Why are so many in Love with AGM's

[Simi 60]

Originally Posted by Westcliffe01

No-one can help you with shipping and I dont know your sources. So here goes
https://bigbattery.com/products/48v-plbr/
48V PLBR - NMC - 186Ah - 9.6kWh $3700

https://bigbattery.com/products/48v-hawk-kit-of-2/
Kit 48V HAWK - LifePO4 - 170Ah - 8.8kWh $3400

https://bigbattery.com/products/12v-...70ah-2-176kwh/
12V OWL - LifePO4 -170Ah - 2.176kWh $979 each (discount on multiples) 4x gets to 8.5kWh

https://hsrmotors.com/products/battery_modules
Tesla battery modules
22V Nominal, 5.2kWh
27x12x3" in size
58lb per module
cost each $1390 + shipping



Usable capacity with any of those batteries would be far superior to an lead acid system since you can go much deeper than 50% discharge if you need.

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.

[foufou]

My AGM's are 15 years old. they do not get hard use. but no maintenance, no acid fumes, are all worth the slight extra cost. They are finally showing signs of being tired and I will be replacing them soon.

[Djarraluda]

Without entering the "high is better" debate, I will point out that AGM, being a type of Flooded Lead Acid (FLA) battery also comes under the category Valve Regulated Lead Acid (VRLA), which is also available in the type. All lead acid battery can gas but the VRLA holds most of the gas in the cell so it gets reabsorbed when the overcharge reduces. The so-called "Sealed" batteries are in fact VRLAs and in extreme cases will off gas.
Roger

[Westcliffe01]

Here in the US the last lead acid system I bought consisted of 4x 6V cells at 400AH each. Connected in series for a 24V system = 9600kWh It cost me $1300 at the time and since I lived close to the regional rep, he delivered the batteries to me no shipping cost. The batteries are made by Crown, which is a forklift company and they must have decided to integrate the lead acid battery production since so much of their product uses them.


Now in use, the capacity of the battery is in fact substantially less that 9600ah, because if you tried to use that capacity you would kill the battery pack in short order. They also weigh 460lb, which is why one cannot afford to ship lead acid batteries anywhere given the weight.


Now the first battery on the list, which was 9.6kWh @ 48V was only 220lb and is already inside a purpose built enclosure. You can probably cycle this battery down to 20% on a regular basis vs the 50-60% one would normally use with Lead Acid. The battery will charge in a much shorter time than a lead acid, assuming the current source has the beef to do it (forget an automotive alternator). This is one of the biggest bears, in winter when one has only a few hours of good sunlight the slow uptake of a lead acid very much limits what can be done with solar and is going to increase the need to run the generator. Because solar panels can actually put out good power in low temperatures and direct winter sunlight.
If I do 2 of the Tesla modules, I get a battery pack that is more than double the effective capacity of the lead acid system that I had at approximately double the cost. NO maintenance other than keeping track of its state of charge and keeping ambient temperature at an acceptable level so that it can accept a charge. I'm pretty sure it would FAR outlast the system I have now. As the cars get more numerous, the price is likely to drop further. at 160lb, about 1/3 the weight of the lead acid system. The difference in weight is equivalent to another 42.8 gal of fuel in the tank. With a very efficient boat, that might be close to 400 miles of extra range.

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.

[Pete7]

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.

Similar issue in the UK. Drop in 2 x 100Ah LFP about £1200-1400 with a life of 3-4000 cycles perhaps? Pair of Trojan 125 a quarter of the price at £360 and life of 1500 cycles. There is also a number of extras like a DC>DC charger to add to the bill for LFP which must be included.

That said the price of LFP is dropping substantially each year.

Pete

[Eder]

I doubt my Lifelines were ever more than 80% charged for about 1 1/2 years in Polynesia. (they were never plugged in, I used 400 watt flexible solar and the generator when I ran my water maker. No worse for wear.


Once arriving in Hawaii I found a plug and they seem as new.

[Simi 60]

Originally Posted by Westcliffe01

. at 160lb, about 1/3 the weight of the lead acid system. The difference in weight is equivalent to another 42.8 gal of fuel in the tank. With a very efficient boat, that might be close to 400 miles of extra range.

Extra weight is an advantage for us
I still have near 1000kg of dead batteries below and could do with another 2000kg in lead in the bilge to settle our girl down when the tanks get low.

[mitiempo]

Originally Posted by Simi 60

Has there been any actual proof yet?
Or is it what the marketing dept and brochures has told you?

Let's run the numbers for comparison.

Victron's Super Cycle Agm batteries are amongst the best at cycling that I know of. They state 700 cycles of 60% depth of discharge followed by an immediate recharge @ 20%C. These are lab cycles so I doubt real life numbers would be this good. But let's give them the benefit of doubt.

Assuming 100 AH battery
700 cycles x 60% = 42,000 AH over stated life.
Cost about 375 Cdn
375/42000 = .009 per AH

Victron LiFePo4 battery 100 AH
2000 cycles @ 80% discharge = 160,000 AH over expected life
Cost about 1200 Cdn
1200/160,000 = .0075 per AH

Note that I used manufacturer's specs for cycle life of the Agm batteries, even though that is very unlikely outside the lab.

For the LiFePo4 battery I used 2000 cycles while the manufacturer states 3000 to 5000 cycles. This likely tips the scales even more in favor of the LiFePo4 battery.

Not to mention the lack of a need to charge fully often (or at all) that is the ultimate death knell of any lead acid battery technology.

I have seen more Agm battery failures than Fla failures in my career as both a marine electrician and provider of batteries. On a sailboat it is very hard to fully charge the house bank as often as it needs on a regular basis if cruising. If at a dock and plugged in for charging any lead acid battery should last a long time.

[mitiempo]

Originally Posted by Pete7

Pair of Trojan 125 a quarter of the price at £360 and life of 1500 cycles.
Pete

Trojan quotes 1200 cycles in a lab. That cannot happen in real life conditions.

T125 is 240 AH so 120 AH usable to 50%

2 LiFePo4 batteries @ 100 AH each gives you 160 AH usable.

Fla GC batteries are the best bang for the dollar, no question.

Agm batteries - not so much.

[Pete7]

Originally Posted by mitiempo

Fla GC batteries are the best bang for the dollar, no question. Agm batteries - not so much.

For me that's the main point. AGM fast charging and the same with LFP, great if you can make use of it with a generator. However, if you can't fast charge, well what are the other advantages you are paying a premium for AGM? Can't spill and don't need topping up, yes I can see that would be useful. How about fast discharge for watermaker or washing machine on a live aboard perhaps.

When AGM first started becoming popular they were hailed as the wonder battery. Same in the 1990s with Gel batteries, yet we know folk are still happily buying FLA today.

[Simi 60]

Originally Posted by mitiempo

Let's run the numbers for comparison.

But this is my point, running numbers off of claims on paper.

Has anyone out there actually got to end of life on LP4 to support these claims or is it still just theoretical projections into the future based on what paper tells you?

I have seen more Agm battery failures than Fla failures in my career as both a marine electrician and provider of batteries. On a sailboat it is very hard to fully charge the house bank as often as it needs on a regular basis if cruising. If at a dock and plugged in for charging any lead acid battery should last a long time.

On ours its easy
Primary charge is 2.5kw of solar (9x250w)
7.5kw genset
75amp @ 24v alt on engine

90% of the time solar has us at 100% SOC by lunchtime
Boat has not seen a marina/ shore power in near 5 years

[mitiempo]

Originally Posted by Pete7

For me that's the main point. AGM fast charging and the same with LFP, great if you can make use of it with a generator. However, if you can't fast charge, well what are the other advantages you are paying a premium for AGM? Can't spill and don't need topping up, yes I can see that would be useful. How about fast discharge for watermaker or washing machine on a live aboard perhaps.

When AGM first started becoming popular they were hailed as the wonder battery. Same in the 1990s with Gel batteries, yet we know folk are still happily buying FLA today.

Fast charging of Agm batteries is nowhere near as fast as some might think. From 50% SOC to 85% SOC is quicker but 85% to 100% takes just as long as Fla batteries. Here's an interesting link showing the results. Scrolling to the end 5 hrs and 42 minutes with a 20 amp charger and 5 hrs and 30 minutes a 40 amp charger. 105 AH battery
https://marinehowto.com/how-fast-can...ry-be-charged/

Gel batteries can be a very long lasting battery if treated properly. 15 years is not uncommon.

[mitiempo]

Originally Posted by Simi 60

But this is my point, running numbers off of claims on paper.

Has anyone out there actually got to end of life on LP4 to support these claims or is it still just theoretical projections into the future based on what paper tells you?

I gave the benefit of the doubt to the Agm batteries. Specs state 700 cycles in a lab and i used those numbers. Doubt one would get much over 400 cycles in real life.

I very conservatively used 2000 cycles for LiFePo4 while most manufacturers state 3000 to 5000 cycles.

If you use the manufacturers numbers for both battery types the LiFePo4 becomes even a much better value.

[SV_Galateia]

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.


I worked at Advance Auto for a couple of years. The automotive/lawn equipment AGM batteries seem engineered to fail right at the end of the warranty date. 2 year batteries seem to fail right at the 2 to 3 year mark and the 3 year batteries fail at the 3 to 4 year mark. Selling batteries is big business. The expensive Optima batteries did not seem to be much better.

At the same time, just replaced the original 9 year old GM batteries (2) on a 2500HD work truck.

Don't know if the marine industry battery manufacturers (could be the same manufacturers as the auto batteries) provide a better product or are designed by the same engineers.

[Simi 60]

Originally Posted by mitiempo

I gave the benefit of the doubt to the Agm batteries. Specs state 700 cycles in a lab and i used those numbers. Doubt one would get much over 400 cycles in real life.

I very conservatively used 2000 cycles for LiFePo4 while most manufacturers state 3000 to 5000 cycles.

If you use the manufacturers numbers for both battery types the LiFePo4 becomes even a much better value.

So that's a no then, no real life lp4 longevity examples only theory on paper

But what is a battery cycle

Battery cycles are a shorthand used by manufacturers to estimate battery life. A battery cycle represents what happens when the battery is fully charged and then used until it empties – that's one cycle.

So how does that work for us when out bank never gets below 80% so apparently, never sees a cycle?