New to LiFePo4 and New Member - Battery, charging and BMS Questions.

[electroneg]

Hi All,

Great forum you have here, I've been reading through a number of threads on here and seems a great source of information and help.
My name is Dale and I live in a small country in the UK called Wales.
I'm an Electronics/Industrial electrical engineer by trade.

I've just started using LiFePo4 batteries and would like to find out more about them and how to make sure I'm getting the most out of them and interested in charging and testing in detail.

My use case for them is a bit mixed, I'm a Radio Amateur so I like to operate my equipment portable. That varies so I take different size batteries with me depending on what I'm doing. From being near the car to being at the top of a mountain.

We are also avid campers so enjoy breaks away in the tent and ideally like to go to quieter more remote locations that tend not to have mains hookup so planning on taking some LiFePo4 batteries with us.

So far I've bought a number of batteries with built in BMS's and I also have some cells I've salvaged from jump starter packs.

Out of the 4x "12.8V" Batteries I've bought with built in BMS unit's I've noticed something happening with them all fresh out of the box.
3x Of these batteries are the same, "12.8V"/ 8Ah and another is a different brand and capacity, that is a "12.8V" / 22Ah (24Ah Nominal)

With the 3x identical batteries I charged each one individually using one of my Bench Power Supplies, I set the current limit to 2A and Voltage to 14.6V
everything seems good through the CC bulk phase, but as soon as the current goes down and it starts approaching 14.6V in CV mode the BMS will disconnect the cells, so one or more cells are hitting the limit causing the BMS to disconnect. This has varied between 14.4V - 14.6V between these batteries.
So I'm only getting seconds on the CV stage before the BMS disconnects the cells which I'm not fond of.

I discharged all 3 of the batteries, left them for a while and recharged them using one of my Bench PSU's, this time I set the Voltage to 14.4V and the Current limiting to 2A and charged them all individually again (I have 5 or more CC/CV PSUs here) again they went through the bulk stage no problem and then the current started tapering off nicely as they approached 14.4V and at 14.4V there was a current draw of approx 80mA, so gradually I increased the voltage on the bench PSU up by .5V at a time watching the current rise then settle to 80mA and so on. I carried on doing this on all 3 batteries till I got to 14.6V and now the BMS is not disconnecting the batteries and will sit there indefinitely (Only left so far for an hour or so to check) and eventually drop to 20-40mA (I assume this is the quiescent current of the BMS?) I pushed the PSU up to 14.62 and it's fine there as well so a little bit of headroom before the BMS disconnects (I took the PSU up a bit higher momentarily to see if the HV disconnect is working and it does disconnect at a higher voltage)

So far so good I'm thinking, 2 of those batteries I've discharged to a safe limit then recharged with the PSU at 14.6V 2A and the BMS has stopped disconnecting, so I'm wondering if by doing that step in the previous charge by gradually increasing the current has allowed the cells to balance somewhat?

Now on to the 4th battery, the "12.8V" 22Ah (24Ah Nominal)

This came supplied with a 14.6V / 3A "LiFePo4" CC/CV charger so I thought let's just use this charger and see how it goes!
I checked the voltage on the battery to see the SOC that it arrived with and I can't quite remember the actual voltage but I think it was around 13.4V or 13.5V

I connected checked the output of the PSU with a multimeter and it is 14.61V exactly. I connected the charger to the battery and had the multimeter connected at the battery terminals to watch the charge voltage and monitor it's progress.

With this charger it states the LED is Red when current is >200mA (CC Mode) and Green when <200mA.

After a few hours, the LED went Green and the Multimeter was showing 14.61V with both the battery and the charger connected.
Great I thought, lets leave it a few more minutes and see if the supplied charger has a shut off and I should see the voltage on the multimeter drop to the SOC Voltage of the battery.

While I was watching I did notice after a few minutes the voltage dropped on the multimer to just below 14V, but it was not the charger switching off, it was the BMS reconnecting the cells as the LED on the charger went Red again and after about 30 seconds turn green.

I got some more test equipment out and could see it was exactly what I thought was happening, if left the BMS would disconnect and then reconnect as the voltage has dropped on one of the cells. I'm not sure whether this would sort itself out or not eventually but I didn't like it.

I took the battery off charge left it for a while then discharged it to start again, this time I put it on my ISDT Q8 so I could get a rough idea of how much current approximately the battery had taken (I know this is very approximate) but I wanted a rough idea to see whether it would take the full 22Ah and would be concerned if that figure was a lot less than that. The ISDT Q8 was set to 4S LiFePo4 (3.65V) 3A Unbalanced as I was just using the battery terminals.

I let that run for some time and kept popping in to monitor it's progress, it did the bulk charge and said the battery had taken about 23.2Ah, so that was partially reassuring. As mentioned if it had taken a less or a lot less I'd be quite concerned.

Then the ISDT Q8 switched over the CV mode as the current had dropped off and the battery was very near 14.6V, then I heard a beep and it had stopped, it was only in this mode for 30 seconds or so, just like it did on the supplied charger.
I then noticed the 23.2Ah measurement had disappeared off the Q8 LCD, which means one thing. The BMS had disconnected and not the Q8 terminating the charge.

So I let things settle for a while and checked the battery resting SOC which was around 13.6-13.7V

I put the battery on my TTI TSX3510 PSU and set the voltage to 14.6V 3A and waited to see what happened. The BMS disconnected the cells, I worked backwards to see where it was disconnecting and it seemed to be around 14.5V. So leaving things settle again for a while I started off at 14.4V waited for the current to drop, then increased it by .5V then worked my way up to 14.6V as the current dropped on each increment, it now went up to 14.6V without the BMS disconnecting the cells. I took it up a little higher and all was fine and the HV disconnect was working correctly.

I discharged the battery a bit and left it, then put it back on the supplied charger and that BMS disconnecting loop has stopped.
I left it there for some time with a pair of multimeters monitoring current and voltage for about an hour, I've just switched it off now as I didn't want to leave it too long, the current draw was 60mA and voltage was 14.61V - I'm honestly not sure how long you should leave a LiFePo4 battery with a BMS at that voltage (or any voltage) with a very small current draw. Is this safe to leave or will that cause damage when there is only 20-60mA current being drawn as the batteries are being held at 3.65V/Cell? I know some/all of that current will be the BMS I'm assuming.

My concern are 2 things, the BMS disconnect loop (I hope this has stopped for good now, but I will discharge and re-charge to check) is this something anyone else has come across and does it just sort itself out if left? And this supplied charger will sit there in CV mode indefinitely, is this <60mA current draw and batteries being held at 14.6V harmful at all? One of the reasons for buying this battery was the supplied charger that I can use for my other batteries. I just wanted to make it easier to put a battery on charge without cluttering my workbench, overnight charge or if I'm out. I assumed (Maybe wrongly) that it will turn off when the current draw was at a certain level.

Obviously It's the same situation if I use one of my lab CC/CV power supplies, any of the batteries will sit there indefinitely with a very low current draw of <30mA @ 14.6V and I'm not sure if it's doing any harm to them.

Being an electronics engineer I'm really curious about how this all works and find it fascinating, I'm not one to just plug something in and forget about it so I like to check things over and also build my own equipment. We are also moving house and I will be putting all my radio equipment in an outbuilding and want to build a battery bank to harvest some energy. Not to mention hopefully building a camper van and plan on putting some batteries in there too.

Just for some clarity, all the equipment here is calibrated, the power supplies and multimeters etc. So there is no discrepancy regarding measurements that I have mentioned between any of the equipment I have been using.

I'm going to buy an Electronic load with Ah/Wh etc so I can get a rough idea of the total capacity of my batteries from a discharge, probably one of those generic 150w/180w units that seem quite popular.

I do have an electronic load that I use for repairing and testing power supplies, but that has no form of accumulated energy/power reading. It just a simple FET based load with V/A meters.

Apologies for the essay, lots to ask and write about and I really do appreciate you taking your time to read this and look forward to reading your replies.

Sorry more questions, what is a healthy ideal 100% SOC Resting Voltage range for a "12.8V" LiFePo4 Pack as I keep finding conflicting information?
And when does a BMS start balancing?

Attached are some pictures of the 22aH battery with the 2 multimeters with the charger sat there at 14.6V and batteries taking ~70mA.
Also a picture of my messy workbench with a small selection of some of my CC/CV Lab PSU's


Dale

 

[999zip999]

My A123 20ah cells are build in two 12s packs no bms just two sets of 6s balance wires. 8 plus years old and mainly bulk charge .I do have a RC balance charger but never need to .
I use them at 24s on my bike.
I charge to 3.5v but 3,45v is full for the most part. lifepo4 can be charged to 3.7v but no need to. A great cell but big and heavy. It all depends on the quality of the cells inside the battery. Good luck

 

[eMark]

While I was watching I did notice after a few minutes the voltage dropped on the multimer to just below 14V, but it was not the charger switching off, it was the BMS reconnecting the cells as the LED on the charger went Red again and after about 30 seconds turn green.

I got some more test equipment out and could see it was exactly what I thought was happening, if left the BMS would disconnect and then reconnect as the voltage has dropped on one of the cells. I'm not sure whether this would sort itself out or not eventually but I didn't like it.

Sounds like the BMS is OK. The self-discharge (after a few minutes) is quite dramatic, but on the other hand it only took 30 seconds to again turn green. Guess you could say that the BMS is finely tuned :wink:

Are you able to identify, remove the bad cell(s) and replace with AOK cell(s) OR have supplier send you a good (fresh) battery ? Those kind of BMS/battery problems are enough to drive a person up the wall or thru the wall.

 

[john61ct]

13.8V is the highest I'd go for longevity with 4S.

14.7V is way too high.

At rest isolated, around 3.33Vpc is Full

That is not "self discharge" there is no actual additional energy stored between there and the charge CV setpoint.

Do not Float, do not let the cells sit at high SoC for long, only charge to Full just before loads need lowering.

For longevity store at around 3.2V when not actively cycling.

 

[eMark]

That is not "self discharge" there is no actual additional energy stored between there and the charge CV setpoint.

OK, how about "cell/p-group imbalance" ? My "s-d" comment was speculating on reason for the slight imbalance at the top among the p-groups in his new 4x battery.

And when does a BMS start balancing?

Being it's not a so-called SMART BMS with "active balancing" that BMS is realistically more for safety than balancing at "20-40mA" which could take hours with the charger green light on. Because resistance discharge balancing is so slow its practical usefulness is only after the chargers' green light remains on with CV at zilch.

Discharging and recharging has apparently helped balance the p-groups closer together in your 4x battery. If the charger is plugged in again (after say a few hours) and the red charge light once again comes on (before again going green) there's most likely self-discharge somewhere ... due either to faulty BMS internal, external connection or inferior cell/p-group.

 

[electroneg]

Thank you all for your replies, it is very much appreciated.

As all 4 of these batteries have behaved the same I imagine they have never been pre-balanced before assembly or something?

I've been monitoring the voltage of the 22Ah battery and sitting there for 2 days now it is around 13.89V, it was about 14.20V for the first few hours after taking it off charge. I'll monitor it for another day and then give it its first discharge to check 2 things, that it is the capacity on the label (Still within the return period for another week) and to see if that BMS dropping in and out behaviour has stopped or come back.

A 150W "DIY More" Electronic load turned up today, I ran one of my 8Ah "Miady" batteries on it @0.25C discharge today and it showed just over 7.8Ah which was better than I expected for a cheap Amazon battery. I would think a lower current discharge will show more capacity.

One thing I noticed about these cheap electronic loads is they do have a tendency to oscillate slightly, which I can clearly see on the oscilloscope, I have a couple of them here that are MOSFET based loads and they all do the same, not ideal for testing power supplies with but probably okay for batteries though not sure the BMS's would be happy with that however.

After I've finished letting the 22Ah battery settle I'll run this up on the electronic load, but I really am not sure what current draw to use. Is there a standard "C Rated discharge" that the manufacturers use to rate the capacity?

@eMark
So I gather from what you are saying in your post, there is some balancing taking place when the charger or power supply is in CV mode?

Is there any harm leaving this connected for a few hours when there is very little current being drawn in CV mode, as none of the so called "Smart" LiFePo4 chargers I have tried (Other than my ISDT Q8) actually switch off when the current draw is very very low, they just seem to be a CC/CV SMPSU. I don't want to have to be here when I need to charge a battery sometimes and I could be sat on CV for quite some time. I put a PoE IP Camera facing one battery today when I had to go to my inlaws as it was on charge.

Picture of the 150W load that arrived today.
Testing a 12V SMSPSU Wallwart:

 

[999zip999]

There's very little energy stored above 3.45 v

 

[eMark]

So I gather from what you are saying in your post, there is some balancing taking place when the charger or power supply is in CV mode?

How effective do you think resistance discharge balancing is at only "20-40mA" during 2A charging.

Here's what I was told by a supplier of 10s5p China-made UPP battery. Once or even twice a month depending on number of c/d cycles each month (and age of battery) "leave the 2A charger plugged in with green light on for 12-16 hours". A statement like that may make some sense, but one wonders if US supplier isn't sure of the quality of the cells even if manufactured by LG Chem.

Is there any harm leaving this connected for a few hours when there is very little current being drawn in CV mode ...

IMO, the risk is very low leaving charger plugged in with green light ON, but i've only done it once and didn't get a good nights' sleep. My 10s5p UPP battery is in a forged aluminum enclosure ... https://www.amazon.com/dp/B086HKV44F/ref=sspa_dk_detail_2?psc=1&pd_rd_i=B086HKV44Fp13NParams&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUE3M1VGSzhYWkkzVSZlbmNyeXB0ZWRJZD1BMDQ3NTk5MDJLTUVBREwyWlA1OVImZW5jcnlwdGVkQWRJZD1BMDA0MjA3NzNSRE45VTRGTTc3N1Ymd2lkZ2V0TmFtZT1zcF9kZXRhaWwyJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ== ... have never followed his instruction for more than a few hours and so far after two years this UPP battery is doing AOK.

It's my understanding that p-groups with good cells will pretty much balance themselves during charging ... as long as battery disccharge usage isn't abusive and reommended charge rate.

Can you adjust charger pot to only charge to 85% and then with green light on for one hour. Then out-of-sight, out-of-mind storage for 5 days. Then using same charger (e.g. 85%) see if red light comes on and for how long before green light? You may decide to leave charger plugged in with green light one for an hour or two at least once a month ... experiment, test, experiment, test :thumb:

 

[john61ct]

That is not "self discharge" there is no actual additional energy stored between there and the charge CV setpoint.

OK, how about "cell/p-group imbalance" ? My "s-d" comment was speculating on reason for the slight imbalance at the top among the p-groups in his new 4x battery.

I have no idea what you are talking about. I see no imbalance, I see no s-d comment.

And when does a BMS start balancing?

At the minimum "start balance" voltage setpoint programmed.

With better balancers, any voltage, or adjustable.

 

[john61ct]

There is no such thing as self-balancing with lithium chemistries, nor between cell/groups in series, physically impossible.

Being it's not a so-called SMART BMS with "active balancing" that BMS is realistically more for safety than balancing at "20-40mA" which could take hours with the charger green light on. Because resistance discharge balancing is so slow its practical usefulness is only after the chargers' green light remains on with CV at zilch.

Discharging and recharging has apparently helped balance the p-groups closer together in your 4x battery. If the charger is plugged in again (after say a few hours) and the red charge light once again comes on (before again going green) there's most likely self-discharge somewhere ... due either to faulty BMS internal, external connection or inferior cell/p-group.

Active balancing can have several different meanings, and "Smart" BMS even more so. The latter is usually associated not with the former but BT comms and adjustability.

Yes most cheap BMS suck at balancing, but then a quality pack that has been well balanced before assembly hardly needs any.

Ideally the pack can be atomized and easily balanced manually when needed.

The term self-discharge means while individual cells are isolated and at rest, nothing to do with circuitry or or other cells.

 

[john61ct]

I really am not sure what current draw to use. Is there a standard "C Rated discharge" that the manufacturers use to rate the capacity?

No, but usually they outright lie a fair bit, unless buying Grade A cells from a top notch maker. If you use the 0.05C rate (20 hours) and get within 80% of claimed, that is pretty good for cheap batteries.

> I would think a lower current discharge will show more capacity.

Yes

Only measure discharge, not charging.

From the top datasheet spec as Full, really that should be the only time you go so high, maybe once a quarter or annually.

down to 3.0Vpc is the lowest I'd risk.

Do not otherwise use BMS LVC / HVC for normal cycling again those are failsafe last ditch extremes only.

...

There is no need (other than stupid balancing algorithms) to use CV at all.

A simple adjustable HVC circuit terminating the charge source's input at 3.45Vpc is best

if you want good longevity and to charge safely unattended with less than ideal "chargers" (as you say dumb PSUs usually)

Even if a certain profile is "safe" as in won't burn the house down, does not mean good for longevity.

If you do "need" every mAh of capacity utilisation, definitely, do not wait for current to trail down past 0.05C or so, even at 3.45Vpc setpoint.

In general the ideal is to use a minimum profile that results in isolated voltage at 3.33 or 3.34Vpc after resting 24hrs.

Any higher than that just stresses the cells for no purpose, just surface charge, no extra stored energy and converting amps to heat and harmful chemical activity.

 

[electroneg]

Thanks for your replies john61ct.

I get the feeling none of these batteries were pre-balanced before assembly and that's why they seemed to behave a bit better when I slowly crept the voltage up during charging.

I'm absolutely not looking to get every last bit of mAh from them and longevity/reliability/safety is more important to me.
So want to charge them in the ideal way. For my 8Ah batteries when I'm not using them I use the Storage option on my ISDT Q8 that will charge or discharge them to what value it has preset for storage.

I may end up using this to charge them as I can set a voltage cut off for charging easily and it also does not stay in the CV stage at all when the current is low which is good.

I was hoping for something more plug and play and wrongly assumed these "Smart" chargers were as Smart as they say they are. But as you say john61ct they are "Dumb CC/CV" But one thing I did notice, it must be either using PWM to charge or it is checking the battery voltage during the charge cycle as I cannot get it to go in to CC Mode by just using some form of a load, be it a completely resistive load or electronic. The LED will blink RED, so at least they do have some form of protection if things went a bit wrong.

Firstly I just want to check that my most recent purchase of the 22Ah battery is okay while I'm in the return period and will use this one mainly for portable amateur radio.

Then I plan on buying cells and BMS's to build some storage for Solar etc.


Today I checked the 22Ah Battery after being sat there for about 3 days and the voltage reading was 13.88V

I've taken it in to the workshop and running a discharge on it at 22Ah/20Hrs=1.10A
For the first hour I could see the voltage creeping down slowly, it was around 13.6V for a few minutes then gradually crept down to 13.225V which it has currently been for the past 2:40Hrs with the 1.1A load active (I have no idea if that voltage is good or bad or what it indicates).

I will leave this run for 20Hrs (If it lasts that long) and continue to monitor it.
The Nominal capacity is quoted at 24Ah and would be interesting to see if it gets.

I've left my bench meter running so I can keep an eye on the voltage as I don't want to run the batteries down on my Flukes.

 

[raylo32]

Hard to tell if you are mostly looking for a battery project or just want reliable portable power supply for your radio gear. If the latter consider this.... using a Makita 18V battery with a step down DC transformer to output what you need, which I assume is 12VDC.... although I don't know what sort of loads in amps you need to meet. These batteries are bulletproof and can be had in 5 and 6AH sizes and be charged easily and quickly with Makita's fast charger. You can bring one battery or as many as you need for extended use cases.

Here is the first one I made with a 6amp transformer. I am in the process of a V2 that has a 3D printed mount with an on/off switch and will have a heavier duty transformer, either 20 or 30 amps.

The Makita 18v battery dock can be had on Amazon for ~$15USD and the transformers that come in various amp outputs are ~$22USD.

 

[electroneg]

Hard to tell if you are mostly looking for a battery project or just want reliable portable power supply for your radio gear. If the latter consider this.... using a Makita 18V battery with a step down DC transformer to output what you need, which I assume is 12VDC.... although I don't know what sort of loads in amps you need to meet. These batteries are bulletproof and can be had in 5 and 6AH sizes and be charged easily and quickly with Makita's fast charger. You can bring one battery or as many as you need for extended use cases.

Here is the first one I made with a 6amp transformer. I am in the process of a V2 that has a 3D printed mount with an on/off switch and will have a heavier duty transformer, either 20 or 30 amps.

Thanks for your reply.

I'm looking for a few things, I've so far bought 4x batteries, 3x are 8Ah and one is 22Ah. These are used for my radio equipment and also for camping (lights, phone charging and will get a larger one for the compressor fridge)

My radio equipment is pretty tolerant to voltage levels and most will work between 12-16V, however I'm yet to find a DC-DC voltage converter that is not RF noisy as they are all based on switching technology and that makes use with the radio unusable due to received noise. There are devices designed for radio but they are very expensive and still won't eliminate all of the RFI.

4S LiFePo4's (and however many that are in parallel) are in the perfect range for radio use. And DC-DC converters are not needed if I stick with that.

In addition to these we are moving house soon and I will build a Solar system with batteries and controllers so wanted to gain some information on this technology before I start ordering things etc. That will be a totally different system and use case and I won't be limited to 12-16V.

Great system you have there with those Makita batteries, I'm a big fan of 3D printing things and have used my 3D printer for lots of projects. Unfortunately Power tool batteries are VERY expensive in the UK, but the bare tools are cheap.

 

[raylo32]

Wow, a battery powered fridge! Now that's camping in style. I am not using mine with any sensitive electronics like your radio gear I guess the noise is not an issue... and these are indeed cheap Chinese converters... although they look pretty well put together. Mostly going to be inflators/compressors, and RC flight box items like pumps, starters and glow... and general purpose in the workshop. Tool batteries are dear here too at retail but can usually be had for a lot less online.... and more recently some vendors are throwing in extras with tools which can be an offer that is hard to refuse.

Enjoy your project, it sounds like you are on the right track.

Thanks for your reply.

I'm looking for a few things, I've so far bought 4x batteries, 3x are 8Ah and one is 22Ah. These are used for my radio equipment and also for camping (lights, phone charging and will get a larger one for the compressor fridge)

My radio equipment is pretty tolerant to voltage levels and most will work between 12-16V, however I'm yet to find a DC-DC voltage converter that is not RF noisy as they are all based on switching technology and that makes use with the radio unusable due to received noise. There are devices designed for radio but they are very expensive and still won't eliminate all of the RFI.

4S LiFePo4's (and however many that are in parallel) are in the perfect range for radio use. And DC-DC converters are not needed if I stick with that.

In addition to these we are moving house soon and I will build a Solar system with batteries and controllers so wanted to gain some information on this technology before I start ordering things etc. That will be a totally different system and use case and I won't be limited to 12-16V.

Great system you have there with those Makita batteries, I'm a big fan of 3D printing things and have used my 3D printer for lots of projects. Unfortunately Power tool batteries are VERY expensive in the UK, but the bare tools are cheap.

 

[john61ct]

Sounds like you're on the right track.

I ignored the below because I've not grokked what you think you mean

I get the feeling none of these batteries were pre-balanced before assembly and that's why they seemed to behave a bit better when I slowly crept the voltage up during charging.

Cells from a quality maker leave the production run all at exactly the same voltage / SoC.

Their capacity however often varies a fair bit.

If the user is going to use that voltage / SoC - usually near the 50% mark as their balancing point, then in theory no balancing is required before stringing the cell/groups into a higher voltage pack.

But in reality no matter the intended balance point, the user should put all the cells in parallel at 1S at that point for say 48hrs to manually balance and check for QA failures, having bought some spares.

Failing to do this before assembly is not a good thing - so can you see how your quote above is confusing?

 

[electroneg]

Sounds like you're on the right track.

I ignored the below because I've not grokked what you think you mean

I get the feeling none of these batteries were pre-balanced before assembly and that's why they seemed to behave a bit better when I slowly crept the voltage up during charging.

Cells from a quality maker leave the production run all at exactly the same voltage / SoC.

Their capacity however often varies a fair bit.

If the user is going to use that voltage / SoC - usually near the 50% mark as their balancing point, then in theory no balancing is required before stringing the cell/groups into a higher voltage pack.

But in reality no matter the intended balance point, the user should put all the cells in parallel at 1S at that point for say 48hrs to manually balance and check for QA failures, having bought some spares.

Failing to do this before assembly is not a good thing - so can you see how your quote above is confusing?

Yes that does make sense, none of these are a "Quality" brand, though the 22Ah claims to be but I'm sceptical.
What I meant was by slowly increasing the voltage I was allowing the other cells to catch up before the BMS triggers a cut off for HV and cease charging.

I ran the 22Ah battery on the 150w load at 1.10A all day yesterday and this morning I could see the BMS LV cut off is about 10.50V
The counter on the 150W load stated it had run for over 22Hrs and the Ah rating it gave was 23.8, give or take accuracy I feel confident that this battery is okay and easily meets the 22Ah rating.

I'm off camping for a few days, so all these batteries have been charged to suitable voltage for storage. But I am taking an 8Ah battery with me to pump up the tent (Air beams) it will be interesting to see if this has enough power to fill all the beams. I am not lazy, I cannot use the manual pump due to medical reasons such as my heart. Last time we went camping it was such a struggle so I'm hoping this 12V pump will help.

I'm also taking some radio equipment and a hotspot and will have a play with communicating in to and through the ISS as it passes over with voice and data.

 

[raylo32]

That 8Ah battery will easily be enough to pump up your tent which I believe will be low pressure. If you saw my other thread in this "Battery Tech" forum of using the tool batteries as 12V sources, a Milwaukee 4Ah M12 battery was plenty to inflate my 12' 3 chamber kayak at least several times, and that required the compressor going into 2nd stage to get to 3 psi (sides) and 6 psi (floor). You should be good to go. And nothing to be ashamed of, I am a fit cyclist and still resort to the electric pump. The manual one is tedious and hot sweaty work in the summer. Electric one makes it an easy 5 minute task so you can get to the fun stuff quicker.

But I am taking an 8Ah battery with me to pump up the tent (Air beams) it will be interesting to see if this has enough power to fill all the beams. I am not lazy, I cannot use the manual pump due to medical reasons such as my heart. Last time we went camping it was such a struggle so I'm hoping this 12V pump will help.

I'm also taking some radio equipment and a hotspot and will have a play with communicating in to and through the ISS as it passes over with voice and data.

 

[eMark]

There is no such thing as self-balancing with lithium chemistries, nor between cell/groups in series, physically impossible.

No where in what you previously quoted of me (pasted below) was there any mention of "self-balancing" or "lithium chemistries" or reason for you posting the above. Why you go off the rails with double talk that misrepresents another member with your misrepresention and disinformation is puzzling and less than helpful. Which by-the-way isn't your 1st time or 2nd or 3rd time.

Being it's not a so-called SMART BMS with "active balancing" that BMS is realistically more for safety than balancing at "20-40mA" which could take hours with the charger green light on. Because resistance discharge balancing is so slow its practical usefulness is only after the chargers' green light remains on with CV at zilch.

Discharging and recharging has apparently helped balance the p-groups closer together in your 4x battery. If the charger is plugged in again (after say a few hours) and the red charge light once again comes on (before again going green) there's most likely self-discharge somewhere ... due either to faulty BMS internal, external connection or inferior cell/p-group.

Thus why i previously mentioned that you may have a type of dyslexia with your double spaced lines with occasional broken sentence structure. AND unfortunately misinterpreting and misrepresenting another members post with disinformation.

On the other hand those with dyslexia are often very knowledgeable of certain subjects that interest them which is true with you. However, you do an injustice to yourself by misrepresenting another member. You usually come across as most knowledgeable, so no need for misinterpretation of another members post with disinformation.

Yes most cheap BMS suck at balancing, but then a quality pack that has been well balanced before assembly hardly needs any.

That's why Lithium Iron Phosphate batteries with built-in BMS (non-SMART :wink: ) will state that its purpose is protection (not balancing), which is the primary purpose of a BMS. For some reason the OP may have thought that the B in BMS also stands for Balancing which is a stretch, but a common misunderstanding (over-reach) by more than a few.

The term self-discharge means while individual cells are isolated and at rest, nothing to do with circuitry or or other cells.

That's not entirely true. Self-Discharge can also take place in a p-group by one of the cells, but not easy to detect which cell.

Here's something else to consider: There can be as many series cells in a lithium-ion battery as parallel cells. That's why both the series and parallel cells can have approximately the same cell voltage (even within millivolts); while being charged and discharged in the battery. The partial interconnecting of both the series cells and parallel cells helps to balance the lithium-ion battery with every cell in each p-group as well as the series cells. There is at least one series cell and more in each parallel group with possibly each parallel cell also serveing as a series cell.

 

[john61ct]

Self-Discharge can also take place in a p-group by one of the cells, but not easy to detect which cell.

No, that is not what self-discharge refers to.

Balancing is included in 99.99% of BMSs sold, and 99.99% of owners use nothing else for balancing.

It's just that few do it well when more is needed than what a healthy pack of new cells requires.

Again your fixation on ambiguous terms like "active" and "smart" is not an indicator of which BMS are configurable and can handle higher balancing current.

...

> There can be as many series cells in a lithium-ion battery as parallel cells. That's why both the series and parallel cells can have approximately the same cell voltage (even within millivolts); while being charged and discharged in the battery. The partial interconnecting of both the series cells and parallel cells helps to balance the lithium-ion battery with every cell in each p-group as well as the series cells. There is at least one series cell and more in each parallel group with possibly each parallel cell also serveing as a series cell.


Sorry that word salad conveys no useful meaning afaic.

From your very first post here I have never perceived your understanding the basic fundamentals of these specific issues.

Only parallel connections allow any flow of energy, whether healthy desired self balancing or destructive effects of a bad component in the group.

Between the units in a series string, any developing imbalance will only be corrected by deliberate intervention, whatever the means used for balancing.

Just cycling at the pack level does not have any impact on the above, other than preventing harm by

avoiding the voltage shoulders at both ends, on a cell/group level rather than just pack voltage, and

keeping C-rates low if possible.

 

[eMark]

Again your fixation on ambiguous terms like "active" and "smart" is not an indicator of which BMS are configurable and can handle higher balancing current.

Whether fortunate or unfortunate those are the terms used by marketing advertisers and repeated in posts by members of this Battery forum ... and pretty much accepted by those interested in purchasing one without making a big deal out of it.

From now on if it upsets you so much why don't you personally take it upon yourself to correct every ES member that refers to a charger or BMS as SMART. Unless you've not noticed of late i say "so-called" SMART beginning today. Does it insult you and Amber's intelligence to see a charger or BMS advertised as "SMART".

What if the owner isn't as "active" or "smart" as their Charger or BMS. What's the purpose/goal of AI (Artificial Intelligence) if not to react faster than a human being when it's required/necessary for their own safety and protection.

 

[john61ct]

I am not upset in any way.

I have no objection to the use of BMS, nor relying on automation, up to a point.

those are the terms used by marketing advertisers

Yes that is exactly why they should not be used as if they are intrinsically meaningful; they simply have no objective meaning.

What defines a good tool for balancing, besides overall build quality and reliability

is these three specs:

1. balancing current, and whether reduced as delta closes

2. start-balance voltage

3. end-balance delta

the last two should be adjustable,

but are optional if the unit is only attached for offline maintenance sessions, then removed before the pack is put back into use.

_______
> correct every ES member that refers to a charger or BMS as SMART.

Only needed if they are using the term as if it has some objective meaning.

Usually they are just using it as part of the name, referring to a specific model, which does not cause anyone to be misled.

Same with its usage as the attribute of a charger.

Many chargers are flawed because they are too "smart"

but that does not mean every charger marketed with the term is a bad one.

 

[john61ct]

If there is anything in the preceding post that you do not understand, just ask and I will clarify

just proceeding without doing so is not conducive to increasing your understanding

 

[raylo32]

You guys need to let this go. Let this go back to the OP's topic. Just sayin'...

If there is anything in the preceding post that you do not understand, just ask and I will clarify

just proceeding without doing so is not conducive to increasing your understanding

 

[john61ct]

Cross reference, may be useful for noobs in future coming across this thread via googling

https://endless-sphere.com/forums/viewtopic.php?t=113058

https://endless-sphere.com/forums/viewtopic.php?p=1671961#p1671961

https://endless-sphere.com/forums/viewtopic.php?p=1671991#p1671991