Tweaking lithium battery charging?

[whitewolf]

Class C, 2 Battleborn 100, 510w solar, Victron controller, Magnum charger/inverter.

Most of the time I don't even think about my system. It works fine. But the other night it was unusually cold and the furnace was too much for the batteries and they kicked off. So we know that lithiums don't like to be fully charged all of the time. Both the Victron and the Magnum are set up to not fully charge them all of the time. The solar usually only charges them to about 13.5v. Someday we'll probably be able to yell at the charger, "Hey, it's going to get cold tonight. Maybe you should take them babies up above 14v". In the meantime I've increased the float charge on the Magnum to 14 even though that is not what is recommended. Then I run the generator for about 20 minutes and go to bed much happier with the higher voltage. Am I even thinking about this in the right way? I'm not very bright. I don't want to be messing with the charging parameters all the time and I don't feel like I need more battery since they're fine 95% of the time. I just would like a little more oomph once in a while.

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[Elbear1]

Im no expert on the topic of lithiums but id research a bit higher charge voltage especially now that its getting colder. Set charge controller to 14.0v see how that does. You shouldnt be able to fill what 180+ah with 500w this time of year anyway.

 

[Elbear1]

May also need to check cell balance

 

[highdesertranger]

are you even supposed to charge and discharge Lithium below 32°? highdesertranger

 

[willprowse]

Yeah you can discharge LiFePO4 down to -20 Celsius. But you can only charge down to 0 degrees Celsius.

And charging up to 13.6 not a good idea with this chemistry because voltage settles a lot. Not like NMC or NCA. Charge curve is a bit different too. In my capacity tests, charging to 14.1 will hit 95% capacity. Charging them up to full is not a big deal. The iron phosphate lattice is crazy strong and electrolyte degradation doesn't occur till 4.2 volts per cell ( and most charge to 3.65v per cell).

So don't worry about it. Charge them up to 14.1-14.5

The reason people are scared to charge up to full for increased cycle life is due to the NMC battery studies. But LiFePO4 is a very different chemistry.

 

[highdesertranger]

so I know that 0°C is 32°F, but without having to look it up what is -20°C.

can you explain the term "voltage settles"? and why should I worry about this?

please define your abbreviations "NMC" and "NCA" how does this relate to our lifestyle?

what is "iron Phosphate" lattice? why should this concern me?

what is "electrolyte degradation"? and why should I be concerned with it?

all this technical jargon is great if you are trying to impress some one. but here you should be trying to teach people not awe them. please dumb it down and explain it so we can understand.

highdesertranger

 

[whitewolf]

Yeah, but we get scared cause we want them to last; they're so dang expensive. Yet so wonderful. It's that time of year again with shorter days and one has to start thinking about the juice more after cruising all summer. Folks have told me to set both bulk and float on 14+, but that is not what Victron or Magnum recommends for lithium. My new 50A Victron has the auto lithium setting as 13.5 float. So you think I should go back to "user defined" with a 14 float? Thanks.
And no I don't charge when it's cold. I'm never anywhere where it's that cold during the day so I don't worry about the solar. And if I'm plugged in I turn the Magnum charger off. I think the BMS on the lithiums is supposed to prevent that anyway but I'd rather not chance it.

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[willprowse]

-20c is -4f

Voltage settling is the decreased voltage after the cells end charging. The voltage simply settles to a lower voltage

Nmc and nca are common battery chemistries. I don't see anyone questioning people like you are questioning me when they say "lead acid". Do you ensure people explain what lead acid is Everytime you help them? Nmc is nickel magenese Cobalt oxide. But there are variations. Nca is nickel Cobalt aluminum oxide. Super common. Nothing I'm saying here is unique or special. Goal zero uses nmc. Ev cars use nca.

Iron phosphate lattice is in every LiFePO4 battery on the anode. Nothing hard to understand here and common lithium battery talk. I'm not trying to impress anyone.

Electrolyte degradation is one form of internal battery damage that decreases batteries life. That's all.

Nothing I said is considered jargon for people who are using solar for their RVs or vans. I have seen this level of difficulty in posts here about lead acid, and no one complained. I could make it a hundred times more complex, but left my comments easy to Google if someone is a beginner.

 

[willprowse]

No, victron recommends a higher absorption voltage. Float doesn't matter as much. It is only there to compensate for loads. Keeping your battle borns at 14-14.5 will be fine.

Biggest issue for ensuring your battle borns last a long time is to use them in a environment that is under 77 degrees Fahrenheit. And never charge at more than a .4c rate (this was mentioned by battle born from their testing). .4c charge rate is 40 amps into a 100 amp hour battery.

Does that help?

 

[willprowse]

I promise that your battle born low temp cut off is dependable. No need to worry. Their warranty is amazing. Just keep the batteries in a cool place and charge them up to 14-14.5v and you are set no need to worry

 

[Ticklebellly]

Storing LiFePo4 at full or near full charge is not recommendednby any source I have seen. I constantly cycle mine so have no concerns there. My circle of fellow users pretty well all charge to 14.1 or 14.2 as 95% and as a way to avoid, mostly, need to balance cells. No float. I use 11.8 as Low Voltage Cutoff, which is about 15%. No one amongst my friends has reported concerns about charging at extreme temps. OAT down to -10C is invariably avoided when the batteries are installed inside. A forecast Max of 45C to 50C ambient just encourages people to charge early in the day. If the day is going to get that high, likely early sunshine will allow solar charge to finish well before 10:00.

I increasing see recommendations to take LiFePo4 to 14.5 to 14.6. I am not going to go there because what I do now works for me and only the EV guys seem to get anything out of the higher charge level.

 

[highdesertranger]

Ticklebelly please define your abbreviations, what is OAT? and convert you Celsius into Fahrenheit please. you are speaking to people who for the most part have know idea what you are talking about. a few do but most don't. highdesertranger

 

[abnorm]

^^^^^^^^""Biggest issue for ensuring your battle borns last a long time is to use them in a environment that is under 77 degrees Fahrenheit""


WHAT ?...……..How is that even possible ?

 

[willprowse]

^^^^^^^^""Biggest issue for ensuring your battle borns last a long time is to use them in a environment that is under 77 degrees Fahrenheit""


WHAT ?...……..How is that even possible ?

With some form of cooling or storing in a well vented battery compartment. In my RV, I have my battery cells in the living area so I can keep them cool.

And yes, keeping them at high state of charge will degrade any battery, much faster. If you keep them fully charged AND in a hot environment, anything over 85 degrees Fahrenheit, degradation will rapidly increase. Keeping them below 77 degrees Fahrenheit is ideal. I actually have a few videos that cover these battery studies in details. Thermal stability of LiFePO4 is much higher than other chemistries though, but capacity loss is problem for RVs and vans that are in 100+ degree weather for prolonged duration.

Let me know if you want me to explain anything further or post some thermodynamics studies. We just discussed this topic amongst my friends. Lots of fun literature available on this

 

[jonyjoe303]

Do you have coulombmeter recording amps in/out, that is the best way to keep from draining the battery too low and also to see if you need to raise the bulk setting on your controller.

If you have voltage drop from controller to battery, you will be undercharging your batteries everyday (not a big deal with lithium) but eventually they will be empty when you need them the most.

I charge my lifepo4 to 14.6 volts every day, the only way I can get them that high on solar quickly is by setting the bulk setting to 15.5 volts, if I set the controller to 14.6 volts they will never reach a full charge. Thats what voltage drop will do. Always check voltage at battery terminals and bounce that with what the controller shows. I learned from charging lifepo4, the higher the bulk setting the more amps they get, which equals a quicker charge. When you spend top dollar for a battery you want to get max performance everyday. After 3 years of daily use, my 220ah lifepo4 is performing excellent.

 

[Cajunwolf]

@jonyjoe303

Good point, and here's the Coulomb Meter I used on my sailboat. They're not expensive.

Coulomb Meter on Amazon

Kudos! :thumbsup:

 

[whitewolf]

Thanks everyone, sorry I was on the road all day yesterday, not responding till now. OK, pump up the volume on the bulk. 15.5. Yikes. Interesting. This stuff is complicated. I do run into people who say "Solar charging? Oh that's simple!" With those people I immediately start inching towards the door.
The batteries will have to be happy in their home under the steps. It did say "drop in". I have no plans on moving them suckers in with me.
Making the roof panels tiltable does intrigue me. But as I said, 95% of the time the system works fine. Boondocking from PA to SoCal.

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[whitewolf]

Here's the Victron read out for the day the batteries shut down. You can see the day before when it started getting colder and the furnace began kicking on, they went down to 12.3v. If I had looked I might have taken that as a warning sign. I still believe if they were charged at 14+ that they would have made it. I usually don't turn off the whole house inverter but I do if I'm worried about having enough juice for the night. As I said shorter days and longer nights are here and one must adjust.

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[tripper]

I have been using Victron controllers with LiFePo4 batteries for several years now. The Victron controllers have a Lithium Iron Phasphate (LiFePo4) setting. When set to the stock lithium setting it will do bulk/absorb at 14.2 volts Absorption and 13.50 volts for float.

Looking at that graph your batteries never reach the bulk/absorb max of 14.2 volts on any of those days (assuming you set the controller to LiFePo4). The white bars on the graph mean bulk mode (absorb and float will show as two differing shades of blue), and it shows your batteries never charged enough to get to absorb or float modes. You are using too much power for the available solar power you have is my guess.

You also appear to be getting only 40% of you rated solar power, which is really low, do you have something shading the panels on the roof? This time of year you should be getting at least 400 watts P max. You could also try wiring them in series to get higher voltage less amps from the panels, which would help if you have really long wire runs or small gage wiring.

 

[Mobilesport]

I promise that your battle born low temp cut off is dependable. No need to worry. Their warranty is amazing. Just keep the batteries in a cool place and charge them up to 14-14.5v and you are set no need to worry



Will , I've been learning this stuff for awhile from a lot of different people and you are one of them , anyways I've been trying to simplify all of the info and I think I got it.

Step one ,,,if you don't know what your doing just pay the xtra money for a prebuilt battery that has everything already  set up for you .
For example  if you buy a 100 ah Battleborn  
Battleborn specs on there website say that there battery wants to be charged from a battery charger  that has a 14.4 volt output.
This is called your target voltage.

So you need the correct target voltage , mine is 14.4 volts since I have a 100 ah Battleborn 

You need the correct duration , 
Duration is just the amount  of time that you charge , this is important because you don't want to overcharge. 
Over charging isn't that big of a deal with a prebuilt Battleborn or simular because the Battleborn has a  internal battery management  system that will protect  from overcharging  , but you still want to shut off charging when the battery is full.
 
I know my battery is done charging  when my  battery is to about 90% soc , I used to go to 100% soc.
I figure out what my state of charge % is by using a state of charge capacity monitor.
The monitor will read 0% when empty and 100% when the battery is fully charged
You could also use a timer to select a shut down time to prevent overcharging .

Charge rate , 
Charge rate is how many amps your charger puts out.
My charger is a 50 amp charger because I have 100 ah lifepo4.
If you have different battery you might need a different charge rate.

I'm no expert on this stuff, I'm still learning but I've learned to build a system that works for me .
And as for having to have a exspensive charger , you can buy a 12 volt 50 amp adjustable voltage power supply for about $150 , dial in your target voltage and you have a cheap Bulk/absorption charger but you would need to add a fan to keep it cool , or buy a actual 14.4 volt charger or whatever you need for your particular battery.
Alternator charging ? I heard that's a bad idea. Too exspensive anyways.
I Believe that you need no more then 100 ah lifepo4 if you have a good charging system because they charge so fast.