Gramu I can hold the meter on the battery while the admiral fires them up but I don’t know what I should see. Looks like automotive should not see less than 10.8 or 10.9 while starter is engaged?

Grahamu

What happens if you start the starboard engine first and then the port. If that works it would suggest low voltage with the port start battery. I'm not familiar with the Volvo system but with my Mercs the port engine supplies the power to VV

Liberty44140

Grahamu said:

What happens if you start the starboard engine first and then the port. If that works it would suggest low voltage with the port start battery. I'm not familiar with the Volvo system but with my Mercs the port engine supplies the power to VV

Yep I will definitely try that Friday. Thanks

Liberty44140

Also the more I think about this the more I question the batteries. Bought brand new in March but they had 12/2020 stickers on them. O Reilly’s super start truck and fleet group 31. 950cca. Same as old batteries but they were interstate. Definitely going to get them load tested, still under warranty. 

Thinking about them as they are something that has recently changed.

Liberty44140

The plan was to work on this tomorrow but I started tinkering tonight. Grounds in engine room look good but I didn’t disconnect, clean and reconnect the battery ground yet. To my pleasant surprise I could not replaicate the issue I saw last weekend whether I started Stbd or port first. Displays never re started. 

That said I could see voltage on the digital display. 12.7 at rest, dipped to 8.4 on both sides while starting, then 13.1 or more in neutral while running.

so I am really questioning these brand new batteries. I had thought that I should be in the upper 9s while starting and preferably 10.5 volts.

thoughts? 

Handymans342

Are they not diesel batteries? LOL

Liberty44140

Lol they exceed what is required handy. 

Grahamu

8.4 volts is low, upper 9s to low 10 is normal. Is the voltage measured at the starter motor? Are the cables connecting the engine to the start batteries original?

Liberty44140

Yes cables are all original 2007. They look brand new, but original. No that was measured at the Volvo digital dash display. 

Grahamu

During my winter repairs I cut off the terminals and shortened the cables as they were too long. I then swaged on new terminals. I have not noted my start voltages but I will next time I'm on the boat. You might not be reading the voltage at the starter which is probably higher, a digital meter on the start battery would confirm this

Liberty44140

Well I think I’m calling this one all good.

both batteries tested good at auto zone and o Reilly’s. I then really cleaned up all battery connections which didn’t seem bad but now look great. I also tightened all grounds.

I am getting 10.8 volts while starting when holding the digital meter right to the battery posts which is pretty good. Did not try the starter.

also still can’t replicate the problem

Grahamu

Good that it is solved

Liberty44140

Thanks for the help!