I've charged all mine to 14.1 or 3.525v per cell Maybe i need to slightly raise the voltage?

Glad it was helpful!

glad it was helpful

3v? Wow. You will use hardly any capacity. I use a victron smart shunt and I still have about 150a left in a 400a pack at 3v per cell. That's still a lot of useful energy ⚡ I typically discharge to 2.8v at which point, I have 80a left in the battery bank which is manageable for a 400a battery pack. I think the cells are safe and in a good window at 2.8v The danger is discharging to 2.6v often which could lead to damage. The bms cut off is at 2.5v

@@wole04 interesting! Check the discharge curve on your cell chemistry. The curves on my lefepo4 drop like crazy below 3v, meaning there's not much capacity below 3v.

3.2 v as standard lower voltage limit is even better. More cycle life.

Glad it was helpfull.

Thanks, here is video: kzfaq.info/get/bejne/e9ScfrZlzcrbm2w.html

Thanks. I've added links to Arduino parts. May be will add a video on how to build tracker if more people are interested.

@@SolarEngineering +1 for this

@@SolarEngineering I would like to see a video on how the tracker is assembled my self, Thanks

@@SolarEngineering Thanks for adding the links. I hope you do produce a vid on building the tracker, even a short vid referring us to where you got the idea and parts.

@@SolarEngineering Please let's have a video on the tracker. Thanks for the efforts.

thanks. I've added links to Arduino parts. May be will add a video on how to build tracker if more people are interested.

@@SolarEngineering Yes, I want to know how to build that tracker too - Does it measure both ways (in/out) - and know the difference? :)

if i only has old inverter (48v/lead acid-agm) that has Bulk and Float charge, can i safely set the bulk voltage at 56V and 55.4V for float voltage to my 16s lifepo4 batteries?

updated the link, try it now

indeed, or just leave enough headroom above the absorption voltage setpoint that balancing isn’t even an issue.

@@frodev728 lifepo4 isn't supposed to have an absorbtion phase

@@eksine it’s just a label. Semantics. The absorption phase is used for series-packs of cells to allow the balancer to do it’s thing. Of course single-cells don’t need an absorption phase, per-se.

@@frodev728, it really has nothing to do with how many cells in series or even parallel. But you’re right that “absorption” is just another name for the CV stage, that tell you even though it at max voltage during charge, its not fully charged, and if you end the charge just when CV (absorption) stage begins, the battery voltage will quickly drop to the voltage corresponding to its SOC, which might be 80% if the CC stage was 0.25C. Many reserve the term “Absorption phase” for chemical batteries like Lead Acid that really need to be held at a certain peak voltage to complete a chemical reaction that won’t fully complete at lower voltages. Since lithium batteries are not chemical batteries, they don’t need to be held at a high voltage. You can charge them to 80% each time and it will last longer, but doing that to lead acid will kill it fast. But when discussing Lithium cells, especially LiFePO4 with such a flat SOC voltage curve, whether its called CV or absorption is not important but rather the effect of that stage at different peak charge voltages. As we know, the intercalation rate during CV/absorption is related to the voltage differential. So using the max voltage that doesn’t immediately damage the cell finishes that stage faster. 3.45v is only 0.15v above the 90% SOC voltage (3.3v) so it will take much longer to get that next 5% than using 3.65v, which is 0.35v higher. Armed with this basic foundation, a person can size his battery to match the application and desired life expectancy. If you want it to last 8000 cycles, charge it slow to 70%. No absorption stage because it never reaches CV voltage. But if you need something that can capture and store energy from the grid at super duper off peak rates of $0.01/kwh but that only last 3 hours then you need to use CC of 2C and CV of 3.65v before rates go back to $1/kwh. Lol However if i know i have 8 hrs to charge, i will set CC to 0.2C with CV of 3.65v so it will will be fully charged but only for 2 hrs. It really depends on the application, budget and other factors. Videos like this help you decide what’s best for you.

@@imho7250 ok I know all of that and of course it’s true, but my point about absorption phase, admittedly this is a misnomer, is that using the “absorption phase” (constant voltage) to hold the voltage above the “balance start voltage” of the balancer to allow the cells to be put back in balance is a useful and necessary strategy. Doing that is ONLY necessary if you have 2 or more cells in series, because by definition any less than that (namely one cell) will always be “in balance” because it’s the only cell.

wow, what is the brand of the cells? Did you measure capacity after 12 years?

@@SolarEngineering they have lost about 20% capacity. Later I will take look for the brand name.

The manufacturer number is against the wall and I am not disconnecting and moving it to find it "weighing 120kg". I bought it trough alibaba China

@@catesolarcatamaran252 can you get the info from other source like order page etc?

And can you tell us what for these batteries Ar being used? Is it energy storage? How many cycles it do per year?

Glad it was helpful!

Assuming that you did top balanced cells, I would install an active balancer that will prevent BMS from shutting down the pack. Depending on size of your battery pack, I can recommend few different balancers.

)) добро пожаловать на канал

спасибо большое

here is video where I'm building tester: kzfaq.info/get/bejne/e9ScfrZlzcrbm2w.html

@@SolarEngineering I found it. thank you.

checkout this video kzfaq.info/get/bejne/jsWllqt5086YeZ8.html from 7:40

probably because charger cannot push same amount of amps as at 3.65V.

3.45-3.5V per cell, with a 3.4V per cell charger might not go at full power while charging pack (it will reach 3.4 and will float there)

glad it was helpful

yeah, I wish it too. Unfortunately, tests like that will take years...

thanks! Arduino is not so complicated, many online step-by-step tutorials.

@@SolarEngineering yeah, but a Salsa (as a metafor) never can be performed as well as by somebody who has dance in it's bones, how hard you practice and try. If I would say a wiener waltz, then you probably would apply too 😁😁😁

56V should be good enough for 16S LiFePo4, make sure your BMS has cutoff voltage set at 3.65

But most LiFePo4 charge controllers, start in CC / Bulk mode but then switch to CV / Absorb mode.

I'd go with 3.55V

thanks

BMS is a 2nd line of control, MPPT should be 1st, so I'd do 28.4 on MPPT.

I personally don't see any problems with connecting different packs into parallel (when packs are not too far in capacity from each other, like 5X diff). Would like to hear and discuss what is the potential issues could be.

@@SolarEngineering There's no downside to this at all. Has been tested and demonstrated over at Andy's Off Grid Garage channel using "extreme" examples. one tiny cell vs a big battery pack paralleled, they both discharge equally regardless of size. If the large pack uses 10% of it's available capacity, so does the smaller one. doesnt matter if its 1000 mAh alongside a 1000 Ah, the little one will be at 900mAh and the other at 900 Ah after a 10% discharge. :)

@@zoe..d thanks for the info

added link to the description, I've got it from Aliexpress

Good question, at 3.5V per cell v diff will show up, so BMS will have a chance to balance cells. Didn't get about low voltage (BMS will disconnect pack if any cell drop below preset voltage)

i would rather use Active Balancer to help BMS on balancing task.

LiFePo4 cells will drop voltage after charging to ~3.45-50V per cell, so in your case 82.8V - 84V. But don't worry capacity is still there.

@@SolarEngineering ya but mine seems to drop further than that like to the point that each cell would be at nominal voltage 3.2

@@MotoAlias ah, that's not normal. Is that brand new pack? Do you have anything else attached to the pack that could draw energy? How quick is voltage drop?

@@SolarEngineering drops by .1 about every 5 seconds... like when I unplug the charger you can watch it drop .1 till it reaches the cells nominal voltage then stops. I guess it could've had a paristic draw going to my headlight but I've disconnected that and still same problem... the pack isnt new I'm afraid I drained it too low. I had 3 cells that were swollen and I replaced them. But I guess even tho the other cells didnt swell perhaps they're all ruined.

@@MotoAlias I'd disassemble the pack (or disconnect cells) and test few cells individually.

It is same for all Lifepo4 chemistry

@@SolarEngineering Do a Video: - ---I hear you, apparently so, but somehow i think that,say, a 30 Ah and a 280 Ah LiFePo4s will have different graphs for voltages and SOCs; i mean,at the mV level, possibly even at the centiVolt?; Do a video on that; Even from different manufacturers,different materials and chemicals, i see different recommendations. ( also i just read that CALB recommends that the very first charge be to 3.80 volts, (then to the 3.65), i wonder why).

Hi, I need more details: battery model, charger model. Do you connect battery balancing leads to the charger? If not then here is why the charger shows an error.

@@SolarEngineering the charger is a HiTec RDX1 Multicharger. I don’t see how to setup balancing for the battery since can’t get to the individual cells. I have an imax charger as well. I didn’t know at the time that Bioenno sold a charger that didn’t require the balancing would have bought it. But, now I hate to buy another charger. I’m using these batteries for portable Ham Radio operation.

Finally found the issue. Had to go into system settings and turn off balance charge.

thanks, will checkout.

at 2.9 battery is fully drained, there may be just a few percent of capacity.

@@SolarEngineering I don’t go below 3v ever. The tiny bit of extra capacity is not worth the extra stress on the battery.

LFP rated upto 50C. 90 will cause accelerated degradation.

Hi, I'd double-check how many cells are there (15 or 16). Also based on my tests I would recommend lower voltage to 3,5V per cell. You'll still get the same charging speed and capacity, but the "safety" range will be a little bit more bigger.

@@SolarEngineering Hi thanks for your reply, I just checked, they are 15 cell batteries. So following your advice I should reduce the maximum charge voltage to 52.5 volts for added protection/safety of the modules, i've tried to prolong the battery lifespan by never discharging below 40% SOC, rarely below 60% SOC in daily use, am I helping doing this? There seem to be a consensus around this practice of limiting DOD to extend battery life so i'd be interested to have your take on this. Once again thank you for any views and information you provide.🙂👍👍👍

@@ambientfish1369 52.5 sounds right then. I think 40% SOC is too generous for LiFePo4, you could use 80% of it's capacity and it's considered as light use, also important C rating you charge and discharge (smaller rating = longer life). (My statement about 80% is based on information I read on multiple resources, I didn't test it since it's taking years).

@@SolarEngineering Thank you bro for the replies I really appreciate your valuable time. I do try to restrict the draw from the modules, most of the day the house is using solar power direct from the panels, at night average draw from the battery is 220 w at circa 4-5 amps with an very occaisional 2000w draw of short duration for the oven (20 mins) max, I know it is worth being careful in how you utilise batteries and I want them to last as long as possible, thank you again you have been a big help🙂👍👍👍🏴󠁧󠁢󠁳󠁣󠁴󠁿

I've just set the charge voltage to 52.50 volts, thank you.

The voltage of the cells will drop to ~3.45V (if I understood your question correctly)

@@SolarEngineering yep. is that an important fact to highlight when comparing LFP charge graphs? aren't most charge graphs based on resting voltage, not charge/discharge voltage? I feel resting voltage isn't highlighted enough by many people.

thanks!

variable power bench supply, на амазоне большой выбор

Do you feel this causes tests to be inaccurate? I think for this case it doesn't matter, I'm monitoring voltage directly from the cell using Arduino so all graphs are pretty accurate. Load is just discharging cell (same condition for all 3 tests), maybe if I run other wires from cell to load, I'll get a few extra mA, but still, it's going to be the same mA for all 3 tests.

@@SolarEngineering I'm not arguing, just merely suggesting to use a feature that is made available for more AH/WH accuracy. We don't know how much AH or mAH is left in the cell because the cutoff happened earlier than 2.5V. In a 25AH cell with 5A discharge it may not be much but e.g. if you measure your 280AH cells at 20A then you can see a huge difference. And also you can measure an accurate WH with voltage sensing. Anyways your tests itself may be accurate as it's a comparison with the same load.

@@DSmartLife I see, thank you for the suggestion, appreceated.

well, here is another one ;)

@Sanwizard - But we need to go to a high enough voltage to trigger BMS Cell Balancing ...

use Active Balancer to assist BMS

@@MrSummitville Use a Balancer that allows you to to set the start voltage and stop balance voltage.

are you sure that cells fully charged? Did you try to charge cells to 3.65V?

@@SolarEngineering When top balancing yes. I charged all cells to 3.65. But now cells won't charge after reaching 3.35V (53.6V)

hm, not sure why it's happening.

what links do you have. you can provide a link

53.7 is 3.356 or 13.425 12v and 26.85. 3.065 is 12.26

@Meran - How do you KNOW that your theory "... BEST for long term cycle life ..." ?

@@MrSummitville its lithium so better not discharge to 0% nor always be at 100% high voltage

@@freetrailer4poor I actually lowered the charging voltage to 53.4

do you mean measure capacity between ~3.0V and 2.5V ?

@@SolarEngineering Yes. Like you did in this test but for lower voltage cutoff. If you start at a fixed voltage (for example 3.45V) and then do discharge test from 3.45V to 2.75V, another discharge test from 3.45V to 3V and another from 3.45V to 3.25V and see how much energy you get out of the cell. Since discharging to 3.25V instead of 2.75V prolongs battery life but it would be interesting to know how much energy you can get if you cut under voltage sooner

@@hugodeandres1497 will add to my TODO list. Thanks

going to be the same results for LFP for any capacity.

@@SolarEngineeringThank you that helps me tremendously

Wrong

There is no liturature out there stating 4.2 volts is safe for Lifep04.... that 18650 lithium style voltage territiory

@@johnd9763 wrong. You can even Google “safe max charging voltage lifepo4” and you’ll see right at the top 4.20V is listed. You can probably find some decade old literature on the internet for controllers and inverters that mentions voltages well above 3.70V. I found one a couple months ago that was likely from 2010-2012 that had the max voltage for a controller at 4.0V per cell. Wish I could remember the company it’s gotta be an old school one that’s likely still around like Morningstar

Big enough for such a small decrease in available energy

I would also like to know that, to perform such test would take years :) Main point is to keep cells away from 3.65V especially when many cells in series (16 for example).

Do you have link where you found information that LiFePo4 could be charged upto 4.2 Volts without affecting it's life time? Thanks.

@@SolarEngineering I personally don't have evidence about charging LiFePO4 cells to 4.2V but I learnt that was even the recommendation of most manufacturers in the earlier days of this chemistry. Will Prowse also said this in a reply to a comment I made on one his videos dealing with a similar subject matter.

@@SolarEngineering You already have some useful links posted by a user named Robert Grant, about 8 months ago, on your video titled "Testing cheap 12V LiFePo4 BMS. Be aware."