How to Calculate Your Battery Capacity?

[757driver]

Originally Posted by hclarkx

A agree with what you read and what you are saying 100%. I have seen this or similar information. But, you make it sound like I suggested regular charging to 16V. I never suggested that; or at least I don't believe I did even if unintentionally (being 77 and typing at 100 WPM can generate some strange word sequences). If I said anything like that, please point it out and I'll correct it.

What we have been discussing is not repetitive cycling. The subject was how well the BMS protection built into the Lifeblue and others works. You indicated (I believe) that 15.8 (your case) or 16V (my case) isn't useful. I don't agree. I would probably have chosen a lower number but 16V does meet the purposes of protection against catastrophic damage which is the purpose of the BMS.

As I've stated, after getting details on my BMS from Lifeblue and determining that other manufacturer's BMS seem to be similar, I call the built-in protection provided by the BMS to be "protection against catastrophic damage." I.e., one won't do untenable damage if one's charger goes awry (or is mis-set) and pushes the LFP voltage up to 16V and thereby triggers the BMS. By the numbers you found, One trip to 16V over the life of an LFP due to a failed or mis-set charging system isn't going to take out significant life. In fact, the numbers you found suggest that discharging to 0% and charging to 16V once will "waste" about two of the typical 3000 cycle LFP life. Though we are not talking 0% to 16V, we are talking just charging to 16V so as a wild guess, that might waste just 1 of those 3000 cycles.

Hopefully LFP "drop-in" owners will realize that the BMS shutting the LFP down is telling them something is wrong and needs to be corrected. In other threads and maybe a year ago I saw people saying they aren't fussy about their LFP charging because BMS will protect it (I didn't agree). One even thought there would be interaction between the LFP BMS and his charger that would take care of things. These folks indeed could have shorter than normal LFP life.

I certainly do think that the manufacturers of LFP batteries AND charging systems could be clearer about the role of the charger and the BMS. I'm sure that LFP makers don't want to make the LFP seem like it requires an engineering degree, but they should do better. For example, I have a PS lithium battery charger. It charges to 14.6V and then sits there until disconnected. I bought it just to get from 20% up to 50% now and then when I need to get through another sunless day. This use is fine since voltage doesn't even get to 14V. But, I happened to mention using this charger to a Lifeblue engineer a few months ago and he interrupted and told me that I had voided my warranty since this charger was not approved by Lifeblue. I calmed him down reiterating that I know what I'm doing with it. Though he did not retract his statement about me voiding the warranty. And, of course, I can understand why Lifeblue does not approve of this charger (it could easily be mis-used). BTW, the charger maker says it can be left on the battery continuously!!!

When I got my LFP Lifeblue did say in the literature that comes with the battery that their warranty is only valid if I use a Lifeblue approved charging system. They don't provide a list of approved charging systems. It seams each buyer must call and ask if his charger is approved, or get it approved. At least that's the way it was 18 months ago when I bought in.

Definitely the LFP and charger manufacturers could do a better job, and I would have the BMS trigger down closer to 15V, but 16V seems to me to be effective given that the LFP will likely never see this voltage and if it does, the harm will be hard to measure. Maybe Lifeblue thinks 15V would result in too many nuisance calls to Starlight Solar.

Incidentally, as you likely know the Lifeblue BMS records abuse (overvoltage, over-discharge, short-circuit, and maybe others). There is a page in the app that reads out BMS protective operations. I would guess that having any of these registered in the BMS would probably void the warranty. I'm going to ask Lifeblue about this I ever talk to them again.

I apologize for getting so long-winded about this.

No, I don’t believe you mentioned that you would charge your LFP battery to 16.0v, in fact you could not, even if you tried. Your LifeBlue batteries and mine are the same vintage with the same BMS and the same Bluetooth app to monitor them. The overvoltage protection kicks in at 3.8vpc or 15.2v, period. There is no protection at 16.0v despite what you were verbally told. What LifeBlue has put in writing via their spec sheet from that time period trumps what someone mentioned over the phone. BMS protection is essential to prevent battery abuse and failure but must not be relied on as a first level of defence, it is meant as a last resort. What I have a problem with is someone looking into LFP batteries reading this thread and taking away that 4.0vpc or higher is just fine and will do no harm. Why on earth would someone ever want to charge much above 3.5-3.6vpc when this voltage is sufficient to recharge to 100% SOC. For fractional “C” users which the RV community is, there is no practical reason to squeeze every last charge amp into a LFP battery. One of the biggest detriments to understanding and maintaining LFP batteries is the baggage that is brought along from all the years of using and charging lead acid batteries. The two are vastly different.

As an interesting side note which I think might surprise you is to watch your individual cell voltages (via the Bluetooth app) as the battery approaches 100% SOC and the voltage approaches 3.6-3.65vpc. They won’t necessarily stay matched with each other as they enter the upper knee.

Yes, your LifeBlue battery records each trigger as an event for over-charge or over-discharge, over voltage, under voltage, over current while charging or discharging and operating over or under specified temperatures. Just because a trigger is recorded such as exceeding a cell voltage of 3.8vpc on a one of basis will not void your warranty but if you are constantly overcharging and tripping the overvoltage trigger of 3.8vpc then LifeBlue would have a case for denying you warranty coverage. If someone is relying on the internal BMS to control the charging parameters of the battery then as you said they are destined to ruin their battery in short order.

By the way LifeBlue batteries are relabeled Topband lithium batteries brought in from China. Starlight Solar and Larry Crutcher is LifeBlue, period.

[Itinerant1]

Originally Posted by 757driver

As an interesting side note which I think might surprise you is to watch your individual cell voltages (via the Bluetooth app) as the battery approaches 100% SOC and the voltage approaches 3.6-3.65vpc. They won’t necessarily stay matched with each other as they enter the upper knee.

If you can see temp readings on the cells you will also notice the internal heat will start rising quickly. I'll see it to start happening after a couple minutes when starting absorb stage (under 10 minutes), the cell temps will rise 10-13f degrees at only 3.52vpc (14.1v). As soon as it goes from absorb to float they'll drop back to were they started. I have not seen the cell temps higher than 84f during one of these events but there is good air circulation. I wonder if your dropins follow this roughly or rise more seeing they're in an enclosed container and charging to 14.4-14.6v (3.6 - 3.65vpc).

[CountryFit]

Originally Posted by 757driver

By the way LifeBlue batteries are relabeled Topband lithium batteries brought in from China. Starlight Solar and Larry Crutcher is LifeBlue, period.

I had been always suspecting LifeBlue of being a relabel of Chinese product thanks for confirming that. Another is Battle Born. I just googled Battle Born website, there is no mention of where it's made.

A side note, Calb, the largest and the earliest lithium cell manufacturer in China, is a state owned enterprise, originally created to cater to the demands of aviation industry (thus the name of CALB - "China Aviation Lithium Battery"). I have used it for 4 years, very happy about it.

[757driver]

Originally Posted by Itinerant1

If you can see temp readings on the cells you will also notice the internal heat will start rising quickly. I'll see it to start happening after a couple minutes when starting absorb stage (under 10 minutes), the cell temps will rise 10-13f degrees at only 3.52vpc (14.1v). As soon as it goes from absorb to float they'll drop back to were they started. I have not seen the cell temps higher than 84f during one of these events but there is good air circulation. I wonder if your dropins follow this roughly or rise more seeing they're in an enclosed container and charging to 14.4-14.6v (3.6 - 3.65vpc).

Unfortunately no individual cell temperatures, just the temperature for each battery (which would not show such an event). I am sure it would show the same result as the GSB cells if it had cell temperature monitoring. That’s another reason for not charging to 14.4-14.6v. I used to charge to 14.2v but now I am stopping at 14.0v.

[757driver]

Originally Posted by CountryFit

I had been always suspecting LifeBlue of being a relabel of Chinese product thanks for confirming that. Another is Battle Born. I just googled Battle Born website, there is no mention of where it's made.

A side note, Calb, the largest and the earliest lithium cell manufacturer in China, is a state owned enterprise, originally created to cater to the demands of aviation industry (thus the name of CALB - "China Aviation Lithium Battery"). I have used it for 4 years, very happy about it.

For the most part the Chinese seem to have the market on lithium batteries. Nothing wrong with that as Topband has been in the lithium business for a long time. From what I have read CALB has a good reputation for building a quality cell. Battleborn claims they are “designed and assembled in Reno NV” but hard to say where the cells come from.

[hclarkx]

Originally Posted by Itinerant1

Have you come across this?

State of Charge (SoC) Estimation of LiFePO4 Battery Module Using Support Vector Regression

It's an easy read and shows interesting results, even graghs for those that don't read. The pdf can be downloaded at...
https://www.researchgate.net/publica...tor_Regression

Whoa, that would not have been an easy read in my prime!! I did skip over most of the math! Yes, interesting. Shows how tricky SOC monitoring is. The authors claims their method makes good SOC estimating a simple process, but I'd bet none of us have SOC monitors that are near this sophisticated. My Volt might have one but I wonder about that as well.

The paper also touches on capacity measurement in that a process is needed to ascertain when the battery is charged to full capacity. The authors point out that the needed full charge followed by a 2 hour rest will likely never happen in practice. It's much more likely to happen in my Volt than in my RV. Though even there I have the Volt programmed to reach 100% charge at 10:00 a.m though it is usually driven by 9:00 a.m. so it rarely has a 100% charge let alone one followed by a rest.

The conclusion I would take from this paper is how approximate our SOC monitors must be. I doubt any of them are any where near as sophisticated as discussed in this paper and even if they could track peukert's law well, as pointed out in the paper, they won't have the rest period from which to start counting down.

Given that lead-acid batteries have much larger peukert exponents, estimating SOC for them must be a whole lot more approximate than for an LFP. At least LA batteries are usually topped off often so get a frequent reset.

This paper makes me wonder how Lifeblue is calculating the capacity of my LFP over time for the purposes of warranty (guaranteed 83% remaining at 10 years). That seems to be an even more challenging task without time in a lab.

[hclarkx]

Originally Posted by 757driver

By the way LifeBlue batteries are relabeled Topband lithium batteries brought in from China. Starlight Solar and Larry Crutcher is LifeBlue, period.

I tried to communicate with Larry via email but he did not respond. I probably asked too many questions. I tried again and did not hear from him but did get a call from a young engineer that seemed to have all the answers.

Below is the only technical information I got from Lifeblue. There was nothing more when I talked to the Lifeblue engineer (not Larry). I did send him my thoughts on a monitor app upgrade and on their weak instructions.

I should have looked sooner. There is much more info on their website now than when I had communications with the Lifeblue engineer. Some of it sounds familiar. I did send him pages of stuff that I thought they should be putting out to new and prospective users.

This list is new since my last visit ...

http://www.lifebluebattery.com/ewExt...0Battery-1.pdf

I can't get the link to the charging instructions to work ... i.e., the words are there but there's no link. Is this where you found info on the BMS protection? I don't see that in the new Safety and Installation guidelines. Do you have the charging guidelines document?

Documents for LiFeBlue RV Boat Lithium Ion Bluetooth Battery

Below is all I got in the fall of 2017 ..........

LiFeBlue Battery Safety Guidelines and Instructions

Please read and understand these Guidelines and Instructions in its entirety before installing, using or charging your LiFeBlue Li-ion battery pack. Failure to do so many result in fire, personal injury or damage to property.

By purchasing LiFeBlue batteries you are agreeing to these Guidelines and Instructions. LiFeBlue assumes no liability or warranty claim for any failure to comply with these Guidelines and Instructions. The buyer assumes all risks associated with LiFeBlue product.

1. Every LiFeblue battery includes a Battery Management System (BMS). The battery pack and cells are monitored and automatically protected by the BMS system against over-charge, over-discharge and other conditions. However, you the user are ultimately responsible for the safe operation of the battery.

2. Always install the proper circuit protection, a fuse, breaker or other current interruption device, designed for any circuit that is connected to a LiFeBlue battery.

3. Always use the proper battery charger to charge LiFeBlue Li-ion batteries. If a non-approved LiFeBlue charger is desired, buyer must submit specifications of the charger to LiFeBlue for review and approval prior to use.

4. Read and understand the specifications of LiFeBlue battery before usage or charging. Always charge and discharge LiFeblue battery within the specified parameters found on the data sheet.

5. Battery must installed to avoid any movement of battery, connections, wiring and or connected electronics. Never connect or use LiFeblue battery if it is not securely mounted to prevent movement.

6. Avoid short circuiting battery cells or packs. A short circuit condition will cause permanent damage to battery cells and packs and possibly create an unsafe operating condition which may result in a fire. Use caution when installing bus bars or cables the cell terminals. Tools, such as screw drivers and wrenches should be an electrically insulated type.

7. Battery terminals, bus bars or cables are must be kept kept clean and dry. All screws must be tightened
properly on the battery terminals before battery is used. Loose connections will result in high contact resistance, heat generation, and can potentially be a fire hazard. Torque each terminal bolt to 9 N-m or 80 In-Lbs.

8. Bus bars, terminal connectors and cables must be adequately sized to handle the maximum charge and discharge current. Inadequately sized bus bars, connectors or cables will cause over-heating and are a potential fire hazard. It is the installers responsibility to properly size all conductors used with LiFeBlue
batteries.

9. There is risk of electric shock when working on a Li-ion battery pack. Always wear personal protective equipment (PPE) when working on a battery pack per Occupational Safety and Health Administration (OSHA) and National Electric Code (NEC) guidelines. For any questions regarding the above Guidelines and Instructions please contact us.

LiFeBlue Battery - 2873 East Fork Road - Sula, MT 59871 920-543-3764

Rev 1.2

[hclarkx]

Originally Posted by hclarkx

I tried to communicate with Larry via email but he did not respond. I probably asked too many questions. I tried again and did not hear from him but did get a call from a young engineer that seemed to have all the answers.

I spoke too soon ...... I just dug into the Lifeblue web site. It's considerably updated since I've been there.

Under the "Sales Price" tab there are "Data Sheets" for the 75 and 100AH batteries. These show the 15.2V cut-out that you referenced. My 300AH unit has a 100AH BMS so these might apply to my 300AH unit. My 300AH was one of the first they shipped or maybe the first one so it might be different. But, I'm okay with 15.2 or 16V, either works.

I gather the newer 300AH units have 200AH BMS in them. I'm not sure where this came to my attention.

The Safety and Installation Instructions have been hugely updated since I bought in but still are vague on the BMS.

The Resources page lists a "Charging Instructions" document but for me it's not a link. Do you have this document? Can you access it?

Documents for LiFeBlue RV Boat Lithium Ion Bluetooth Battery

H

[hclarkx]

Originally Posted by 757driver

As an interesting side note which I think might surprise you is to watch your individual cell voltages (via the Bluetooth app) as the battery approaches 100% SOC and the voltage approaches 3.6-3.65vpc. They won’t necessarily stay matched with each other as they enter the upper knee.

Do you know why this happens? Might it be associated with the automatic balancing? Do you know when or how automatic balancing occurs in the Lifeblue?

I did ask the Lifeblue engineer about balancing right after getting the LFP but didn't take enough notes to regurgitate it later. Mostly I got that it exists and I need to charge to 100% to reset the SOC monitor anyway so don't worry about it. I.e., it occurs at or near or beyond 100%; but that's no surprise.

As I've mentioned, the end of the charge occurs over just minutes and I've never managed to catch it.

[hclarkx]

Originally Posted by C.Martin

While I do not have Lithium Batteries,,,I do have two Battery Monitors. I guess when Inadd Lithium eventually, I will have three.

When I got a Lifeblue LFP about 18 months ago, it was, from my research, the only "drop-in" to have Bluetooth. Do others have this now as well?

[hclarkx]

Originally Posted by 757driver

In the example you linked I take with a grain of salt. First charging at .2 C to 14.6v and then holding it there until .02 C which is quoted as a standard charge is an unnecessary damaging overcharge. I would not follow such a charge regime but to each there own. I am confident that when desired and I charge to 14.0v my batteries are 100% charged.

I agree. Always have. Though when I got my Lifeblue LFP all I had to go on was the label on the side which said "Absorbtive Charge Voltage : 14.6 +/- 0.1V". It also says "Float Charge Voltage: 13.8 +/- 0.1V" Clearly Lifeblue thought then that even 14.7V was okay. While nothing I've ever read says 14.6V will measurably shorten life and I have read that LFP is quite tolerant of overcharging, but I do agree that lower should be better.

Sometime since Lifeblue posted more detail found at this link:
http://www.lifebluebattery.com/ewExt...%20sheet-1.pdf

Interestingly Lifeblue is now okay with 14.0-14.6V Absorption voltage and 13.6-13.8V Float.

And, Lifeblue now recommends 15 minutes of absorb time. I wonder if this has something to do with cell balancing since that does take some time. Though most LFP charging curves show the battery not quite at 100% when voltage rises quickly at the end of the bulk charge.

If they are okay with 14.0V, then presumably cell balancing (when needed) occurs at or below 14.0V.


I'm thinking it's time for another call to Lifeblue.

[757driver]

Originally Posted by hclarkx

I agree. Always have. Though when I got my Lifeblue LFP all I had to go on was the label on the side which said "Absorbtive Charge Voltage : 14.6 +/- 0.1V". It also says "Float Charge Voltage: 13.8 +/- 0.1V" Clearly Lifeblue thought then that even 14.7V was okay. While nothing I've ever read says 14.6V will measurably shorten life and I have read that LFP is quite tolerant of overcharging, but I do agree that lower should be better.

Sometime since Lifeblue posted more detail found at this link:
http://www.lifebluebattery.com/ewExt...%20sheet-1.pdf

Interestingly Lifeblue is now okay with 14.0-14.6V Absorption voltage and 13.6-13.8V Float.

And, Lifeblue now recommends 15 minutes of absorb time. I wonder if this has something to do with cell balancing since that does take some time. Though most LFP charging curves show the battery not quite at 100% when voltage rises quickly at the end of the bulk charge.

If they are okay with 14.0V, then presumably cell balancing (when needed) occurs at or below 14.0V.


I'm thinking it's time for another call to Lifeblue.

From my experience and take on LifeBlue literature I get the impression they do not have active shunt based cell balancing which is fine by me. The short Absorb time is to keep them from being held in the upper knee for any length of time.

[hclarkx]

Originally Posted by 757driver

From my experience and take on LifeBlue literature I get the impression they do not have active shunt based cell balancing which is fine by me. The short Absorb time is to keep them from being held in the upper knee for any length of time.

Could very well be. Though when I talked to a Lifeblue engineer balancing was one of my questions. I didn't get a complete answer; he was more interested in telling me what kind of use causes unbalance. But, it did seem clear that balancing is provided.

You mention shunt based cell balancing. As you likely know, shunt based balancing removes energy from cells that get ahead of the others then brings all cells to 100%. The other method is routing more current to lagging cells. I would think that either would affect individual cell voltages during the rebalancing. I've long wanted to see signs of cell balancing but never seem to be there at the right time. It seems you have. If the cell voltages move apart but later come back together, what you are seeing must be balancing activity.

The label on my LFP uses the word "Absorb" but only to indicate the highest voltage reached (14.6 +/- 0.1V); there's no mention of absorb time. When I talked to the Lifeblue engineer, he was fine with my using 0 minutes of absorb. Clearly that has changed.

As for the 15 minute absorb time recommendation, I would think if it's to limit absorb time, they would suggest 0 minutes (or the minimum your charger allows -- since some do not accept 0). My best guess is that Lifeblue calling for a 15 minute absorb time is either to facilitate balancing, or to get SOC to 100%. Their new absorb voltage range (14.0-14.6V) may be behind it. Perhaps using a lower voltage does not facilitate complete balancing without some absorb time. Or, since most LFP charge curves show SOC is still a bit below 100% when voltage hits the "absorb" voltage, the 15 minutes may be to fully top-off the LFP.

[Itinerant1]

Originally Posted by hclarkx

You mention shunt based cell balancing. As you likely know, shunt based balancing removes energy from cells that get ahead of the others then brings all cells to 100%. The other method is routing more current to lagging cells. I would think that either would affect individual cell voltages during the rebalancing. I've long wanted to see signs of cell balancing but never seem to be there at the right time. It seems you have. If the cell voltages move apart but later come back together, what you are seeing must be balancing activity.

You will not see cell balancing off your bt, you can't see individual cells. You only see battery voltage as a whole and once it's at the set point it just stays there. Now if you had an individual cell screen with live time viewing you could watch your cells flux till the cows come home.