Batteries... wet versus AGM

[Mary B]

Half my battery string is dead and the other half is close to it(6 years of fairly heavy use on golf cart batteries). But I am transitioning from trying to run appliances to heating water because it is the biggest electrical user in my house. Main fridge is a chest freezer on a temp controller. Chest freezers are both stuffed to the top with food so pretty dang efficient.

So I am leaning towards a smaller AGM bank just to run the pellet stove(during power outages)/radio gear(full time). Save wear and tear on my spine with having to do battery maintenance every month and with my back getting worse that is a major plus. Looking at battery life charts it seems the AGM would work fine in this application, they will be set to drop the load back to grid at 70% charge to prolong life.

I would prefer to go lithium but a 200 amp hour lithium pack is NOT in the budget...

[SparWeb]

Got my AGM batteries used, babied them since then, only abused once by the wrecking crew that hauled them out of a building before I came to their rescue... still going 10 years later.
It's pretty easy to forget to do even simple checks on them, not because I'm careless, but because they just don't ever change.  It gets pretty boring, seeing the same float voltage on all cells for so many years.  There's one "bad" cell that's always a hair below the rest, but always by the same amount; it never got lower.

With AGM's you get what you pay for.  If your candidates come with life charts, that's a good sign.  What do you have in mind?

[John Bouchard]

I assume your using these as a grid tie back up source?   If so I would think agm as wet cell battery require being 'exercised ' for good battery health.  Trojan does have usage data on their batteries web site.  I use their industrial batteries  fewer cells to water / maintain  and longer periods between watering.

[kitestrings]

I am transitioning from trying to run appliances to heating water because it is the biggest electrical user in my house.

Not sure I understand.  Are you transitioning to heating water with PV, or PV with batteries?  Do you have commercial power and just some loads served off-grid, or are you fully off-grid.  You're probably aware, but DC (compressor) frig/freezers are small but do the job with a fraction of the power of conventional units.

We've mainly had flooded lead acid, though I've used and installed some others (no li-ions).  Generally I still think of wet cells as being much more resilient.  We've had some go 15-years.  The ones we currently have (Trojan IND, 4V, single-string) are the heaviest, most industrial that we've ever owned, but haven't had them long enough to report on longevity.

[John Bouchard]

Kitestrings.  I've been using the Trojan industrial -17 now about 6 years going strong but I charge slightly higher voltage for my off grid solar application. Basically I charge them  like L16 batteries mostly during low solar/amp winter months.

[DamonHD]

Just to be unpopular here, I'm coming to the end of life (I think, ~7Y) of a decent set of off-grid gels (12V, 400Ah), and think I will replace with the same.  Though this time I'll try and treat 'em right...

I do have a separate 1kWh of Lithium, on grid.

Rgds

Damon

[Mary B]

Got my AGM batteries used, babied them since then, only abused once by the wrecking crew that hauled them out of a building before I came to their rescue... still going 10 years later.
It's pretty easy to forget to do even simple checks on them, not because I'm careless, but because they just don't ever change.  It gets pretty boring, seeing the same float voltage on all cells for so many years.  There's one "bad" cell that's always a hair below the rest, but always by the same amount; it never got lower.

With AGM's you get what you pay for.  If your candidates come with life charts, that's a good sign.  What do you have in mind?

Looking at these(not necessarily form this source but they are the lowest price so far) https://www.walmart.com/ip/12V-100Ah-AGM-Sealed-Lead-Acid-Battery-UB121000-Group-27/172904380 Universal Power Group...

[Mary B]

These were running only a few house loads, fridge/freezer and power for my ham station. No grid tie, fridge and freezer both have transfer switches that drop them off battery at 40% discharge.

My water heater is by far my biggest electrical load so I was going to float batteries for the ham radios and when they are charged switch the raw solar DC to a water heater preheat tank. With groundwater temps in the mid 40's this time of year it would be a huge power saver, and even mid summer water temps are still low to mid 50's.

I am on a budget so no Trojan or other high end batteries, not an option, I do not have that kind of cash and I want to get away from the stooping over a battery bank doing maintenance all the time(My spine is very very very bad... as in I was supposed to be wheelchair bound 6 years ago but I am to stubborn to give in!)

[Mary B]

I assume your using these as a grid tie back up source?   If so I would think agm as wet cell battery require being 'exercised ' for good battery health.  Trojan does have usage data on their batteries web site.  I use their industrial batteries  fewer cells to water / maintain  and longer periods between watering.

No grid tie, requirements are to strict in MN with everything having to be UL approved/CA solar approved garbage that is 3 times the price. Plus a ridiculous 600k liability insurance policy.

[John Bouchard]

Holy sh*tola !   Washington currently does not require any of that for off grid.  Stevens country assessor don't even tax or require inspection.  I can read the writing on the wall and better buy/ install all I can while the gettin  is still good!

BTW  I'm a humbled newb. Your all seemingly in some way experts in off grid renewable energy living.

[clockmanFRA]

Looking at these(not necessarily form this source but they are the lowest price so far) https://www.walmart.com/ip/12V-100Ah-AGM-Sealed-Lead-Acid-Battery-UB121000-Group-27/172904380 Universal Power Group...

I find its an issue if the batteries being sold are actually AGM, ie, are they really ABSORBENT GLASS MATT

I have had AGM batteries for over 10 years, using them continually with a 1300ah battery bank.  Most of them are Used and from Mobile phone transmitter masts where they ticked over giving a UPS to the transmitter/receiver. I would normally get them at their end of service life of about 4 years from new.

So for the last 10 years I have had many sizes and types of 12v AGMs but nothing under 100ah, ie about 28kg about 60lbs each.

As one or two of you may know that I have examined several different types of real AGM batteries and those that are not AGM.

By examine I mean that I have disassembled.  But please! please! do not do this your self unless you have chemical clean room, chemical fume extraction sealed chambers etc, and know how to deal with hazardous materials.

The interior of a true AGM 12v is lead based plates with absorbent matts in between the plates. the matts are damp with acid, there is NO liquid acid. There is a also a separate sealed expansion chamber normally covering the complete top of the AGM battery.

After time the cell, normally 6 cells per 12v battery, expands and buckles and the plates are buckled upwards and touch the main lead buz/buss bars that have the main battery terminals attached, normally about a 5 to 10mm clearance, and then that cell is dead.
 
I find that a dead cell with a 12v AGM will give a holding voltage of about 11v after a 12 hour rest, ie a holding voltage. 

I normally become suspicious of a 12v AGM when the holding voltage is below 13v. and then that particular AGM will require observation and less arduous duties, but with a bit of care you may get a few more years.

In Conclusion.

I have had well over 60 different size and types of AGM's and for my use AGM's are not really feasible. I put up with them as they were cost effective solution for battery storage. But they were a lot of work swapping them into matching strings etc.

However, like everything, things change and the Mobile masts have changed, and I can no longer get AGM's that have a known history life.

I have also tested and used SLA for the last 7 years and had good results, and 5 years ago moved to a SLA, sealed lead acid, 12v batteries that are Marine use, and phasing out my AGMs as they fail. I now have only one string of 110ah 12v AGM's operating as they should.

Middle men have got involved with Used AGMs so their used price is about $90 each for a 12v 110ah and no history.

My SLA Marine deep cycle 12v 110ah, New are about $110 each when I get 12.

 

[SparWeb]

Hi Mary,

I'm seeing the 45% discount price on those batteries today, which is really good (you should see what they charge for these in Canada).  Bottom line; it looks like a good boxing-day deal.  Time to jump!  These types all seem to come from the same line in the same factory in China, now, despite a thousand different labels you find on them.  Replacing a bad one if it happens to fail probably isn't a hassle.

The only risk to your back is hauling the old ba**ards out and the new ones in.  Work carefully!  (I know you always do)

[Mary B]

Friends 17 year old grandson is my lifter! I will not lift a battery anymore. Way to hard on my spine.

[Mary B]

Looking at these(not necessarily form this source but they are the lowest price so far) https://www.walmart.com/ip/12V-100Ah-AGM-Sealed-Lead-Acid-Battery-UB121000-Group-27/172904380 Universal Power Group...

I find its an issue if the batteries being sold are actually AGM, ie, are they really ABSORBENT GLASS MATT

I have had AGM batteries for over 10 years, using them continually with a 1300ah battery bank.  Most of them are Used and from Mobile phone transmitter masts where they ticked over giving a UPS to the transmitter/receiver. I would normally get them at their end of service life of about 4 years from new.

So for the last 10 years I have had many sizes and types of 12v AGMs but nothing under 100ah, ie about 28kg about 60lbs each.

As one or two of you may know that I have examined several different types of real AGM batteries and those that are not AGM.

By examine I mean that I have disassembled.  But please! please! do not do this your self unless you have chemical clean room, chemical fume extraction sealed chambers etc, and know how to deal with hazardous materials.

The interior of a true AGM 12v is lead based plates with absorbent matts in between the plates. the matts are damp with acid, there is NO liquid acid. There is a also a separate sealed expansion chamber normally covering the complete top of the AGM battery.

After time the cell, normally 6 cells per 12v battery, expands and buckles and the plates are buckled upwards and touch the main lead buz/buss bars that have the main battery terminals attached, normally about a 5 to 10mm clearance, and then that cell is dead.
 
I find that a dead cell with a 12v AGM will give a holding voltage of about 11v after a 12 hour rest, ie a holding voltage. 

I normally become suspicious of a 12v AGM when the holding voltage is below 13v. and then that particular AGM will require observation and less arduous duties, but with a bit of care you may get a few more years.

In Conclusion.

I have had well over 60 different size and types of AGM's and for my use AGM's are not really feasible. I put up with them as they were cost effective solution for battery storage. But they were a lot of work swapping them into matching strings etc.

However, like everything, things change and the Mobile masts have changed, and I can no longer get AGM's that have a known history life.

I have also tested and used SLA for the last 7 years and had good results, and 5 years ago moved to a SLA, sealed lead acid, 12v batteries that are Marine use, and phasing out my AGMs as they fail. I now have only one string of 110ah 12v AGM's operating as they should.

Middle men have got involved with Used AGMs so their used price is about $90 each for a 12v 110ah and no history.

My SLA Marine deep cycle 12v 110ah, New are about $110 each when I get 12.

For shipping if they are sold as AGM they better be AGM, if they are involved in an accident and spill acid onto something reactive the entire truck goes up in flames. Pretty regulated!

[kitestrings]

Sorry to hear of the spine issue.  Hopefully you have plenty of help.  Schlepping batteries around is always a challenge even with a sturdy frame.  Good luck.