A couple basic questions about starting with lifepo4

[Chotu]

just got half of my electrical system set up this morning.

I pulled out 440 amp hours of Trojan T105s

I put in one of the two 200 amp hour LIFEPO4 batteries.

I needed to do this because 75% of the capacity of my other batteries were wrecked. Not by me. This caused me not to be able to keep up with the refrigerator and freezer aboard.

Questions:.

1). I set my outback charge controller to 14.4 bulk voltage and 13.2 float. these were numbers that were from my manual. I could have done 14.6, but I went with the more modest one. it seems to be working gangbusters getting about 30A on average from 2 of my 4 panels.

The question is, why is it charging at 13.6???? I would have expected to see 14.4 and then 13.2.


2) I am supposed to charge each of these batteries individually to full capacity to balance the cells, then hook them up in parallel together to balance the cells amongst each other.

I can’t do that. I’m off grid. And I was losing some food. So I took one of them and put it into the system and I am charging it up with solar right now. It’s partially cloudy so I may kick on the generator for a couple hours to make sure it charges up nicely. All of the loads I have on today are less than what is required to charge the battery, so there is still juice always going into the battery. It’s just varying from around 18 A to maybe 7 A when the clouds go by.

is this going to be all right? Is this enough of a charge? It’s continuously positively charging, but it’s not charging quickly. I just have to make sure I get it all the way up by evening. Which means I probably have to use the generator. I have a 90 amp charger that can blast this thing up pretty quickly.

any guidance from the LIFEPO for pros? This is my very first time using them.

[CaptainRivet]

Originally Posted by Chotu

just got half of my electrical system set up this morning.

I pulled out 440 amp hours of Trojan T105s

I put in one of the two 200 amp hour LIFEPO4 batteries.

I needed to do this because 75% of the capacity of my other batteries were wrecked. Not by me. This caused me not to be able to keep up with the refrigerator and freezer aboard.

Questions:.

1). I set my outback charge controller to 14.4 bulk voltage and 13.2 float. these were numbers that were from my manual. I could have done 14.6, but I went with the more modest one. it seems to be working gangbusters getting about 30A on average from 2 of my 4 panels.

The question is, why is it charging at 13.6???? I would have expected to see 14.4 and then 13.2.


2) I am supposed to charge each of these batteries individually to full capacity to balance the cells, then hook them up in parallel together to balance the cells amongst each other.

I can’t do that. I’m off grid. And I was losing some food. So I took one of them and put it into the system and I am charging it up with solar right now. It’s partially cloudy so I may kick on the generator for a couple hours to make sure it charges up nicely. All of the loads I have on today are less than what is required to charge the battery, so there is still juice always going into the battery. It’s just varying from around 18 A to maybe 7 A when the clouds go by.

is this going to be all right? Is this enough of a charge? It’s continuously positively charging, but it’s not charging quickly. I just have to make sure I get it all the way up by evening. Which means I probably have to use the generator. I have a 90 amp charger that can blast this thing up pretty quickly.

any guidance from the LIFEPO for pros? This is my very first time using them.

Better post in lithium section

[rslifkin]

If there are any settings for temperature compensation, disable it.



Beyond that, you may not be getting to 14.4 because the batteries aren't full yet, so the current power flow into them isn't able to push the voltage that high. Once they're closer to full, voltage will come up.

[Adelie]

Originally Posted by Chotu

just got half of my electrical system set up this morning.

I pulled out 440 amp hours of Trojan T105s

I put in one of the two 200 amp hour LIFEPO4 batteries.

I needed to do this because 75% of the capacity of my other batteries were wrecked. Not by me. This caused me not to be able to keep up with the refrigerator and freezer aboard.

Questions:.

1). I set my outback charge controller to 14.4 bulk voltage and 13.2 float. these were numbers that were from my manual. I could have done 14.6, but I went with the more modest one. it seems to be working gangbusters getting about 30A on average from 2 of my 4 panels.

The question is, why is it charging at 13.6???? I would have expected to see 14.4 and then 13.2.


2) I am supposed to charge each of these batteries individually to full capacity to balance the cells, then hook them up in parallel together to balance the cells amongst each other.

I can’t do that. I’m off grid. And I was losing some food. So I took one of them and put it into the system and I am charging it up with solar right now. It’s partially cloudy so I may kick on the generator for a couple hours to make sure it charges up nicely. All of the loads I have on today are less than what is required to charge the battery, so there is still juice always going into the battery. It’s just varying from around 18 A to maybe 7 A when the clouds go by.

is this going to be all right? Is this enough of a charge? It’s continuously positively charging, but it’s not charging quickly. I just have to make sure I get it all the way up by evening. Which means I probably have to use the generator. I have a 90 amp charger that can blast this thing up pretty quickly.

any guidance from the LIFEPO for pros? This is my very first time using them.

Why 13.6v? My guess is that the battery is discharged enough that at full amps the charger can provide, that's the voltage that results. As the battery approaches full voltage will rise to 14.4v.

[Chotu]

Ohhhh!

That’s why I asked. I thought that the BMS was basically just receiving power essentially from the charging system and converting it to whatever it wants. So I figured it would always be at the set voltage.

but these answers makes sense. It’s working kind of like FLA. which I hadn’t expected.

Just to make sure I get the battery balance set up and charged up nicely before actual discharge tonight, I’m running the generator for a few hours and pissing everyone off around me. Lol

It's accepting 72A from the charger right now. Holy cow!!! On a 200A battery.

[wholybee]

When bulk is set to 14.4V, that doesn't mean the battery will be charged *at* 14.4, rather, that battery will be charged at whatever current the charger can provide, *until* the battery reaches 14.4V. That then triggers the next charging stage. With solar, that is going to depend on available sunlight, so the voltage can vary significantly.

It sounds like everything is working fine. It might take a long time (maybe a couple days if it's cloudy) to get to full charge, but you will, and then can proceed to charge the next battery.

[Adelie]

Yep, I think it’s like bulk charging a LA battery, when the battery can accept more power than the charger puts out voltage drops.

The BMS doesn’t not control charging except a simple On/Off switch when the battery is too hot or cold. The point of the BMS is to keep all the cells in a string equally charged. If 4 cells in a string are at 100% and the 5th is at 80% voltage will be high enough for the series that all the cells look full to the charger. On discharge if you go low enough the low cell will be fully discharged before the monitor on the string realizes so it will continue to discharge which permanently damages the battery. Or maybe it’s the other way around, it can’t detect when it’s full and 4 cells are overcharged and damaged.

[Chotu]

An wow! When these things are done, they are done!

I was resting a few minutes after lunch and heard a load drop from the generator.

I figured something went wrong and I overloaded the battery or something.

I got up to investigate and the batteries were full.

Solar is keeping them at 13.2/13.4 now and solar is powering everything while the battery has a nice charge that will power my refrigerator and freezer overnight for 2 nights. From one battery and half my electrical system hooked up.

Gotta revive that spectra watermaker and take some long showers once this is all hooked up.

[Adelie]

Yeah, it’s not like FLA, when they get to the end the voltage spikes fast.

[Chotu]

One more. Is it really a problem to have them full all the time? I can’t even use enough power to take up all the energy of one of my batteries. I have another one waiting in the wings to join the system. For redundancy mostly. My nightly energy budget is about 80AH. Maximum.

during the day, all I’m doing is creating a ton of power from the solar array.

The problem is I’m running off the shelf extremely efficient refrigerators and freezers here. My standup regular household refrigerator uses about 2A and my chest freezer not much more.

and this is only half of my electrical system. The other half is not hooked up yet. I have twice as much solar installed and ready to hook up. And I have twice as much battery installed and ready to hook up.

This whole electrical system was devised to be extremely efficient for lead acid batteries. As in, it would pull that 80AH each night out of a 440AH bank.

That saved tremendous weight as compared to an oversized bank as I took usage patterns into account (I sleep at night, no power is used). All the big loads happen during the day and are taken care of by the solar panels.

I hope to get my watermaker online sometime soon. That should take some power. But I am kind of stuck on what else to do with all of this electricity.

How bad is it for these batteries to leave them full all day? The one that's currently installed does cycle down in about 50% each night.

[rslifkin]

On solar where they're being cycled daily, I wouldn't consider it a problem to get to 100% and stay there for a few hours. Lowering the float voltage slightly will lower the SOC they settle at.



For a shore charger, I'd want the float voltage a little lower so they don't stay at 100% long term if you're somewhere that the boat is plugged in for a few days.

[CaptainRivet]

Originally Posted by Chotu

One more. Is it really a problem to have them full all the time? I can’t even use enough power to take up all the energy of one of my batteries. I have another one waiting in the wings to join the system. For redundancy mostly. My nightly energy budget is about 80AH. Maximum.

during the day, all I’m doing is creating a ton of power from the solar array.

The problem is I’m running off the shelf extremely efficient refrigerators and freezers here. My standup regular household refrigerator uses about 2A and my chest freezer not much more.

and this is only half of my electrical system. The other half is not hooked up yet. I have twice as much solar installed and ready to hook up. And I have twice as much battery installed and ready to hook up.

This whole electrical system was devised to be extremely efficient for lead acid batteries. As in, it would pull that 80AH each night out of a 440AH bank.

That saved tremendous weight as compared to an oversized bank as I took usage patterns into account (I sleep at night, no power is used). All the big loads happen during the day and are taken care of by the solar panels.

I hope to get my watermaker online sometime soon. That should take some power. But I am kind of stuck on what else to do with all of this electricity.

How bad is it for these batteries to leave them full all day? The one that's currently installed does cycle down in about 50% each night.

you will soon figure out what to do with your excess of energy. starting from induction cooking, over a a nice big freezer, washing machine till an ice maker all makes life on anchor more enjoyable :-)
and well there will be 3 days of bad weather when you are down to 20%. Having it full every day not a problem, just use more conservative end of charge 3,55V and recharge at 3,4 or lower. on long passage I raise to 3,65V and recharge 3,5V the day before so I have max capacity in the bank underway.
the hot water heater via an inverter is a welcomed power dumb too, my Elcyrodacus BMS switches it on when bank is at 80% SOC and off at 50% so always a hot shower when wanted. massive overpowered too so an AC for the owner cabin is approaching :-)
I can use 500AH a day if I want, average at 250-300AH but can scale down to 200AH if needed, there off my 2 big fridges and a big 160l freezer need 100-130AH alone plus Induction cooking.

[jordanbigel]

Originally Posted by Chotu

One more. Is it really a problem to have them full all the time? I can’t even use enough power to take up all the energy of one of my batteries. I have another one waiting in the wings to join the system. For redundancy mostly. My nightly energy budget is about 80AH. Maximum.

...

How bad is it for these batteries to leave them full all day? The one that's currently installed does cycle down in about 50% each night.

If you are concerned about longevity, there are a lot of people saying it is a problem.

And there are people out there saying it's NOT a problem.

I err on the conservative side and assume for the sake of argument that it IS a problem.

My solution was to wire my Alternator, battery charger (shore power), and solar controllers with cutoff relays wired to a Victron BMV and CerboGX. The relays turn on and off (enable disable) the charging sources based on SOC%. They can be adjusted at will, and I can set them separately, depending on needs. For the shore power charger, for example, I have it set to cycle between 30% and 75%.

For the Alternator I have it set to turn on at 50% and turn off at 75%, but I have a push button switch I can override (easier than fiddling with displays and settings) so that if I know I will be motoring a while and then plan to immediately use power from the bank, I will sometimes let it charge up to 90% then turn off the override.

For the Solar, I have it set to cut off at 90%, though frankly we use so much power and live aboard that the moment we stop charging at the SOC target, we are already using power, which means there is never a time where the bank sits at or near 100%. And I am a bit under-powered when it comes to Solar, so this never happens (we supplement solar with a genset which runs the AC battery charger just like the shore power would).

I will only charge above 100% once every 3 months to allow top balencing to kick in. Some say this is even too much, but most agree if you have quality cells in sync to begin with, it should be more than enough. And only when I know I plan to use power once the charge cycle is complete, so as not to leave the bank near 100% for more then a few moments/minutes.

Bottom line, as long as you keep drawing power, then a system which starts and stops charging sources, even if you go to 100%, will help your bank last longer. Float seems like a bad idea no matter what voltage you set. You need to manage charging using SOC% - that's a big mental shift but it came naturally to me in a short time.

So, if you charge to 100%, kill all charging sources completely, the bank's SOC% will begin to go down immediately, as long as you keep using power and get it down below 95%, and don't stop drawing power and let it sit for more than a few hours above 95% ever. But if you plan to completely stop drawing power, do not charge it anywhere near 100% - in that case, charging should stop well before 90%. Like I said, its a real shift in paradigm and way of thinking to divorce your thought process from thinking about voltage and focus on SOC%. (note that the only time voltage is really important is when you are attempting to charge to 100% periodically for the purpose of top balancing, in that case, I just override the SOC% relays and let the battery charger manage the bulk stage till it gets to absorption and float and then holds it at float for an hour, then shuts off. Then I re-enable the relay when the cycle is complete.

I know this is a lot. It took me 2 years to absorb all this, I hope I have most of it right! So far my bank has been in service for 9 months and it has been a joy.

A note about "cycling":
I don't worry about how many cycles I use with this approach - some say better to leave them at float and avoid "cycling" (some even claim there is a thing called "Micro-Cycling" which from my research does not exist) - but I quickly realized (with the help of mathematics) that a bank which is rated for 3,000 cycles will last me 16 years if I change it 90% every other day, but 32 years if I only charge it 50% each day (thus, I go from 30-75% every 2 days) - this is based on my understanding (also gained from CF) that a "cycle" is not if you charge 10amps and then draw 10amps, its when you draw 100% of the rated power and then replace 100% of the rated power, so I size my bank to be 400% of my avg daily need, and thus every 2 days I have used 50% of my bank, which then gets me to 1 cycle every 4 days. My bank will last 32years. Of course, the other factor is atrophy over time unrelated to how much power you put in or take out - they lost capacity by some percent each year just from aging, but still, I don't want to risk shortening their lives for no good reason, and I dont see any good reason to charge to anywhere near 100%.

Hope some of this helps.

[Chotu]

Thanks, Jordan. I only just saw this.

I have noticed a strange change. But maybe my battery monitor is not set up properly for these batteries I don’t know.


The day I got them, I charged them all the way up like it says to do, and I was getting 70 amp charging rates on a 200AH battery.

Now I am down to say, 140-160AH missing and I’m not seeing charging rates of even half that on the same charger.

These figures are all read on my linklite battery monitor. Going through the shunt.

What might be the cause?

They seem to take the solar charging rate just fine at 20-30amps. But they seem to limit my 90 amp AC powered charger as compared to the first day

[jordanbigel]

Originally Posted by Chotu

Thanks, Jordan. I only just saw this.

I have noticed a strange change. But maybe my battery monitor is not set up properly for these batteries I don’t know.


The day I got them, I charged them all the way up like it says to do, and I was getting 70 amp charging rates on a 200AH battery.

Now I am down to say, 140-160AH missing and I’m not seeing charging rates of even half that on the same charger.

These figures are all read on my linklite battery monitor. Going through the shunt.

What might be the cause?

They seem to take the solar charging rate just fine at 20-30amps. But they seem to limit my 90 amp AC powered charger as compared to the first day

I wish I could help, your description certainly makes it sound like something has changed, but not knowing much about your setup, I hesitate to spout off like I am qualified!

I do know that the amount of amps a LFP battery can accept is governed by the BMS, the first thing I would do is check the specs on the battery/BMS and see what the max charging amps is - some drop-in batteries of that size, from what I have seen, have a max charging capacity of only 50amps (.25C), a better battery would be 100amps (.5C) or even 200amps (which would be 1C). For example Battle Born drop-ins are .5C max.

If the battery was taking 70amps one day and another day its only taking 30amps, if I understand you correctly, and nothing has changed on the charger side, I would wonder if something in the BMS has changed - I have no idea what these things do when the "go bad", or if this is a feasible outcome of something failing internally, but this is where I would investigate.

Hopefully someone more knowledgable will pipe up here and offer better advice.