Battery Charging

[Lee Hadjiosif]

I want to change from sealed/flooded to AGMs. I have three banks. The charger has an AGM setting. How about the alternator? I have an internally controlled alternator. Will it be able to handle AGM or do I have to change the alternator as well?
Also my solar charger controller has a Flooded or Sealed setting which I thought they were the same thing! Can anyone decode? Thanks.

 

[jssailem]

Also my solar charger controller has a Flooded or Sealed setting which I thought they were the same thing! Can anyone decode?

I will give it a try...

Lets start with AGM....

The acronym stands for “absorbed glass mat” and that’s one of many improvements made to Planté’s original train light battery. Glass mats, cushioning the ultra-thin lead plates, will squish like a sponge. In turn, manufacturers can squeeze more glass mats and lead into one battery. More lead equals more power. Plus, that squish factor means the battery’s insides are packed tightly.​

​

AGM batteries also have valves regulating the amount of hydrogen and oxygen gas allowed to escape during charging. They fall under a broader category of valve-regulated, lead-acid (VRLA) batteries, typically used for storing a lot of power for a long time or for long-running power uses.​

A way of thinking about it is an AGM is a LeadAcid battery with a sponge. It keeps the electrolyte (the acid mixture) in contact with the lead plates, reducing the stratification of the electrolyte common in Flooded batteries.

Your image is of a solar battery charge controller. If it is going to be used on an AGM (think sealed) battery, then move the switch down as indicated. If you are using a FloodAcid battery then move the switch up.

Using the described internally regulated alternator will charge the AGM battery, but the method will not be optimum for the battery. This is the reason external regulators have been developed that better manage the alternator charging performance

 

[Stu Jackson]

Why do you want to change to AGMs? Serious question.

I suggest that before you do so you read these:

AGM Batteries - Making The Choice (from Maine Sail)

AGM Batteries - Making The Choice

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
Darn AGM Batteries

Additional Observations on the Limits of AGMs Electrical Systems 101

How Alternators & Regulators Work PLUS External vs. Internal Regulators (by Maine Sail): Musings Regarding External Voltage Regulation

 

[dlochner]

@Stu Jackson beat me, I have an excuse of course I was motoring into 15 knots on the nose...

AGMs may or may not be the best choice for you. Let's make sure they are before spending a lot of money on them.

Once you decide that AGMs are the best choice for your sailing and cruising life, then contact the manufacturer and ask for the proper charging protocol for your batteries. Generic settings may be OK or may not, best to go with the manufacturer's recommendation. The gold standard for battery documentation has to be the Lifeline AGM documentation. It will be on their site.

Knowledge Center - Lifeline Batteries

If you cannot find what you are looking for below, we are standing by to help you with your battery needs. Feel free to contact us anytime and talk to a real

lifelinebatteries.com

The stock internally regulated alternator that presumably have on your motor will most likely be unable to properly charge the batteries. It is probably not set up to properly charge basic flooded lead acid batteries because the charging voltage is too low. The settings can not be changed or changed easily.

The Solar controller will not adequately charge AGM batteries and will need to be replaced. A sealed battery and an AGM are different critters. Sealed batteries aren't really sealed, they have a valve that will release excess pressure.

Without knowing more about the charger, particularly the capacity of the charger (how many amps) and the charging profiles it is not possible advise on the charger.

AGMs are finicky batteries, they have some advantages but are easily trashed. If you have been shopping for them you know how expensive they are.

 

[Ken Cross]

I put AGM batteries on our boat because I already had them and didn't want to change the engine battery as well. It was that or changing the battery charger because our charger can't mix battery types. So we are all AGM. I don't think our alternator was altered from the original, but when on shore power our charger tops them off nicely. After 6 years they seem to be working about like when they were new. The idea with adding solar is to keep me above that magic 50% SOC longer than without. Otherwise, we could only manage 24 hours without shore power or running the engine unless we didn't use the fridge. The solar greatly extends the time we can spend without plugging in. I don't know how long because we haven't been without power this summer except for one night.