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Old 12-03-2021, 12:32 AM   #57
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Originally Posted by RoadTrip2084 View Post
One thing that I wonder about is how the Float charge stage will work out. My understanding is that the converter will stop charging completely once the Absorb phase completes, then the battery will discharge with use over time. Once the battery voltage drops to the Float charge voltage (e.g. 13.3v), the converter will once again begin charging, but only to the low "float" level of voltage. So at this point the most the converter will charge the battery is the Float level (e.g. 3.3v, approx. 90% SOC). In order to initiate a Bulk charge sequence, I will have to turn the converter off/on again, or cut the shore or generator power and restore it. However, having the Float charge kick in whenever the battery drops below 90% SOC and keeping it at 90% SOC is probably just fine.
You've got it nailed. When the charger drops to the float voltage, the battery voltage will drop to that voltage over time. Very slowly if there is no load on it, faster if there is some load. During this time of voltage dropping to float, the battery will be supplying load and the converter will be doing nothing. The battery effectively is being discharged though it takes only an Ah or two to bring the battery down to the float voltage.

There will be no charging once in float mode unless you put load on the system. Firstly, if you put more load on than the converter can supply in float mode, the battery will supply the rest and voltage will drop. Secondly, even a load that is within the converter's capability will pull converter voltage down a bit (below float) and this will result in some current coming out of the battery and a bit of discharge. In either case, the converter will re-charge the battery up to the float voltage. This won't be a very quick re-charge but that's fine.

One caveat, the float voltage needs to be over 13.3V to hold or return the battery to 100%.

The oft touted life benefit of floating an LiFePO4 at less than 13.6 volts is very slight. When floated with no load on the system, the LiFePO4 current will go to zero at any credible float voltage. With zero current there is very little chemical activity going on in the battery so little or no life is used.

In my own case, when camping, I want the battery to be at 100% whenever possible to help me get through inclement weather without running a generator. That means floating around 13.4V or above. Because there is not a tight correlation between my solar controller's set float voltage and the battery cell voltages, I float at 13.5 or 13.6 to be sure the cells are at 13.4 or more.

Sorry about belaboring this. I think we covered some of this earlier.
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Old 12-03-2021, 02:13 AM   #58
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To each their own, my PD9260 converter does bulk charging at 14.4VDC for up to 4 hours, then floats at 13.4VDC, before dropping into "storage" mode at 13.2VDC (actually 13.267VDC) after about 30 hours of minimal battery activity, unless someone manually overrides this with the charge wizard button. The result of this is the battery draining down to about the 70% state of charge point over time. I have no problem with this when the coach is in storage, as it helps extend the life of the LiFePo4 battery, and in 2-3 hours the engine alternator alone can bring it back up to full charge. Given the shortest distance we ever go is over 100 miles, this again works out ok. While actively traveling with the solar panels exposed to sunlight, etc. it easy enough to keep the converter from going into storage mode.
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Old 12-03-2021, 01:24 PM   #59
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A good question at this point in the discussion is what is the life impact on an LiFePO4 of having a non-ideal charge regime. The answer from my research is small or very small. With most LiFePO4 batteries having 80% or more capacity remaining after about 3000 thousand cycles, even significant loss of life from mild abuse would surely leave 2000 cycles.

If one camps two of months every year, always boondocking or dry camping, and cycles the LiFePO4 down to 20% daily, 2000 cycles is 33 years.

In 33 years, the future value of the dollars saved by not buying the spiffiest charger today would surely purchase a whole lot of capacity of LiFePO4 (or whatever technology is good at that time).

So, IMHO, spending money to get a few extra years out of a battery that is going to last so many years is not an economically beneficial decision.
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Old 12-03-2021, 04:19 PM   #60
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As I see it there are 2 major aspects to an ideal charging scheme, how low do you go and how high do you go / float. I have yet to see any global numbers that apply to all types of LiFePo4 cells, cylindrical, pouches, etc.


First is the practice of discharging to 0% (meaning BMS low voltage cutoff not fully dead which will damage / kill cells), my take on this one is that one should avoid this when possible, and try to stay about 20% when possible, ie if you are going to crank the generator to refill the batteries do it at 20%, not 0% to maximize battery life, exact loss of capacity draining to 0% vs 20% may be on the order of 20-30% percent of total charge cycles, by some estimates.


Second don't charge to 100% on a routine basis, only do so occasionally if your BMS top balances, perhaps once every 10-20 charge cycles, otherwise stop at 95% or so, there is a good bit of evidence showing that you can loose another 20-30% of your maximum charge cycles by charging over 97-98% each charge cycle


Third, or maybe Second part B, when in long term storage float at around 70% charge, is 13.2VDC for 12v system, or just charge / discharge to 70% then disconnect and don't float, again there is a BIG difference between floating at 13.4-13.6VDC vs 13.2VDC (is about 70% state of charge). A common mistake here is to charge to 100% then disconnect, due to their low self discharge rates, it will take months for a 100% charged LiFePo4 battery to drop below 95% SOC.



Some early adopters that cycled 0-100% daily and float at 13.6-13.8VDC or higher have found that they have lost 20-30% of their battery bank capacity after only 1-2 years. The big thing to remember here is the LiFePo4 is not like Lead Acid, they really do not want to be kept at 100% state of charge long term, 95-98% state of charge is a MUCH better routine charging level to aim for at least 9 out of 10 charge cycles, then have the 10th time go to 100% for balancing. (exactly how often balancing is needed will depend on how well matched the cells are in your specific battery)
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Old 12-03-2021, 06:01 PM   #61
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So in my case my usage scenarios are pretty basic:
  1. Driving. Loads are handled from the house battery. Battery is charged via 60A DC-DC charger from chassis battery, chassis battery is charged from 200A alternator. House battery should generally be fully charged by the time we arrive at our destination.
  2. Boondocked. Loads are handled from the house battery. When/if the battery drops to 20% or so, fire up the 7.5KW diesel generator for a few hours to fully recharge the battery via the converter.
  3. Camped in powered site. In this case house battery is charged by (if needed), and loads handled, by the converter via shore power.
While I haven't done the detailed math, my expectation is that we should typically be able to run 3 days on the 280Ah house battery, basically powering the residential fridge, led lights, water pump, maybe more.

The vast majority of the time the house battery will sit fully charged, either sitting at a powered campsite, or in storage after finishing a drive home from the campground.

I re-watched a couple of the "Off Grid Garage" videos last night, specifically the ones that deal with the impact of absorption charging on the charge level / capacity of the battery, and the impact of charging using lower (13.6v) and higher (14.0v) max voltages. Andy's findings were very interesting (tests were done charging/discharging a single LiFePO4 110Ah cell):

Quote:
1, Test:
CV Charge 3.5V, no absorption
CC Discharge 20A: 107.37Ah (97.6% SOC)

2. Test:
CV Charge 3.5V, with absorption
CC Discharge 20A: 109.67Ah (99.7% sog)

3.5v Charge Time: 45 mins.

3. Test:
CV Charge 3.4V, no absorption
CC Discharge 20A: 97.96Ah (89% SOC)

4. Test:
CV Charge 3.4V, with absorption
CC Discharge 20A: 108.02Ah (98.2% SOC)

3.4V Charge Time: 4 hrs 30 mins
So this shows that it is possible to charge "fully" using a much lower voltage than normal (13.6v equiv.) using absorption, but the charge time extends from 45 mins @ 14v to 4hrs 30mins @ 13.6v. Clearly this is not efficient if I'm running the generator simply to charge the battery, or planning to have a fully charged battery after driving a shorter distance to my campsite.

Will Prowse (of diysolarforum.com fame) claims that cycling LiFePO4 fully (from 100% to 0% and back) regularly is not a significant issue. However, leaving the battery at 100% or 0% for long periods can be.

Given that my battery will likely sit "full" most of the time, it might be prudent to limit how fully I am normally charging it so it isn't sitting at 100% most of its life. Not really a big deal since I should be able to use the generator to recharge whenever it's required.

The other consideration is that there is some evidence that LiFePO4 cells can lose capacity just from age alone, regardless of the number of cycles. This might indicate that there is limited benefit in not fully cycling the battery if it's going to gradually deteriorate from age anyway. Realistically, there's no way I'd ever be able to "cycle out" the battery with my very light usage requirements.

All this is a long-winded way of saying that I'm leaning toward using the lowest converter charger config, 13.9v bulk / 3.3v float (90% SOC), or possibly 14.3v bulk, 13.4v float. It will also depend on the how well the balancer in the BMS works at the lower voltage levels. I'll test both modes and see how they differ in terms of charge-time, balancing behaviour, and capacity.
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Old 12-03-2021, 06:21 PM   #62
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Seems fairly reasonable to me
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Old 12-03-2021, 07:22 PM   #63
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I am late to this party. My credentials are I have a 1000 amp hour LiPo bank that I have used for 6 years, home made BMS(Arduino based), and as recently as this spring load tested the bank proving it still had over 1000 amp hour capacity. The point is not to brag, but to assure that what I am recommending is not theoretical.

That being said, I have seen 100’s of threads where folks got into brawls over 0.1 volts. I read them all with intense scrutiny wondering if I was cooking my bank or undercharging.

Then I read one person’s comment that I did not fully understand at first. The comment was “the batteries will tell you”. Let me explain how I came to understand that was the most valuable sentence I ever read when it came to LiPo batteries.

First of all who is to know if the voltage you read on your charger, with your cables, and all the connections in your system, is the same voltage I read on mine to 0.1 of a volt? And if you use a Fluke, and I use a Harbor Freight Voltmeter who is to say which one is closer to the truth. After all, few of us have meters traceable to NIST. If you take the time to measure the voltage at the batteries during a charge cycle you may be surprised at how different it is than the voltage indicated on the inverter/charger panel. The batteries do not care what the panel says. They care about the voltage present at their terminals.

So, here is a very simple way to have the batteries tell you. It is undeniable the flat charge discharge profile of LiPo with the steep slopes at either end of the cycle. Take the time to connect your voltmeter to the terminals of the battery bank. Run the bank through whatever charge cycle you choose. Plot the voltage until you start to see the upward curve. Take it as far up the curve as you dare. At the same time record the voltage shown on your charger panel. You know have a tool to evaluate whatever charge profile you choose to use. It is applicable to your batteries, with your charger, and your cable, and your connections. Is it time consuming. Yes. Is it confidence inspiring. Absolutely.

For grins, use the inverter and some decent loading and do the same voltage recording as the bank discharges. You will eventually start to fall off the voltage cliff. Again, record both the voltage at the bank recorded by your meter, and the voltage indicated on your inverter. You know have data to decide where to set the low battery cutoff, and recharge initiation setup.

Because I have an external BMS, I also used this data to set the BMS just outside the charge / discharge parameters I put into the charger/inverter. I call that the belt and suspenders approach.

I have not mentioned one single voltage/current setpoint intentionally. What works for my bank may be different than what works for yours. What I outlined above is a simple method for KNOWING how your bank behaves so that you can make informed decisions about how to set up the parameters.

Being a techie nerd, I did not have the patience to record the data by hand so I used a data logger talking to my laptop.

And one last non standard thought. Sticking with ‘the batteries will tell you”, I do not use time or voltage to determine when bulk is complete. I use return amps. As the bank fills, it’s internal resistance changes, and the bank begins to accept less and less current for a given voltage. I use 5% of C to stop the bulk charge.
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Old 12-04-2021, 12:45 AM   #64
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Quote:
Originally Posted by RoadTrip2084 View Post
So in my case my usage scenarios are pretty basic:
  1. Driving. Loads are handled from the house battery. Battery is charged via 60A DC-DC charger from chassis battery, chassis battery is charged from 200A alternator. House battery should generally be fully charged by the time we arrive at our destination.
  2. Boondocked. Loads are handled from the house battery. When/if the battery drops to 20% or so, fire up the 7.5KW diesel generator for a few hours to fully recharge the battery via the converter.
  3. Camped in powered site. In this case house battery is charged by (if needed), and loads handled, by the converter via shore power.
While I haven't done the detailed math, my expectation is that we should typically be able to run 3 days on the 280Ah house battery, basically powering the residential fridge, led lights, water pump, maybe more.
I have a 322 Ah LiFePO4 and get three days with a CPAP machine, 12V fridge, microwave and lots of other stuff totaling about 80 Ah in 24 hours. A lot will depend on the fridge and how warm it is where you camp. My 12V is well insulated and fairly miserly to start with. A residential unit may not do as well. My fridge (without my added insulation) does a 50% duty cycle at 70F and 100% duty cycle at 100F. ((100F about doubles the temperature difference between the inside of the fridge and the ambient relative to 70F so doubles energy use))

Quote:
The vast majority of the time the house battery will sit fully charged, either sitting at a powered campsite, or in storage after finishing a drive home from the campground.
I store in my yard so it's easy to drain the battery down to 50% over a couple of days after arriving home. I'm guessing this isn't an option for you.

Quote:
I re-watched a couple of the "Off Grid Garage" videos last night, specifically the ones that deal with the impact of absorption charging on the charge level / capacity of the battery, and the impact of charging using lower (13.6v) and higher (14.0v) max voltages. Andy's findings were very interesting (tests were done charging/discharging a single LiFePO4 110Ah cell):

So this shows that it is possible to charge "fully" using a much lower voltage than normal (13.6v equiv.) using absorption, but the charge time extends from 45 mins @ 14v to 4hrs 30mins @ 13.6v. Clearly this is not efficient if I'm running the generator simply to charge the battery, or planning to have a fully charged battery after driving a shorter distance to my campsite.
Yup. With ample life, go with convenience. Mine stores at 50% but on the road it hits 100% (more or less) on sunny days, ready for inclement weather. We camp a lot on the CA Central Coast where clouds and fog are not predicable.

Quote:
Will Prowse (of diysolarforum.com fame) claims that cycling LiFePO4 fully (from 100% to 0% and back) regularly is not a significant issue. However, leaving the battery at 100% or 0% for long periods can be.
I have a Lifeblue that is warranted to have 83% remaining capacity after 2800 100% DOD cycles. Prismatic cells. Though this is with a battery that actually delivers up to 10% more capacity than rated, so a 100% DOD is really more like 90% DOD.

Quote:
Given that my battery will likely sit "full" most of the time, it might be prudent to limit how fully I am normally charging it so it isn't sitting at 100% most of its life. Not really a big deal since I should be able to use the generator to recharge whenever it's required.

The other consideration is that there is some evidence that LiFePO4 cells can lose capacity just from age alone, regardless of the number of cycles. This might indicate that there is limited benefit in not fully cycling the battery if it's going to gradually deteriorate from age anyway. Realistically, there's no way I'd ever be able to "cycle out" the battery with my very light usage requirements.
Agree totally.

Quote:
All this is a long-winded way of saying that I'm leaning toward using the lowest converter charger config, 13.9v bulk / 3.3v float (90% SOC), or possibly 14.3v bulk, 13.4v float. It will also depend on the how well the balancer in the BMS works at the lower voltage levels. I'll test both modes and see how they differ in terms of charge-time, balancing behaviour, and capacity.
Do monitor actual battery voltage via the BMS. You may see some difference between that and the charger setting. This kind of equipment is not very precise. I.e., floating at 13.3 might be 13.2 at the cell terminals.

My prismatic batteries (both Lifeblue and home brew) get to 99% before any absorb time. I'm not sure cylindrical cell batteries like BB do. I've also charged at 13.5V (set precisely) and gotten to 99%. It took six hours to get from 90 to 99 so it's slow but does get there. 13.4V should as well. So, there's no way, at least with prismatic cells, to not charge to near 100% (without interrupting the charge). Some people say 13.8 will get the battery only to 90%, but in my experience and from what I've read, there's no good way to stop at less than 99-100%. So one might as well live with whatever life 99% brings.
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Old 12-04-2021, 01:05 AM   #65
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Second don't charge to 100% on a routine basis, only do so occasionally if your BMS top balances, perhaps once every 10-20 charge cycles, otherwise stop at 95% or so, there is a good bit of evidence showing that you can loose another 20-30% of your maximum charge cycles by charging over 97-98% each charge cycle
I'd appreciate a reference to any data suggesting 20-30% life loss from the last 2 or 3% charge.

Quote:
A common mistake here is to charge to 100% then disconnect, due to their low self discharge rates, it will take months for a 100% charged LiFePo4 battery to drop below 95% SOC.
I agree re prismatic cells. Interestingly BB recommends charging to 100% then disconnecting. I'm guessing, but would bet they make this recommendation to make life simple for themselves and their customers. Who's going to notice 10% loss of life in a battery than may last 10-20 years!! Or maybe their stated 2-3% charge loss per month brings the charge down soon enough. Incidentally, this 2-3% to me suggests a difference between cylindrical and prismatic cells.

Quote:
. . . . . . MUCH better routine charging level to aim for at least 9 out of 10 charge cycles, then have the 10th time go to 100% for balancing. (exactly how often balancing is needed will depend on how well matched the cells are in your specific battery)
The need for balancing is more related to the currents you draw. Microwave and A/C users will see more need for balancing.

Another reason to get to 100% fairly often is to avoid the SOC reading drifting up relative to actual SOC. Most monitors including BMSs with BT ignore the small but non-zero Peukert's constant for LiFePO4 batteries. Monitors reset only at the end of a charge cycle and are accurate only if that charge cycle hits 100%. Some LiFePO4 makers suggest getting to 100% weekly for this reason.
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Old 12-04-2021, 06:35 AM   #66
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I will try to find you reference on that when I get a chance, we are getting ready to go on a trip leaving in about 4 or 5 days, so am a bit busy with things right now.


As to the need for periodic balancing, I would partly agree with your statement, but would say heavy load use, such as running microwaves, etc. reveals how well matched the cells are.
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Old 12-04-2021, 10:04 AM   #67
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Quote:
Originally Posted by RichardE View Post
I am late to this party. My credentials are I have a 1000 amp hour LiPo bank that I have used for 6 years, home made BMS(Arduino based), and as recently as this spring load tested the bank proving it still had over 1000 amp hour capacity. The point is not to brag, but to assure that what I am recommending is not theoretical.

That being said, I have seen 100’s of threads where folks got into brawls over 0.1 volts. I read them all with intense scrutiny wondering if I was cooking my bank or undercharging.

Then I read one person’s comment that I did not fully understand at first. The comment was “the batteries will tell you”. Let me explain how I came to understand that was the most valuable sentence I ever read when it came to LiPo batteries.

First of all who is to know if the voltage you read on your charger, with your cables, and all the connections in your system, is the same voltage I read on mine to 0.1 of a volt? And if you use a Fluke, and I use a Harbor Freight Voltmeter who is to say which one is closer to the truth. After all, few of us have meters traceable to NIST. If you take the time to measure the voltage at the batteries during a charge cycle you may be surprised at how different it is than the voltage indicated on the inverter/charger panel. The batteries do not care what the panel says. They care about the voltage present at their terminals.

So, here is a very simple way to have the batteries tell you. It is undeniable the flat charge discharge profile of LiPo with the steep slopes at either end of the cycle. Take the time to connect your voltmeter to the terminals of the battery bank. Run the bank through whatever charge cycle you choose. Plot the voltage until you start to see the upward curve. Take it as far up the curve as you dare. At the same time record the voltage shown on your charger panel. You know have a tool to evaluate whatever charge profile you choose to use. It is applicable to your batteries, with your charger, and your cable, and your connections. Is it time consuming. Yes. Is it confidence inspiring. Absolutely.

For grins, use the inverter and some decent loading and do the same voltage recording as the bank discharges. You will eventually start to fall off the voltage cliff. Again, record both the voltage at the bank recorded by your meter, and the voltage indicated on your inverter. You know have data to decide where to set the low battery cutoff, and recharge initiation setup.

Because I have an external BMS, I also used this data to set the BMS just outside the charge / discharge parameters I put into the charger/inverter. I call that the belt and suspenders approach.

I have not mentioned one single voltage/current setpoint intentionally. What works for my bank may be different than what works for yours. What I outlined above is a simple method for KNOWING how your bank behaves so that you can make informed decisions about how to set up the parameters.

Being a techie nerd, I did not have the patience to record the data by hand so I used a data logger talking to my laptop.

And one last non standard thought. Sticking with ‘the batteries will tell you”, I do not use time or voltage to determine when bulk is complete. I use return amps. As the bank fills, it’s internal resistance changes, and the bank begins to accept less and less current for a given voltage. I use 5% of C to stop the bulk charge.
That is solid advice, thank-you. Since my rig's converter is 24 years old the panel uses an analog needle for voltage and a 8 step led light for amperage. lol. So yeah, don't need to worry too much about .1v variances here.

I am planning on using the Smart BMS bluetooth via smartphone app to monitor voltages, etc., and am also hoping to install the battery right next to the converter, so I expect that voltage drift due to long wire runs, etc. won't be a factor here. To your point, it will be interesting to see how the converter's set voltage charge points reflect in the actual battery voltages.


Quote:
Originally Posted by hclarkx View Post
I have a 322 Ah LiFePO4 and get three days with a CPAP machine, 12V fridge, microwave and lots of other stuff totaling about 80 Ah in 24 hours. A lot will depend on the fridge and how warm it is where you camp. My 12V is well insulated and fairly miserly to start with. A residential unit may not do as well. My fridge (without my added insulation) does a 50% duty cycle at 70F and 100% duty cycle at 100F. ((100F about doubles the temperature difference between the inside of the fridge and the ambient relative to 70F so doubles energy use))
It's a crap shoot in terms of capacity for me, but since we're far from full timing, and with the genny right there it's less critical. I'm the opposite of a generator-head so would like to avoid using it a lot, but every couple or 3 days for a few hours is manageable. I'd like to add a bunch of solar but then might as well sell the generator to pay for it since I'd have no use for both.

Quote:
Originally Posted by hclarkx View Post
I store in my yard so it's easy to drain the battery down to 50% over a couple of days after arriving home. I'm guessing this isn't an option for you.

Yup. With ample life, go with convenience. Mine stores at 50% but on the road it hits 100% (more or less) on sunny days, ready for inclement weather. We camp a lot on the CA Central Coast where clouds and fog are not predicable.
I have to store it at a lot not super close to the house. The cells self discharge at up to 3% per month, so not a lot. Thinking about it now, I might try just leaving the 12v on in the coach when stored (with the inverter off), it would probably takes weeks to discharge the battery with only that load on it.

Quote:
Originally Posted by hclarkx View Post
My prismatic batteries (both Lifeblue and home brew) get to 99% before any absorb time. I'm not sure cylindrical cell batteries like BB do. I've also charged at 13.5V (set precisely) and gotten to 99%. It took six hours to get from 90 to 99 so it's slow but does get there. 13.4V should as well. So, there's no way, at least with prismatic cells, to not charge to near 100% (without interrupting the charge). Some people say 13.8 will get the battery only to 90%, but in my experience and from what I've read, there's no good way to stop at less than 99-100%. So one might as well live with whatever life 99% brings.
Yeah, with any charger that forces absorption it seems impossible to not eventually charge to 100% anyway. Just less efficient with lower voltage.

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Originally Posted by hclarkx View Post
I have a Lifeblue that is warranted to have 83% remaining capacity after 2800 100% DOD cycles. Prismatic cells. Though this is with a battery that actually delivers up to 10% more capacity than rated, so a 100% DOD is really more like 90% DOD.
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Originally Posted by hclarkx View Post
I'd appreciate a reference to any data suggesting 20-30% life loss from the last 2 or 3% charge.

I agree re prismatic cells. Interestingly BB recommends charging to 100% then disconnecting. I'm guessing, but would bet they make this recommendation to make life simple for themselves and their customers. Who's going to notice 10% loss of life in a battery than may last 10-20 years!! Or maybe their stated 2-3% charge loss per month brings the charge down soon enough. Incidentally, this 2-3% to me suggests a difference between cylindrical and prismatic cells.
I think a lot of that type of "wisdom" stems from Li-ion in EVs and such. It's counter-intuitive to think that you can just charge the battery to 100% and drain it to zero without consequences. We've all got "battery PTSD" from the difference best-practices we had to learn with each new generation of battery tech (lead-acid: don't discharge below 50%!, NI-MH: drain the battery before charging!, Li-ion: live between 80%-20%!)

If you think it about it, voluntarily limiting your charge cycles to 80% of capacity to avoid possible 10-15% capacity degradation over thousands of cycles seems asinine. You're choosing to lose 20 % of your capacity the entire time you own the battery to avoid potentially losing 15% years down the road...

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Originally Posted by hclarkx View Post
The need for balancing is more related to the currents you draw. Microwave and A/C users will see more need for balancing.

Another reason to get to 100% fairly often is to avoid the SOC reading drifting up relative to actual SOC. Most monitors including BMSs with BT ignore the small but non-zero Peukert's constant for LiFePO4 batteries. Monitors reset only at the end of a charge cycle and are accurate only if that charge cycle hits 100%. Some LiFePO4 makers suggest getting to 100% weekly for this reason.
I'll be cycling infrequently anyway, so maybe once a season would do it, though as noted above, I doubt I can prevent my battery from going to 100% most of the time, even charging to lower voltage the absorption will probably fill the tank.
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Old 12-04-2021, 11:01 AM   #68
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Note above I never advocated limiting charge to 80%, though I did advocate limiting to 95-98% charge most of the time. What I said was to limit to 80% charge while in long term storage, or when not camping off grid, ie when you plan to have full hookups for weeks/months
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Old 12-04-2021, 11:28 AM   #69
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Originally Posted by Isaac-1 View Post
Note above I never advocated limiting charge to 80%, though I did advocate limiting to 95-98% charge most of the time. What I said was to limit to 80% charge while in long term storage, or when not camping off grid, ie when you plan to have full hookups for weeks/months
The thing is the SOC degradation in storage seems to come from the higher voltage per cell lithium chemistries like NMC that are used in EV's. LifePo4's are lower voltage per cell at full charge 3.4v-3.6v per cell vs 4.2v, based on the little I know around battery chemistry and degradation the potential driven aging is not as pronounced on LifePO4 because its at a lower voltage, 3.6v per cell is only like 60% charge on an NMC battery.

Battelborn's CEO says months and months floating at 13.6v is "perfect" while 14.4v they would recommend not doing for extended periods but will not really be that bad. What is bad however is storing at high temps say above 100f constant, the lower the temp the longer they can be stored actually.

Here is some research I dug up on LifePO4 aging at different temps and SOC's as you can see temperature has a very large effect while the difference between 100% and 50% SOC is negligible at any of those temperatures, 10% SOC seem to be more noticeable however you would not want to do that normally because of self discharge unless you floated that low.

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Old 12-04-2021, 01:37 PM   #70
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Quote:
Originally Posted by Isaac-1 View Post
Note above I never advocated limiting charge to 80%, though I did advocate limiting to 95-98% charge most of the time. What I said was to limit to 80% charge while in long term storage, or when not camping off grid, ie when you plan to have full hookups for weeks/months
Right. Sorry if I made it sound like that, I wasn't directing that at you at all, was just a general observation that I've made.
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