AGM or GEL Batteries? Which is best?

[SageOldmann]

Ampster as I said in my original post Lithium is out of the question due to cost right now. Maybe in a few years.....

[Ampster]

If you are concerned about safety have you considered Lithium? I just purchased 28 kWh of Lithium for $125 per kWh, delivered to my door in Northern California.

[Mike90250]

No, just 2 GC2 batteries would only give 12V 200ah If you need close to 400ah, you would have to get Floor Scrubber AGM batteries,

Big batteries = big price expect about $500 each, 6v 370ah sealed AGM

https://www.trojanbattery.com/product/motive-l16-agm/

[SageOldmann]

That was very helpful Mike 90250. GEL is definitely out now. Do you know any brands that are TRUE deep cycle AGM if I stick with 12 volt? I can't tell one from another. I Iike your 3 year game plan. Lithium has to come down in price by then. Would the golf cart batteries give me 12 volt, 400 AH if I wire in series with just 2 batteries? The Duracell AGM Golf Car Battery at Sams are out of stock. Any other suggestions for an AGM version?

[Mike90250]

Gel is useful for emergency exit lights, that only get used 1 every 4 years. They do not recharge quickly and would be a bad choice.

AGM is available in true deep cycle construction.

AGM, at end of life, or in an overcharge condition, begin to vent (they have emergency 3psi vents) the same gasses and fumes as flooded, so their container still needs explosion proof venting.

My suggestion, use the expensive, short lived AGM, and in 2 or 3 years, when they fail, there may be some realistic plug-play Lithium batteries to use instead.

Also, consider building the bank out of two series wired golf cart batteries (6v, 200ah) which solves the AGM "battery in parallel" problem.
(AGM is so low resistance, that the parallel interconnect wires will steer power to one battery which will end up doing 80% of the work and fail earlier than expected)

https://www.samsclub.com/p/duracell-agm-golf-car-battery-group-size-gc2agm/prod3870119

[SageOldmann]

Ok SunEagle you seem to agree with Sunking about the GEL batteries. I've seen other posts from you around this forum and you seem pretty sharp with a lot of experience so I'll 86 the the GEL idea and focus on the AGM. So do you think if I duplicate the 270ah battery bank with four 100 watt panels and a 1,000 watt pure sine wave inverter that I'll be able to run the refrigerator like that guy says he does, or should I upgrade everything a bit like the other guy?

[SunEagle]

Can't use flooded. Batteries are in a confined space with open flame water heater. No other option. But you have answered my question Linus. In your opinion, No GEL. The Guy with the AGM is actually more on target given the big load from the compressor start up based on what you said. Anyone else care to weigh in?

AGM ,while expensive compared to FLA type, are useful in enclosed areas. GEL are just about useless as a deep cell with high cycle rate.

The AGM are probably your best choice unless you want to play with one of the Li chemistry type but that brings on a whole new set of rules to keep them charged and happy. They may also be much more expensive then the AGM depending on what you get.

[SageOldmann]

Can't use flooded. Batteries are in a confined space with open flame water heater. No other option. But you have answered my question Linus. In your opinion, No GEL. The Guy with the AGM is actually more on target given the big load from the compressor start up based on what you said. Anyone else care to weigh in?

[Sunking]

Never ever use Gel, and AGM is a niche application. Best bet is always flooded.

AGM and FLA both come in deep cycle versions. However AGM cost is about 100% higher and only about half the cycle life of FLA batteries. AGM has its place in solar, but you really need to justify the cost. AGM has two advantages you are paying up for.

They have extremely low internal resistance which means they can handle larger C Loads of up to 15 minute discharge times which is real important if it is a rocket motor pumping the fuel in the expansion chamber, or attic cold where temps dip to -40 degrees.

So is this for a rocket motor or snow mobile? Or perhaps an aircraft where spills cannot be tolerated. If not your best bet is Flooded Lead Acid, half the cost up front and last twice as long. and longer than lithium. Pay your money, take your chances.At the end of battery life, AGM wil be about 400% higher than FLA.

Leave the gel cells for morons. Gel cells are for alarm panels and egress lighting using a Float Charger.

So with all that said use Gel battery Charlie Brown.

[SageOldmann]

I have been putting this off for a long time due to cost, but I was just about to buy some new AGM batteries when I saw a post somewhere that said AGM are not true deep cycle batteries that are not good for solar use. Is that true? I found that interesting as I followed a discussion involving two preppers. They both have set up their systems to be able to run a kitchen refrigerator in a power failure, or so they claim. They both use mppt controllers. They both say their compressors draws about 7 amps during start. One uses AGM and the other GEL batteries. The AGM guy claims his batteries provide better initial surge power when starting and are trouble free. His bank is 270ah with four 100 watt panels and a 1,000 watt inverter. The GEL guy claim his batteries are true deep cycle batteries with thicker plates that can provide double the cycles (1200 verse 500 for AGM) and are better for daily use. He has a 300ah bank to give extra power for the starting surge, and five 100 watt panels, don't remember what size inverter but I think it was 1500 watt. If I wanted to be able to run my refrigerator during a power failure, which happens several times per year for 36 to 48 hours, which of these two would be better for me to use, the AGM or the GEL system, and why? (I use a generator now when power goes out, which is getting very old). Is a 1000 watt inverter really enough to start a compressor? I have my doubts. I have limited funds but have enough to bring my current system up to either of these levels. (Lithium is out of the question due to cost.)