Equalizing AGM batteries - Page 3 - SailNet Community
LinkBack Thread Tools
post #21 of 26 Old 01-24-2011
Senior Cruiser
sea_hunter's Avatar
Join Date: Jul 2000
Posts: 512
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 17
WARNING: Do not equalize gel or AGM batteries!!!!!!!!!!!!!!!!!!
one of two things might happen; screw the batteries (burn out) or screw the boat (burn up). Read your battery manual 1st.
sea_hunter is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
post #22 of 26 Old 01-25-2011
Senior Member
Maine Sail's Avatar
Join Date: Jan 2003
Location: Maine Coast
Posts: 6,412
Thanks: 22
Thanked 305 Times in 236 Posts
Rep Power: 18
Originally Posted by sea_hunter View Post
WARNING: Do not equalize gel or AGM batteries!!!!!!!!!!!!!!!!!!
one of two things might happen; screw the batteries (burn out) or screw the boat (burn up). Read your battery manual 1st.

Again, SOME AGM batteries CAN be equalized and considering the short lives this type of battery has had in the marine market many Lifeline owners are darn happy Lifeline designed their batteries to withstand an equalizing or conditioning charge..

I will post this again:

This is a DIRECT quote from Lifeline Battery:

"Conditioning/Equalizing Charge: 15.5 volts for 8 hours. Conditioning/equalizing should only be done when the battery is showing symptoms of capacity loss. If conditioning/equalizing is necessary, first go through the normal charge cycle. Once the battery is as fully charged as possible, start the conditioning/equalizing charge.

To apply a conditioning charge, first go through the normal charge cycle to bring the battery to full charge. The conditioning charge should then be applied by charging for 8 hours. At 77F (25C), the conditioning voltage should be set at 2.58 VPC (15.5 volts for a 12 volt battery). The conditioning voltage at other temperatures is shown in Table 5-2. By using the temperature compensated conditioning voltage, batteries that are not in controlled temperature environments may be conditioned without bringing them to room temperature. If temperature compensation is not available, it is best to bring the battery as close to room temperature as possible before applying the conditioning charge.

For maximum battery life, a battery must be recharged to 100% capacity. Recharging to less than 100% may result in premature battery failure. Lifeline batteries are not covered under warranty if they are not recharged properly. For more information, please refer to our warranty policy."

A more accurate statement would have been to say that some manufacturers say it is okay to equalize AGM's and some or many others prefer that you don't. As always and as you said at the end read the manual or check with your manufacturer before equalizing AGM batteries. But some AGM's CAN be equalized!

Because each manufacturer has specific requirements for their own AGM's a blanket statement can not be made for all AGM batteries. Here is Trojan's statement on equalizing AGM's.

Direct quote from Trojan Battery:

WARNING: Do not equalize gel or AGM batteries.

If you had left your statement as; "Read your battery manual 1st" it would have been accurate information.

Clearly blanket statements do not always work as applied to all brands of AGM batteries and seeing as Lifeline is perhaps the #1 AGM maker in terms of marine market volume, here in the US, that means that a lot of boaters can equalize their AGM's to get more life from them....

-Maine Sail / CS-36T

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Images In Posts Property of Compass Marine Inc.

Last edited by Maine Sail; 01-28-2016 at 08:04 AM.
Maine Sail is offline  
Quote Quick Reply Share with Facebook
post #23 of 26 Old 02-06-2011
Junior Member
Join Date: Aug 2003
Posts: 5
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
Thanks, I talked to a tech at lifeline and he said its ok to condition in the salon just ventilate well in case there is a release of hydrogen it becomes dangerous at only 4%! I'll wait till the weather warms up and I have to do some glass work on the companion way coaming.
divicolouis is offline  
Quote Quick Reply Share with Facebook
post #24 of 26 Old 03-23-2011
Senior Cruiser
sea_hunter's Avatar
Join Date: Jul 2000
Posts: 512
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 17
This is the problem with mixing batteries. Some AGMs can handle equalization while others will just run away; all bad. I would suggest removing the connections to the ones that CAN be equalized (make sure the other batteries are fully charged) and equalize them with a separate battery charger as that will allow you to leave the settings alone on your charger or inverter/charger if you have one. Once equalized, disconnect the external battery charger and reconnect those batteries. This is why I caution most not to equalize any AGM until you read your manufacturers manuals, considering the average boater's electrical/electronic skills.
rnman likes this.

Last edited by sea_hunter; 03-23-2011 at 10:23 AM.
sea_hunter is offline  
Quote Quick Reply Share with Facebook
post #25 of 26 Old 12-11-2014
Junior Member
Join Date: Dec 2014
Posts: 1
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
Re: Equalizing AGM batteries

My opinions, use them at your own risk, and research them as you feel the need to before using them until you content you "get it".

AGM batteries are great for quick energy release and ease of charge, but equalizing them like you would a wet cell battery (flooded vs AGM "absorbed glass mat") has been a bad idea the two times I tried it (against my better judgement ). A little research on my end suggest that 14.7 volts is as high as these batteries should ever be charged, and that should only be with enough current/amperage to get the voltage there, but never more that 0.75 amps on a 6 volt - 3 cell, or 1.5 amps on a 12 volt - 6 cell battery regardless. Like someone else said, fully charge your battery, then maybe even float it at 13.5-13.6 volt and <100 milliamps for a couple of days to really saturate the battery, then equalize it. Never start equalize charging any battery until it has had a full charge done, and never do this inside your home or garage, but only outside or in a well ventilated shop with all the safety precautions that make sense.

The charging algorithms for AGM batteries do not exceed 14.7 in my Midtronics GR-8 charging system I don't believe (a 3000.00 charging system), nor do the voltages go as high in my Schumacher algorithms for AGM's as they do for "wet cell" batteries. That said: LISTEN, - BUT!!!!!, WATER FROM THE BATTERY ELECTROLYTE BEGINS TO SUBSTANTIALLY BE BOILED OFF AT ONLY 14.4 VOLTS, so if you go above this often or FOR A LONG PERIOD OF TIME ON AN AGM, or even on a sealed WET lead acid battery - you will eventually dry out one of the cells, and the battery will be no good, and the dry state could allow the battery to create and electrical arc and result in an explosion; I did not experience this on my AGM's, but I did dry out the cells most likely as both AGM's I tried to equalize a few times, lost ~ 2.1 volts o/v across the battery indicating a killed cell, and the battery sides shrunk in as though negative pressure from lost volume in that cell had been created. Bottom line in my opinion, if you must equalize your AGM, don't go above an average of 0.25 amps per battery cell (0.75 and 1.5 for 6v/3cell and 12v/6cell batteries respectively) and don't even do that unless your going to invest in a battery tester (Harbor Freight Tools sells one that is about $75 bucks that does just fine for measuring internal resistance and open voltage across the terminals (o/v). Use the tester to determine when equalizing is actually helping vs. hurting. If equalizing your battery doesn't decrease the internal resistance of the battery, improve it's resting voltage after a charge is completed and the battery rested for a 12-24 hour period, or for sure if equalizing is increasing your internal resistance, then your not doing your battery any favor by equalizing it unless your trying to put it out of it's misery. It's also great to use to track and assess the general condition of your batteries health and state-of-charge. The ohms resistance (< than 3 is excellent battery condition in my experience, 3-4 is very strong, 4-5 is still really good, 5-7 is starting to suggest the needs to be serviced or replaced, and over 7 is for sure a weak battery ready to let you down when you don't want it to. There's a lot of information and knowledge required to safely equalize a battery, so please be careful, do this at your own risk...(my opinions are mine and are "as is..." without any warranty of safety or efficacy). Battery care can be dangerous, so have eye and skin protection on, never do it without being able to get medical help for yourself, or without being able to access fire control/extinguishers. Just be damn careful. Safe boating!!!

My steps in synopsis:
1. Charge my battery completely
2. Float it at 13.5 - 13.6 volts for a couple of days
3. Measure the electrolyte specific gravity (can't do this in an AGM or Sealed wet Lead-Acid)
4. Equalize at less than 1.5 amps total on the 12v/ 6cell battery and 2.5 to 2.65 volts per cell (15 - 16 volts on a 12 volt battery) HERE IS WHERE THE VOLTAGE FOR AN AGM OR SEALED BATTERY IS RELAVANT BECAUSE YOU CAN'T REPLACE THE ELECTROLYTE OR MONITOR THE INDIVIDUAL CELLS
5. Recheck electrolyte specific gravity and quit equalizing when no further evidence of improvement is noted or if battery starts getting hot, or electrolyte becomes colored at all.
6. Determine if battery if good after 24 hours of rest following any charge or equalization.

AGAIN.....AT YOUR OWN RISK! THIS REALLY IS ONLY SAFE TO DO IF YOUR AUTOMATIC CHARGER HAS AN EQUALIZATION MODE (genius, xantrax, and progressive dynamics make automatic chargers that equalize) BECAUSE DOING IT MANUALLY WITH A DC POWER SUPPLY REQUIRES SOME KNOWLEGE TO AVOID INJURY, FIRE, EXPLOSION, OR EVEN DEATH!!! I wouldn't even do them on my boat, and I don't have a big boat...just sayin'. Take them out and do the equalization in a controlled environment!!!! Did I say...AT YOUR OWN RISK YET????
rnman is offline  
Quote Quick Reply Share with Facebook
post #26 of 26 Old 02-27-2016
Junior Member
Join Date: Feb 2016
Posts: 1
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
Re: Equalizing with Link 2000

I have changed everything I own with a starting - type battery to AGM. I have discovered that around normal boating outdoor temperatures AGMs will show an open circuit voltage around 13 volts.

Around means an older battery will be around 12.8 to 12.9. A new battery will be about 13.1 to 13.3. Higher voltages for newer batteries. I have had occasion to need to equalize or revive a severely discharged battery. I have a squadron of smart chargers and the standard roll around big boy too. A severely discharged battery will show charging, then after the expected time, based on charger capacity and battery size, 'Fully charged'.

But it will not be. The smart chargers will bring battery voltage up in the high 14s or 15s of volts for a while, then trickle back and declare the battery charged. If the battery is allowed to rest about 10 minutes or so, the open circuit voltage will droop to about 12.4, to 12.7 or maybe 12.8.

The battery now is about 2/3 charged. I now put it on a voltage regulated, current regulated lab power supply and set the voltage for 16 volts and 1 amp for small batteries, in the range of 15 to 35 Ahours. IE Jet Skis, lawn equipment, and motorcycles. For 100 AH batteries I set the current limit to 1.5 amps to 2.0 amps. When the pwer suply is powered on it will go to full set current, (1.0 Amps in small battery case) and will current limit at about 13 volts and change. As the battery continues to charge, the current will stay the same, and the voltage will gradually rise, until the voltage reaches the voltage set point. At this time the voltage will not rise, and the current will begin to decrease. At this time I consider the battery as fully charged as practical, and disconnect it.

I have AGM batteries in lawn tractors, Jet Skis, a motorcycle, the tow truck, and a dual setup in a boat. There are other things like gensets, etc with AGMs also, but they do not get the attention the other stuff does.

That's what I do.

Last edited by SRQJohnson; 02-27-2016 at 07:02 PM. Reason: typo correction
SRQJohnson is offline  
Quote Quick Reply Share with Facebook

Quick Reply

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Similar Threads
Thread Thread Starter Forum Replies Last Post
Use of AGM/Glass mat batteries santorinidon Gear & Maintenance 7 07-15-2006 12:59 AM
Alternator and Batteries NewsReader Mass Bay Sailors 2 06-27-2006 06:09 AM
Re: Alternator and Batteries NewsReader Mass Bay Sailors 0 06-25-2006 06:15 PM
Batteries - Mixing Different Ah ken346 Gear & Maintenance 1 05-27-2001 11:59 AM
Batteries & Charging capedory30 General Discussion (sailing related) 2 04-27-2001 04:05 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome