Why are so many in Love with AGM's

[hzcruiser]

Originally Posted by manitu

LiFePo and AGM are suited for entirely different situations.

As LiFePo degrade quickly when kept fully charged while AGM degrade when stored uncharged, [...]

Not sure where you got that info from? What is being stated by most manufacturers is to ideally store LFPs at 50%-70% charged. That does not mean they otherwise "degrade quickly"! It's a recommendation to achieve the longest life or smallest capacity loss over time.
My LFPs are not stored, but also not used very often. Hence I reduced the charger cut-off voltage by about 10%, which they reach every day through solar. Then they drop back during the rest of the day and through the night.
When I need their full capacity, it's a matter of minutes to change the cut-off back to 14.4V.

[manitu]

I dont think people are getting smarter from this discussion.
There are so many parameters important to battery choice which aren't discussed here.

If you are cruising in the tropics or batteries in the engine room, AGM might not be for you.
Even though AGM batteries can be charged with a high bulk voltage, the do NOT like a high float voltage.
If you are a long distance cruising and go several weeks between fully charging the batteries, your AGM's will not thrive.
If you keep your boat on shorepower most of the time, float charging , your LiFePo batteries will die prematurely.

AGM battery types.. You have starter, deep cycle, dual purpose and telecom backup batteries , each with their own nuances.

I use my boat on weekends, occationally for a week, and for 4 weeks during the summer holidays .
I use Marathon M12V190FT VRLA AGM telecom backup batteries , which I DO NOT BULK CHARGE! I'm charging them at a constant voltage of 13,6 volts.

I use them partly because I get them for cheap. I pay 120$ per battery , after they have been used for two year in a GSM basestation. Mine did one cycle during that time. They are pretty much ideal for me, and will last 10 more years with my use.

I never discharge them more than 50% during a week's sail. With 400W solar panels, and maybe one night per week in a guest harbour during the summer vacation, they usually stay between 60 and 90%SOC.
When the weekend/week/vacation is over, the batteries stay on a constant voltage of 13,6 volt , as they are designed to.

They don't need topping up, I don't have to watch bulk cycles to avoid overcharging, They can stay on the charger for 200 days/year without damage.
They don't need to be looked after at all in my setup.

Thats 10years of trouble-free battery life on a 960Ah battery bank ,for 500$


.manitu

[hzcruiser]

Originally Posted by Simi 60

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

But what is a battery cycle
[...]

From wikipedia:

Apple Inc. clarifies that a charge cycle means using all the battery's capacity, but not necessarily by discharging it from 100% to 0%: "You complete one charge cycle when you’ve used (discharged) an amount that equals 100% of your battery’s capacity — but not necessarily all from one charge. For instance, you might use 75% of your battery’s capacity one day, then recharge it fully overnight. If you use 25% the next day, you will have discharged a total of 100%, and the two days will add up to one charge cycle."

IOW, if you discharge 20% per day and recharge that amount, you get one cycle every 5 days.

[hzcruiser]

Originally Posted by manitu

[...]
If you are a long distance cruising and go several weeks between fully charging the batteries, your AGM's will not thrive.
If you keep your boat on shorepower most of the time, float charging , your LiFePo batteries will die prematurely.

[...]

Then just set the floating voltage to about 13.3V.

Problem solved and you keep all the advantages of LFPs.

[mitiempo]

But what is a battery cycle
Quote:
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?

------------------------------------------------------------------------------------------------

A battery cycle is determined by drawing the battery down to a certain SOC and then recharging. The number of cycles for a particular battery depends how far down the battery is drawn.

The cycle life below is for Victron's Super Cycle Agm batteries.


Cycle life
≥ 300 cycles @ 100% DoD (discharge to 10,8V with I = 0,2C₂₀, followed by approximately two hours rest in discharged condition,
and then a recharge with I = 0,2C₂₀)
≥ 700 cycles @ 60% DoD (discharge during three hours with I = 0,2C₂₀, immediately followed by recharge at I = 0,2C₂₀)
≥ 1000 cycles @ 40% DoD (discharge during two hours with I = 0,2C₂₀, immediately followed by recharge at I = 0,2C₂₀)

[Simi 60]

Found this one that took it to 30%
So would like to think us doing 20% would be say 1250 cycles, 1 every 5 days = 17 years.
Of course I don't expect that but 8 + will be good



https://federalbatteries.com.au/news...t-so-important

[Simi 60]

Originally Posted by hzcruiser

IOW, if you discharge 20% per day and recharge that amount, you get one cycle every 5 days.

Thanks

[manitu]

Originally Posted by hzcruiser

Not sure where you got that info from? What is being stated by most manufacturers is to ideally store LFPs at 50%-70% charged. That does not mean they otherwise "degrade quickly"! It's a recommendation to achieve the longest life or smallest capacity loss over time.
My LFPs are not stored, but also not used very often. Hence I reduced the charger cut-off voltage by about 10%, which they reach every day through solar. Then they drop back during the rest of the day and through the night.
When I need their full capacity, it's a matter of minutes to change the cut-off back to 14.4V.

The problem with storing LiFePo cells, is that voltage is not a good indicator of SOC. The dominate component of calendar decay is based around potential related decomposition and temperature, and the potential is buffered to be roughly the same from 20-80% SOC.
Ideal storage is between 40-50%SOC, while 30-80%SOC is acceptable.


So, discharge the LiFePo batteries at least until the voltage stabilizes , then keep them there.
If you are on the hook or cruising, discharging a bit every night ,a correctly sized LiFePo bank is great.
If you like me keep your boat at the dock most of the time , not so much.


.manitu

[Westcliffe01]

The Tesla battery is not using Lipo4 chemistry but there are examples of those vehicles out to 500 000 miles (800k km if memory serves).


Here is a write up on that topic with mileage based degradation. https://electrek.co/2020/06/06/tesla...n-replacement/


Apparently, since the release of the model 3, there are now warranty limits on battery degradation based on time or mileage and according to the writers, Tesla should be safe based on the limits specified.

Originally Posted by Simi 60

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

But what is a battery cycle


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

[manitu]

If you want to research Lithium tech and longevity, search the https://endless-sphere.com/forums/.

Here, we have used different lithium chemistries for more than 10 years to run home made electric bikes and motorcycles.

Check out liveforphysics and doctorbass' post in particular. I consider them some of the most knowledgeable people in the world , when it comes to lithium batteries.

.manitu

[mitiempo]

Quote:
Originally Posted by hzcruiser View Post

IOW, if you discharge 20% per day and recharge that amount, you get one cycle every 5 days.
Thanks
------------------------------------------------------------------------------------------------

You realize that is referring to an Iphone or Ipad battery.

Using 50% of a battery is a cycle. Using 20% of a battery is still a cycle. Obviously the less use per cycle the more cycles you get. Batteries will degrade over time without cycling at all. Temperature, either much above or below 77F can have a large impact on battery life as well. Batteries should never be in an engine space for this reason.

But the Agm batteries you have and the Lithium Ion batteries in an IPhone are quite different.

[mitiempo]

Originally Posted by manitu

If you want to research Lithium tech and longevity, search the https://endless-sphere.com/forums/.

Here, we have used different lithium chemistries for more than 10 years to run home made electric bikes and motorcycles.

Check out liveforphysics and doctorbass' post in particular. I consider them some of the most knowledgeable people in the world , when it comes to lithium batteries.

.manitu

This is my go to for LiFePo4 information.
https://marinehowto.com/lifepo4-batteries-on-boats/

[manitu]

Originally Posted by mitiempo

Quote:
Using 50% of a battery is a cycle. Using 20% of a battery is still a cycle. Obviously the less use per cycle the more cycles you get. Batteries will degrade over time without cycling at all.

A full battery cycle is a full battery cycle (100%)
A cycle of 30% is 30% of a full cycle.
You need to read the text in each case to determine what the author is saying.
The charts from battery manufacturers usually talks about partial cycles.

.manitu

[mitiempo]

Originally Posted by manitu

A full battery cycle is a full battery cycle (100%)
A cycle of 30% is 30% of a full cycle.
You need to read the text in each case to determine what the author is saying.
The charts from battery manufacturers usually talks about partial cycles.

.manitu

If you "full cycle" the batteries using your description I doubt you would get a year or 2 out of them.

The term "cycle" is meaningless without qualifying the depth of discharge.

I posted this earlier but here it is again from Victron:

Cycle life
≥ 300 cycles @ 100% DoD (discharge to 10,8V with I = 0,2C₂₀, followed by approximately two hours rest in discharged condition,
and then a recharge with I = 0,2C₂₀)
≥ 700 cycles @ 60% DoD (discharge during three hours with I = 0,2C₂₀, immediately followed by recharge at I = 0,2C₂₀)
≥ 1000 cycles @ 40% DoD (discharge during two hours with I = 0,2C₂₀, immediately followed by recharge at I = 0,2C₂₀)

Every battery manufacturer I know of states depth of discharge when quoting number of cycles. One without the other is meaningless.

As they are lab cycles in perfect conditions with immediate recharge best to not expect much more than half the lab cycles in the real world.

[captnknopf]

[QUOTE=geoleo;3348429]I have 2 mastervolt 200 AH in my boat. 2 years old. With the charger off they always drop from 13.2 to 12.1 in 2 days unattended . I dont think there is a leak as 12 volt panel is turned off. Is this drop in volts unusual??[/QUOTE

I have the same batteries in my boat and they do not drop below 12.5 after two days running the frige. If they are droping to 12.1(check with a separate meter to make sure) either the batteries are shot or there is a draw you do not know about. I have a clamp on DC amp meter that reads below an amp that will find any leak. My guess is you have a current leak you are not aware of.