House Voltage dropping below 12v

[dbsea]

I have a battery mystery. I have 4 of the universal battery group 31agm batteries, two years old. That should give me 220ah of usable capacity in an ideal world (50% discharge). I’m on the hook currently; and woke up and checked my batteries like normal. SOC is registering at 74%, but yet my house bank is only at 11.4v. What’s the problem here?? Bad batteries??

 

[Hydraulicjump]

Dave,

I am sure the experts will weigh in shortly. But as you know voltage on your batteries can be greatly reduced if they are under load. You need to turn everything off and either throw a towel over your solar panel or pull the fuse to see how much the voltage recovers. Then you are going to get a clear picture of their true state of charge.

 

[watson1987]

The stock batteries don't have a good track record.

Mine would charge and hold a good voltage, but under a very small amount of load (a few hours on anchor), I would get similar voltage drops even after turning all the house loads off.

I'd start to consider getting them replaced. I'm local and if you have any questions about going lithium let me know - I wrote my changes up here - viewtopic.php?f=24&t=20419

 

[Hydraulicjump]

But even under normal load (fridge, lights) that is too low. I have (or about to be "had" since the boat is about to sell....fingers crossed) those batteries. I worked them pretty hard and they only lasted two years. They would hold charge fine, but their capacity was shot. I replaced them with the same and then was super careful with them and installed a Balmar Smartgage to track capacity, and always left them plugged in at the dock. They have held up very well, hanging onto their capacity this time. I can safely say the factory installed batteries are "delicate".

Good luck

Jeff

 

[gswearin]

Martin and Brian set me straight on this at:
viewtopic.php?f=5&t=20670

I was using the electric coffee pot and while I had plenty of battery, it caused a voltage drop.

 

[dbsea]

Mine were replaced in 2020, so they are 2.5 years old. Sounds like I need to plan for some new batteries at the end of this season. What do people recommend as replacements?

 

[Ralf H]

Hi Dave,

As others have mentioned, you will need to remove all load and see where the voltage is at that point. Also, as the saying goes, your mileage will vary. And that all depends on how the batteries were used over their lifespan. As for replacements, I'll let the skippers at large here give their opinions on what has worked best for them.

Cheers,

Ralf

 

[sjreib]

Dave,
Replaced my batteries a few months ago and followed recommendations of Ronnie Gonzales from Bellingham Yachts. Two Northstars for the start and thrusters and 4 lifeline for the house group. All AGM, group 31's. Expensive, but not an area I wanted to skimp on.

Steve

 

[dbsea]

Thanks Steve. I just replaced start and thruster with the optima group 31 blue top, and I’ll very likely go with the lifelines for the house bank.