AGM batterias

[mike cunningham]

"La batteria è uno strumento musicale composto da tamburi, piatti e altri strumenti a percussione disposti in modo tale che possano essere suonati da un solo musicista." thanks Wikipedia

Sorry - can't edit the thread title I did not mean an Italian drumset I meant my batteries.


I have two house and one start 110 AH Lifeline AGMs which I installed in May 2007. They will be about 9 years old come the big event.

I have treated these batteries well. Physically they are in excellent condition, look brand new. Rarely take them below 75% SOC, Location in boat is near hull just below waterline so they stay reasonable toasty in winter and don't get too toasty during the summer.

During LongPac I saw no issues. The batts seemed to manage loads as they always have. I did notice it seemed to take a long while to charge but that may have been perception. Given where I live (on the Delta) I tend to do a lot of motoring and, of course, the batts charge throughout so I am not used to watching the grass grow with respect to charging while I am sailing the boat and moving at 1.5 kts. During first four days of LongPac I couldn't wait to turn the damn engine off, the ruckus was negatively impacting my Chi.

The one thing I have not done, by necessity, is bring them back to full charge after a cycle down to 75 or 80%. In theory this is a no-no for AGMs. I am sure most sailors who own AGMs can relate.

So I am wondering what I can do to test the batteries and get a feel for whether they are good to go for Hawaii despite their age which is getting up there for an AGM. Any suggestions?

 

[BobJ]

Beaker can check those batterias for you.

View attachment 1269

 

[Gamayun]

Ha, ha. I so relate to Beaker!

Mike, as you know, I'm the resident newbie, so take this all with a big grain of salt. I have 4, 6-volt AGMs and have been reading a lot about what to do or not do. Have you ever reconditioned them? Lifelines are great in that you can do this without blowing them up (or some such really bad thing Info is online but you could also call Lifeline directly. I called them the other day about upgrading my alternator and getting solar panels. The guy on the line was really helpful. Do you have a good battery monitor? I bought a "used" Victron from Bob that is a thing of beauty. This is really helpful to see how much current is being used and the levels of charging going in. You just have to sit there and write down the numbers over time. It's a PITA if you're easily distracted like me, but this might be a simple way of testing what you got.

 

[mike cunningham]

I don't know what you think is so funny, that's pretty much what I looked like at the end of the LongPac and my compass looked like the green guy to the right.

Anyway, yes I do have a xantrex batt monitor and it operates similar to what you have described. I will look into equalization and call Lifeline. Who knew someone would actually answer. I'm impressed. I'll see what they have to say about verifying the condition of the batteries. The Xantrex has a bunch of archived data saved on board, maybe i can make use of that in some way.

 

[Harrier]

I change batteries (gel and then AGMs) every 7 years, even tho they tested out OK. There are no replacement sources between SFO and Hawaii and (1) I don't rig my pendulum self steering vane for the SHTP, preferring electric auto pilot solely and (2) I don't want to even think of hand steering for days on end due to battery failure. Just a thought...but if you're trying to set a record for battery life......

 

[todd22123]

From the Lifeline website, the 50% state of charge would measure 12.2 V. So for a 110 Ah Lifeline, can you leave it on a trickle charger for a couple days to get it to 100% SOC, then hook up 1 amp load for 55 hr and look at the voltage? If it is sig below 12.2 V, then the battery is not performing as expected.

American Battery Co in Hayward CA, proprietor is Mr. Ramos I believe, Address: 3496 Arden Rd, Hayward, CA 94545
Phone510) 259-1150

I have been there a few times and purchased batteries for boats. He is nice and helpful, sells Lifelines, among others. Perhaps he would have some way of testing the battery. He has a booth at the boat show, and he gave me a "boat show discount" even when it was not the boat show for whatever that is worth.

Knowing when to recharge:

The open circuit voltages listed below correspond to the various states of charge:



State of Charge 2 Volt Battery 6 VoltBattery 12 VoltBattery
100% 2.16V or more 6.50V or more 12.8V or more
75% 2.08V 6.25V 12.5V
50% 2.03V 6.10V 12.2V
25% 1.98V 5.95V 11.9V
0% 1.93V or less 5.8V or less 11.6V or less

 

[solosailor]

A true load rest as Todd suggests is the way to go. I would try to use at least a 3-5 amps load as that is the minimum average you will likely use to give you a real world Amps available test. The total output of the battery does change based on load so a battery with a 1 amp draw output more amps than a battery with a 20 amp draw. Use them, test them, know them.

There are no flooded (Lead, Gel and AGM) batteries that can accurately be measured using voltage as a state of charge as the voltage spread from a full charge to discharge is very narrow. There would be no need for an amp monitor if this were the case. Even with LFP lithium where the voltage range from charged to discharge is 4 volts it is very difficult to use voltage for SOC as the bulk of the amps drawn are in the very flat portion of the discharge curve. Some of the latest cells types can use voltage as an accurate SOC indicator.

 

[mike cunningham]

I change batteries (gel and then AGMs) every 7 years, even tho they tested out OK. There are no replacement sources between SFO and Hawaii and (1) I don't rig my pendulum self steering vane for the SHTP, preferring electric auto pilot solely and (2) I don't want to even think of hand steering for days on end due to battery failure. Just a thought...but if you're trying to set a record for battery life......

Harrier,

Yea, I realize the best thing to do is simply replace the things but the reason I am struggling with the decision is I am looking at the prep budget and yikes! it is getting to be a big number. I have a leaking shaft seal and, in evaluating replacement yesterday, looks like a $3K job to replace a $300 seal due to my boat configuration, scoring of shaft, motor alignment, motor mounts etc etc. Anyway, the bucks are adding up and I want to try to avoid the $1200 for new AGMs if I can convince myself the old are OK. But I hear you, it would suck to loose batteries half way there.

I think I will talk to Lifeline and run a load test before I make a final decision.

 

[pbryant]

From the Lifeline website, the 50% state of charge would measure 12.2 V. So for a 110 Ah Lifeline, can you leave it on a trickle charger for a couple days to get it to 100% SOC, then hook up 1 amp load for 55 hr and look at the voltage? If it is sig below 12.2 V, then the battery is not performing as expected.

After discharging 55 amp/hours, it's important to disconnect all loads from the battery and let it "rest" for at least four hours before measuring the terminal voltage. The voltage readings listed in the post above are based on "open circuit voltage." Otherwise, with the load still connected, you will get an artificially low and inaccurate terminal voltage reading.

As another poster here mentioned, drawing only 1 amp from the battery will cause the battery to appear to have a larger capacity than it has under a "standard" test load. This is due to an affect called Peukert's Law. The battery was rated for 110 A/H at a constant-current discharge rate for 20 hours at a current of the amp/hour capacity/20 (the resistance was lowered in the test as the battery voltage dropped to maintain a constant current). You need a lab setup to duplicate that sort of test (or lots of patience with a variable resistor and an ammeter), but you can approximate the test by drawing that current at the start and using the amp/hours totalizer on your battery monitor. Stop after 55 A/H have been drawn (in about 10 hours), disconnect one battery terminal, wait at least four hours for the voltage to settle, and measure the terminal voltage.

Lifeline defines "end of life" on their batteries as being the point where the capacity has dropped to 80%. I change mine out (I have a total of 400 amp/hours) after they test at 90%. Lifeline makes good batteries. If you've treated them gently, used a good three-stage charger, and especially never allowed them to remain in a partially discharged state for long, they may still test as nearly new.

The full technical manual is located here: http://lifelineb.wpengine.com/wp-content/uploads/2015/12/manual.pdf. The capacity test and voltages under-load and open-circuit are listed on page 30 of that doc. That doc also describes the "conditioning" process (AKA: "equalization"), and when it should be attempted.