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Very well said. Throwing in a current calendar / cycle example here: 1650 + days/cycles on bank "A" (LFP) and still performing quite nicely. These are the smaller versions - but many - that you are using PNjunction. It's never boring being part of a living experiment - although there's always a few eyebrow raising moments to keep complacency from taking over!
I sincerely wish him the best, but it is wise to remember that NONE OF US has demonstrated a real-world calendrical lifespan reaching the mythical 2000+ cycles (ie daily cycle, not hammering them repeatedly). Ie, nobody I know that uses LFP has ever said something like "yeah, I'm on my second bank now - my first one lasted 8 years and about 2000 cycles, so I just replaced it with the same". If a cell / bank that is sitting around between 40-80% SOC on a float-standby basis, that doesn't count for us daily-cyclers.
Thing is, instead of just talking about it, get some cells from Dax, put it together and join the fun for a small experimental bank. Or any of the prismatics. 12v even with a simple 4S setup!
I tell ya' lurkers, actually doing it physically beats the pants off talking about it.
The problem is that there will never be a one-size-fits-all solution with LFP, and thus a never ending thread.
~CrazyJerry
Edit: Actual number or days / cycles on these batteries is 1,670, so, in 330 days from today they will hit the 2,000 cycle (and days) mark. There are 32 of the 20ah cells configured to 12 volt and 160ah. They are predominantly charged from solar.[B]I'm around...[/B]Comment
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Congratulations, you are one of the very early adopters of LFP batteries that is still commenting online. I don't know of any older systems.
I would be interested to know more information on your system, what sort of battery management/checking you use, what voltage or range of SOC you keep you battery between, what your experience with battery balance has been, whether you have noticed any change in the the performance of the battery over the four and a half years you have had it, and of course what your eyebrow raising moments have been. Not asking for much am I?
I think complacency is probably a major killer of batteries of all types.
SimonOff-Grid LFP(LiFePO4) system since April 2013Comment
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We all bemoan the anecdotal bench tests that are out there as not anything you can hang your hat on, it's just as bad trying to decipher the data from regular users. I reached my one year anniversary this week and it's milestone if the fact they made it a year makes a difference. I consider all my data worthless for a couple reasons, one the temperature exposure during the summer was above 90° and I have now made the decision to put them into a storage mode this winter.
The basic internet contention is to drop the SOC to 50-60% and leave them alone to self discharge. It then becomes that 5 months could present some problems in a remote location and un-monitored. The choices are, remove everything and let the cells sit naked, maintain a low float voltage or use a VCS and have a low set point and raise the voltage to a high point within a given range.
I see any meaningful data as needing lot's of footnotes, calendar years and cycles are nice to look at, but having a Capacity tests along the way will be the most important , assuming that there is not a rash of cell failures.Comment
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Thanks Simon. Recently I stumbled across this forum and then discovered that there wasn't a lot of historical data with lipo in the off grid systems - so maybe some folks can benefit from my experiences.
Upfront, my standard disclaimer is:
1) I'm not selling anything. Not a business owner. Most people I deal with have very, very, limited funds and are off-grid. This makes us very accountable for the energy we use.
2) When referencing items I would only use a name brand as a specific example so there's some context. “Generically speaking” works in certain situations but actual names or part numbers can be very helpful when researching or validating claims. Moderators please feel free to edit out if necessary.
3) Based on the ongoing 13 year experiment here at 9 Main, I call'em like I see'em. If something works I share that, if something is sub-par that also is shared. If I've destroyed something due to ignorance or any other reason, I'm happy to include that also to provide context.
4) Anyone who reads what I've written should also note that I have zero responsibility if you try any of this. My experience is that some people "skim" or "thumb" over information and then find themselves in a pickle because one or more important "details" were missing.. Aside from the safety aspect, operating in this manner can deplete a piggy bank fairly quick so understand the risks and benefits, then proceed with caution. Onward ho!
GBS 20ah Lithium batteries: Part 1.
The batteries referenced a couple of posts back were purchased in March 2011 for a transportation experiment and actually put into service on April 4th, 2011. Listed as LiFeMnPO4 chemistry, they were originally purchased online (from GBS) as four pre-assembled 12 volt 20 ah packs that were then assembled in series totaling a larger 20 amp hour main pack at 48 volts. This was for a Go-One3 velomobile that I rebuilt and then "electrified". These batteries were used hard for the first 6 months (all summer) every day in that trike. The batteries were mounted in enclosed saddlebags on each side of the trike - so it got a little warm in there at times – partly through use and party from baking in the sun.
The charging and discharging regime for those first 6 months were dictated by the spec sheet on the batteries / charger /balance boards - EX: charge them up to the point at which point the balance boards would come on: 3.7 volts per cell.
In doing so, I did notice the warm feeling in the saddlebags where the batteries were. To try and get more data as a baseline, I used an infrared heat gun at the terminal posts, the temperature on all 16 cells in the 48 volt series pack would climb from about 75 degrees starting temp - to 96 or so at the end of the complete charge cycle. NOTE: This would be after using the trike with the pack voltage depleted and then resting at 48-48.5 volts (roughly 3 volts per cell). The recharge time would take a few hours with the supplied 6 amp output charger - significantly less time (about 1 hour and 15 mins using 600 watts of solar - more on that in a bit..)
As a side note, just about a month or so into the project (still 2011), I ended up purchasing a second identical pack of these batteries (so I could rotate them), and noticed the stark difference at the point the new balance boards came on - . Seemed the early balance boards were now reconfigured and the kick on point for the balance function was indeed lowered to just 3.55 volts per cell. I still have the 2011 spec sheets as noted above whereby the balancing function is listed to begin at 3.7 volts per cell... There must've been a reason for the big change..
Via the GBS website, the spec on the batteries changed as well. No longer was the recommendation to keep the voltage on these batteries between 2.80-3.80 volts per cell. As of this writing, GBS lists their 20ah cells operating voltage range at: 2.8-3.6 volts. The change is only to the upper end of the voltage range.
At that point in the experiment, I had two identical packs consisting of 16 cells each (48volts total / 20 amp hours) - but the balance boards engage at different set points - what to do?
Using the infrared heat gun on the new pack with the lower charge voltage / balance boards, I notice a lot less heat at the terminals. In most cases it wasn’t exceeding 82 degrees - so assuming the second set of batteries were manufactured exactly the same as pack #1, I now have a measurable difference between them based on a voltage charge recommendation. I opted to go with the lower charging voltage simply for the heat reduction.
Discharge on the trike was within GBS 20ah cell recommendations - that is until such number was also reduced. The 2011 spec on these cells for max continuous discharge was 3C (60 amps) and pulse at 10C. Today, their website lists the same battery max continuous discharge current at 2C (40amps) and 10C impulse. I largely ignored this new spec and set the trike's controller to deliver a “compromise” at 50amps max to the rear hub, and that happened quite frequently - mostly because at only 110 lbs – the trike would zip right along! It was a blast. Many times the ending voltage after a 50 or so mile trip would be around 50-51 volts. There were a couple of 100 milers where the ending voltage was 46-48 volts resting.
Early on, charging these cells was also an experiment. I could (and did) do this from a variety of ways. The ac 110 volt input (GBS supplied) charger that came with the batteries was the easiest - but slow at only 6 amps output. Piping 600 watts of solar into an Outback MX-60 MPPT controller was considerably faster and to be the main "charging station" for the Go-One3. (These controllers are discontinued and Outback now uses the FM60 as the new model). Programming the MX-60 to mimic the ac charger for the batteries was pretty easy. I set bulk to 59 volts, the absorb setting for one hour, and end amp current set to 2 amps. So when the sun was shining, 600 watts of solar went into the MX-60 controller and then would raise battery pack voltage to 59 volts. The controller would then display the absorb mode and hold the voltage. During the absorb 1 hour timeframe, the charging amps would taper down. When they reached just 2 amps the controller would end the absorb stage and then go to float (float was set to 13.2 - basically terminating any further charging). This would generally happen before the 1 hour absorb timer ended. It was a pretty slick setup - the off-grid home system was now providing the fuel for the 30 mile round trip work commute and plenty of other trips too - very cool indeed. With the ability to quickly swap out a depleted pack for a fresh one, the Go-One3 was already ready to go!
Another charge source was introduced for emergencies. I assembled my version of a regenerative brake system into the Go-One3. Using the 3 phase wires (from the Crystalyte rear hub) through a large alternator rectifier, gave me direct current to play with - but the voltage wasn't high enough to regen into the batteries unless I was going down an olympic ski jump at 60 miles an hour. I needed a way to step the voltage up and I found a unit that did exactly that. Incorporating that into the system allowed for a manually engaged brake regen unit at much lower speeds - very useful. For emergencies/roadside charging, piping any DC source of 7 volts - 48 volts (that has some ooomph behind it) into the regen auxiliary plug, would be stepped up to, and not beyond, 56 volts for the batteries. So, in a pinch I could easily charge from any 12 volt car battery. The 20ah cells were now being pelted from a variety of charging sources and sometimes during extreme scenarios as in the case of the regen unit in the hills. I seldom had to use the regular cable operated brakes – the drag from regen worked excellent as a brake..
This was just the beginning of this lithium journey. These batteries showed promise but the need to expand quickly set in. They needed to do more....
To be continued in Part II!
~CrazyJerry
The Aurora project (velomobile) webpage for summer of 2011 is available at the following weblink:
[B]I'm around...[/B]Comment
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Can you give me an executive summary?
Comment
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Jerry, excellent setup description on the life of your batteries so far. I think we can all make allowances and extrapolate from your data. I re-read it twice to make sure I absorbed all the little nuances. Looking forward to the rest of it.Comment
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Thank you for your replies folks. What I'm presenting is by no means a "be all end all" - not by a longshot. But this off-grid venture is slated for the long-haul so I'm always looking or trying different things. If something works it gets passed on and maybe someone can improve upon that - we all benefit. The final chapters on these topics may never be written though.
Anyway, while I have some time I'll continue the write-up to present day..
Stay tuned.
~CrazyJerry[B]I'm around...[/B]Comment
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GBS 20ah Lithium batteries: Part 2.
GBS 20ah Lithium batteries: Part 2.
To expand the use of the batteries, I simultaneously adapted them into a 20” electric push mower: Homelight Model UT13126. This was a 24 lead acid mower and extremely heavy as factory equipped. Two 12volt GBS 20ah packs fit nicely into the same bay as the factory lead acids. The velomobile has one 24 volt pack in each saddlebag (Two 12 volt units wired in series.) A single 24 volt pack was plug-n-play between the two. The runtime with the mower was 50 minutes to an hour depending on the sharpness of the blade and thickness of the grass. With four 24volt packs at my disposal, there was never a problem finishing the lawn. The packs are numbered so I would use these in sequence every time the lawn needed to be mowed and they were always discharged to 24 volts (3 volts per cell) when used. For better or worse, EVERY time the packs were used they were always recharged up promptly. To accomplish this on the separated 24 volt packs, I purchased a GBS ac powered 24 volt charger that charged to 29 volts or roughly 3.625 volts per cell.
The balance boards that came with each battery remained affixed from the time I put them into service. Within the first 6 months I did notice another difference between the first set of batteries (that used the higher voltage engage point of 3.7 volts in the balancing boards) and the second set of batteries (that used the lower voltage engage point of 3.55 volts in the balancing boards). The difference was the red led balance indicator on the boards was no longer consistent in lighting up together at basically the same time on the higher voltage ones. Two or three lights would come on, then minutes later a few more and so on. The pack with the higher voltage boards was cell voltage drifting. The pack with the lower 3.55 boards was pretty much perfect in that all lights turned on within a 10-30 second span.
My understanding was the balance boards were supposed to balance these cells but that didn’t seem to be happening. I decided to continue to let them do their jobs anyway. I tried using the supplied lithium charger to correct this – but that charger had no communication with the pack so the boards would mostly just glow red until the charger shut-off. Using the charge controller from incoming solar, I could fine-tune the charge a little better and manually pull the leads to let a balance board bleed down a high cell. This was time consuming and really didn’t accomplish much.
I did some digging on the internet and discovered the hobby market. Using a couple cell-log8’s, a project enclosure, speaker jacks, trailer lighting whips, two fuse panels, shoe-goo, and some low voltage chargers from portable equipment, I made a pack monitor and the speaker jacks corresponded to the cell-log cell values, so I could individually apply a charge or discharge to any cell(s) and watch them. This worked great once I got a procedure down. What I didn’t quite piece together at that time was using the balance boards as a primary indicator of nearing full charge. Using the 3.7 volt units as the indicator were creating more problems then they solved. The 3.55 volt balance board equipped cells were pretty rock solid. The homebrew monitor I built can be seen online here:
It took an additional month before it really hit me about the difference in the balance boards. On a hunch, I manually balanced the cells and then started charging that pack at the lower value of 3.55 volts per cell and for the most part – every cell in the problem pack was now steady and not voltage drifting apart…. One month later the cells were all very close in their voltages, so out of interest I decided to try once again charging up at the 3.7 volts per cell mark. After just three charge cycles 9 of the 16 cells were drifting. Once a total of 15 charge cycles had been completed the entire pack was a mess. The lowest cell voltage was 3.28 and the highest was 3.70. The distribution was interesting although I’m not sure I can draw any concrete conclusions from it. All but 3 of the original 16 cells that used the 3.70volt balance boards reached 3.70 long before the 16 cells that had the 3.55volt balance boards. Could charging each pack at their recommended (and different) voltage be responsible? And there was a measurable heat difference charging at the higher rate.. Was I seeing damage to those first set of batteries? To this day those cells from the first batch will climb faster IF separated from the pack and charged singly.
Life was great for the velomobile and mower but could these batteries serve a third purpose and be used in the house?
This was worth considering since the 1700ah of Surrette lead acids had seven years on them at that point and were starting their decline….
More in Part III..
~CrazyJerry[B]I'm around...[/B]Comment
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Here's another reason why no one here seems to have a clue about lifepo4 technology and where's it's at, what you have posted has no relevance to lifepo4 cell packs, you're talking about another lithium technology and this is a lifepo4 thread, not li-poly,li-ion. Anyone using the voltage parameters you're quoting will destroy their lifepo4 cells quickly and is incredibly misleading.GBS 20ah Lithium batteries: Part 2.
To expand the use of the batteries, I simultaneously adapted them into a 20” electric push mower: Homelight Model UT13126. This was a 24 lead acid mower and extremely heavy as factory equipped. Two 12volt GBS 20ah packs fit nicely into the same bay as the factory lead acids. The velomobile has one 24 volt pack in each saddlebag (Two 12 volt units wired in series.) A single 24 volt pack was plug-n-play between the two. The runtime with the mower was 50 minutes to an hour depending on the sharpness of the blade and thickness of the grass. With four 24volt packs at my disposal, there was never a problem finishing the lawn. The packs are numbered so I would use these in sequence every time the lawn needed to be mowed and they were always discharged to 24 volts (3 volts per cell) when used. For better or worse, EVERY time the packs were used they were always recharged up promptly. To accomplish this on the separated 24 volt packs, I purchased a GBS ac powered 24 volt charger that charged to 29 volts or roughly 3.625 volts per cell.
The balance boards that came with each battery remained affixed from the time I put them into service. Within the first 6 months I did notice another difference between the first set of batteries (that used the higher voltage engage point of 3.7 volts in the balancing boards) and the second set of batteries (that used the lower voltage engage point of 3.55 volts in the balancing boards). The difference was the red led balance indicator on the boards was no longer consistent in lighting up together at basically the same time on the higher voltage ones. Two or three lights would come on, then minutes later a few more and so on. The pack with the higher voltage boards was cell voltage drifting. The pack with the lower 3.55 boards was pretty much perfect in that all lights turned on within a 10-30 second span.
My understanding was the balance boards were supposed to balance these cells but that didn’t seem to be happening. I decided to continue to let them do their jobs anyway. I tried using the supplied lithium charger to correct this – but that charger had no communication with the pack so the boards would mostly just glow red until the charger shut-off. Using the charge controller from incoming solar, I could fine-tune the charge a little better and manually pull the leads to let a balance board bleed down a high cell. This was time consuming and really didn’t accomplish much.
I did some digging on the internet and discovered the hobby market. Using a couple cell-log8’s, a project enclosure, speaker jacks, trailer lighting whips, two fuse panels, shoe-goo, and some low voltage chargers from portable equipment, I made a pack monitor and the speaker jacks corresponded to the cell-log cell values, so I could individually apply a charge or discharge to any cell(s) and watch them. This worked great once I got a procedure down. What I didn’t quite piece together at that time was using the balance boards as a primary indicator of nearing full charge. Using the 3.7 volt units as the indicator were creating more problems then they solved. The 3.55 volt balance board equipped cells were pretty rock solid. The homebrew monitor I built can be seen online here:
It took an additional month before it really hit me about the difference in the balance boards. On a hunch, I manually balanced the cells and then started charging that pack at the lower value of 3.55 volts per cell and for the most part – every cell in the problem pack was now steady and not voltage drifting apart…. One month later the cells were all very close in their voltages, so out of interest I decided to try once again charging up at the 3.7 volts per cell mark. After just three charge cycles 9 of the 16 cells were drifting. Once a total of 15 charge cycles had been completed the entire pack was a mess. The lowest cell voltage was 3.28 and the highest was 3.70. The distribution was interesting although I’m not sure I can draw any concrete conclusions from it. All but 3 of the original 16 cells that used the 3.70volt balance boards reached 3.70 long before the 16 cells that had the 3.55volt balance boards. Could charging each pack at their recommended (and different) voltage be responsible? And there was a measurable heat difference charging at the higher rate.. Was I seeing damage to those first set of batteries? To this day those cells from the first batch will climb faster IF separated from the pack and charged singly.
Life was great for the velomobile and mower but could these batteries serve a third purpose and be used in the house?
This was worth considering since the 1700ah of Surrette lead acids had seven years on them at that point and were starting their decline….
More in Part III..
~CrazyJerryComment
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The average consumer like myself may choose to look at the specs provided buy the vendor.
Here's what I see:
LiFeMnPO4 chemistry
Operation Voltage Range: 11.2 to 14.4V
-------------------------------
CALB EV Lithium LiFePO4
MAX CHARGE VOLTAGE - 3.65
The writing I'm doing is to an earlier response if you took the time to review. If it needs to be moved to a more relevant spot then by all means move it. The info contained within may be valuable to someone else even if you find it of no use.
Best,
~CrazyJerry[B]I'm around...[/B]Comment
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To some degree all the manufacturers use a little different make up in their LiFepo4 family of cells as far as I can tell and have patents to prove it. Winston is LiFeYP04 and GBS is LiFeMnPO4, the charging and discharging specifications seem to be all the same. Winston claims the Yttrium extends cycle life. Manganese no clue. Some of it is to enhance the temperature range. I am not really a chemist and I don't sleep in a Holiday Inn Express.
PNJ has made this his quest in life, I'm sure he'll be along to tell us how it all works.Comment
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Your data is not worthless. As we know there are a huge number of variables, some we have control over and some we don't that will determine how long our LFP batteries will last and how well they will operate. Because of this, the data from your system alone can't be used to make any definitive statement about how long an LFP battery will last, but when amalgamated with data from others can be used to infer how long an LFP battery will last and what factors affect how long they will last. This is rather like having to do epidemiological studies to work out factors affecting peoples health. The more data the better.For some reason the Reply with Quote is not working? WillyT We all bemoan the anecdotal bench tests that are out there as not anything you can hang your hat on, it's just as bad trying to decipher the data from regular users. I reached my one year anniversary this week and it's milestone if the fact they made it a year makes a difference. I consider all my data worthless for a couple reasons, one the temperature exposure during the summer was above 90° and I have now made the decision to put them into a storage mode this winter.
I think the safest approach is to remove the balancing boards and disconnect all external cables from the battery.The basic internet contention is to drop the SOC to 50-60% and leave them alone to self discharge. It then becomes that 5 months could present some problems in a remote location and un-monitored. The choices are, remove everything and let the cells sit naked, maintain a low float voltage or use a VCS and have a low set point and raise the voltage to a high point within a given range.
I wouldn't think there is much risk if you did leave the balance boards connected. If they draw 4mA I calculate they will they will only draw 14.4Ah (.004*24*30*5) from the battery over the five month period.
If you did leave the balance boards connected and one of them did fail having an external power source connected would not stop damage to the battery.
SimonOff-Grid LFP(LiFePO4) system since April 2013Comment
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Thanks for sharing all the information, I think your trike look great! We have put 1kW electric motors on our mountain bikes so we can get across the paddocks and up some of the steep hills with all the shopping.
It does look like charging up to 3.7 volts was damaging your batteries, I would be interested to know what current your charger was pushing into the battery at 3.7 volts before it started to current limit.
SimonOff-Grid LFP(LiFePO4) system since April 2013Comment
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