Battery troubles

[Captain W]

Bought two new AGM batteries before the sailing season last year. Sailed the entire year without issue. Last weekend I noted one of the two batteries (Battery 1) was dead, but was able to start the engine on the opposite battery. Bought a new solar charger and applied it to Battery 1 noting the starting voltage was 10.3 VDC (probably should have clued in that this was pretty low).

Arrived at the boat yesterday and noted 11.7VDC for Battery 1 on the solar charger. Used that battery for phone charging, water pump usage, radio and lights while we stayed at the mooring overnight. This morning I switched to the battery 2 to start the engine - nothing. Switched to battery 1, but it wasn’t enough to start the engine. Put the solar panel on batter 2 and it read 6.7 VDC. I assume it is a goner.

I borrowed a battery jumper from yard and was able to get the engine running when connected to battery 1 and motor sailed for about two hours, but noted no amps were going to the battery.

So…..I think it is fair to say I have two useless AGM batteries at this point (need to see if there was a warranty). What would have caused them to die so quickly? I have a very simple electrical system - is there any way to see what could be draining them when my three-way switch (1-2-Both) is ”off”. Previous owner was able to go two days on charge. Alternator failure? How do I check to see if the alternator is working? I must be doing something wrong….

 

[jssailem]

Learning about batteries and their care is not a simple "Do this all your troubles will be solved" answer.

I would encourage you to go through this site by a member and professional Marine Electrician, MaineSail.

Marine How To - DIY for Boaters - Marine How To

For DIY boaters in an attempt to try and keep the sport as affordable & safe as possible. How To articles for sailboats and powerboats.

marinehowto.com

You will find answers to many of the perplexing battery questions. Educating yourself on your battery system is how you minimize the costs and maximize the benefit of your boat battery.

Or you can run out and find a couple of cheap car batteries at a box store. You will get a temporary fix to the problem.

What is the challenge, the battery is not just a part it is a system.

Your battery receives, stores, and releases the power you put into it. How you feed in the power, where you hold your battery to store the power, and how you connect to the battery to withdraw the power all affect the life of your battery. If your system is not up to the challenge, your battery will live a short life and you will be back again at the store seeking replacements.

 

[dlochner]

So…..I think it is fair to say I have two useless AGM batteries at this point (need to see if there was a warranty). What would have caused them to die so quickly? I have a very simple electrical system - is there any way to see what could be draining them when my three-way switch (1-2-Both) is ”off”. Previous owner was able to go two days on charge. Alternator failure? How do I check to see if the alternator is working? I must be doing something wrong….

AGM batteries are very sensitive to the charging routine. If left in a partial state of charge for any length of time, they start to sulfate and lose capacity.

AGM batteries should only be used if the boat has a smart 3 stage charge of sufficient capacity for the bank and are on shore power almost everyday.

If the boat is on a mooring, unless you have a very large solar array, AGMs will have a very short life. A stock internally regulated alternator will not provide a sufficient charge to maintain the batteries health.

To help sort this out, is the boat on a mooring or at a dock? How big is the "solar charger"? What kind of alternator and regulator do you have? What size are the batteries?

 

[Captain W]

Thanks to both - I bought two Decca Group 27 AGM batteries last year. I am at a mooring and I just bought a 90W solar panel that I put in the cockpit while moored, but I just put it out last Thursday.
I thought I had done my homework on the AGM and they seemed to be the right mix of starting and deep cycle, but perhaps not. The previous owner had two gel batteries that had lasted him for years at a mooring with no solar.

 

[kloudie1]

Type of charge controller is connected between the solar and the battery?

 

[dlochner]

Thanks to both - I bought two Decca Group 27 AGM batteries last year. I am at a mooring and I just bought a 90W solar panel that I put in the cockpit while moored, but I just put it out last Thursday.
I thought I had done my homework on the AGM and they seemed to be the right mix of starting and deep cycle, but perhaps not. The previous owner had two gel batteries that had lasted him for years at a mooring with no solar.

I wish I had good news, but I don't.

Boats on moorings shouldn't use AGMs because they can't be kept fully charged. And to make it worse, Deka makes great Flooded Lead Acid deep cycle golf cart batteries, but their AGMs fall short of the mark.

The 90w solar panel with an appropriate charger will be good maintaining a charge on a set FLA batteries, but fall well short of the mark for AGMs.

This article from Practical Sailor gives a good overview on AGM maintenance. There are a couple of links to other articles about AGMs.

Don't Kill That New AGM Battery - Practical Sailor

Few cruising boats return their batteries to 100-percent state of charge after each cycle. This typical battery use, or abuse, is called partial state of charge operation, and if it continues, a sailor can see his AGM battery perform noticeably worse than a less costly, deep-cycle flooded...

www.practical-sailor.com

Before you buy new batteries, read this article from Rod Collins, aka Maine Sail.

What is a Deep Cycle Battery? - Marine How To

Light Cycle vs. Deeper Cycle NOTE: This article deals with FLOODED marine batteries, not AGM or GEL batteries. The Problem: The problem, as I see it, is one of dishonest marketing where multiple battery types wear the same clothes (sticker) and will perform differently when

marinehowto.com

Personally, I"m a fan of 6v golf cart batteries, lots of power, relatively inexpensive, and pretty robust.

 

[Stu Jackson]

In addition to Maine Sail's linked website, this may help you, too:

Electrical Systems 101 Electrical Systems 101

 

[Don S/V ILLusion]

I borrowed a battery jumper from yard and was able to get the engine running when connected to battery 1 and motor sailed for about two hours, but noted no amps were going to the battery.
.

That implies the battery wasn’t getting a charge from any source. Good place to start before installing new batteries would be to find out why.

 

[dLj]

The only AGM's that I'm aware of that list equalization are Lifelines. But I might be tempted to try an equalization cycle on your Deka's to see if it helps. Other's have mentioned most other advice that I can think of.

dj

 

[Head Sail]

motor sailed for about two hours, but noted no amps were going to the battery.

Your alternator is dead.

 

[Captain W]

How would I test my alternator?

 

[jssailem]

If you have a Digital Volt Meter you can test it to see if it is outputting 12 or more volts. If no experience working around DC current, you might ask a knowledgable friend to help.

Better yet, remove the alternator and take it to a shop. They can test all of the functions and let you know the status.

USE CARE AND DISCONNECT THE BATTERIES BEFORE YOU START TO REMOVE THE ALTERNATOR.

 

[Head Sail]

How would I test my alternator?

Start with volt meter readings at the battery before and after the engine starts. Report back.

 

[shemandr]

I think you can test the alternator by using a voltmeter across the + and negative posts. I'm the last one to give advice on anything electric but a survey report of my Ranger 29 said that my alternator was putting out 14 volts. The surveyor thought that was good.

 

[twistedskipper]

As an aside, 11.7v is generally considered to be a fully discharged battery.

 

[dlochner]

Voltage from the alternator is one part of the equation, the other is the current output. That is best measured by a clamp on meter which reads amperage.

Stock internally regulated alternators usually have the max voltage limited and the current limited well below the rated amperage to avoid damaging the alternator.

Checking the alternator output is certainly worth doing. An auto electric shop, one that rebuilds and repairs alternators, can test it. It is quite possible the alternator is faulty, however, that won't resurrect the batteries and if it is an internally regulated alternator it won't keep an AGM battery properly charged unless the boat is on a dock with shore power and an appropriately sized smart charger.

 

[MikeHoncho]

You may want to map out your DC system. Specifically where you alt + and panel controller connects to the system. You don’t mention a controller. I’ve read some panels will discharge batteries due to parasitic draw during the night without a controller.
AGMs draw a lot of amps when charging. This heats up the alt and fries them if not externally regulated.

 

[dLj]

Equalization volts are typically 15.8 to 16.2 volts so your top end of 15.5 is too low. Controlling out gassing can be done through current control. You also want to control temperature - basically don't let them get warm.

dj

 

[TomY]

Bought two new AGM batteries before the sailing season last year. Sailed the entire year without issue. Last weekend I noted one of the two batteries (Battery 1) was dead, but was able to start the engine on the opposite battery. Bought a new solar charger and applied it to Battery 1 noting the starting voltage was 10.3 VDC (probably should have clued in that this was pretty low).

Arrived at the boat yesterday and noted 11.7VDC for Battery 1 on the solar charger. Used that battery for phone charging, water pump usage, radio and lights while we stayed at the mooring overnight. This morning I switched to the battery 2 to start the engine - nothing. Switched to battery 1, but it wasn’t enough to start the engine. Put the solar panel on batter 2 and it read 6.7 VDC. I assume it is a goner.

I borrowed a battery jumper from yard and was able to get the engine running when connected to battery 1 and motor sailed for about two hours, but noted no amps were going to the battery.

So…..I think it is fair to say I have two useless AGM batteries at this point (need to see if there was a warranty). What would have caused them to die so quickly? I have a very simple electrical system - is there any way to see what could be draining them when my three-way switch (1-2-Both) is ”off”. Previous owner was able to go two days on charge. Alternator failure? How do I check to see if the alternator is working? I must be doing something wrong….

What a shame!

If I were you, I'd get a couple of lead acid grp 27's, install and go sailing. The boat is pretty new to you so I doubt the alternator is faulty (just touch a voltage meter to any + - when the engine is running-should be above 13V).

On a mooring with deep discharges and not enough charging, LA batteries should serve you for 5 years more or less.

The only thing I would caution is overcharging with your solar panel when the boat is left on the mooring until you're sure your controller is safe for that. Use it as a solar 'generator' when you're on the boat to fully charge the batteries. Without refrigeration you should be able to keep the 2 LA fully charged.

You can spend next winter getting a PhD in marine batteries, or not.

 

[TimFromLI]

As others have said it sounds like your alternator is not putting out a charge. I had a similar problem last season - the alternator (balmar) was bad. I took it off and brought it to a shop where the bench tested it and repaired it for a fraction of the cost of a new balmar.