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AGM or GEL batteries?

5K views 20 replies 10 participants last post by  eherlihy 
#1 ·
Hi all,

I know there are several other threads more or less related and that most of your wisdom on this topic is already in some of them, but I would like your advise on this specific choice:
AGM or Gel batteries for the house bank?

To put everything in context, I'm refitting an old 40 ft steel yacht, with the purpose to do some cruising in western europe. I have one gel battery for the house bank now (100 Ah) and want to add two more to reach 300 Ah total. I just ordered a good charger and now I want to be sure to have good batteries as well. Since I have to add two batteries anyway, I might as well buy all three of them new. Also because the one I have is over a year old which might not work well with new batteries connected to it.

Hope to hear from you!
 
#2 ·
Get AGM batteries. Gel have basically the worst features of any battery and the most vulnerable to overcharging...
 
#3 ·
#5 ·
AGMs look good when you check their specs out and listen to the marketing. If you search the web a bit you'll find a lot of cases of early AGM failures on cruising boats. Some from under charging -- they don't like it. But others seem like just premature failures. If you are using these for cruising, I'd at least check out some of these failures before I'd jump into AGMs. Gels seem to have a much better reputation in practice for long service life. Yes, they can be ruined by charging at too high voltage. That's what the regulator is for.

Paul L
 
#6 ·
Neither the AGM or Gel cell is bulletproof but AGM's generally stand up a bit better to abuse. If you get AGM's you must have a good 3 stage charger AND bring them to a 100% charge every couple of weeks at a minimum. they do NOT do well if you never get the last 15% or so of charge into them so you must plug into dockside or have some passive system that can really top them up. If this works for you AGM's are a GREAT choice for FULL TIME cruising where the economics of their higher initial price make sense due to increased cycling and lower fuel costs to recharge. The VonWenztel site that Larry and Sue cite above makes a pretty good case of this.
Flooded batteries make more economic sense if you are not full time cruising and don't require the additional benefits of AGM's (non maintenance etc.).
If you plan on extended cruising you may wish to consider the new Odyssey batteries we've been talking about recently here as they clearly have huge implications for the full time cruiser despite their expense.
http://www.sailnet.com/forums/gear-maintenance/40324-way-cool-new-battery-technology.html
 
#9 ·
Neither the AGM or Gel cell is bulletproof but AGM's generally stand up a bit better to abuse. If you get AGM's you must have a good 3 stage charger AND bring them to a 100% charge every couple of weeks at a minimum. they do NOT do well if you never get the last 15% or so of charge into them so you must plug into dockside or have some passive system that can really top them up. ....
This is the rub. Most full time cruisers cannot reasonably get a their batts back to 100% every couple of weeks. It is just too much time on a generator and solar generally won't do it. To compensate, you will probably have to equalize the AGMs once a month or so. This has its own risks. As in everything else on boat, it is all a trade-off. As far as getting what you pay for. I think you'll find that the early failure AGMs anecdotes are not limited to cheap batts.

Paul L
 
#7 ·
I have 4-6v Prevailer house and 1-12v generator gel cells that will be starting their 11th year. After installing them in 1997, I practically never look at them. At the end of last season I thought that they were starting to show signs of weakening. After winterizing in the fall, I charged them overnite on land. Today I was at the boat and checked them. 12.62v after sitting all winter. They have never been deeply discharged, I don't know if that has anything to do with their longevity.
Marc
 
#8 ·
I second pretty much everything Cam said. However, I will add that there are a LOT of positives about AGM's that make them better for sailors/cruisers than wets, including: Can be mounted on sides, no water needed, quicker recharge rates, etc.

Also, like wet cells, AGM's are not created equal. You get what you pay for. The comments about some AGM failures are true; I have heard some of those too. But I have also spoken with many full time cruisers that have had them trouble free and would never go back. I will never use wets again, I doubt Cam would, and well as many other people.

- CD
 
#10 ·
If your charging system is properly designed and sized, there shouldn't be too much of a problem getting AGM's up to 100% once every two weeks IMHO.
 
#11 ·
Paul...I was out for 6 years an spent most of my time on the hook. We had no difficulty getting a full charge into our batteries every couple of weeks and I disagree with the statement that "most" cruisers can't get a full charge in as there are multiple options for doing so. Doing it passively with solar IS problematic for most since panels tend to be undersized for the job at hand. It is much more likely with solar and wind...running the boat under power...plugging into a dock overnight...or running the generator for an extended time once every couple of weeks.
EQ'ing AGM's is not to be undertaken lightly and not without specific instructions from YOUR battery manufacturer as there is no single standard for this and damage is likely if not done carefully.
I agree with you that many AGM's of all price ranges have had unsatisfactory performance for cruisers over the last 10 years. Part of this is due to poor quality control in some places, part is due to inappropriate charging sources, part is due to a lack of understanding of how AGM's must be cared for and part is due to AGM's being used in non-cruising situations and being constantly charged to excess without cycling.
I would never go back to flooded or use gels for cruising having experienced AGM's and their benefits but they are only part of a well designed energy system and they must be taken care of properly to insure the user gets all their benefits.
The typical hits on AGM's vs. gels are:
1. Special charging settings and intolerance of ANY deviation...easy to damage gels.
2. Slower charge acceptance as a % of capacity. Extra cost to charge.
3. Less vibration resistance.
4. Fewer life cycles below 50%
Of course these ARE generalizations and individual brands and models may not compare in this manner...but the BEST AGM's compared to the BEST Gels seem to have these properties.

I would add another caveat that is simply my own opinion. The industry is moving away from gels and towards advanced AGM type batteries (Odyssey/Firefly). Replacement of gels down the road and in out of the way places may be more difficult due to this change.

Clearly, many people have been happy with gels on board for extended periods of time and see little reason to change their choices but if one is starting from scratch, I do thing that good AGM's are a somewhat better choice for full time cruising use in a well designed energy system.
 
#12 ·
Cam,
I'm in the market to replace my wet-cell batts with a large bank and setup for offshore. I have decided that given the location and use, I want a sealed battery. I have convinced myself at times that AGM is the way to go, based on the specs and marketing. Then I started talking with people who have used them and find a far higher number of failures than I would expect from just normal sailor BS. I work with one of the engineers at one of the better marine charger/monitor companies and hear his stories on AGM vs Gel. They always recommend wet-cell or Gel for cruisers.

You listed the following:
1. Special charging settings and intolerance of ANY deviation...easy to damage gels.
It is a setting on the regulator. That's all. If you have a failed regulator and don't catch it in time, you will fry any battery. Gels cannot handle high charging voltages. I don't see this any great deal, either way.
2. Slower charge acceptance as a % of capacity. Extra cost to charge.
If you have a larger alternator that can put out at high amps even when warm, AGMs will take their bulk charge much faster. The last 10% of the charge is still slow.
3. Less vibration resistance.
I don't think any of the AGM, GEL or Wet-cells have a great problem with vibration on a cruising sailboat. They all work fine in this regard.
4. Fewer life cycles below 50%
Gels are generally spec to have longer life with more discharges than AGM

Sailingdog
"If your charging system is properly designed and sized, there shouldn't be too much of a problem getting AGM's up to 100% once every two weeks IMHO."
I think this is much harder than you are making it out on a cruising boat. Getting a batt from 85% charge to 100% charge takes a long time. Are you going to run a generator for 4-hours -- do you even have a generator? Going from 50% charge to 85-90% charge can happen reasonably quickly. If you have the charging source, AGMs can take this very quickly. The next 10-15% are slow and inefficient.

It's all trade-offs. I'm not pushing Gels here. My jury is still out. Just wanted to point out that the marketing pitch on AGMs is a lot better than a lot of cruisers experiences.

Paul L
 
#15 ·
My Lifeline AGM's stay 100% charged with just my solar array. Now I DID put in a large solar array, but designed it with that in mind. I am, and have been, solely running off of solar since the early part of this last summer.

The truth is that I am not sure that there is a battery that will do well with long term short-charging. WHen we cruised before, we had wets. I was always putting water in those and hated it and hated carrying it. Now I understand you can minimize that with recomb caps, but I have no first hand experience with that. I do have first hand with Lifeline AGM's and a large solar array and have been very pleased. COuld it also be argued that if you can bulk/accept out your batteries faster, that leaves more available time for floating?

Are AGM's some percentage of hype? Certainly. They are in the business of making money and will tout all of their benefits. But the knowledge of being able to put my batts in and always count on them without having to screw around with maintenance (other than checking the lugs every blue moon) is worth something to me.

Again, I will NEVER go back to wets and am a big advocate of Lifelines. I do not have any connection with that comapny, but gladly reccomend their product. They have been very helpful in my installation and support of my product and have helped everyone I have sent their way. They know their stuff. I reccomend calling them directly (not a 3rd party) and discussing your concerns with them. Ask for Andrew. Tell him I sent you over:

Lifeline Batteries
626-969-6886.

Here is a picture of my Solar Bar (sorry, it is not the best picture... my good pics are on my other computer). It is sitting across the stern. You can just make out the panels. I have 4 4D Lifeline AGM's for a house bank. They are charged by 4-Kyocera 130's wired in series to an Outback MX60 MPPT Charge Controller. I have put back OVER 200AH/day which exceeds most cruisers total daily budget.

 
#13 ·
One more item that is interesting. Check the the warranty on new, expensive Lifeline AGMs.
For maximum battery life, a battery must be recharged to 100% capacity. Recharging 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.

I have talked to people who purchased new Lifelines that failed in a year and they do enforce this when dealing with cruising boats.

Paul L
 
#14 ·
Well...I'm not gonna argue about it further since we disagree based on our own experiences. Anyway...instead of doing gels again...why don't you become the Sailnet test monkey for the new Odysseys?? We need some real user reports instead of all the hype from Nigel Calder. (They are technically AGM's but hope can overlook that!):D
 
#17 ·
Cam,
You miss-read or I miss-wrote. I currently have wet-cells and am going to replace them. I am waffling between Gel and AGM as the replacement. I just wanted to not let the 'AGMs are all great msg' go out without some counter point. I don't think it is a clear cut choice for a cruiser.

CD,
I spent a about an hour with the Lifeline rep at the last Seattle boat show. He told me in a cruising situation you are just going to have to bite the bullet and equalize these once a month. At the same time I also talked with a cruiser who had an early failure on Lifeline AGMs that he could get no warranty support from LL at all. He was kind of bitter on them.

Paul L
 
#16 ·
CD—

Did you remove most of the solar panels so that they could see it was actually a boat you were photographing?

Normally, the entire deck is covered with flexible amorphous silicon solar panels he had custom designed to fit around the ports and deck hardware.
 
#19 ·
I'm going on my 2nd year with WM branded AGM's. I looked at Lifelines, as well as the Odyessy (it was just coming out then), but got the WM's for two reasons. Cost, and service. With Lifelines, you have to ship the battery back to the manufacturer, with WM, I can go into any store, where ever I happen to be.
 
#21 · (Edited)
Since I have to add two batteries anyway, I might as well buy all three of them new. Also because the one I have is over a year old which might not work well with new batteries connected to it.
If you are adding or replacing any battery, it is best to upgrade the entire bank at one time. That is; all the batteries on the same bank should be the same age.

RE: Nigel Calder on batteries;
His "net-net" reccomendation is that AGMs or Gell-Cells are better than wet cells for most sailors. Part of his rationale is that wet cells are almost never properly maintained. Other issues with wet-cells include: equalization, topping off, potential for spillage/leaks, high rate of self-discharge, expolsive potental. If you are really anal about maintaining wet-cells, they can last longer and be cheaper.

He seems to lean toward AGMs over Gell Cells because of their higher charge acceptance rate.

HTH!

Ed
 
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