A couple basic questions about starting with lifepo4

[Chotu]

Originally Posted by newhaul

The Peukert Exponent setting of 1.00 would be correct as there is almost no losses in charging. Lifepo4 are iirc 97% efficient when charging and discharging .

Agreed. I think that’s what’s tripping up my amp hour counter

[SV Confianza]

Battery monitoring for LFP is just not great because of how it's measured and the voltage curve. I have to recalibrate my viltron smartshunt every couple of weeks if I don't get to a full charge (which is rarely as a full time cruiser).

Does your battery manufacturer have monitor settings listed? If not, I would just use the ones battle-born lists (this is for a victron):

Battery Capacity: Total Ah of your bank of batteries
Charged voltage: 14.4V but note that this number should be about .1 or .2 volts below the charging voltage set in your charging device
Discharge Floor: 0%
Tail Current: 2-4% is good
Charged Detection Time: 3m
Peukert Exponent: 1.05
Charge Efficiency Factor: 99%
Current threshold: 0.10A
Time to go averaging period 3m
Battery Starts Synchronized: blue button should be to the right
State of Charge: leave alone
Synchronize SOC to 100%: Leave alone, this device will sync itself at the top of the charge
Zero Current Calibration: Leave alone

If you have your charging sources set up properly, you won't overcharge.

I was just looking at your original images again. And I'm not sure that your charging profile is set right on your solar controller. There should be three stages: bulk, absorption, and float. LFPs don't really need absorption or float, but FLA and AGM do, so you need to set them.

I believe that what's on the panel is actually the output voltage, not what it's reading from the battery, so it's too low. 13.6v is very much on the safe side, and nothing bad will happen, but you won't get charged all the way up, and it'll be slower. From what I understand, you can eek out some extra cycles being this conservative, but you also want to get as much from your solar as you can while you have sun.

Again, this is from battleborn, but they are all relatively the same:

absorption voltage: 14.6 volts (acceptable range is 14.4 to 14.6 volts)
Absorption Time: The recommended settings for our lithium batteries is half an hour per 100ah of LiFePO4 battery (for example if you have 2 -100ah batteries select 1 hour).
Float Voltage: 13.5 volts (13.6 volts or lower is acceptable for LiFePO4 batteries)
Equalization voltage: 14.4 volts (you do not need to equalize Lithium ion, you will have equalize turned off, but incase it ever runs a cycle the batteries will be fine at this voltage)
Temperature Compensation: should be disabled on Lithium Deep Cycle batteries because they do not need to be compensated, leave this off.
Low Temperature cut-off: Our Battle Born Batteries have low temperature charging protection built into the battery, it’s monitored by our Battery Management system which is also built in. You can leave this off too, some other brands do not protect your battery against damage from low temp charging, we do, we have got you covered.

Also, when you're adding the second battery...

The thing you're worried about is hooking them together at different SoC (state's of charge), because the batteries will try to balance themselves. LFP's can put out a TON of power if asked of them. So if you connect a low SoC battery to a high SoC battery, the high SoC battery will send TONS of amps to the low SoC battery. You could even overheat your cables. LFP batteries will charge and discharge at rates that can damage the batteries and/or burn up your cables.

That's why you want to get them as close as possible. If you only have solar, I would recommend charging one battery to close to full (or full), and then swapping it out for the second battery. Charge that one up, and then connect them together.

I did managed to add a 5th battery to my bank when they all weren't fully charged. I had to shut off the bank first, measure the bank with a multimeter at rest, then put a draw on the 5th battery (disconnecting every once in a while to get the actual resting voltage), and then connect. No light show...

Ah, and one more thing. You said you were charging at 70A on a 200AH battery. Depending on your battery, that might not be great. Most LFP batteries seem to be perfectly happy accepting .25C (or 50A in the case of your 200AH battery) all day every day. The C rating is the comparison of AH in the bank to the Amps charging. So 100AH bat, charged at 100A, is 1c. 200AH bat, charged at 100A is .5C, etc.

Your battery might be rated for .5C or even 1C charge rate (100A or even 200A), but charging that fast will degrade it. Sure, it will accept it, but it's not good for it (for MOST LFP batteries).

When you add the second battery, 70A is just fine, as you'll be below .25C. YOu'll have 400AH capacity charging at only 70A (.175C).

I would double check with your battery manufacturer though to see what C rate they recommend charging on a daily basis

[Chotu]

Thread closed! Ha ha ha. (No its not, Pete7)

SV Confianza has singlehanded written the beginner’s intro to LFP batteries.

Very well done. Thank you.

About my charge controller settings. They have those stages automatically. But you just set them to various voltages. So you set absorbing to 14.4. Then the float goes to 13.2. Which essentially just shuts them off for float.

Those are the settings I’m using. I think that’s correct. Right?

Also the equalization charge is set to happen “as never as possible “ and set at 14.4 if it does.

My instructions do not show anything about the battery monitor. Unfortunately. But with the numbers you posted above and me reasoning out that the Peukert exponent needs to be set to 1, hopefully it will work out pretty well. Along with the other settings you put in above. Which I will try to enter into my battery monitor if it accepts them.

I got a little bit lucky. I am at a Rigger right now. So, I can plug in and charge both batteries all the way up before connecting them together. I will do that before leaving the dock.

[Chotu]

there is one little oddity with my installation.

I am now running all 400AH of lifepo4. ridiculous amount of power. I conserve a lot of power so this is a lot for me. Extra.

The problem I’m running into now is they fill all the way up, and then I get these weird little voltage spikes when they fill up all the way.

I don’t understand it. The outback flex 60 charge controller is set for 14.3 V cut off on charging. I lowered that from 14.4 which is what the manual had said for my batteries. Just because I thought that had something to do with the voltage spikes.

The outback alsi has a float voltage set at 13.2. essentially that should eliminate float voltage as a charging source.

The problem is once it gets all the way full and it starts to change over to that float voltage, I get this spike to 15 point something for a second or two. Then my inverter explodes and sets off alarms for overvoltage. And everything is all messed up. it will keep doing this over and over again. Within about a 2 to 5 minute interval.

I will reset things, then it will be charging a little bit, and then boom I have I hear the alarms going off.

I don’t understand what could cause this.

I do know what stops it however. If I turn off the solar panels, providing no power to the charge controller from the solar, it draws down the battery just fine from 100% full.

it only does this weird voltage spike when it is 100% full.

This doesn’t occur until the batteries are trying to transition from a charging state to a completely full state.

Note: this was a lot more likely to happen with my 200AH bank than my currently completely hooked up 400AH bank, Since it only happens when the battery is completely full and something is deciding that it’s done. i’m hoping to waste a lot more power and keep the state of chargeva bit lower so I don't run into this walk too much.

However, I’d really like to figure out why it’s spiking like that.

[newhaul]

Originally Posted by Chotu

there is one little oddity with my installation.

I am now running all 400AH of lifepo4. ridiculous amount of power. I conserve a lot of power so this is a lot for me. Extra.

The problem I’m running into now is they fill all the way up, and then I get these weird little voltage spikes when they fill up all the way.

I don’t understand it. The outback flex 60 charge controller is set for 14.3 V cut off on charging. I lowered that from 14.4 which is what the manual had said for my batteries. Just because I thought that had something to do with the voltage spikes.

The outback alsi has a float voltage set at 13.2. essentially that should eliminate float voltage as a charging source.

The problem is once it gets all the way full and it starts to change over to that float voltage, I get this spike to 15 point something for a second or two. Then my inverter explodes and sets off alarms for overvoltage. And everything is all messed up. it will keep doing this over and over again. Within about a 2 to 5 minute interval.

I will reset things, then it will be charging a little bit, and then boom I have I hear the alarms going off.

I don’t understand what could cause this.

I do know what stops it however. If I turn off the solar panels, providing no power to the charge controller from the solar, it draws down the battery just fine from 100% full.

it only does this weird voltage spike when it is 100% full.

This doesn’t occur until the batteries are trying to transition from a charging state to a completely full state.

Note: this was a lot more likely to happen with my 200AH bank than my currently completely hooked up 400AH bank, Since it only happens when the battery is completely full and something is deciding that it’s done. i’m hoping to waste a lot more power and keep the state of chargeva bit lower so I don't run into this walk too much.

However, I’d really like to figure out why it’s spiking like that.

Then you have your answer something is not correct set on controller or misfires between the controller and battery .

[newhaul]

Originally Posted by Chotu

there is one little oddity with my installation.

I am now running all 400AH of lifepo4. ridiculous amount of power. I conserve a lot of power so this is a lot for me. Extra.

The problem I’m running into now is they fill all the way up, and then I get these weird little voltage spikes when they fill up all the way.

I don’t understand it. The outback flex 60 charge controller is set for 14.3 V cut off on charging. I lowered that from 14.4 which is what the manual had said for my batteries. Just because I thought that had something to do with the voltage spikes.

The outback alsi has a float voltage set at 13.2. essentially that should eliminate float voltage as a charging source.

The problem is once it gets all the way full and it starts to change over to that float voltage, I get this spike to 15 point something for a second or two. Then my inverter explodes and sets off alarms for overvoltage. And everything is all messed up. it will keep doing this over and over again. Within about a 2 to 5 minute interval.

I will reset things, then it will be charging a little bit, and then boom I have I hear the alarms going off.

I don’t understand what could cause this.

I do know what stops it however. If I turn off the solar panels, providing no power to the charge controller from the solar, it draws down the battery just fine from 100% full.

it only does this weird voltage spike when it is 100% full.

This doesn’t occur until the batteries are trying to transition from a charging state to a completely full state.

Note: this was a lot more likely to happen with my 200AH bank than my currently completely hooked up 400AH bank, Since it only happens when the battery is completely full and something is deciding that it’s done. i’m hoping to waste a lot more power and keep the state of chargeva bit lower so I don't run into this walk too much.

However, I’d really like to figure out why it’s spiking like that.

Alternatively set your controller for 13.8v which is about 99% charged . Which should solve the issue

[Chotu]

Originally Posted by newhaul

Alternatively set your controller for 13.8v which is about 99% charged . Which should solve the issue

OK. I’ll give that a try. Because there really aren’t many settings in the charge controller. Just voltage settings for the cut offs.

Seeing as how the battery documentation says 14.4, and I am currently at 14.3, maybe I’ll just go down in .1 increments until I see this behavior stop.

Plenty of chances to try it as my solar panels are bonkers. Only half the array hooked up and no idea what to do with all the power.

I'm sure that will change with extended cloud cover and the rig up. But for now it's a lot of excess

[newhaul]

Originally Posted by Chotu

OK. I’ll give that a try. Because there really aren’t many settings in the charge controller. Just voltage settings for the cut offs.

Seeing as how the battery documentation says 14.4, and I am currently at 14.3, maybe I’ll just go down in .1 increments until I see this behavior stop.

Plenty of chances to try it as my solar panels are bonkers. Only half the array hooked up and no idea what to do with all the power.

I'm sure that will change with extended cloud cover and the rig up. But for now it's a lot of excess

I have a holding plate fridge and a watermaker that can use my excess power. Alternatively run the water heater.

[Chotu]

Originally Posted by newhaul

I have a holding plate fridge and a watermaker that can use my excess power. Alternatively run the water heater.

Yes! I have a Spectra water maker I need to revive and hook up. That should help.

I am already running a refrigerator and freezer and a deep freezer chest and still have too much power. But the water maker should take care of some of that.

[rslifkin]

You'll definitely find ways to use the extra power over time. And ideally, having more solar and battery than you know what to do with on a good day is perfect. Because that means you can handle that much more bad weather before you have to fire up a generator just to charge batteries.

[Chotu]

Originally Posted by rslifkin

You'll definitely find ways to use the extra power over time. And ideally, having more solar and battery than you know what to do with on a good day is perfect. Because that means you can handle that much more bad weather before you have to fire up a generator just to charge batteries.

Which could be good and bad. As those generators sit out there, not exercised, that’s not the best thing. Ha ha.

My original electrical system design consisted of a lot of solar and small battery bank. It also consisted of planning to run the generator almost daily. For a short amount of time for large draw items.

The theory behind that, which was very successful, is that I sleep at night. There’s nothing on but a refrigerator and anchor light when I am sleeping. I also actually do leave LED lights on all over the boat to light it up. To help with any collision potentials. So I don’t need a lot of power at night.

Then, during the day, The large solar panel array and potential genset run for some items takes care of all of my actual usage. No batteries required.

This is how I was able to engineer a very lightweight electrical system for this Catamaran, using FLAs. By doing it differently than people normally do.

But when my helper destroyed my battery bank, that left me open to needing to buy new batteries. So, it made sense to get the lithium batteries because they weigh less. However, they hold a lot more power as well. And they have that limitation that you aren’t supposed to keep them fully charged up. My system was always designed to keep the lead acid batteries fully charged.

So it’s an adjustment.

[bdgWesternMass]

LiFePo batteries don’t really suffer a memory effect keeping them topped up shouldn't cause you any problems.

[rslifkin]

Originally Posted by Chotu

Which could be good and bad. As those generators sit out there, not exercised, that’s not the best thing. Ha ha.

My original electrical system design consisted of a lot of solar and small battery bank. It also consisted of planning to run the generator almost daily. For a short amount of time for large draw items.

That's still a viable method. You'll still find times you need the gensets for A/C. And if you go electric for cooking and hot water, you'll have times where you want to cook a big meal on a cloudy day and it makes more sense to fire up a generator while you're cooking (and have hot water for a shower when you're done).

Generally with my generator, I don't worry much about time between uses as long as it doesn't sit for more than about 2 weeks. If it goes that long without needing it, I'll give it a good 30 - 40 minute run under load for exercise. But that tends to only happen early or late in the season if we're not traveling at that point.

[newhaul]

Originally Posted by Chotu

Which could be good and bad. As those generators sit out there, not exercised, that’s not the best thing. Ha ha.

My original electrical system design consisted of a lot of solar and small battery bank. It also consisted of planning to run the generator almost daily. For a short amount of time for large draw items.

The theory behind that, which was very successful, is that I sleep at night. There’s nothing on but a refrigerator and anchor light when I am sleeping. I also actually do leave LED lights on all over the boat to light it up. To help with any collision potentials. So I don’t need a lot of power at night.

Then, during the day, The large solar panel array and potential genset run for some items takes care of all of my actual usage. No batteries required.

This is how I was able to engineer a very lightweight electrical system for this Catamaran, using FLAs. By doing it differently than people normally do.

But when my helper destroyed my battery bank, that left me open to needing to buy new batteries. So, it made sense to get the lithium batteries because they weigh less. However, they hold a lot more power as well. And they have that limitation that you aren’t supposed to keep them fully charged up. My system was always designed to keep the lead acid batteries fully charged.

So it’s an adjustment.

Eventually it will come down to my mother's advice . If you don't use it in a year you likely don't need it. Goes for everything except tools.
Eventually I want to eliminate my yanmar portable generator and still cook on induction.

[sailorboy1]

Originally Posted by Chotu

there is one little oddity with my installation.

I am now running all 400AH of lifepo4. ridiculous amount of power. I conserve a lot of power so this is a lot for me. Extra.

I don’t understand it. The outback flex 60 charge controller is set for 14.3 V cut off on charging. I lowered that from 14.4 which is what the manual had said for my batteries. Just because I thought that had something to do with the voltage spikes.

However, I’d really like to figure out why it’s spiking like that.

Have you actually checked the battery voltage and calibrated the Flex 60 to it?

Did something like the frig cycle at the same time?
Have ou gone into the Flex 60 advanced settings and set a current and time for dropping into float?

I only have my Flex 60 set to 14.2V for 20 minutes or 10 amps before dropping into 13.5v float. What difference does it matter if batteries are only at 99% instead of 100% before float?