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s/v Passport, Bianca 111
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Discussion Starter · #1 · (Edited)
Sorry as I know this question has been exhausted but I feel its relative to each boat and user.

My wife and I are the proud new owners of a new to us 36' boat. It currently has 24D AGM house batteries (and a DP24 start battery) from 2006 that are dead. We closed at the end of October and despite having a pretty good notion of what the outcome would be, I tried to put a charge on them and it wouldn't take.

So my question is to replace with either new 4D AGM or Flooded or downsize to AGM or Flooded. Cost is an issue (of course) but I want to do whats right in the end.

Right now there are 400AHs and although that would be nice I don't think its necessary. Aside from the usual lighting, there is radar, refrigerator,radio, autopilot, old GPS, stereo, and shower/head pressure water. No windlass, no electric bilge, no microwave, or any other high amp components but it does have a Freedom 2500 charger/inverter with the Heart Interface. Of course I do plan to make a couple small additions (pressure water, electric bilge) but these are maybes and probably not too soon.

We sail on Lake Michigan mostly. I assuming 75% day sails, and the remainder a couple overnights and hopefully a once a year vacation for a week or so but that could still involve a night or two in a slip. The only charging system on the boat at this time is the engine and I don't plan to change that in the near future.

What I like about AGMs is that they are sealed and, if properly maintained, last longer. What worries me is that it seems the charging profile requires a long absorbtion period to get from 85%ish to 100% SOC. I understand it is very important to get AGMs back to 100% SOC or you will negate a lot of their benefits. It I understand correctly, with no other charging source, this means an inordinate amount of engine run time. Is my assessment correct?

Then what about Flooded? Clearly they have been used for decades and are still in use by probably the majority of boats. Would switching be penny wise and pound foolish?

Last is size. Whether AGM of Flooded, how about Group 31s for about 200AHs? 2 for the House and I will likely just replace the DP24 for the Start battery. The battery bay/mount is custom made for 4Ds but I think I can make an easy mod to secure Group 31s (we'll see in the Spring).

One other wrench....We have an Alpha Spectra Autohelm which I'm excited about. In researching it, I saw they added a comment on their website just this past May that says charging outputs that exceed 14.2V could damage or cause erratic behavior with the Autohelm. Is is correct that AGMs are best served by a higher initial charging voltage? If so, this adds to case against them unless there is a way to protect the Autohelm.

Thanks and I look forward to the input.
 

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Learning the HARD way...
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Your question falls into two parts; what is the best bang for the buck battery, and how big of a bank do you need for your anticipated loads.

The answer to the first question is easy. Right now the best bang for the buck is in FLA batteries. There are, however, other reasons why AGMs may be more appropriate (space restrictions, need for maintenance of FLA, etc)

Because you state that your entire bank is dead, you are in the position of replacing the entire bank. BTW - You should always replace an entire bank in one shot.

The second part of the question is how big... You need to figure out what your need between 100% recharges will be (most people figure 1 or two days), and at least double that to calculate capacity needed (so that you don't discharge more than 50%). From an electrical standpoint, bigger banks are always better, as it means that you are discharging less, but the budget and space may not allow.

Hint when figuring out your needs; from what you describe above, your biggest draws are your autopilot and radar. Figure out how much they draw, and the number of hours per charge cycle that you'll use them on battery power, add in the other loads multiplied by the hours that they are used per typical cycle, and the sum is your energy budget.
 

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Learning the HARD way...
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Then let me point you to this thread for more discussion.
 

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You're doing well to consider all the factors. It's not just the batteries, it's how their features work with your electrical system and the way you use the boat.

My considerations were a little different. My boat came with 4D AGM and I received very little advantage from them at first. The only feature that really helped me was that AGM has a very low self-discharge rate in the winter. That means I didn't need to worry about trickle charger or removing the batteries for winter storage (Wisconsin & Lake Michigan). Since then I've added things that make better use of the AGM feature of high discharge and charge rates. I upgraded to a 140 Amp alternator so I can recover from 18 hours of sailing in about 30-40 minutes of motor time. Charge rate is 100+ Amps and flooded batteries would not live through that. The other thing was the addition of a bow thruster. With flooded batteries I would have wanted a battery dedicated to serve the 170 Amp discharge of the bow thruster. With the AGM banks I see an insignificant voltage drop even when the bow thruster is running.

Another suggestion I'd have is that, if Maine Sailor chimes in here, you should do whatever he suggests. His postings, his web site, and some paid consulting from him have been my primary guidance as I've improved my electrical system.

GJ
 

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s/v Passport, Bianca 111
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49 Posts
Discussion Starter · #6 ·
Thank you, great feedback.

The winter discharge rate is a good point.

Regarding charge rates, we have a 125Amp Alternator. I believe I can set the charge rate with the Heart Interface but not sure but I'll definitely set up for whichever battery we go with. As I mentioned, I may have a limit to what I can put out because of the autopilot unless I can isolate it somehow.

I have read and re-read everything on MainSails site and agree. I'm hoping he will chime in. I drafted a letter to him but then realized he probably gets flooded with this stuff.
 

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I am not sure why you have to write to Maine Sail after you've read all his stuff. :) He's on vacation in the BVIs now anyway. :)

4Ds are not true deep cycle. They are back breakers, literally.

AGMs are not always the right choice for most boaters. They do NOT always last longer. Maine Sail wrote these:

AGM Battery Issues (from Maine Sail)
AGM Batteries - Making The Choice - SailboatOwners.com

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

eh is right - you need to do an energy budget.

With a fridge you will need the 400 ah. A fridge uses 60 ah per day. If you ever want to anchor out for a night, or if your dock power goes out when you're on the boat, you'll be pound wise and penny foolish for not putting 400 ah in your house bank.

The All-Important Energy Budget:

Energy Budget

Record of Daily Energy Use of 100 ah per day:

"Breaking In" New Wet Cell Batteries

In our experience, a mid 30s size boat like yours would do well to have around 400 ah in a house bank. By far the best bank for the buck is flooded deep cycle, even better are golf cart batteries.

With a Freedom 25 (we have a F15), and any plan to use the inverter, the bigger house bank is very good, and even is considered necessary for large, albeit short duration, power use with the inverter.

Charging with the alternator has nothing to do with the Freedom. You didn't explain what you mean by "Heart interface." Is it a Link 2000R? If so, it's a very good battery monitor as well as an alternator regulator. If it's just a remote for the Freedom, it won't deal with the alternator at all.

FYI, I've collected a lot of what Maine Sail has written, beyond what's on his website (which is "how to" material wonderfully presented), but doesn't get into some of the details he's presented over the years on electrical system design.

Electrical Systems 101 Electrical Systems 101

Winter discharge advantages for AGMs also don't factor it: fully charge a wet cell and it'll last all winter, 'cuz the lower the temperature the lower the self discharge.

Good luck.
 

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Learning the HARD way...
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Thanks Stu! I didn't notice the 'fridge.
Aside from the usual lighting, there is radar, refrigerator,radio, autopilot, old GPS, stereo, and shower/head pressure water.
Upgrading from incandescent to LED will cut the lighting requirement by 85%.

However the fridge will EASILY draw 6 amps when running.
The autopilot (if you plan to SAIL) 5 amps.
The radar 5 amps.
GPS about 1 amp.
Stereo about 1 amp.
Water pressure about 4 amps.

Estimate how long each is RUNNING between charges (you're not showering for the entire time, are you?) and multiply by the number of amps.

If you don't know how many amps something draws, the formula is watts/volts=amps.
 

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s/v Passport, Bianca 111
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Discussion Starter · #9 ·
Your right...that is all great stuff.

I've been digging into all this stuff quite a bit. I'm very handy with about every mechanical system on the boat and descent at individual electrical components but have a lot to learn about everything electrical as a system.
 

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You've probably educated yourself on this point already, but just in case. You battery choice needs to be compatible with your charging system. Just because you found AGMs doesn't mean it is. The PO may have switched without making the right charging alternations. A very common way to kill AGMs, as I understand it.

That said, I do prefer batts with low discharge and maintenance free. Flooded are clearly a better value, but I leave mine aboard all winter. I only want to have to top up the charge every couple of months max.
 

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My choice was simply on which batteries would take the most abuse. I got six years out of my first bank of eight golf cart batteries. They would still keep me sailing continuously but voltage was down to 12.4 cold fully charged so I decided not to push it any further. Ive been topping the batteries off with an epsom salt/distilled water solution and I really believe it adds to the batteries life.

Ive been getting mine at sams club. The six volt golf cart batteries cost me around 500 for eight of them.

I was sold after taking a starting battery that was basically dead, it would crank for maybe three seconds and give up, doing an epsom salt restoration and it passed a load test afterward. Its been in full time service for a year now and still passes a load test.

My batteries get a lot of use. I run a canvas business aboard and there many days when Im running lights, computer and speakers, 400 watt sewing machine and fridge for days on end. Often I run them down to 12.1 before a jobs done and the solar and windgen have a chance to catch up. Living as i do I dont know how long agms would last, given the abuse I would put them through.
 

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Bill SV Rangatira
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My choice was simply on which batteries would take the most abuse. I got six years out of my first bank of eight golf cart batteries. They would still keep me sailing continuously but voltage was down to 12.4 cold fully charged so I decided not to push it any further. Ive been topping the batteries off with an epsom salt/distilled water solution and I really believe it adds to the batteries life.

Ive been getting mine at sams club. The six volt golf cart batteries cost me around 500 for eight of them.

I was sold after taking a starting battery that was basically dead, it would crank for maybe three seconds and give up, doing an epsom salt restoration and it passed a load test afterward. Its been in full time service for a year now and still passes a load test.

My batteries get a lot of use. I run a canvas business aboard and there many days when Im running lights, computer and speakers, 400 watt sewing machine and fridge for days on end. Often I run them down to 12.1 before a jobs done and the solar and windgen have a chance to catch up. Living as i do I dont know how long agms would last, given the abuse I would put them through.
for best bang for tyhe buck the wet cell la cells are still best and golf carts even better
i buy used golf cart from local golf couse tested to 80% and find they are good for several years
$30 ea for 6v 235 aH 6v is good budget
 

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......I got six years out of my first bank of eight golf cart batteries. ........ Ive been topping the batteries off with an epsom salt/distilled water solution and I really believe it adds to the batteries life.
Epsom salt treatment is a method to desulfate the plates. Golf cart maintenance crews do it to get a bit more life out of them.

I think it's better to practice battery care that limits sulfation in the first place. It's most common cause is over draining the battery or reuse without full recharge, which happens too often on golf carts.

Getting six years out of a properly maintained and charged house battery is fairly average, without epsom treatment.
 

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Find it unusual major benefit of agms not mentioned. Went from four wet cells=800Ah to four lifelines of exactly same dimensions = 1020Ah.
Means even when it's cloudy and there is no wind I can wait it out for days. I hate gensets. Mine is particularly noisy and I figure the sun will shine on my backdoor some day.
 

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I've had good luck with golf cart batteries of 1200 Ahrs going on 13 years now. However, there is one weak cell so it might be time to think about replacing the bank. I say bank because I treat it as one bank (there's a separate AMG starting bat).
I keep the batteries fully charged, never go below 50%, hydrated, and equalize at the end of the season. Guess what type I'll buy?

Ronbo
 

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Another vote here for wet cell golf cart batteries. It is well established that you get the most 'bang for your buck' in terms of capacity and longevity.

Yes you need to top up in my case once a month does the job except in high summer when I look at them every 2 weeks.

They will deal with abuse MUCH better than AGMs.
 

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Find it unusual major benefit of agms not mentioned. Went from four wet cells=800Ah to four lifelines of exactly same dimensions = 1020Ah.
Means even when it's cloudy and there is no wind I can wait it out for days. I hate gensets. Mine is particularly noisy and I figure the sun will shine on my backdoor some day.
I'm not sure which batteries you have but Lifeline 6 volt (GPL-4CT) are the same size as a Trojan T-105 and have 220 AH - the same as the Trojan. The Fla golf carts I sell are 242 AH for the same dimensions.

Lifeline has a higher capacity golf cart battery (GPL-6CT) but it is larger.
 

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s/v Passport, Bianca 111
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Discussion Starter · #19 ·
Everyone, thanks for all the input!

So wet cells it is! I'm on board with golf cart but before I go down that path I have to make sure I can fit them but am a little reluctant to reconfigure the battery compartment and as I'm not sure they would fit.

Honestly I think I may go with 12v just for the ease of installation at this point.

Does 200 AHs seem like enough with our predicted usage? Again, there are 2 4Ds in there now with custom mounts and a separate area for a DP24 start. From all that I've read it seems like 3 of all the same kind is the best way (1 bank of 1 and 1 bank of 2) maybe all Group31. Or should I go with 4D wet cells for 2 and a Group 27 or 31 for the "Backup/start"?

I have not had good luck coming up with anything searching for 4D wet cells.

Last, can you point me to some makes/models and/or places to buy? We live near Milwaukee, WI.

Thanks
 

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4D and 8D batteries are not true deep cycle, they are truck starting batteries. If they are labeled deep cycle it is only in comparison to the same size starting battery. There are very few exceptions - Lifeline Agm for one. The golf cart batteries are true deep cycle and the same size as a group 24 but taller. They will outlast any 12 volt battery by a large margin.
 
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