AGM as house Bank

[duncan_ellison]

Anyone using AGM as their primary house bank?

How was it?

Did you make any changes to your alternator set up?

Please no comments along the lines of "install Lithium instead"

[NewMoon]

In two boats over the last 20+ years, I've used AGMs for both house and start banks. They work well if not often left in a partial state of charge. One set lasted 11 years.

[Calif.Ted]

On a prior boat I had Trojan AGM's group 27 that lasted 10 years, and I have a pair of 4D AGM's now that I put in service 6 years ago. I've gotten about 6 years from Lead Acid batts and 10 or more from AGM's in my boats. They are in use year round and no freezing temperatures.

[michaeld]

Yes, we have four group 31 AGMs, totaling 400+ Ah. I installed a 130A Balmar alternator, ARS-5 regulator, and SG200 monitor. Solar consists of 350 Watts feeding an MPPT controller. I'm adding another 175 Watt panel. Shore charging is handled by a ProNautic 1250P. We burn about 100 Ah overnight (refrigeration, lights, chart plotter, AIS, etc.) Solar normally recharges the bank by early afternoon. Two cloudy days and the alternator has to be used. We rarely have shore power away from our home dock.

[jordanbigel]

Originally Posted by NewMoon

In two boats over the last 20+ years, I've used AGMs for both house and start banks. They work well if not often left in a partial state of charge. One set lasted 11 years.

This is the key - as many here will tell you over and over - "if not often left in a partial state of charge". So if you are a weekend boater who keeps their boat at the dock plugged in 5 out of 7 days, or a marina live aboard, AGMs will be great.

But if you are actively cruising you will kill them quickly if you do not frequently (*debate about how frequent can now ensue*) charge them to 100% (ie. until they reach float). I was not able to meet that requirement and mine died in 18months.

I replaced them with Gel (which are not as sensitive to being left in a partial state of charge) and got 7 years out of them. (now I use LifePo4).

[rslifkin]

Originally Posted by jordanbigel

This is the key - as many here will tell you over and over - "if not often left in a partial state of charge". So if you are a weekend boater who keeps their boat at the dock plugged in 5 out of 7 days, or a marina live aboard, AGMs will be great.

But if you are actively cruising you will kill them quickly if you do not frequently (*debate about how frequent can now ensue*) charge them to 100% (ie. until they reach float). I was not able to meet that requirement and mine died in 18months.

I replaced them with Gel (which are not as sensitive to being left in a partial state of charge) and got 7 years out of them. (now I use LifePo4).

That's a good point. AGMs aren't terribly tolerant of being charged less than fully on a regular basis. But given enough solar to get them full most days, they can work fine.

We've done fine with not abusing our AGMs. Solar gets them full daily unless it's too cloudy. One day of not getting topped off doesn't worry me, but if it's more than 1 day we'll either be underway (powerboat) and get some charging from the alternators to help the solar get things topped off or I'll run the generator for a bit to help out the solar.

[fxykty]

Our boat came with 6x 110Ah Victron Energy AGM batteries installed in 2014 by the previous owner and we finally removed them in 2020. In the three years we had the boat prior to 2020 they rarely made it to 100% as we did not have shore power at our berth - just solar, wind, a diesel generator, and very poor engine alternators with internal regulators.

So they were mostly at PSOC, down usually no further than 60% and generally below 95-97%. Occasionally we’d visit a marina with shore power or when we were hauled out and I assume they got to 100% then. Also one very windy passage.

When we removed then they tested at 105Ah each and we sold them for $2K. So, from our experience, quality AGMs can certainly handle PSOC and don’t degrade quickly. YMMV

[Simi 60]

Originally Posted by duncan_ellison

Anyone using AGM as their primary house bank?

How was it?

Did you make any changes to your alternator set up?

Had them, they served a purpose
Until they didn't
And technology changes

Please no comments along the lines of "install Lithium instead"

Install Lithium instead
For us it was a cheaper and vastly superior result.

Even if AGM were free I wouldn't go back.

[smac999]

Agms are great. But they do need to be fully charged often.

Flooded batteries are gross, I would never use them.

[Jamme]

Originally Posted by duncan_ellison

Anyone using AGM as their primary house bank?



How was it?



Did you make any changes to your alternator set up?



Please no comments along the lines of "install Lithium instead"

In my view, it all depends on intended use and recharging capabilities. I am a mostly weekend sailor, and because I have no solar or genset, my AGMs were done in a couple of seasons — the issue being that I was out for a couple of 2-week trips and AGMs did not appreciate the extended partial charge I gave them from my standard alternator.

So, back to old flood for me. As said, your experience may vary.

Fair winds.

[Senojev]

I have an 880 Ahr Lifeline AGM house bank made up of 8 6v batteries installed in 2010. The boat is used from April to October each year and rarely sees shore power. My daily usage averages 250 Ahr which represents about 1/3 of the current capacity. I have 1500 w of solar and regularly cycle from around 70% at daybreak to 100% by end of day with fairly significant usage during the day. Engine charging is not a significant contributor as we spend days at anchor at a time with a typical run of less than three hours to our next anchorage.

While my bank is slowly getting to end of life, I will continue using them hopefully for a few more years. At that time, lithium will be the cost effective replacement. Right now, a new set of Lifelines would be $3200 and I could easily get a quality 400 Ahr lithium setup for that. I have an alternator externally regulated and two chargers capable of lithium profiles so expenses beyond batteries should be minor. I will continue to keep my AGM batteries for my thrusters, davits and starter.

[GILow]

I had one try of AGMs. They were pretty cheap and nasty and were kaput in just two years.

I don't doubt good quality AGMs would have done better. Not sure how much better though.

But, if I understand things correctly, the main advantage of AGMs is their ability to handle higher charge and discharge rates, while the disadvantage is that they need to be kept at 100% very regularly.

Since lithium has the high current advantages of AGM without the PSOC problem I really wonder why anyone would go AGM over lithium these days. (And then there's weight too)

[Tupaia]

Originally Posted by GILow

I had one try of AGMs. They were pretty cheap and nasty and were kaput in just two years.

I don't doubt good quality AGMs would have done better. Not sure how much better though.

But, if I understand things correctly, the main advantage of AGMs is their ability to handle higher charge and discharge rates, while the disadvantage is that they need to be kept at 100% very regularly.

Since lithium has the high current advantages of AGM without the PSOC problem I really wonder why anyone would go AGM over lithium these days. (And then there's weight too)

Agreed but lithium are not without their problems. Cannot be left at 100% SOC for long periods an issue with solar if you leave the boat unexpectedly. Nothing is perfect.

[carstenb]

We have 660AH AGM housebank. They are 4 years old Victron. We liveaboard 24/7 and they generally are charged by our solar (710watts). Since we live aboard we use somewhere around 200AH per 24hours

So far so good. Ours charge to full every day there is some sun - if we have cloudy days or when we were in alaska, we run the engine

[CarlF]

Another person who got tired of the PSOC problems with AGM house batteries. Had three sets on two different boats die in two-three years.

As others say, if you are normally plugged into a dock they are great. Also great for start batteries that never go below 90% charge.

On the first boat I replaced with gels that were going strong when I sold the boat after seven years.

Now have Lithium and - as others say - wouldn’t take AGM for a house bank if they were free. If you absolutely refuse to do Lithium, do gel or high quality flooded like Trojan T-125’s. But lithiums are now the cheapest “per year” cruising boat battery.