LiFePO4 batteries and maintenance

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3 hours ago, SwampNut said:

Exactly $4.44.

 

 

 

 

 

Supplies for the new RV batteries...

 

Carlos.....I'm not sure what you know or how familiar you are with LFP batteries, and I have no idea how much or seldom you use your camper...so here's a little nugget for you.  LFP batteries, generally speaking do not like to be stored at a full State of Charge (SOC)....and most manufacturers usually will tell you no longer than maybe a month.  Any non use after a month and they really need to be discharged down to between 40% and 60% SOC.  Doing that will help preserve the cells inside the battery for longevity.  In the winter time, when I do my winterization for the camper, after I'm done with that, I will hook up a 12V, 200W heating element and let the battery SOC start dropping until it's somewhere around 50%, then turn the main battery disconnect off so that there is NO load on the battery.  By springtime, I'm down in the mid to upper 30s on SOC.  They will self discharge a bit over the storage time, plus my BMS uses a very small amount of the battery since it's hooked directly up to the cells....but we're talking milli-amps....15 maybe 20 Ma

[DaveK]

My Lipo battery was used this past weekend - it ran a huge refrigerated and freezer cooler for 12 hours and only used 20% of its capacity. I was amazed. Having a fridge and freezer on a boat is a game changer. 
 

No ice rules. 

[SwampNut]

Every manufacturer says to store them at 100% if possible, and definitely never below 50%.  Maybe you're thinking of straight lithium.  Ferric-phosphate must be regularly charged to 100% to calibrate the BMS, and can be stored at 100%.  Tesla says to never go more than a week between full charges.  All of my RC toy LiFePO4 batteries say that too, but the lithiums (-ion and -poly) of course say to store below 70.

 

I'm considering buying a small solar panel to keep them full, and I suspect I can run it without a controller since these have a BMS, but not sure.

 

 

You can store a fully charged LiFePO4 battery. It is recommended to fully charge these batteries if you want to store them for longer. These batteries usually have a very low self-discharge rate. They normally discharge at 2% per month. It implies that when you store these batteries, they will lose 2% of their monthly charge. Discovering the battery from any attached load is recommended to ensure that no load draws additional charge and power from the battery. If you want to store the battery for a long time, it is recommended to charge it at more than 50% and, ideally, store it in a fully charged condition. The higher the charge, the larger the charge-retaining power of the battery during storage.
Users often assume there is no need to charge the battery as they won't use it and keep it in storage. They do not consider that batteries undergo self-discharge whether used or stayed idle. If you store your battery in a low or zero-charge state, then prepare to face major consequences. It is so because if your battery does not have enough charge, then after self-discharge of 2% per month, the discharge level reaches a limit where even BMS cannot protect the battery. Over-discharging can cause serious and irreversible damage to your battery even when it is under warranty. That is why storing the battery with a state of charge of more than 50% is recommended to be at a safe end.  

 

9 minutes ago, DaveK said:

My Lipo battery

 

Probably not Lipo.  This may seem pedantic, but as pointed out above, each type has vastly different needs.

 

 

 

[DaveK]

You helped me pick it out. It’s a Lifpo4

[DaveK]

I called the manufacture and they told me to leave it on the trickle charger all winter - nothing negative will happen. So I did. Hopefully I didn’t fuck it up. 

[SwampNut]

I was pretty sure that's what we were talking about.  Lipo would be in bad shape if you did that, this is the preferred method for this chemistry.  There's a reason they are the hot ticket right now for server power backup; they can live at 100% for 10+ years.

[DaveK]

So I don’t or do have a Lipo or is what I have different. 

[SwampNut]

You do not have Lipo, you have LiFePO4.  Lithium-ferric-phosphate.  Lipo is lithium-polymer, generally for small things like phones.  And there's lithium-ion which is common for cars and large storage.  LiFePO4 is vastly better in every way EXCEPT for size; it's much larger for any given power.  This is one reason most cars are still lithium, but the Tesla standard range uses LiFePO4.

[DaveK]

My bad. Apologies - I should have known better than to stick my nose in an electric related convo. 
 

All I know is - MY battery (lol) performed like a trooper this weekend. I was shocked with how little energy the Alpicool uses. I could run that thing for days on a single charge. 
 

 

[xrated]

2 hours ago, SwampNut said:

Every manufacturer says to store them at 100% if possible, and definitely never below 50%.  Maybe you're thinking of straight lithium.  Ferric-phosphate must be regularly charged to 100% to calibrate the BMS, and can be stored at 100%.  Tesla says to never go more than a week between full charges.  All of my RC toy LiFePO4 batteries say that too, but the lithiums (-ion and -poly) of course say to store below 70.

 

I'm considering buying a small solar panel to keep them full, and I suspect I can run it without a controller since these have a BMS, but not sure.

 

 

You can store a fully charged LiFePO4 battery. It is recommended to fully charge these batteries if you want to store them for longer. These batteries usually have a very low self-discharge rate. They normally discharge at 2% per month. It implies that when you store these batteries, they will lose 2% of their monthly charge. Discovering the battery from any attached load is recommended to ensure that no load draws additional charge and power from the battery. If you want to store the battery for a long time, it is recommended to charge it at more than 50% and, ideally, store it in a fully charged condition. The higher the charge, the larger the charge-retaining power of the battery during storage.
Users often assume there is no need to charge the battery as they won't use it and keep it in storage. They do not consider that batteries undergo self-discharge whether used or stayed idle. If you store your battery in a low or zero-charge state, then prepare to face major consequences. It is so because if your battery does not have enough charge, then after self-discharge of 2% per month, the discharge level reaches a limit where even BMS cannot protect the battery. Over-discharging can cause serious and irreversible damage to your battery even when it is under warranty. That is why storing the battery with a state of charge of more than 50% is recommended to be at a safe end.  

 

 

Probably not Lipo.  This may seem pedantic, but as pointed out above, each type has vastly different needs.

 

 

 

This is a screenshot of the data manual that came with the cells that I used to build my battery.  There is zero difference between these cells and any other LiFePO cell out there in every single LFP battery made......other than the shape of them.  BattleBorn uses Cylindrical cells in their overpriced and expensive batteries, other manufacturers use the style that I pictured above.  From a battery chemistry standpoint, there is not difference between the two other than shape.....here is the screenshot and the recommendations for storage of longer than a one month period of time.  The cell manufacturer is EVE and they are in the top two or maybe three LFP cell manufacturers in the entire world.  I spent months and months on the DIY Solar Forum before diving into the build, asking questions, reading countless posts about anything everything related to building, top balancing, BMS usage, long term storage, you name it.  I spent hours on the phone with one of the moderators who lives out in AZ and is probably the smartest individual I've ever spoken to about batteries in general, and LFP in particular.  His advice matches exactly what the Data Sheet from EVE states about storing them longer than a month.  There is simply no good reason to keep them full SOC when not being used unless it's going to be a short period of time.

 

Edited May 27 by xrated

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1 hour ago, DaveK said:

My bad. Apologies - I should have known better than to stick my nose in an electric related convo. 
 

All I know is - MY battery (lol) performed like a trooper this weekend. I was shocked with how little energy the Alpicool uses. I could run that thing for days on a single charge. 
 

 

Dave, your battery is Lithium Iron Phosphate....or Li (Lithium) FE (Iron)PO (Phosphate)(4) some manufacturers will put a 4 on the end of it........ or even simpler....it's an LFP battery

[SwampNut]

Interesting that one vendor has a vastly different recommendation.  I don't get it, since as you said they should be the same.  Tomorrow I have a meeting at a place that makes LiFePO4 and lithium systems for commercial aircraft, I bet they will have an opinion.  Since it would be exceedingly difficult to store them at low charge levels, I hope EVE is wrong.  And also all of the LiFePO4 12v in vehicles (Zero, Tesla, etc) are always at 100%, along with all of the battery backup systems.  I've always maintained all of them at 100%.

 

[xrated]

4 minutes ago, SwampNut said:

Interesting that one vendor has a vastly different recommendation.  I don't get it, since as you said they should be the same.  Tomorrow I have a meeting at a place that makes LiFePO4 and lithium systems for commercial aircraft, I bet they will have an opinion.  Since it would be exceedingly difficult to store them at low charge levels, I hope EVE is wrong.  And also all of the LiFePO4 12v in vehicles (Zero, Tesla, etc) are always at 100%, along with all of the battery backup systems.  I've always maintained all of them at 100%.

 

Make sure when you ask them, that it is in reference to "long term" storage.....more than a month is the defining point for EVE and others.  I'll be interested to hear what they have to say also.

[SwampNut]

I hope it's cool that I moved all our posts.  I think this needs its own discussion.

 

Another factor here is that my vendor's manual says mostly, "do what the fuck you want, it's guaranteed for ten years."

 

Let's define storage.  Is a battery in a UPS "in storage?"  It hopefully gets no use, but is constantly topped off.  Same with the aircraft batteries, probably.

[xrated]

Taken from the manufacturer "Li Time"s website for long term storage.....

Long-term Storage

Long-term storage increases the self-discharge rate. Self-discharge also increases when the battery warms up and is stored outside the recommended storage temperature. To address this issue, place LiFePO4 batteries in a warm location and charge them adequately before actual disconnection. The ideal temperature range is 10℃ to 35℃ (50°F to 95°F).

When the battery storage time exceeds three months, it's best to run a charging and discharging cycle every three months to keep the battery healthy and in good operating condition when removed for use.

Cold temperatures stop the internal chemical reactions of the battery, improving its health. Therefore, keeping the battery at freezing temperature is a good thing for long-term battery storage health. However, the battery self-degradation rate should be considered. It is best to charge the battery to 40% to 50% of its capacity to keep it in optimal condition.

 

Here is another manufacturer.....Renogy....which is very well known in the LFP battery world....

Battery Charge

Before disconnecting your battery from the system that it supports, charge it between 30% and 50% charged. You don’t want to fully charge it before placing the battery in storage, but you should charge it every 3-6 months so that it doesn’t lose too much of its charge over time. When you are ready to use the battery again, take it out of storage and charge it fully prior to use.

[xrated]

I'm good with that......now to find it!  🤣   Link Please for where the discussion is now.

Edited May 27 by xrated

[SwampNut]

If I have to deal with maintaining these, and it causes a problem, I will be using the warranty.  I won't be fucking managing them.  At all.  The point is to hook up and go and never give it a thought.  The truck will fully charge them on the way home, unless I disconnect the trailer switch.  Which I'm unlikely to remember.  Ah well.

 

OTOH, 3-6 months is a long time.  I guess if I really were "storing" them in that time range I might pay attention.  Not for the 1-3 month usage range.  Too lazy, forgetful, and lazy.

[SwampNut]

Reminds me...the Zero doesn't charge the cells to 100% when you tell it to charge to full.  It has a long distance mode that charges to "110%," which really, is the full 4.2v per cell of "full."  The daily usage is always slightly below, to maximize life. 

[xrated]

Your LFP battery cell chemistry is 3.65V Maximum per cell or 14.6 for the entire battery.  The internal BMS should be set to take out an voltage that exceeds 3.65/cell voltage.  I've obviously got an external BMS for mine since I built it, and I've got the HV cutoff set to 3.6.....just as a bit of cushion.  The cells are considered to be fully charged at 3.45 volts per cell or 13.8 volts.  Most people with LFP batteries, at least the guys in the know, never use the 14.6 to charge them....they are always at a lower voltage....I use a max of 14.2 on my system.  It takes a little longer to get to full SOC than say 14.4 or even 14.6V, but it's less stressful on the cells themselves.

 

So the Zero sounds similar to maybe what I just described for the long distance mode.....in that battery, 4.2 is max, in LFP, 3.65 is max.

[SwampNut]

Why don't any other BMS do this...  DJI drone lipo batteries are self preserving.  After a few days (3?) they will drop to something like 97%.  Then in a week or so they go to 70%, on their own.  

 

Right, a "full" lithium is much higher than LiFePO4.  I'm not sure how my RV converter will be dealing with these since I think its max charge voltage is under 14.  And it's a piece of shit.  But it's a board that can be replaced easily, not a box.  It lives behind the power panel.

 

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57 minutes ago, SwampNut said:

Why don't any other BMS do this...  DJI drone lipo batteries are self preserving.  After a few days (3?) they will drop to something like 97%.  Then in a week or so they go to 70%, on their own.  

 

Right, a "full" lithium is much higher than LiFePO4.  I'm not sure how my RV converter will be dealing with these since I think its max charge voltage is under 14.  And it's a piece of shit.  But it's a board that can be replaced easily, not a box.  It lives behind the power panel.

 

It's going to depend on the charger itself and what the manufacturer of the charger unit has designed as it charging profile/voltages.  A lot of the RV Converter/Chargers (CC) will actually output a bit over 14 volts for Flooded Lead Acid (FLA) batteries in their bulk charging mode, eventually settle on a float voltage of around 13.6 or 13.4 volts.

 

A couple of things working in your favor with LFP vs. FLA....the LFP batteries will have a much lower internal resistance in the battery so the charging rate is usually quite a lot higher than that same charger trying stuff a FLA battery full.  And remember, if you get 13.8 volts out of it, that would eventually bring the LFP up to between 98 to 99% SOC.....it would just take a lot longer for that to happen vs. 14.2 volts.  A lot of the RV folks.....maybe I should say some, especially the ones that don't want to spend more dollars for a LFP specific battery charger or CC in the RV, will just use the OEM CC that is for FLA and depending on the brand of CC and how the manufacturer designed it, will get their LFP batteries to around 80 to 85% SOC, then they let the solar panel(S), and charge controller bring it up to a full SOC.  That obviously works better  for smaller AH batteries, or if you have a large LFP bank...think 600/800 AH, then a lot more solar capability for topping them off to full SOC.  One of the CCs that frequently find their way into the RV market is a brand called WFCO, and their FLA units end up either never switching to bulk mode or Constant Current for long enough to really do much good.  Then the switch to float voltage which is a constant voltage mode and that is usually right at 13.6.......just below being enough to get the LFP battery to full SOC.......the 80% to 85% that I spoke about.

 

I replaced my WFCO OEM CC after trying it on my new battery build.  It was one of them that would never or almost never go into bulk charge mode and if it did, it would only stay there for maybe 5 minutes tops.  I've had my new one for right at two years now, and it is adjustable, via DIP switches on the front of it for FLA, AGM, of LFP.  I've actually got that one set for 3 stage charging, and on the FLA setting.  With that setting, it starts out in Constant Current mode or bulk, then after the current dies down to 10% of the rated output of the charger, it will switch to Constant Voltage mode, and then it will float.  Constant Current mode voltage varies and as the battery is charging, the voltage increases (keeping the current constant).  When it reaches that 10% setpoint, it switches to Constant Voltage which is 14.2 volts, and when the battery is fully charged, it will switch to float, which is 13.4 volts.  So my battery setup is such, that I can fully charge it to 100% SOC, and if I'm not using the trailer for a while, the self discharge of the battery, along with it powering the BMS, will take the battery down all the way to 13.4V......but it won't go lower because the float voltage is there to keep it at that level........as long as I have the trailer plugged into my shore power connection at the house and my main battery disconnect is left turned on.  The ONE QUIRK about that CC, is that as long as the input power stays on (120VAC), it will never reset itself to kick back into Constant Current mode and start the process of fully recharging the battery......but I knew that going in, when buying it, and it is just something that I know to do.  So if I want to fully recharge the battery again, I simply kill power to the CC for a couple of seconds, then turn it back on, and it goes back into Constant Current mode and starts the entire charging process again

 

I like that charger because it is so adjustable and I also have the ability to use a FLA mode instead of LFP mode, and I know the output voltage will top out at 14.2 and not stand a chance of stressing the cells/battery....it just take a bit longer to fully charge with it set up like that though, but nothing I can't live with very easily.

[DaveK]

Jesus H Vern - you know your shit. 

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31 minutes ago, DaveK said:

Jesus H Vern - you know your shit. 

If you only knew the number of hours of time I spent going down the LFP rabbit hole BEFORE finally deciding to buy all the stuff and build my own battery, you would be shocked (no pun intended...LOL).  In all fairness though, a couple of factors to consider here.  1.  I'm retired so trying to balance my time between work, studying the LFP stuff, staying caught up with other stuff, and just life in general, was not much of a factor since I could cross out the WORK part of it and that of course opens up a huge time slot.  2.  Having spent almost all of my adult life in the Electrical field as a Journeyman Electrician, obviously gave me a much better understanding of terminology, theory of operation, and most of the skill set to do the actual build with a lot of confidence that it would work.  Even given all of that, I was probably on the phone with a guy that lives in AZ that is on the DIY Solar forum.....probably 8 hours or more over several weeks.  We talked a lot via PM on the forum, and many times I would have questions and then we'd get on the phone to talk to speed up the process...vs. PMing each other and sometimes taking a day or two to get a response.  Simply put.....I had a lot of questions, as LFP battery stuff was 100% new to me and I knew NOTHING about it, and I got a LOT of help from him and others on the forum.  

 

One of the things that he provided to me was the suggestion of a certain piece of equipment to buy and use, to do the initial "Top Balance" on the battery once I had it built and was ready to top balance.  The idea behind the top balance part of it is to make sure that Each of the 4 cells that make up the battery, are all very, very close to the same voltage after the full charge is complete.  When I was done with the top balance, three of the four cells were at 3.65 volts......the other cell was at 3.64 volts according to the top balancer I was using.  After actually hooking the cells up to the BMS again, my eyes about popped out of my head when I saw the results....all four cells were within .001 volt of each other...  1/1000 of one volt.  And today...a little over two years later after the build, I look at the voltage differential between all 4 cells and I see .002 or .003 differential, which says to me that all four of the cells are still in almost perfect balance.  That's an indicator of a couple of things.  1.  The cells that I bought are Top Quality and extremely well made.  2.  I did a great job during the build process.  3.  The Top Balance was done just as it should be done.