460 - AGM dead

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AGM dead

Printed From: myHanse.com
Category: Hints & Tips
Forum Name: 460
Forum Description: Model Hints, Tips and News
URL: https://www.myhanse.com/forum_posts.asp?TID=15437
Printed Date: 27 March 2026 at 03:29
Software Version: Web Wiz Forums 12.06 - https://www.webwizforums.com

Topic: AGM dead

Posted By: Lhsrris218
Subject: AGM dead
Date Posted: 13 November 2025 at 19:03

Boat was on the hard for hurricane season. All battery switches were off for engine and house.

Came back and everything is dead.

Engine battery at 5v, house at 5v, thrusters are good at 24v

Tried to charge the Engine battery- wont gi past 5-6 volts. Same with house.

Are these defective? I can see them discharging passively to 10-11v but 5?

Not sure if any will be salvageable - replaced the Engine battery so I can get in the water and to my slip

Any advice? Any warranty? Boat laun ed last December

Thanls

Replies:

Posted By: marsella
Date Posted: 13 November 2025 at 20:13

Those switches dont disconnect batteries completely, there are some elements of the circuits that are kept alive therefore if you leave the boat for a longer period either use a solar panel or wind generator to charge them. You can also hire a boat manager who will plug your boat into shore power once a month or so. Very easy in Caribbean, cost about $60/month. If you want the batteries to be competely disconnected, detach the red cable from them.

Posted By: Lhsrris218
Date Posted: 13 November 2025 at 20:39

Any idea if they can be recovered?. I thought the blue sea remite disconnect would also prevent them from getting too low.

Posted By: marsella
Date Posted: 13 November 2025 at 20:55

Those AGMs hate to be completely discharged, if you tried to charge them back and they did not pick up the charge, likely they need to be replaced. Even if they would show some life, I wouldnt gamble going out sailing if there is a chance they will die somewhere in the middle of nowhere.

I had similar experience when my boat stayed in Greifswald for several months waiting for me, but at that time the dealer didnt transfer the ownership to me and they had to put brand new batteries when I arrived

Posted By: Andiroo
Date Posted: 08 December 2025 at 06:44

Hi I managed to recover 1 of 2 AGM 160 ah batteries which were both drained to around 6V.

I connected the depleted battery to a healthy charged 12 volt battery (car starter battery) and then connected the battery charger to the healthy batteries terminals. This allowed the charger to charge without error. Left overnight and voltage of AGM battery had moved up to about 10 V. Now I connected the charger directly to the AGM and left it for over 1 day. It reached 12.6 V and has held that charge for past two weeks. I tried this on my other AGM battery and this didn't work, never charged properly.

Good luck

Andrew

Atomic Blonde Hanse 415

Fremantle Sailing Club