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Old 12-01-2021, 07:54 PM   #225
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One point I don't see yet in this thread is battery losses. If you run appliances that draw more than the 5% (20 hour) discharge rate, you lose some Ah to losses in an AGM. Possibly 10% or more. With LiFePO4 the losses are under 1% with typical loads. This is the old Peukert's constant thing. This really should be takin into account when comparing attributes of the two batteries.

Then there's charge time, amount of solar required if you go solar and all the other differences.
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Old 12-01-2021, 08:36 PM   #226
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One point I don't see yet in this thread is battery losses. If you run appliances that draw more than the 5% (20 hour) discharge rate, you lose some Ah to losses in an AGM. Possibly 10% or more. With LiFePO4 the losses are under 1% with typical loads. This is the old Peukert's constant thing. This really should be takin into account when comparing attributes of the two batteries.

Then there's charge time, amount of solar required if you go solar and all the other differences.
The Peukert factor on LA/AGM is around 125% and on LiFePO4 it's more like 105%..... this is a dramatic difference with high draw devices like Microwave, hair dryer, etc...
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Old 12-01-2021, 08:49 PM   #227
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Please tell me where you can find a 12V 200AH AGM for $200
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Old 12-01-2021, 08:50 PM   #228
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The Pukert factor on LA/AGM is around 125% and on LiFePO4 it's more like 105%..... this is a dramatic difference with high draw devices like Microwave, hair dryer, etc...
I tested my two 206ah SOK's by running my air conditioner for 3 hours pulling around 130amps continuous and got 405ah out of them to inverter cutout at 11.2v, yep basically no Peukert, my two AGM's could do 30-45 minutes under the same test.
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Old 12-02-2021, 08:21 AM   #229
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if you discharge a 200 Ah AGM to 50% 1500 times, you've reaped 150,000 Ah. If you discharge it to 70% for 900 cycles, you will get 126,000 Ah.
This isn't being calculated correctly. Amp hours and DOD are not on the same scale. 80% DOD is 100% of rated amp hours, not 80%. So factoring this shift, two data points for a 200Ah battery would look like this:

40% DOD = 50% Ah = 100Ah
80% DOD = 100% Ah = 200Ah

Applying the cycle life values from the cited chart for these DOD points you get:

40% DOD/100Ah * 1700 cycles = 170000Ah
80% DOD/200Ah * 800 cycles = 160000Ah

So the net difference in lifetime delivered Ah between 40 and 80% DOD is now within about 6%, which tracks with what you typically see for deep cycle batteries at C/20. Since there are other operational influences to battery performance that can have this or greater impact to service life, I don't consider this range of DOD to be a significant factor. The "peak" service life will be around 30% SOC max but to recharge a battery between 70% and 100% means most of that time will be spent in absorb mode, which is the least efficient and most time consuming charge phase. So the tradeoff then becomes actually using the battery or spending time and energy to achieve "maximum" service life. Since the delta between maximum and minimum service life irrespective of DOD is less than 10%, trying to hit this or any other cycle life target seems a bit of diminishing return especially when you apply the calendar life limitation and having the battery expire before service life is expended.

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This is the old Peukert's constant thing. This really should be takin into account when comparing attributes of the two batteries.
True. Peukert can be both calculated or measured. It is what it is, and you factor that into the system operational and budget criteria.

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Old 12-02-2021, 08:45 AM   #230
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This isn't being calculated correctly. Amp hours and DOD are not on the same scale. 80% DOD is 100% of rated amp hours, not 80%. So factoring this shift, two data points for a 200Ah battery would look like this:
Maybe I am missing something but standard lead acid battery capacity is rated at c/20 to 1.75v per cell which is definitely 100% DOD. A 6v 200ah rated battery should pull 200ah if discharged at 10 amps for 20 hours and be left at 3.5v or 100% DoD.

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Old 12-02-2021, 09:46 AM   #231
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Through out the years we get between 7 and 9 years from flooded cell battries. Only value of lithium for me are the deap discharge and fast recharge. Nice if you do alot of dry camping. But that has never been a issue.

But if you do fully discharge lithium (0v) the battery will never hold a charge.
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Old 12-02-2021, 10:18 AM   #232
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But if you do fully discharge lithium (0v) the battery will never hold a charge.
Not exactly true, they will be badly damaged but usually recoverable, you can even go to negative voltage on the cell which usually kills them dead but not always. They are actually pretty resilient.

Lead will also be badly damaged at 0v the difference is Lithiums have a BMS that shuts down around 2.5v per cell and you really don't start getting damage until 2.0v and can still have 70-90% capacity if revived from 1v leaving a significant buffer to sit at "100%" DoD, Battleborn recommends no longer than a week which is conservative, lithiums only self discharge at 2-3% per month.

Flooded are fine if you don't use them much and are ok with dealing with water maintenance and corrosion and venting but you could probably get away with a much smaller LFP bank in that situation and never deal with it again and get better performance.

The way prices are going LFP it won't be a debate in the next few years and the market for deep cycle lead will probably disappear anyway.
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Old 12-02-2021, 11:38 AM   #233
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But if you do fully discharge lithium (0v) the battery will never hold a charge.

I would consider this severe battery abuse, as the only way to fully discharge a modern LiFePo4 battery is to run it down to the point where the BMS disconnects on low voltage, then let it sit for several months while it slowly self discharges down to zero.




Note somewhere along the way AGM's have made their way into this conversation. On that topic I will just say that AGM out performs flooded lead acid, but cost more, though most of the AGM advantages are a small step up in performance, not a giant leap like it is with LiFePo4.


Another point that has not made it into the conversation which seems to keep focusing on cost, are the secondary expenses, like amount of fuel burned in a generator to fully recharge each type of battery. This is another place where LiFePo4 tends to win with 1C charge rate up to about the 99% charge point. No need for that slow absorption cycle for the last 20% like on lead acid, and no penalty for not fully topping off (Sulfation in lead acid)
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Old 12-02-2021, 11:43 AM   #234
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Not exactly true, they will be badly damaged but usually recoverable, you can even go to negative voltage on the cell which usually kills them dead but not always. They are actually pretty resilient.

Lead will also be badly damaged at 0v the difference is Lithiums have a BMS that shuts down around 2.5v per cell and you really don't start getting damage until 2.0v and can still have 70-90% capacity if revived from 1v leaving a significant buffer to sit at "100%" DoD, Battleborn recommends no longer than a week which is conservative, lithiums only self discharge at 2-3% per month.

Flooded are fine if you don't use them much and are ok with dealing with water maintenance and corrosion and venting but you could probably get away with a much smaller LFP bank in that situation and never deal with it again and get better performance.

The way prices are going LFP it won't be a debate in the next few years and the market for deep cycle lead will probably disappear anyway.
I agree if the price continues to drop LiFePo4 batteries in climate controlled applications will replace lead acid and we may soon see some motor home manufactures but in heated bays for LiFePo4 batteries like they now do for the wet bays. For cold conditions lead acid will still have a place, if SiO2 Silicon Dioxide Batteries drop in price they will work under the widest rang of conditions.
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Old 12-02-2021, 11:52 AM   #235
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Another point that has not made it into the conversation which seems to keep focusing on cost, are the secondary expenses, like amount of fuel burned in a generator to fully recharge each type of battery. This is another place where LiFePo4 tends to win with 1C charge rate up to about the 99% charge point. No need for that slow absorption cycle for the last 20% like on lead acid, and no penalty for not fully topping off (Sulfation in lead acid)
Well noted Isaac,
I posted a while back that my experience over the past year is that my 170ah LiFePo4 will charge from 30% to 100% SOC in less than 2 hours with my inverter/charger programmed for 80amps. Perfect timing to meet the restricted generator hours of national parks, NFS, and some state parks. I also reported that I get about 30 hours of charging time from my miserly 2500w generator on one 20lb propane tank. That’s 15 LiFePo4 full charge cycles, for a very small cost in propane. (About one dollar per charge cycle) I wonder how much diesel or gasoline a 6500w onboard Onan will use to charge a bank of FLA from 30% to 100%.
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Old 12-02-2021, 01:05 PM   #236
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I am not sure, but I can tell you that my Onan 4000 gas generator is rated at .57 gph of gasoline at half load, ie 2000 watts output.
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Old 12-02-2021, 02:45 PM   #237
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I agree if the price continues to drop LiFePo4 batteries in climate controlled applications will replace lead acid and we may soon see some motor home manufactures but in heated bays for LiFePo4 batteries like they now do for the wet bays. For cold conditions lead acid will still have a place, if SiO2 Silicon Dioxide Batteries drop in price they will work under the widest rang of conditions.
They won't need heated bays, the batteries will have built in heaters just like some of the more expensive ones you can buy now. They will also limit charging current when cold as a few really new ones seem to be doing. They will take care of themselves thats the trend with better and better BMS's built in. There is also LifeyPo4 batteries with Yttrium added that do -45c charge/discharge.

SiO2 is a lead battery (lead crystal) so it still has the same weight and voltage drop profile and need for absorb charging, they are also as expensive as a higher grade LFP ($500 for 100ah 12v) with not as much movement in price and there is basically one brand you can get in the US (Soneil). They have about the same cycle life of a 100% DoD LFP at only 50% DoD and if you discharge them to 100% DoD like you can with LFP they are basically the same as any other deep cycle lead at around 600 cycles. At -20c looks like they lose 25% capacity so yes they can be used in low temps but just like any other lead they lose significant capacity and they still suffer peukert losing 20% capacity discharging at only .5c. They look like a decent choice if you need a battery to work in a bay below -20c (-4f) albeit expensive my Lifeline AGM's worked down to -55c and where less expensive just less cycles at 50% DOD.

There are cheap 100ah LFP's showing up at $200 US in Australia and on Ebay I wouldn't trust the quality at this point but it shows where the prices are going the cheapest LFP 100ah was around $700 two years ago.
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Old 12-02-2021, 03:26 PM   #238
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They won't need heated bays, the batteries will have built in heaters just like some of the more expensive ones you can buy now. They will also limit charging current when cold as a few really new ones seem to be doing. They will take care of themselves thats the trend with better and better BMS's built in. There is also LifeyPo4 batteries with Yttrium added that do -45c charge/discharge.

SiO2 is a lead battery (lead crystal) so it still has the same weight and voltage drop profile and need for absorb charging, they are also as expensive as a higher grade LFP ($500 for 100ah 12v) with not as much movement in price and there is basically one brand you can get in the US (Soneil). They have about the same cycle life of a 100% DoD LFP at only 50% DoD and if you discharge them to 100% DoD like you can with LFP they are basically the same as any other deep cycle lead at around 600 cycles. At -20c looks like they lose 25% capacity so yes they can be used in low temps but just like any other lead they lose significant capacity and they still suffer peukert losing 20% capacity discharging at only .5c. They look like a decent choice if you need a battery to work in a bay below -20c (-4f) albeit expensive my Lifeline AGM's worked down to -55c and where less expensive just less cycles at 50% DOD.

There are cheap 100ah LFP's showing up at $200 US in Australia and on Ebay I wouldn't trust the quality at this point but it shows where the prices are going the cheapest LFP 100ah was around $700 two years ago.
Why are the owners of LiFePo4 batteries in denial of the glaring fault with LiFePo4. They are ill suited for a low temperature environment. LiFePo4: have to rely on a BMS to protect the battery some are cheap and they fail, just look at the test. When the BMS works you cannot recharge the battery!!
When you rely on LiFePo4 heaters they requires power reducing efficiency.
SiO2 Silicon Dioxide Batteries can be direct replacement for LA batteries where Li causes problems like killing alternators and shutting down in the cold
SiO2 charge as fast as lithium to 90% and easily top off to 100%.
SiO2 Silicon Dioxide Batteries have an unique chemistry. The non-corrosive electrolyte in SiO2 batteries forms crystalline salts when charged/discharged. SiO2 batteries use 95% less sulphuric acid than Lead Acid batteries. They are essentially a "dry-cell" battery with no liquid to freeze, spill or off-gas. Eliminating most of the acid, means that the lead plates last longer and weigh less. Sulphation does not build-up and reduce capacity over time. With the crystalline structure, they can also be used in any orientation.
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