Why are so many in Love with AGM's

[mitiempo]

Originally Posted by Dockhead

Even if that is true, those advantages you state are very important, even critical, for some people.


I use Trojan T105's in my present boat, but we could only use AGMs in the previous boat because the only space for batteries was not accessible in a way which allow you to water or maintain FLA's there. We had no choice.

With a watering system you could have used T105's in your previous boat as well.

https://www.trojanbattery.com/produc...tering-system/

There are others as well.

[The Sun King]

AGMs fail because they ARE (sort of) sealed and DO gas off. The gas is decomposed electrolyte and there is darn little in there to start. So you don't have electrolyte. The trick is to charge them without gassing and to restore the electrolyte when they do. I have commented on the care and feeding of AGMs before and have been shut down by people who see themselves as having more expertise than I have.


I live daily with something along the line of 9000 pounds of FLA and AGM batteries in my electric boats, electric utility vehicles and home solar, so I'd like to think I know a thing or two. Most of my AGM batteries cost new about $1200 each and there are 14 of them. They are over 6 years old and I'd like to think of them as not very old as they are heavy and inconvenient to move about, not to mention pricey.



I also have some older, 12v/106ah AGM batteries that were twice discarded as being dead and they are doing fine, now. Feel free to send me your "dead" AGM batteries.



My advice to battery users is this: If your batteries are lasting 10 years or more, DON'T CHANGE A THING. You are doing it right. If your batteries are only lasting a year or two, then expecting the next set to last longer is madness. CHANGE YOUR WAYS.


Find the information sheet on your batteries. There is almost always a pdf online. Find what the manufacturer says about voltage and current. DO THAT. Charging them too hard or too high makes them gas. Then examine your usage. Avoid going below 50% state of charge and don't leave them discharged. Leaving them discharged encourages sulphation. Do a desulphation charge or equalization charge every now and then, as needed. Some armchair experts say you don't do that with AGMs. It is in the data sheet of my batteries. Read the sheet closely. There is an emphasis on charging my 48v bank at 54v.4, but that is float and there is poor capacity at that rate. Closer reading and I find that I have to run up to a bit over 60v for a few hours in cold weather.



RTFM. Read The (Fine) Manual

[sailorboy1]

Originally Posted by Dockhead

Even if that is true, those advantages you state are very important, even critical, for some people.


I use Trojan T105's in my present boat, but we could only use AGMs in the previous boat because the only space for batteries was not accessible in a way which allow you to water or maintain FLA's there. We had no choice.

Which was 1 of the 2 i listed. Everything else is marketing hype

[Simi 60]

Originally Posted by Dockhead

Even if that is true, those advantages you state are very important, even critical, for some people.

Yep, I have enough shyte going on aboard without having to add watering the batteries to the list.

Now, where's those olives for the martinis. (-;

[sailinglegend]

Originally Posted by The Sun King

...I have commented on the care and feeding of AGMs before and have been shut down by people who see themselves as having more expertise than I have....

Let me join those who do clearly have more expertise than you have....A lot of what you say I'm afraid makes little sense!!!!

Originally Posted by The Sun King

AGMs fail because they ARE (sort of) sealed and DO gas off.

All batteries gas at the Absorption voltage but AGMs are Valve Regulated Lead Acid (VRLA) batteries and the 'valve' is set to about 6 PSI which holds the gas Hydrogen (H2) and Oxygen (O) in the cell and helps it to recombine back into water (H2O). AGMs fail, like all batteries, mainly by loosing their capacity through permanent sulfation caused by not recharing them to 100% regularly.

Originally Posted by The Sun King

The gas is decomposed electrolyte and there is darn little in there to start. So you don't have electrolyte. The trick is to charge them without gassing and to restore the electrolyte when they do.

You can't charge batteries without causing them to gas. The gas is a natural by-product of the charging and discharging process - not the decomposing of the electrolyte. Hydrogen, H2, forms at the negative plate and oxygen, O, forms at the positive plate. AGMs are also known as starved lead acid batteries because only 95% of the fibreglass matt is saturated with electrolyte, so the electrolyte will never be seen. You should never 'top up' an AGM with distilled water as it will cause huge and catastrophic venting of gasses.

[SimonFirth]

QUOTE=
I did consider LiFePo4 technology, but did not want to change existing charging system, and I'm a pretty old and conservative sailor ...[/QUOTE]

I changed from AGMs to Lithiums with no difficulties. Pulled out the AGMs, dropped in the lithium’s. The Lithiums’ own battery management systems handled the different charging profiles. Very happy with Lithium’s.

[capn_billl]

I don't know if this has been mentioned in this thread yet, but in my opinion having a quality Battery management system will go much further to extending battery life, and reducing battery troubles than focusing on a particular brand, or type of battery.

I used to use FLA's, and used to cook them regularly with an old big iron charger. Even trying to top them off , and turn off charger when not in use tended to kill them quickly.

Replacing the old charger with a smart charger helped a lot, and greatly reduced water usage.

Later I started replacing with AGM's as the price difference came within reason, and now only use AGM's. (after selecting the correct battery type on the smart charger of course).

I haven't had any issues since, and will always buy AGM's from now on,...Until I can afford a good lithium pack, about the time they are a mature technology.

[ben2go]

Originally Posted by flyingfin

I have had nothing but problems with AGM batteries, from early failure after 18 months in lawn equipment, failure after 24 months in road vehicles (seems the batteries have insider knowledge of the warranty expiration date), to full blown melt-down and fire at cell tower standy power cabinets. Never had theses issues with lead-acid batteries. Is it because the AGM's are sealed and cannot gas-off?

I've run AGM in a lot of stuff including aircraft since the early 2000's. Never had an issue as long as the batteries and charging systems were kept in good order.

[ron17571]

I like LIFEPO batteries. I see no issues besides being careful not to charge them in freezing conditions. So much better than lead acid or AGM batteries.

[hzcruiser]

Originally Posted by mitiempo

[...]
The cycle life below is for Victron's Super Cycle Agm batteries.


Cycle life
≥ 300 cycles @ 100% DoD (discharge to 10,8V with I = 0,2C₂₀, followed by approximately two hours rest in discharged condition,
and then a recharge with I = 0,2C₂₀)
≥ 700 cycles @ 60% DoD (discharge during three hours with I = 0,2C₂₀, immediately followed by recharge at I = 0,2C₂₀)
≥ 1000 cycles @ 40% DoD (discharge during two hours with I = 0,2C₂₀, immediately followed by recharge at I = 0,2C₂₀)

I'm aware of that "school". Yet, it comes down to about the same numbers, give or take: if you draw double the Ah out of the battery, you get about half the numbers of cycles. Although I'm aware that the deeper you discharge, the fewer overall Ah (or correctly: Watt-hours or Wh, as it's energy) you get out of a battery.

The practical problem here is, the discharge is not the same every day, you can limit it to 50% DOD but on sunny days it might only get down to 20% DOD. The next day you might need the 50% DOD to keep the beer cold or the fish frozen.
Hence a good monitoring system counts the Ah in and out of each individual batt over its lifetime. Then you can compare them more accurately to see which performs better.

You realize that is referring to an Iphone or Ipad battery.

Yes, I was quoting Apple there as just one quote, and they're using Lithium Polymer. The chemistry should not be relevant for defining what a cycle is. Otherwise it's even more difficult to compare batts of different chemistries or manufacturers.
A bit like using HP or kW to compare engine "power", no matter what type of ICE it is.

[hzcruiser]

Originally Posted by manitu

The problem with storing LiFePo cells, is that voltage is not a good indicator of SOC. [...]
.manitu

That's correct, it's not a "good" indicator, but it is one nevertheless. IOW, the higher the resting voltage, the more "juice" is still left in that batt. Only with LFPs, that voltage difference is much smaller than with lead-based ones.

[Kokanee]

I switched to AGM about 6 years ago because I wanted to move the battery banks from beside the engine to an enclosed storage area under the sole. The first set of cheap no-name AGM's lasted 5 years and then died due to increased load with 2nd fridge/freezer added and nightly drawdown exceeded 50%. I then bought 5 x 120 Ah better quality (Full River) AGM's. Now I draw down 10% at night and solar tops up by midday.

But be careful - there are some crap AGM's being sold online. Before I purchased the Full Rivers I ordered 4 x 220Ah "Extreme" brand batteries. When they arrived they each weighed 12 kg less than what was advertised. When tilting them, I could hear liquid sloshing around. They were not obviously not 220Ah or even AGM's. I finally got a refund after many emails, phone calls, and battery review posts. It seems they only took notice of the review posts.

I even heard of one customer of the same company cutting open the battery case and finding floor tiles packed in the bottom to make up the weight. Be careful buying online. It's crap like this that gives AGM's a bad name.

[Lost Horizons]

Unbelievable! Thank you for sharing that experience.

[fxykty]

Originally Posted by Simi 60

No shipping to Australia, tis why I asked

Here that (owl) $4000 US battery bank would probably cost closer to the moon by the time shipping was added in



As a comparison, my 8x 220ah @ 12v AGM cost $2300usd delivered to the boat cockpit.

700Ah 12V Winston LFP cells USD2800 + USD150 shipped to Auckland. Total cost was just over NZD5k. Another NZD1.5K for BMS and relays.

This is roughly equivalent to a 1200Ah lead acid bank, so the cost isn’t too bad. Plus more efficient charging, higher load draws, and no voltage sag.

Our Victron Energy AGMs are 8 years old and have spent a lot of time at PSOC - no shore power connection. They voltage sag a lot more now but otherwise should be just fine for another couple of years.

[Iains boatyard]

Quote “.Until I can afford a good lithium pack, about the time they are a mature technology.”
Unbelievable comment, sorry but the technology is matured Do some research.
I use Lithiums have done for 3 boats in the last 10 years when comments were the boat will blow up catch fire etc ��*♂️ Please if you have not researched and used Lithium do not make unfounded comments.