how to determin what charger to use?

[MK2R]

Simple question, how to choose charger for a battery pack.

Voltage is "easy" to pick,if u want to charge up to 100%, take your cells max voltage capacity times cells in series. for me it's going to be 4.2*13= 54,6V.

But how to choose current, and why? pros and cons?

BMS: daly 13S 48V 60A. max current charging is not going to be close to reached, it's somewhere in the range 30-60A.
Cells: 91 samsung 18650 26J (13s7p). tested at 2400-2500mah at 1A drain (brand new rated at 2600mah). so the cells are in regards to capacity not far from new

Standard charge is at 1.3A, rapid charge is at 2.6A, max nominal discharge is at 5.2A.


So let me get my thinking out there, if each cell is going to be charged at 1.3A, it comes down to 91*1.3A = 109A at 4.2V, which is around 450Watt. Feeding the bms with 54.6V gets this to a bit over 8A charging current at this voltage.

What if i don't charge them to 100% (4.2V) and i settle with somewhere between 4.0-4.1V, is it an bad idea? or is it a reasonable idea?
What if i don't charge it with the 450Watt, and instead get something slower that might charge them at 200watt, which is just over 0.5A per cell. Is it just going to result in a longer charge time, or can a lower amp have some cons when charging the cells?

This is what i am mostly looking into rn:
https://www.ebay.com/itm/Mean-Well-LRS-350-48-power-supply-350W-48V-7-3A-ultra-flat-30mm-1HU-metal-case/164111779661?epid=669142881&hash=item2635d3074d:g:j24AAOSwkbReYRp9

will be lower than 1.3A per cell, and it will not be 100% charged
350W at maximal 52.6V gives around 1A per cell in charging, and the cells will reach a charge of 4.04V, so about 96% of full charge.

Or am i doing every thinking wrong here and need to rethink everything :lol:

Best Regards! =)

 

[goatman]

this is how i do the math

7p x 1.3amps = 9.1amps

9.1amps x 54.6 = 496.86 watts

Grin Cycle Satiator will do 8amp charge
read their page
https://ebikes.ca/product-info/grin-products/cycle-satiator.html

 

[MK2R]

a more simple way i agree i just estimated roughtly.

still good info, it was a bit more complicated, i forgot the sigmoidal shape of the charge/discharge curve when i did my percentile estimate, 80% is a pretty healthy charge number i guess, many EV cars do limit their batteries charge capacity to increase overall lifetime of the batteries.

This "just" 91 cells battery pack is a test pack, i have ordered 250 more cells which i have to test from one supplier, and another 200 from another person. so total amount of kwh will probably increase by 100 or more %

So if i get a charger for the test pack, can i use it for a much bigger pack, but it will take longer time, or do i need to invest in a bigger charger with more amps to even get it to work?

 

[goatman]

i think you can stack satiators but $$$$

https://endless-sphere.com/forums/viewtopic.php?f=14&t=60169&hilit=stack+satiator&start=725#p1537630

 

[flippy]

Amps only dictate how long it will take. Voltage sets how full the battery is going to be. Amps is just the rate of water coming out the hose, not how far you can fill the bucket.

With that in mind you need to charge as slow as praxtically possible. Fast charging kills batteries.

 

[MK2R]

Amps only dictate how long it will take. Voltage sets how full the battery is going to be. Amps is just the rate of water coming out the hose, not how far you can fill the bucket.

With that in mind you need to charge as slow as praxtically possible. Fast charging kills batteries.

Okay, so practically speaking, i could charge my close to 1kwh battery pack at 50watts, but it would take me up to 20 hours to charge it. Well we all know that a 1kwh battery pack can't deliver 1kwh, the useable range might be somewhere around 0.8kwh, but still, something like that if i understand this correctly.

Anyways, i did order my power supply now, will be able to charge my battery to around 4.10-4.15 V per cell. the inbuild cutoff is at 56V (and that would be equal to 4.3V per cell). so i just need to stay at max 53-ish volts and it should be safe, and i also got the bms to help out with overcharging protection.

now i just need to decide what cables i need to use. should i pick the diameter of what the pack will maximally be able to provide, or to what i am intending to use. I have ordered everything, and i have a lot of copper cables at home etc, many sizes and a lot of lenght.

Charger is at 8,3A (48V, output 400w)
BMS is at 60A (48V, output 2880w)
Inverter is output 2500/5000w 230V AC. 92% efficiency. so input 2717/5435w, at 48V = 57/113A.

My thinking was bms nominal effect max at 2880w, inverter max nominal effect 2717w. at short max bms is at 150+A and inverter at 113A. should be safe.

The question is: I am going to use Max 2000w from the inverter, that is around 45A from the bms to the inverter.
Do i need to pick cables that can handle maximal nominal current at 60A, or do i need to pick cables that can handle the short max current at 150A + (180A +-30) ?

 

[flippy]

unless you have a programmable bms to match your lower voltage the bms will do nothing until a inbalance will get too far.

you spec the cables always to ensure that nothing will happen to the cable (until you reach the fuse) even in the case of a dead short and a bms faillure.

personally with an inverter i would not use a bms on the discharge side. just connect the charger to the bms. the inverter has a cutoff at ~42V or so the bms would do nothing, the inverter will never get close to draining the pack.

also you are wrong to use 13S. you need 14S otherwise you will lose the bottom 20~30% of your capacity under load with a 42V cutoff. or you willl get an instant shutdown once you load it down when the battery gets below 50% soC.

you need a smart bms and a dumb charger. for the charger its simple: 2 HRP-200-24 in series. that will work in your use case perfectly. any form of smart-ness in your charger will cause it to stop charging once it has reached its set level. a grin will NOT work in this application and is WAY overpriced for what you actually need. if possible: cancel that order and buy the mean wells.

your offical discharge limit is 37A. that is 1.7kW from the battery. you will need more then 7P if you want that pack to survive for a meaningful time.

 

[MK2R]

unless you have a programmable bms to match your lower voltage the bms will do nothing until a inbalance will get too far.

you spec the cables always to ensure that nothing will happen to the cable (until you reach the fuse) even in the case of a dead short and a bms faillure.

personally with an inverter i would not use a bms on the discharge side. just connect the charger to the bms. the inverter has a cutoff at ~42V or so the bms would do nothing, the inverter will never get close to draining the pack.

also you are wrong to use 13S. you need 14S otherwise you will lose the bottom 20~30% of your capacity under load with a 42V cutoff. or you willl get an instant shutdown once you load it down when the battery gets below 50% soC.

you need a smart bms and a dumb charger. for the charger its simple: 2 HRP-200-24 in series. that will work in your use case perfectly. any form of smart-ness in your charger will cause it to stop charging once it has reached its set level. a grin will NOT work in this application and is WAY overpriced for what you actually need. if possible: cancel that order and buy the mean wells.

your offical discharge limit is 37A. that is 1.7kW from the battery. you will need more then 7P if you want that pack to survive for a meaningful time.

The inverter i ordered has a range from 40-60V. at 40V 13S gets it to 3.07V per cell, at around 3V the samsung 26J drastically drops, it is about there the sigmoidal end of the curve begins.


I don't understand how to calculate the official discharge limit really.

Please explain, i want to learn (i can add 259 more cells to the pack if it doesn't work, but 250 of them are untested, but rated around 2.1mah, so if i am lucky 200 or more of them are good)

I did order a mean wells 400watt 48V (adjustable to 52.8V) power supply. depending on my output current in the socket, it might go over 52.8V, only way to find out is to actually measure it later. but my ebay order had a problem, the unit was not in stock so i have an option to either wait or re-order it. maybe i should look at something else then

 

[MK2R]

or am i supposed to think like delta voltage * A. so 3.7/48 * 5.2 = 0.4A per cell "at equal to 48V" ?

So a pack of 7 cells will just be able to provide 2.8A at 48V, and at 13 packs i get 36.5A. I think u are right, i did miss-assumptions. lucky i got more cells then. so at 45A consumption, i need around 9 cells in paralell (8.65 cells) to run it at max nominal current for the cells.

and in this case at 2.1kw i will have no real margin on the cells, i will be using them att full current, which will be around 2C per cell. and i don't want to push them that hard, so with margin i should go to somewhere between 18-20 cells in paralell to at least get it to around 1C i think

 

[flippy]

I don't understand how to calculate the official discharge limit really.

technically there is no limit. but lower = better.

Please explain, i want to learn (i can add 259 more cells to the pack if it doesn't work, but 250 of them are untested, but rated around 2.1mah, so if i am lucky 200 or more of them are good)

if you CAN add 200 cells (even shitty ones) you should. more cells = better. if you were to add those 250 cells and do capacity testing on them and distribute the cells so each block has the same capacity you can massivly increase the performance and capaicty of the pack. if you were to make a 13S battery as your plan is now then you would get with 2200mAh average and you end up with a 13S25P battery (25 cells of the worst cells can be tossed) you end up with a 2.5kWh battery capable of delivering a HUGE amount of power. even at full load of 2.5kW it would mean each cell only has to give about 2A each. something even crappy cells can do.

I did order a mean wells 400watt 48V (adjustable to 52.8V) power supply. depending on my output current in the socket, it might go over 52.8V, only way to find out is to actually measure it later. but my ebay order had a problem, the unit was not in stock so i have an option to either wait or re-order it. maybe i should look at something else then

what model meanwell EXACTLY? not every model can be used in this manner. and your grid voltage/current has no influence on the output of a meanwell charger. power is only reduced below 100V AC. if the spec sheet says 52.8V then its 52.8V. nothing more.

 

[MK2R]

I really like this forum, it made me realize a lot of things. a 60V power supply that can be adjusted +-10% (meanwell, many more) still provide me with anywhere between 54-66V. and it covers both a 13 and a 14S bms. Right now my order is pending. i should probably cancel that order (since i have the option now for free) and get a ~400W 60V supply instead. it makes more sense! and it is about same price, about 40-50USD with shipping.

But finding 14S bms:es was harder, at least when it comes to higher Amps. I find daly there as well, around 50-60 dollars. but there is also this smart bms from the brand JBD. never heard of it. but here is a link:
https://www.ebay.com/itm/JBD-Smart-BMS-14S-60A-52V-Li-ion-Battery-Protection-Board-UART-Bluetooth-APP-PC/164766076678?hash=item265cd2cf06:g:1iIAAOSwBCFgU1J7

not to pricy. if it can do 60Amps, i don't know, is it reasonable? when u look at the drilling holes in the board it looks kinda thick materialwise.

with my inverter, going a 14S bms will give me 40V at 2.85V per cell (which is around cut off voltage from the bms), and at full charge the battery pack will be at around 58.8V, and the inverter can manage up to 60V. so to use the maximum capacity, a 14S bms makes much more sense.

So the question is. can u trust a "cheap" smart bms like that? or do i need to get something more trusted (as i understand it, daly is pretty trusted?)

 

[flippy]

that bms will not do 60A reliably.

get this one: https://www.aliexpress.com/item/4000529723243.html you can do with the JK-BD6A24S10P.
it can do active balacing. very handy if you have a lower quality battery. it pumps the power around instead of burning it off as heat. and it does it 10x faster then a normal bms. and because its smart you can program it to start balacing at 4V.
you can also watch the power consumption with the app.

PLEASE be more specific with your charger selection. i fear you are looking at the wrong models. cancel any orders you might have before checking here first to prevent you from making the wrong buy.

 

[MK2R]

something like this: https://www.ebay.com/itm/DE-60V-400W-DC-Switching-Power-Supply-6-6A-For-12N-m-Servo-Motor-LED-CNC-Router/113721202640?hash=item1a7a4fd7d0:g:hioAAOSwlYNctwbt

I know at 400w it's going to take about 5-6 hours to charge the pack, but i can take the time
Interesting bms

 

[flippy]

something like this: https://www.ebay.com/itm/DE-60V-400W-DC-Switching-Power-Supply-6-6A-For-12N-m-Servo-Motor-LED-CNC-Router/113721202640?hash=item1a7a4fd7d0:g:hioAAOSwlYNctwbt

I know at 400w it's going to take about 5-6 hours to charge the pack, but i can take the time
Interesting bms

as i expected.

that is not going to work. these things are not CC/CV capable. they will either (and hopfully) instantly just shut down or more probable: blow up if you connect them.

if you keep on planning on 13S you can use a single HRP-450-48. for a (better) 14S you can get 2 HRP-200-36 in series. the latter is actually passive. and either allows you to crank the voltage to 4.2V per cell once you start losing capacity and want to compensate.
i do recommend slapping a 120mm pc fan on the passive models as they can get REALLY hot without some airflow if you burn them for many hours at full load.

i am personally a fan of the 300W models. can be stacked with VHB tape and placed nearly anywhere. they also crank out 400W in real life. i have used many dozens of these. they dont break. warranty is also 5 years. they are originally meant for medical equipment.

 

[MK2R]

okay, i don't understand what the difference is between them. i see people charge lithium cells with bench power supply
to me it's direct current with amount of electrons and voltage. what is the difference?

I guess it's something like this unit might work?
https://www.ebay.com/itm/Regelbar-Digital-LCD-DC80V-5A-Einstellbar-Converter-Netzteil-Buck-Modul-CC-CV/233534007367?_trkparms=ispr%3D1&hash=item365fb62847:g:5JsAAOSw49BedGwS&amdata=enc%3AAQAFAAACkBaobrjLl8XobRIiIML1V4Imu%252Fn%252BzU5L90Z278x5ickkai8xCwosGKpC0NWj85e%252FByurJ8abOpAy3xCMxQPVJkrQQm5plMw4kJiUP8PcSguhNPk6TGQ%252FsohqQHxDdyllR2AJh9UT99rt55B9L00Qi8c8UqEo7w2FCpttVq9SSsDlq%252FZHitNDWoZTBb9XIZm%252By22NZ0CwjlL9wcc6mO8dd7%252BvJiuvwwZdOuUVlMDFBxpfG0yjZpbRByjxopWztMeN1Pca9nHBkQi3F3jek26yzvAlU6ryXH3pooTPP7Z8ibAsKQajCyCW4wNdvobfWzZAwvHmrzTfmAAaffZe5Nl3J%252FT8YjgFRLpYBjgx5%252Bw0KQkraZeonuMEF7DlV58F1WgZyoarRbFwgXMK3mM7K1IMr4CxFO%252BDvzno6AVtwTgIePJF97x1nseFOwJvrAcnGtquNWssrcjy%252Ffd02ubxONMNYNpWcfnIgQ42r9BNpZwPC4bWIOWKu1wx1jC%252B9Ejo4%252FGWlG13uhXuYqBpTvoZ1CE0hbowmiToNDzj5%252BnL35s5fAhrTImvGwJXd%252B6CM8jCBlNwErgZ3tBo2gE9SpPegtGplXTeEHaMBl3bIv4Y1Gv25STdRasJYZLZTGIvBi5Vs7%252BIu1fJbYJSEC3cffpGv%252BKTjqdBz8O27u1msEwvjTmzjlrfDZFbKVMSjp3qBY9DEe9AWfy%252FDlejYQgbKMxdJbozWBJl2EXSymIhs0Kp6XEdlJKxi151OJtir5Q5Jd6bUyeJeF4loiauErr0cX6DNWdKgBsk9WBpzyaESDvlCpOcwuOP6iFZ9uk6UJT75wAl2ZrAeBGNI0ihQEF0gx56fC1SLJjz%252B8jo1V%252FzvhPKilblQTIX%7Ccksum%3A2335340073672d59489607ff4954a28dc1ccbbf37955%7Campid%3APL_CLK%7Cclp%3A2334524

or is simply just being cc - cv not enough and there is more things

 

[amberwolf]

There are two ways a power supply can current limit. Ones that can be used as chargers must do so by lowering their voltage during limiting. The bench supplies that are used for charging are "lab psus" and such that have what is called a CC or constant current capability, though they may not list it that way depending on the technical ability of the seller.

The Meanwell HLG and ELG (and some others) LED PSUs can be used as chargers. Other Meanwells that don't have that can't be used.

Ones that can't be used limit by "hiccup" mode, which turns off the output until the load goes away, then turn back on, or they blow a fuse or other component and stay off until they are repaired.

The most recent link you've posted does not appear to be a power supply at all, but only a converter from one DC voltage to another. If you already have a power supply at a higher voltage than your batteyr needs, but within the limits of that DC-DC, then you could use this device to convert to the battery voltage in the way that is needed.

 

[markz]

Some power supplies can work with charging batteries directly, like the Meanwell HRP and others like it.
https://endless-sphere.com/forums/search.php?keywords=Meanwell+HRP

You cant just hook up any old power supply, not like the server psu's because those you can use to power iChargers because they have so much amperage and you can connect them in series to get the voltage you want. They are 12V 60A, so if you have a powerful iCharger, you can go ahead and connect in series 4x12V = 48V 60A, just be sure that the inputs and outputs are isolated. People go that route because the server psu's are so cheap to power specific chargers.

okay, i don't understand what the difference is between them. i see people charge lithium cells with bench power supply
to me it's direct current with amount of electrons and voltage. what is the difference?

or is simply just being cc - cv not enough and there is more things

 

[MK2R]

asking questions makes me learn more! yay!

but what this CC-CV does it constant voltage and amps, if i plug it in at the power supply it will not be constant voltage and current, and that could hurt my cells ?

Ok. yes just before i read your answers from searching around on ebay i kinda figured those CC-CV supplies need to be feeded with DC. but i assume if i do get a "400W" DC supply, i can never get more than than 400W output. and with those adjustable dc-dc (cc-vc) i could charge different packs.

I know i heard something about some "luna chargers" but i didn't find them online really. is there any already made "alright" priced chargers u can use out there to charge a 2.5kwh + pack? or is mainly build it yourself that is the way to go in this matter?

 

[amberwolf]

is there any already made "alright" priced chargers u can use out there to charge a 2.5kwh + pack?

Charge at what rate, and to what final voltage? Either how much current, or how much time.

What specificaly does "alright priced" mean to you?

Without knowing that we can only keep giving you general things to look for.

Without any other info, I would just say to use the Meanwell HLG-600H-54A for a 13s or 14s pack. It's weatherproof (if you need that ever), fanless (no fan to fail and cause it to burn up), and adjustable voltage up to 57.7v and adjustable current up to 11-12A on the ones I have here. I have one set that is paralleled for up to 24A, and two that are individual for just 12A. I've used one of those two for a few years now built onto the bottom of the SB Cruiser trike for onboard charging without any problems, and the other for offboard charging of spare packs, etc.

If you want a really adjustable one, I've also used the Cycle Satiator from Grin Tech for years. Mine is the 48v 8A version, and it also can go up to at least 58v (60v I think), and mine has profiles for several packs I have here from 12.4v up to 58v; it's mostly used for one at 16.4v at 8A.

 

[MK2R]

one "final" question to make sure i do understand this. if i get this

https://www.ebay.com/itm/DC-DC-400W-15A-module-Step-up-Boost-Converter-Constant-Current-Power-Supply-LED/402644940679?hash=item5dbf823787:g:OS4AAOSwn0Ff~4VL

https://www.ebay.com/itm/114666090531?mkevt=1&mkpid=0&emsid=e11051.m43.l1123&mkcid=7&ch=osgood&euid=053e8df8a4d04d2fab2c566f2e65c23d&bu=45287487175&osub=-1%7E1&crd=20210325020716&segname=11051&sojTags=ch%3Dch%2Cbu%3Dbu%2Cosub%3Dosub%2Ccrd%3Dcrd%2Csegname%3Dsegname%2Cchnl%3Dmkcid

I use the 230V AC to --> 48V DC 400W then DC-DC module and set it to either 54.6V (13S) or 58.8V (14S) and then choose what current i like to charge with (but max 400W minus losses in conversions)

Is this basically how it works and what i need to overcome to charge my pack/packs safely?

 

[markz]

I have found that the prices for Meanwell charger psu's are the same no matter what voltage and current under the same model number. Now there maybe price differences in mw model xyz when it comes to 48V vs 5V, but not so with 24/36/48/52V mw's I've seen.

When I've hooked up a dmm to my mw hrp, I noticed that the current was maxxed out with the voltage rising slowly, then at a certain point the current slows down and continues to go down to a trickle.

There are some no name, generic charger psu's that others have used on ES, which look a lot like what you've linked to but I can't be certain.

MW-ENC
https://www.meanwell-web.com/en-gb/technote-different-electric-vehicles-use-different-chargers

 

[MK2R]

but generally what happens when u reach target voltage, the charger gets triggered by drastically lowering the current to not overcharge the cells?

I need to look more into this then. if i don't get a dedicated charger i need to get both a dc supply and a dc-dc.
I do assume that inside of this chargers you buy, all of this is built inside the box of the chargers etc

 

[amberwolf]

if i don't get a dedicated charger i need to get both a dc supply and a dc-dc.

No, you don't. You just need a PSU (like many LED PSUs, and many other constant-curent CC type PSUs, or Lab PSUs, etc) that will do the current limiting necessary to charging a battery, that does not operate in hiccup mode, but CC mode.

See my previous post about the MW I use, it is one of the many CC type power supplies out there.

I could try to point you to others but you haven't answered the questions.

 

[MK2R]

if i don't get a dedicated charger i need to get both a dc supply and a dc-dc.

No, you don't. You just need a PSU (like many LED PSUs, and many other constant-curent CC type PSUs, or Lab PSUs, etc) that will do the current limiting necessary to charging a battery, that does not operate in hiccup mode, but CC mode.

See my previous post about the MW I use, it is one of the many CC type power supplies out there.

I could try to point you to others but you haven't answered the questions.

So basically, anything with a DC CC-CV function is usable to charge lithium ion cells from what i understand. correct?

A module like this could do the work, but it need to be feed with some kind of a DC source, and a lab unit or a propper charger you just plug into the wall socket.
https://www.ebay.com/itm/Regelbar-Digital-LCD-DC80V-5A-Einstellbar-Converter-Netzteil-Buck-Modul-CC-CV/233534007367?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D4d8f3fad64b646ba9942b54b729c7649%26pid%3D100675%26rk%3D5%26rkt%3D15%26mehot%3Dnone%26sd%3D222176450625%26itm%3D233534007367%26pmt%3D1%26noa%3D1%26pg%3D2380057%26brand%3DMarkenlos&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3Aecd8c42f-8e32-11eb-add3-1e318864c08d%7Cparentrq%3A6e9d1d671780a1b767982561ffd1428c%7Ciid%3A1.

What i really didn't understand at some videos i tried to watch, how does the charger know when to lower current? if you just have a cc and reach a target voltage it will just stop, charing the cells to (what i heard) 80-90%. and after that it will charge the last 10-20% with a gradually reducing current until it reaches 100% soc.
What makes the current drop? since the battery is peaking at 4.2V all the time, how does it determine when to lower the current? is it just a programmed cycle with an equation, or does it get feedback from the battery when it is getting more filled and response with reducing the current gradually?

 

[flippy]

how does the charger know when to lower current?

it does not. the battery controls the current. the only thing the charger does is limting the current to protect itself and/or the battery until the battery is almost full and the current naturally drops to zero.

dont overthink it and get the meanwells i mentioned before depending on what you want to do. you are making way too complicated for yourself.