Battery Voltage question

[CLBeerbower]

How do you determine the house battery voltage while underway? My situation: 2021 212XD while engines are running start battery is usually charging at 14.0 and the house battery at 13.7. I go to foot for a while and the house battery will start at around 12.3 and after 45 minutes or so it is around 12.1 or 12.0. However, this is when there is a load on the battery. This to me is very low, but I know that there is a load applied so I am unsure of how to tell what it should read at this point.

Once home I let it sit for a day and then checked and the voltage is back to 12.7. I also placed my battery tender on it and it says within 24 hours it is back to fully charged. These are the batteries provided to me by the dealership and I am not confident that the house battery is good and not suffering from sulfation.
Thoughts?

 

[Dave burke]

Lots of posts on this topic but in my experience the only way you can tell what the voltage is underway is with a voltmeter. The Connext screen doesn’t really give you an accurate reading.

Plus the charging system on these boats is not very strong which is why you actually might see the voltage drop under load. This is why many people have chargers in the boat so they can ensure the battery is fully charged.

I’m still using my original battery and the boat is a 2017. But I keep it charged when not in use and in the off-season.

 

[CLBeerbower]

Lots of posts on this topic but in my experience the only way you can tell what the voltage is underway is with a voltmeter. The Connext screen doesn’t really give you an accurate reading.

Plus the charging system on these boats is not very strong which is why you actually might see the voltage drop under load. This is why many people have chargers in the boat so they can ensure the battery is fully charged.

I’m still using my original battery and the boat is a 2017. But I keep it charged when not in use and in the off-season.

Thanks. I might have to take my meter with me next time I am on the water. Just wish I had something to bounce my numbers off of.

 

[Julian]

Thanks. I might have to take my meter with me next time I am on the water. Just wish I had something to bounce my numbers off of.

You are correct that numbers at 12 or around 12 are pretty low. My dealer installed a standard starting battery as my house battery, when it died, I replaced with a deep cycle. I don't sit for hours on end cranking music...and honestly since I put in the deep cycle haven't really monitored it.....its never given a low battery warning. If it did, I'd pull it out and charge it, and take it to Advance Auto for a free load test.

 

[CLBeerbower]

Mine are Interstate dual purpose batteries. I simply don’t know how close the under load reading (12.1v) is to what I would bounce it off for a normal reading, say 12.5 to 12.7

 

[Dave burke]

My house battery is a deep cycle just like @Julian. I was working on my stereo system the other day and the voltage (before I turned anything on) was about 12.6 (I have a voltage meter) on my amp board.

But when I started turning the amps on the voltage dropped pretty quickly (to about 11.9) because of the load and I started one engine to charge it.

Hope this helps

 

[CLBeerbower]

Wow. I guess that is my point to a certain extent. Is 11.9 bad when you have a moderate draw on a good battery? I understand it should be 12.6 or so with no draw, but what should it be with a reasonable draw?

 

[Dave burke]

Not sure I’m following you. If you’re drawing down without charging, the voltage will keep dropping. If you’re charging, it shouldn’t be.

If you’re interested, next time I’m out in the boat, I’ll check the volt meter on my amp board when the engines are running. I’ll send you a pic

 

[Dave burke]

So I went out in my boat a couple of hours ago. The voltage on my amp board (wired directly to the house battery) was 12.4. Boat was last used 2 days ago.

I then started the engines and checked the voltage at fast idle a couple of minutes later. On the Connext screen the voltage was 14.1 (both numbers) and on the amp board it was also 14.1.

I got back to the dock about an hour later and check the amp board immediately after shutting down the engines. I wasn’t blasting the stereo but two amps were powered up. Voltage was 13.2. This was higher than I expected. My guess is if I were to check an hour later, it would be back down to12.4-12.6.

Hope this helps.

 

[CLBeerbower]

Dave thank you very much. It does help.