New AGM batteries - what am I doing wrong?

[Icarus]

Originally Posted by moseriw

Of course you can always buy proper deep cycle flooded batteries - Trojan is probably the best one.



Oh my - stay off Trojans. Every cell needs 1/8 l of water every 2 Months!
And chargers? Victron? My shunt says 97% and the batteries drop over night to 12.2V
The SmartSolar can not be adjusted to float - even if I set 12,8V as float (should be 13,6V for the Trojans.)

Looks like the Trojans are done after two years due to lack of water as the plates were blank 2x during the wintertime.

Solutions: still waiting for an input of Trojan and Victron since 3 months. The Trojan seller says plank plates should not harm the batteries - they are build for this lack of service.

So what? I am just a user an do not want to go in for a battery charge system engineer.

Strange..my T-125, four of them need water every 6 month or so, the last set lasted 6 years although the had an accidental 80% discharge for a month which damaged two cells.

[Icarus]

Originally Posted by goboatingnow

I’m not a fan of gel batteries. Yes they do not have the issues with undercharging that AGMs have. But they are very sensitive to overcharging

I fail to see what’s wrong with good old wet acid VRLAs.

Nothing wrong with lead/acid types at all.
Bought 4x6V T-125 used as house batteries...AUD 260 each..last for 5 to 6 years, cheap as chips.

[Stu Jackson]

It is good that you have begun/continued your detective work, congratulations for figuring this out.


Baffled? None of us was born an electrician. Really. We all learned, and many, if not all of us, used to say: "...but I know I'm not alone in being utterly baffled by electrical systems."


Here's another "BUT:" "...but we all learned more about it every day and oddly enough it is not always like a lightbulb coming on above your head." (pun intended!)


You have to work at it. I tried putting my books under my pillow in college...didn't work!


You have received a lot of good input here, and let me share how we did it: WE STUDIED THE SUBJECT.


Many of us started with a good book. Charlie Wing's is a good one. Send me a pm and I'll email you a copy of it that I downloaded for free many years ago when it was free. If not, go buy it.


When many of us started in boating and electrical systems were becoming more complicated, the internet did not exist. Now it does and in addition to forums like this, there are many of us who not only help, but "build" resources. Like this one, which appears daunting at first, but like eating an elephant, one bite at a time is all it takes:


Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html


Skim through the subjects, there's even one on books.


And when it comes to electrical systems, my motto has been: "Photos of wiring without a wiring diagram are useless." So learn to draw wiring diagrams and you WILL begin to see how it all works together.


Good luck. Like mom always said, "Apply yourself and you'll do fine. Denial is not a good place to start."

Originally Posted by aisleorwindow

Thanks again for all the contributions to this thread, here's an update, admittedly some of this is a bit embarrassing, but hopefully other newbies can learn from my errors:

What I originally thought was a bank of 2 engine batteries on the Starboard side of the boat and a bank of 3 house batteries on the Port side of the boat, were actually 1 engine battery + 2 house batteries on the Port side.

The 2 batteries on the Starboard side of the boat are optional/extra house batteries. see below (nevermind that port and starboard are switched in the manual )

https://photos.google.com/share/AF1Q...VFbGVZaWhhTkxR

So I disconnected everything to check each battery individually. These "optional" batteries were the old batteries and are reading at 12.55 volts.
The new batteries are all showing 12.9 - 13+.

So I figured if I disconnected the old ones, and just used the two new house batteries, which I know are 12.9+, that might solve the problem - i.e. the old ones were "dragging the new ones down."

So after doing that, my new house batteries were reading at 12.77 or so, but my battery monitor was showing that I was only at 12.4, using 3-4Amps.
Then I turned on my MFD/instruments and that added another 4 amps or so. My batteries immediately started dropping to 12.6, then 12.5 using my batter tester.... my monitor showed 12.2.

So at this point I'm not sure what exactly is going on:

Have I already ruined my new batteries?
Is something drawing on them higher than it should be?
Is my battery monitor incorrect? (not sure why the monitor number doesn't match my battery tester reading)

A few other data points:
The the engine battery and auxiliary battery (for windlass/bow thruster) are totally fine. So that leads me to believe it is not an issue with the charger and/or alternator.
The "old" batteries are the exact same type/brand as the new ones (Deka AGM 31s - 100AH). Embarrassingly I may have killed them as I left them on the boat all winter in Chicago - so that may be why they are only at 12.5?

Anyways, going to charge everything overnight and come back tomorrow and see how things look.

Go easy on me, I know some of you old salts must be shaking your head at me, but hopefully someone else can learn from this. I'm a pretty smart guy in many areas, but I know I'm not alone in being utterly baffled by electrical systems.

Again, thanks to all for their help (and patience!) with my journey.

[MikeHoncho]

Originally Posted by Stu Jackson

You have to work at it. I tried putting my books under my pillow in college...didn't work!

I listened to my A&P lectures at night while I slept that I recorded on micro cassette. Did work either.

[HC Mike]

All battery’s have three change voltages and time requirements. I have 4 AGM CB12-260s, and solar charged for 6 years with all Victron monitoring units and never a problem. I don’t use any dock current and cruise quite a bit. All batteries have specific bulk, absorption and float rates that Must be followed to gain maximum battery life. My AGMs must maintaine a (float voltage of betwee 13.6 and 13.8 volts. check your specks on the manufactures (specifications) Realize that a full 12 volt battery should read 12.8 when full. Anything over that is float and is not an accurate reading. It will take 24 hrs with no charging or load to determine what your real battery charge is.
Charge your batteries to what you think is full, and come back in 24 h.You may be surprised. When checking your battery’s always use a digital volt meter that reads out to the 100th not an analogue. 12.8 is full, 12.6 is 75%, 12.5 is 50%’ 12.25 is 25% and 12.0 is DOA. Battery that are left for extending time with less than a full charge will deterate rappadly.
I have learn all of this by making many mistakes in the past.

[Eder]

I'm glad I didn't know Lifeline AGM's needed all that charging before I left Mexico and spent 2 years without them ever plugged in and normally under 75% SOC.

[PaulCrawhorn]

2 years is a small fraction of their potential lifespan when well cared for. Abused, even the best lead bank, of any type, can reach EoL in just one season.

For apples to apples, you need to define your terms.

EoL is supposed to be at 80% SoH many owners push well past that and risk "unexpected failure modes"

[aisleorwindow]

Another quick update after many tests and lots of reading and a consultation with an electrician.

As it turns out, (and a few of you suggested this) the voltage reading I'm getting on my panel is just flat out wrong - to the order of .25 to .3 volts - pretty consistently in fact. So my starting reading at 12.5 was actually 12.8 and after 6 hours my 11.9 reading was actually 12.2 - not totally unreasonable given the autopilot was on the entire time, as well as fridge, freezer, etc. and with the high-level math I've done with the amp hour draw for everything, this checks out (will post my math later - still want to confirm actual Ah from a couple of the manufacturers).

So in the end it was something VERY simple, but I learned a TON.
Really appreciate everyone's help and encouragement.
Will still do a load test on the batteries, just to be sure, but everything seems to be working as it should.

Again, thanks to everyone that responded.

Side note: I have been referring to the below book, and have found it quite helpful.

Boatowners Mechanical and Electrical Manual

[PaulCrawhorn]

Great!

And yes Nigel is the OG, canonical