Amount of cells? many or few

[flippy]

Before i connect this to my cc/cv unit i wonder, is this correct? I just copied what was on the picture and i checked that the ground cable is the correct one. Does blue/brown order even matter?

https://www.allaboutcircuits.com/textbook/reference/chpt-2/wiring-color-codes-infographic/
Since i am in EU, as i understand it brown is "Live", blue is "Neutral" and the green one is ground
20210421_190056.jpg

Just checked it: everything works just fine, just need to find a safe way to test-charge a lithium cell. will get cellholder with cords in a bit so i might have to wait until that thou.

its fine, ground/live does not matter. just dont mix up the earth lead.

 

[MK2R]

Okay, it worked fine but i realized a little flaw with my setup, since my psu only can give about 67V i can only get out about 65.5V from my cc/cv unit. touche... It will not affect my current pack at all, but for the future if i want to make a 16S pack for a 60V motor i need to use the full potential of my unit, i'll even need to charge it to 67,2V and if i only can get 65.5V with my current psu i'll be lacking a little. input is 0-90V. so simple question:
I know amberwolf said u could pair several 12V psu to get a higher voltage (i assume u need to use the exact same psu). but can i do anything to increase my voltage to about 90V with my 60V psu? like add an 24V psu to it and serial connect them. or am i simply stuck with my 60V and if i want higher i need to buy a new one?

 

[flippy]

https://www.aliexpress.com/item/32983648084.html

get the 90V 5A model and you will have plenty of power and never have to worry. get a box to fit it in and a pc fan or something to cool it (you do need a fan on that cc/cv thingy, it gets HOT.) so you can touch it without killing yourself.

1 little box to rule them all.

 

[MK2R]

1 little box to rule them all.

:lol: LoTR joke, i like it :lol:

90V 5A makes alot of sense tbh, since maximal output is 80V 5.1A (5A).and i doubt i'll ever use that much from it. but for now this set up will work just fine, i just need to make a box for it (just as you said) and i have some fans laying around from old computers, quiet a lot of them actually :wink:

I am so happy i visited this forum, it really opened up some of my dreams from when i was younger, and now when i am a bit older and have an alot better economical situation i can fund all my ideas. i know i've said this before but thanks to everyone that have been so helpful, thanks once again!

 

[flippy]

i doubt i'll ever use that much from it

trust me, that is a VERY dangerous proclemation to make.... :wink:

 

[MK2R]

i doubt i'll ever use that much from it

trust me, that is a VERY dangerous proclemation to make.... :wink:

i guess you're right, i better take it back before it is too late :wink:

 

[flippy]

i guess you're right, i better take it back before it is too late :wink:

when i started i first had 50V 5A, then 90V 5A, then 90V 40A, then 120V 10A, add some years and the baddest boy i built for a custom battery job can be cranked to 400V 25A on a 32A CEE plug. (its the defenition of "thats not a plug, THIS is a plug" )

 

[MK2R]

i guess you're right, i better take it back before it is too late :wink:

when i started i first had 50V 5A, then 90V 5A, then 90V 40A, then 120V 10A, add some years and the baddest boy i built can be cranked to 400V 25A.

" (its the defenition of "thats not a plug, THIS is a plug" )" such a nice Crocodile Dundee reference :wink:

400V... interesting i am listening O.O

I actually am interested in something that goes up to 400V, or well i have a lexus at home with a 288V battery, i've always wanted to be able to charge those NiMh cells. i know some guys have used a 320V charger for priuses, but i never found anything that can go higher than those 320volts.
it is 40 cells in paralell at nominal 7,2V, 8,4V max. so 336V. i know some expensive options out there where u get a "set charger" at 350mAh but they cost 500usd. but i am pretty sure that u could make it cheaper yourself, or at least for the same price get something that u can adjust the amp and voltage with.

But i haven't found anything that goes higher than what i got, what should i search for to get good search results for higher voltage charge/psu ?

 

[flippy]

But i haven't found anything that goes higher than what i got, what should i search for to get good search results for higher voltage charge/psu ?

https://www.aliexpress.com/item/1005001591926617.html

should do fine for your needs. just run it no higher then 75% of rated current. so dont run the 400V version higher then 5A. should still hit 1800W so plenty and you wont pop a fuse with long charging runs.

or this one: https://www.aliexpress.com/item/4000057350800.html

that would be your best bet cost wise. i REALLY dont recommend going DIY on this unless you actually have an electrical degree like i do.

 

[MK2R]

But i haven't found anything that goes higher than what i got, what should i search for to get good search results for higher voltage charge/psu ?

https://www.aliexpress.com/item/1005001591926617.html

should do fine for your needs. just run it no higher then 75% of rated current. so dont run the 400V version higher then 5A. should still hit 1800W so plenty and you wont pop a fuse with long charging runs.

or this one: https://www.aliexpress.com/item/4000057350800.html

that would be your best bet cost wise. i REALLY dont recommend going DIY on this unless you actually have an electrical degree like i do.

yeah this is lethal voltages, but okay, still pretty interesting. I don't know much about NiMh cells thou, if there is a reason they charge with low current. i know the car itself charge the battery pretty quick, some measured that when you break at high speeds what flows in to the battery is closer to 350V and 100A. and i know some "prius" converter guys used to make what i think they called range exension packs for their priuses by charging the prius battery with something like this while driving. but then again, i am not really sure what the NiMh cells do think about that :?

but 1.8kw sounds nice, however it is 1C charging since the battery is "just" shy of 1.9kwh, but then again i am having a hard time to find any good data on the toyota/lexus prismatic cells. some say discharge up to 15C (makes sense with 6,5Ah * 15C * 7,2V *40 cells = 28kw). but i don't understand how the cells are able to make an output for a short time to deliver 147kw. For some reason i find Li-ion easier to understand than the NiMh cells with memory effect and how it self balances at top etc. oh well, many questions, probably many ways to answer them as well

 

[flippy]

nimh cells are a bitch to charge properly. the only way to do it "dumb" is by charging at 10%or less of its capacity and just let the current flow for 12~14 hours.

if i were to get some car to play with it would not be anything with nimh. lipo only. or lead and replace it with lipo.

 

[MK2R]

nimh cells are a bitch to charge properly. the only way to do it "dumb" is by charging at 10%or less of its capacity and just let the current flow for 12~14 hours.

if i were to get some car to play with it would not be anything with nimh. lipo only. or lead and replace it with lipo.

yeah it's kinda what i "fear". NiMh shouldn't be mixed with anything really. i have seen people converting their NiMh priuses with lithium, not sure how it works in long term thou, and from what i understand NiMh shouldn't be made into paralell configurations since if one of them is balancing at the top and the other cell in paralell isn't there might be some strange current flows between them or overchargings etc.

did some calculations.
current car: 288V nominal, 336V maximal.
if replaced with li-ion: 80 cells at 4,2V is 336V. but how the rest of the car would react to that i don't know, an 80S BMS? how, and how would the react to the regenerative charging?
on paper it looks "yay" but in reality i don't know

Oh well we're kinda getting off the original topic here i guess, unless it could be put into the perspective of "how many cells" would you need to cover the need of a car like that? i am looking at those sanyo cells, rather cheap solution for high output. 560cells at an 80s7p at 1.2mAh and 18A output per cell it is 18*7 * (80*3,6=288V) = 36kw. so nominally it sounds "good". and it gives 2,4kwh.

 

[Ianhill]

Ive been worried about my bms choice i seen 60v 45amp fits what i need so got it, then realized its only got 60ma balance current and thought ive dropped a clanger.

Luckily it seems i should be ok my pack is 16s1p 10ah lipo cells ive balanced charged them on a rc charger and it took about 5 mins at end of charge the cells have IR values within 1mohm so i should have a pack that balances fine within 10 mins on the 60ma bms if not then theres likely an issue with one the cells anyway giving me the cause for concern that i will spot when my shunt gauge has missing watthours from premature bms shutdown and a higher than usual end voltage from most the cells being at a higher charge all but a fail one etc.

 

[MK2R]

Ive been worried about my bms choice i seen 60v 45amp fits what i need so got it, then realized its only got 60ma balanve current and thought ive dropped a clanger.

Luckily it seems i should be ok my pack is 16s1p 10ah lipo cells ive balanced charged them on a rc charger and it took about 5 mins at end of charge the cells have IR values within 1mohm so i should have a pack that balances fine within 10 mins on the 60ma bms if not then theres likely an issue with one the cells anyway giving me the cause for concern that i will spot when my shunt gauge has missing watthours.

kinda same thing i need to worry about when i use my daly bms,same balance current and i also need to see what i can do in regards to building my pack. lucky i got my other bms on the way with 2A active balance. but i will try with my other bms to see what results i can achive since it will take quiet a lot time for me to get my other bms here.

as flippy said in the thread a lot earlier, if you have a balancer of 60mA it balances 60mA per hour. if your cells are fresh and not leaking anything really the pack will be able to balance around 1.440Ah per day. so if your cells are at 10Ah. so in a scenario where 15 out of 16cells are at 10Ah, the last cell need to be at 9,990 mAh charge becuase in 10 minutes you only balance 1/6 of 1 hour, so 60/6 = 10mah.

at least if i understand this correctly it should balance 10mah difference in 10 minutes. and on a 16s1p at 10Ah it is 160Ah it would balance 0.01Ah, or 0,00625% of the total capacity in 10 minutes

 

[Ianhill]

Cheers for that gives me something to work back from, I'm new to the bms game and these balance resistors caught me off gaurd ill just have to get it on the road next few days and do a hard world test.

 

[flippy]

as flippy said in the thread a lot earlier, if you have a balancer of 60mA it balances 60mA per hour.

its actually less in most bms as they stop for a second to measure the correct voltage before continuing to drain every 5~10 seconds or so. some bms dont allow all of the balacing resistors to be active at the same time, some are alternating between even and uneven numbers for example due to the topolgy.

 

[Ianhill]

So assuming my bms only balances during the charge cycle at 60ma and thats probably being pulsed in some way dropping that total down.

If the bms uses a straight half on half off affair i could in theory half that 60ma and end up with a 30ma average meqning if one cell was getting out of tune by 10% 1ah it would take best part of 34 hours to get it back in tune.

That seems crazy long i hope i dont get to much cell drift, the packs ive opened and checked in past have had equal cells after years they seem to wesr into eachother when load is being applied i get issues when things are stood still for a long time and i got a kuberg battery that needs to be cycled and no bike to cycle it in, i may have to rig a few car lamps up and make a dummy load.

One last question do bms heat up alot under use how many watts typical do they disapate? on my old a2b metro the bms was mini no heat plate but my china one has alloy playe for heat so ive made a plate to get external air on to a heat sink close as i could to it.

https://endless-sphere.com/forums/viewtopic.php?f=35&t=110896&start=25

 

[Ianhill]

I wanted to charge at 10a 1c and have around the hour mark to charge it and i think i should at least get 2 hours 0.5c from it but occasionally ill have to set a balance current on the charger and let it balance down the shed, the longer that process takes i can have a guess how bad the issue is.

So 2a balance current etc would be for parralled pack with quite a few 18650s etc to account for the 60ma in each cell say ×20p needing a 1.2a balance current or a very large cell say 50ah with a 1% drift would be .5Ah and a car with lots of cells in p would need many amps to bleed i can see the logic of that.

 

[flippy]

with active balacing you are not burning off power, you are moving it. the highest group is discharged into the lowest group. ad infinatum until the bms has reached the allowed imbalance level. this is MUCH more effcient (And faster) then the bleed off method.

 

[Ianhill]

with active balacing you are not burning off power, you are moving it. the highest group is discharged into the lowest group. ad infinatum until the bms has reached the allowed imbalance level. this is MUCH more effcient (And faster) then the bleed off method.

Right i got you pass the parcel till everyone got a equal piece, im not sure what my bms will do but i hope it can at least keep up on the discharge side and ill have to live with what ever i can safely charge at.

Do you have any recommendations flippy on the setup ?

 

[flippy]

Do you have any recommendations flippy on the setup ?

not without knowing a lot more. but its best to start your own thread for that.

 

[Ianhill]

 

[MK2R]

I stand corrected then as flippy said then about the lesser balancing due to delays etc

Good luck Ianhill! hope you find the solution that suits your battery pack! =)

 

[Ianhill]

Thank you mk2r

Ill find out soon enough if alls well lessons will be learnt im sure ill repeat the mistake somewhere down the line again lol.





https://endless-sphere.com/forums/viewtopic.php?t=110896&start=25

 

[MK2R]

Question related to the FST cells mentioned a lot lot earlier in the thread.
I try to find information and test about them. maybe i need to test them myself also.

but when it comes to discharging them how should i read the information?
0.5C 100% (of mah capacity) ~1A
1C 95%
2C 90%
3C 90%
rated IR ~35mohms

max discharge at 10A

What am i supposed to find out of this numbers? specs are quiet lacking, or hard to read. what could i actually discharge them at? or should i just try my way out and see how they react to different loads.
I got 2 led lamps 12V 10w, i did a 3S pack for testing earlier with 3 fully charged cells (1600mah tested, so 80% original capacity), they started out at 12,68V as i stated b4, dropped to 12,58V at first plug in (so IR around 40mohms per cell, as they where tested b4 the test, the liitokala said the same IR so it seem to be in the right ballpark). would it make sense to connect the second led so i push those 3 cells at 20w @ 12V? it's around 1.66A. or well looking at the cells that is a 12V 1.6Ah pack, it is around 1C. or should i buy some of this units out there where u can set them to many different amounts of A when testing:
https://www.ebay.com/itm/265042951890 like this for example