Battery advice for new Hunter 36 owners? And Northstar early death?

[Kupe]

Hey gang-

We're the happy owners of a new-to-us 2004 Hunter 36. We're coming from a 1984 Tartan 28 with old school flooded batteries so reading up furiously to catch up on battery technology. We're looking for A) replacement recommendations for the dying batteries on our Hunter, and B) any thoughts on our current installation with the unusual battery type we now have.

We just had our first nights away from the marina/shore power and woke up day two to nearly dead batteries. Overnight we were running only two dc fans, our dc fridge, and anchor light. Daytime use at anchor was similarly light. Heck we don't even run a big stereo- just a portable Bluetooth speaker.

The batteries are two NorthStar SMS-AGM 400. These things are monsters- 132 lbs each and nearly twice the size of Group 27 batteries. Priced around $800 each and also listed as Northstar NSB 190FT BLUE+. In particular they are far too tall for the battery box and so the box lid just rests atop the batteries. They were installed new in September 2019. I've attached photos.

Our charging system is the original Xantrex Freedom Marine 20 Inverter/Charger. The alternator output tests good at 14.1 volts.

Anyhow, advice on new batteries or thoughts on our current setup much appreciated!

Cheers!

[sailingharry]

We have 4 of them on our boat. They came with the boat when we bought it in 2019, and I think they were at least 5 years old then. We've done some distance cruising, which is brutal on AGM because if you don't get to a marina it's hard to get them charged to 100%. But they seem to still be working. I frequently discharge to at least the 50% mark, so I know they still have at least that much in them. Why do you think they have had an early death? What are your symptoms?

[sailorboy1]

I don't see how any recommendation can be made with the info provided.

[Kupe]

Originally Posted by sailorboy1

I don't see how any recommendation can be made with the info provided.

Sorry- I thought I actually went into way too much detail for the initial post anyhow. No worries thanks anyhow!

[sailorboy1]

If it makes any difference I have replaced my Hunter 410 batteries twice with 4 GC2 golf cart batteries, once with 4 G31 Firefly carbon foam batteries, and once with $300ea "G31" LFP drop in batteries (my current batteries)

What you decide to use all depends on how much you want to spend, how you use your boat, what and where you can fit them, and how long you hope they last.

I know I would never get those Northstar batteries!

[desodave]

We had a 2006 H38 for over 14 years with the 40hp Yanmar. I suspect that your boat has the same useless alternator as ours had. We had flooded batteries (4 × 105 Ah capacity) and the alternator would struggle to recharge them even in some of the wndless constant motoring we endure in our summer cruising. The AGMs will like that even less. That may have contributed to your batteries' declining health.