UPG 250 amp hour agm batteries

mena661 wrote:
There's a caveat to this though. FLAs work perfectly for high wattage draws. There's tons of people here that do this all the time. The advantage with AGM's in this situation is if you only have room for TWO batteries but want to repeatedly use the MW or other high draw device with a partially discharged battery (say less than 60% SOC). 4 6V's (FLA's) work just fine for high draws IF you have the room for them. Also, 12V FLA's only have a little less sag than AGM's. It's the 6V's that have the biggest sag but you can simply add more then there's no problem.

Well said!

Just realize that when you use 4 x GCs or better, you are lowering the Amp draw per battery, and therefore moving towards another low Amp draw where I agree that deep cycle FLA will run longer.

In the two battery case, the higher draw capability of the AGM shows up in longer run times.

E.g., In a capacity test, I used a 900W elec kettle to boil a a qt. of water in 7 min with a single Deka 79AH 53lb AGM. That represents a ~100% C20 draw, or 78A. The battery was 4+yrs old. In 6V GC terms you would need a 220A draw for 7min to match that.

Compared to a pair of GCs, a pair of equal weight 100AH AGM 12Vs or 6Vs is a reasonable choice and would give a more dynamic usage.

Almot;

In my recent research re 6V GCs, I learned that 30A/battery is normal for golf carts, therefore wouldn't that be exactly how those batteries are designed? Why wouldn't they last longer?

westend:

I guess I misunderstood your meaning for dynamic. I viewed it as the ability for a bank to do a days camping in the manner the RVer desires.

If you meant life cycles, a person may find no valuable difference between battery types on an 80% drawdown life cycle(discharge-recharge) basis.

Suppose we did a study and found that AGM cost $1/month more. Is that a valuable difference? If one type does 1000 cycles and the other does 500 cycles is that valuable? 500 weekends is 10 years!

HTH;
John

full_mosey wrote:

westend wrote:

...
There is little information to prove that AGM batteries will last any longer than FLA batteries in a very dynamic situation like an RV, where current draws are high relative to the capacities involved. Most of the anecdotal information I've read points to the FLA, larger plate batteries, like GC2 or larger deep cycle batteries garnering the longevity crown.
...

To be fair, running a fridge is not exactly a dynamic situation re comparing AGM to FLA. It is simply another low Amp draw that accumulates AHs over a long period. This is exactly the usage that gives a deep cycle FLA a decided advantage.

AGM does have the advantage whenever dynamic includes high wattage inverter draws. That is, draws that cause the deep cycle FLAs to sag and precludes desired use of the bank by the RVer.

Each RVer needs to choose the battery type that fits their style.

HTH;
John

Agreed about the style. I was using dynamic in the context of the charging/depletion schedule and not in overall amount of draw. If a user had AGM batteries and enough so that the depletion would be less than 80% SOC, the longevity title might go to the AGM's. From my limited experience with AGM, I'm seeing that they are more similar to FLA in use and charging than I first believed.

FWIW, my little dorm fridge operates at almost exactly 80w.

full_mosey wrote:

To be fair, running a fridge is not exactly a dynamic situation re comparing AGM to FLA. It is simply another low Amp draw that accumulates AHs over a long period. This is exactly the usage that gives a deep cycle FLA a decided advantage.

I'm wary of those 120V big volume fridges. They are not like 12V Danfoss compressors with 4-5 A draw. The OP mentioned 1A @120V (as I recall somewhere in this endless thread), 3A at startup. This is 10A and 30A, respectively, from 12V battery. 10A can still be called a low-amp draw, though in combination with something else like MW or heater it can make a difference. 30A I would not call a low-amp for sure.

full_mosey wrote:

AGM does have the advantage whenever dynamic includes high wattage inverter draws. That is, draws that cause the deep cycle FLAs to sag and precludes desired use of the bank by the RVer.

Each RVer needs to choose the battery type that fits their style.

There's a caveat to this though. FLAs work perfectly for high wattage draws. There's tons of people here that do this all the time. The advantage with AGM's in this situation is if you only have room for TWO batteries but want to repeatedly use the MW or other high draw device with a partially discharged battery (say less than 60% SOC). 4 6V's (FLA's) work just fine for high draws IF you have the room for them. Also, 12V FLA's only have a little less sag than AGM's. It's the 6V's that have the biggest sag but you can simply add more then there's no problem.

westend wrote:

...
There is little information to prove that AGM batteries will last any longer than FLA batteries in a very dynamic situation like an RV, where current draws are high relative to the capacities involved. Most of the anecdotal information I've read points to the FLA, larger plate batteries, like GC2 or larger deep cycle batteries garnering the longevity crown.
...

To be fair, running a fridge is not exactly a dynamic situation re comparing AGM to FLA. It is simply another low Amp draw that accumulates AHs over a long period. This is exactly the usage that gives a deep cycle FLA a decided advantage.

AGM does have the advantage whenever dynamic includes high wattage inverter draws. That is, draws that cause the deep cycle FLAs to sag and precludes desired use of the bank by the RVer.

Each RVer needs to choose the battery type that fits their style.

HTH;
John

I think first time I heard of 12V units here - in Truck Campers forum. Today, practical info on larger 12V units, like 5-7 cu.ft, will be either in camper van posts - US, Canada, Oz - or in yachting forums. These groups are mobile, camping pretty much anywhere. Trailer people, if they ever install electric fridge, tend to choose cheaper 120V because don't do much drycamping.

Almot wrote:

crosscheck wrote:
... the reason that the marine fridges cost more/cuft than residential fridges was that they are more efficient, do not require an invertor,have better compressors which in the end will save you money.

Manufacturers don't care how much money you save. Marine fridges... Why are they "marine", btw, and not "truck fridge" or "camper fridge"? On Australia forums you will find 12V units of all kinds, used in campers and vans, thousands miles from any substantial body of water... "Marine fridges", or, rather, "12V compressor fridges" are more expensive because it's a kind of a custom product. Something that you outfit your boat or Rv with. A lot of customers are boaters, and this partly explains why they are so expensive. Because boating items are always expensive, for no reason. Seriously though, they are sold in fewer numbers than residential 120V units, it's a shallow market, so you can't expect low prices. It's unfortunate for "solar" campers that 12V compressors are preferable to 120V.

I called them marine fridges because that is what they called them on the yachting forum. That would be funny if they said they were installing an RV fridge in their catermaran now would,t it?

I agree with the fact that they are also more expensive because of lower unit production.

Dave

crosscheck wrote:
... the reason that the marine fridges cost more/cuft than residential fridges was that they are more efficient, do not require an invertor,have better compressors which in the end will save you money.

Manufacturers don't care how much money you save. Marine fridges... Why are they "marine", btw, and not "truck fridge" or "camper fridge"? On Australia forums you will find 12V units of all kinds, used in campers and vans, thousands miles from any substantial body of water... "Marine fridges", or, rather, "12V compressor fridges" are more expensive because it's a kind of a custom product. Something that you outfit your boat or Rv with. A lot of customers are boaters, and this partly explains why they are so expensive. Because boating items are always expensive, for no reason. Seriously though, they are sold in fewer numbers than residential 120V units, it's a shallow market, so you can't expect low prices. It's unfortunate for "solar" campers that 12V compressors are preferable to 120V.

crosscheck wrote:
In reality, yachts are just RV's on water

Yes. Didn't want to say it and hurt the feelings of either yachties or Rv-ers or both. This is why 12V fridges are popular on water. (120V compressor fridges, obviously, are not). RVs are catching up - slowly, because they are spoiled with proximity to of all kinds of fuel, and many won't even camp where there are no hookups.

The OP fridge is 120V compressor, not 12V - from what I could gather from his posts. A different creature, usually larger volume and needs an inverter (= more losses). With 120V compressor fridge of really "residential" size (10+ cu.ft) you have to have hookups or run a generator daily (and have enough batteries to last between those runs). Can it work with solar? It depends... This all boils down to size. What size of 120V fridge, what size of solar, what "size" of average full sun time.

Normally, 120V residential unit is not a good idea for long-term offgrid, unless it is small like an under-counter dorm fridge and you have plenty of sun (and yet not too hot), and keep your generator ready. And even then, 12V unit of the same volume is better than 120V compressor. In the example above, 1000 WH daily draw of modern and very efficient residential fridges is A LOT. This translates into 100 AH from the battery. It means at least 130 AH, possibly 150 AH, to cover all your needs including the fridge. Will you collect 150 AH from 200W solar panel? 300W? 500W maybe?

It seems the OP is at least approaching the battery capacity resolution with an open mind, hopefully able to disregard some of the less than accurate information.

There is little information to prove that AGM batteries will last any longer than FLA batteries in a very dynamic situation like an RV, where current draws are high relative to the capacities involved. Most of the anecdotal information I've read points to the FLA, larger plate batteries, like GC2 or larger deep cycle batteries garnering the longevity crown.
Most AGM batteries are not able to be installed with vents down, check the product installation specifications.
I've found that my AGM bank tolerates charging close to FLA charging, the principle limiting factor being high voltage settings for bulk phase and limiting any equalization phase to only occasional use. Not all AGM batteries are built the same so product-specific charge profiles are the best for individual brands.

Some of the newer residential refrigerators are getting very efficient with daily draws often below 1KWH. This brings them into the range of medium sized RV battery banks and there are a lot of attributes that make them superior to absorption fridges.

I had a thread up in this section of the Forum asking much of these same questions regarding running a 120v fridge with only small solar capacity and a medium sized battery capacity (<400 AH). I was told it wouldn't work by some and I should return the refrigerator. I am now running the small dorm fridge through a 1000w inverter using 320 AH of batteries and 230 w of solar. Yes, there will be times when harvest does not keep up with use but my findings, so far, are much the same same as Crosscheck, it can be done and is not as difficult as some surmise. If you have a generator to afford backup for cloudy/rainy weeks, it can work well.