Building battery from MAKITA Konion PACK

want to build said:

ok
just after charging them with lii 500 all of them showed 4.17 418 4.19 or 4.20

after 3 weeks i have 4 cells at 4.15
14 at 4.16
54 at 4.17
26 at 4.18
7 at 4.19

total 105on paper
110 cell over 4.15 total concretely
so i guess i have 5 cell using a number already used(concentration mistake) it happens

now are they all suitable to put in a battery usable ? here is the sheet i have to see how much they lowered.

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bump

Better to have charged them to 3.70 volts and let them sit because its not good to have them full voltage for a long time like that.

i though of separating my battery in 2 sections 2p 14 s for city . this means that if it got stolen i wont hurt me as much as if the whole battery is stolen. is 2p14 s relatively safe with a bms to use or i'm completely dreaming? i would charge it at 1 amp . what is the minimum of cells in parallel . Could one use a 1p 13 s to ride (total of 2.1amp x 48v= 100amph) divided by 20 it would mean 5 miles possibility..

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1P is no good because the discharge amperage is only 8-10A (I am guessing as to what the specs say, but do confirm bc I cant remember) so when you do that, and you get 20-30A you hurt your babies.
2P means you can do 16-20A
3P means you can do 24-30A
4P is 32-40A.

Now you go with a 30A 18650 then its 1P = 30A, 2P 60A, 3P 90A, 4P 120A discharge.

You could have a small 1P or 2P and 13S pack which would net you 48V(nominal) and 30A or 60A but with them Makita's its only 10A and 20A.

HI i purchased opus bt c 3100 and got all my cell out of the makita packs . It did keep the 2,5v and more. Now , before choosing which cells to put in parallele with which , it seems i need to know their capacity.

I have a need for clarity about what mode i need to use and what current because it seems to allow 200 500 and 1000 ma both for charge and dischage.

there is a refresh mode ?? that i read on a blog i dont know if it is a reliable synthesis see bottom

some places i read just charge the cells . Somewhere else charge it discharge it and charge it so i feel confuse and need you knowledge advice and a bit of help on which is the best setting . (i want to build a quality long lasting battery..

thanks

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The unit has 5 selectable modes including Charge, Discharge, Test, Quick test, and Refresh.

Charge Mode: The rechargeable battery is charged up to its maximum capacity. Accumulated charging capacity is displayed at mAH display mode.
The charger will charge 4 cells at once charging each at 1 amp. But if you are charging only 2 batteries you should put them in the outer slots (slots 1 and 4) to increase the charging rate to 2 amps a piece. This is especially good for charging 2 26650’s at the same time

Discharge Mode: Discharge mode is used to reduce memory effect, The rechargeable battery is discharged to a preset battery voltage (0.9v for Ni-Cd & Ni-Mh, 2.8v for Li-ion batteries). Once discharge is finished, total accumulated discharging capacity is displayed at mAH display mode.

Refresh Mode: The rechargeable battery is charged and discharged repeatedly to optimize to its maximum capacity. Old rechargeable batteries or rechargeable batteries that have not been used for a long period of time can be restored to their rated capacity

hi ,
anyone has used this charger ? Me and my questions would like to be sure i m using the right modes and current
here is a owner manual on line. (english is not my first language by the way)

Dude, just use 1000 mA (C/2)... It's much faster to test each cells. 500 mA (C/4) will take twice as long and 200 mA (C/10) will take 5 times as long.
In any case, the capacity you'll get on your eBike will be slightly different from that you test, whatever the setting, because you'll very likely drain these cells above 2 to 3C anyways... But these cells are 10C capable (they will heat up however at that rate...) ao no worries.

On think to keep in mind though, for sake of comparing what is comparable, whatever rate of charge/discharge you use to test capacity, use the same rate between all cells, so you compare apples with apples.

Matador

Yes i understand that i have to test all cell again.

I m new to 18650 so i dont know concretly witch mode do i have to set my opus3100 to in order to know it s capacity.
maybe that is not what i have to do but that is what i have understood that needs to be done to match equal parallel total capacity group.

so do i need to charge and discharge?

The unit has 5 selectable modes including Charge, Discharge, Test, Quick test, and Refresh.
Concretely , one i have inserted 4 cells in the charger,and plug the charger, what mode do i put it in?

I read the charger in refresh mode goes down to 2,8 v wich might be detrimental? Do i even need to use the discharge refresh mode(it runs 6 times)

Both. Charge, then discharge. What you want is discharge capacity. Charge capacity is not reliable because all the cells from different packs are not necessarly in the same state of charge (some cells may be 52% charges, some 23%, some 97%). So some will need less charge time to become full. But once full, discharge to minimum voltage will give you capacity.

2.8V is not dramatic, so as long as they do not ever reach below 2.5V, you're good.

Learn about your VTC4 cells. CHECK THE DATASHEET which has all the specifications: View attachment Specification_US18650VTC4.pdf

On that datasheet, you will see that the manufacturer (Sony), specify it's okay to discharge as low as 2.5V (resting voltage).

See page 5, line 2.5...

Matador

HI
i am planning a 4p13 s battery with copper stips and tin for a 7amp controller kt

1how can i test my connections ? it might seem simple but i do not know how to use the multi meter i have appart for vlotage.

2 i ll install a bms on it . iwould like to know what will happen if while im riding, one cell gets loose and loose connection and hence greate a 1 cell parallele group?
3how will i know?

4what will be the impact on battery and distances?

thx

hi i have charged and decharged all my cell and noted their discharge capacity. after couple weeks they show all from 4.10 4.11 4,12, 4.13, 4.14, 4.15 v I am in front of a decision here.

I read that it is better to assemble cells of same voltage in a parallele group. ok . Also i read it is better to assemble cells so that the general total capacity of all parelle groups are the same . there is a softwere SITE https://secondlifestorage.com/repackr.php ).
it tells you wich cell to put together so that you create almost exact same total capacity for each parallele group.

is it possible to do both?
if i use the sofware, i will have 4,10 4,12 4,15 4,14 cels in one same group, is that ok or is it too big of a diffence of voltage to be in one same parallele group?.

if on the other hand i do groups of 4,10 only 4,11 only,ect the total capacity of those group will differ.

what is most important, similar total capacity or same voltage i a paralle group? thx

I’d tell you to let them sit 2 more week before deciding which cell goes with which cell. I had some still move more than they should weeks after matching the the cells and then building the pack.

It’s easier, MUCH easier to let them sit a bit longer than remove cells from the middle of a pack.....it’s always the middle cells, go figure!

Tom

hi
i understand you suggest me to let them sit longer, they already have been for like 6 months for the majority of them.

do you know someone who could answer my question ?

Parallel automatically means the same voltage.

Matching capacity if possible helps reduce balance problems, maybe buy 5x what you need then sell off the non-matching ones.

hi in an ideal world yes i would buy 5 times what i need but it would be king of long to open that many packs hahaha.

is 4.10 4.13 4.15 v to big of a difference to be put together in a same parallel groupe?
What is the consequence of having to big of a difference in full capacity voltage?

If they are small (low Ah) batteries and you use decent wiring size to parallel them, that should be no problem and they will equalize.

But their similarity in **capacity** will determine how much in-use balancing they will need, how much total pack capacity will be sacrificed, etc.

want to build said:

ARE THE VTC4 I USE THE ONES DR BASS IS PRESENTING WHAT YOU CALL LOW AH? 2.1 AMPHOUR CAPACITY

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Yes


> MY PARALELLE WIRE IS 30 AMPS CAPACITY 1 CM LARGE LEAF OF COPPER

no idea but sounds OK


>> But their similarity in **capacity** will determine how much in-use balancing they will need, how much total pack capacity will be sacrificed, etc.


> I ll use a bms does that solve this PROBLEM? CAN YOU EXPLAIN YOUR LAST SENTENCE IN OTHER WORDS?

capacity = mAh, needs to match as close as possible.

BMS keeps the imbalance from harming the cells, but most don't balance well enough

look for tutorials about balancing

Want to build

First off, number each cell and carfully take note of all resting voltage drift that occured with time, for each cells (make an excell file... To keep a logbook of all cells health parameters).

Then figure out the exact manufacture date of each cell from the numbered labelling of the cells... This will help you match the cells for age (calendar aging does affect performance of cells, even if they stay on the shelve without being used for 10 years).

Now determine capacity of each cell and take note in your excel logbook.

Now determine DCIR either using an Imax B6 or by using the load method (requires a set of high power (aka 50 to 150W) resistor of differnet values (aka 0.5, 1.0, 2.0 and 5.0 Ohms), a voltmeter, an ammeter and a camera to take pictures of A and V values simultaneously)... You need the DCIR of each cells. Note in you cell logbook. In my experience, VTC4 of DrBass that are 2-4 yers old should have a healthy 21-23 mOhm DCIR. Warning some of these Makita Pack was lower standard VT4 cells that have DCIR in the 26-28mOhm range...

So that s the start if you want to make things right...

Now charge all your cells to the exact same voltage with + or - 0.01V difference at most. I recommend a voltage of 3.55V, so if you accidently short your pack during assembly you'll have less chance of a big fire (or explosion) than if you do so at 4.20V.

All cell being the same voltage, you can now start.
Lets say you make a 10S5P pack... For sake of example.

You need each 5P pack to be the same capacity (ex:10.5Ah each). If one of the 5P pack is lower capacity (ex: 10.1 Ah), then the whole pack will only be 10.1 Ah max (the weakest link).

Make each 5P pack the same DCIR (ex: 4.6 mOhm... Wich is 5 parralleled 23 mOhm cells). If one pack is higher DCIR, it will heat up, voltage sag, trigger early BMS LVC, and go out of balance... That weak link will make balancing by BMS a lot harder and the BMS will have to balance for longer times... Making charging time much longer... Avoid pack wich have extreme DCIR resistance. Ex avoid puting a 5P group with DCIR of 23, 23, 23, 23 and 23 mOhm in series with a 5P groups that has DCIR of 18, 22, 23, 24 and 28 mOhm, even is the overall average DCIR seem similar. Rather, try to even thing out as much as you can. 18, 23, 23, 23, 24 and 22, 23, 23, 23, 28 pairing would probably be less extreme, but also keep all 10 5P groups the same overall DCIR.

Make each 5P group the same age. Example each pack is on average 2.5 year old. With some cells 3.0 and others 2.2 , 2.8, 2.6 and 2.0 year old... For example). Dont make one 5P group 1.8 year old and the next 5P group 4.5 year old... Or the older 5P group will die way before the others . "Calendar aging of lithium cells is no joke. It's one of the most important factor to consider. Cycle number is too, but DrBass cell all have low count cycles because Dr Bass dont sell cells with higher than 100 cycles...

Once all 5P pack are constructed, each having around 10.5Ah capacity, 4.6 mOhm DCIR, and average same 2.5 year old... Assemble each 5P groups into a 10S5P battery pack.

Can t really explain into more details than that...

PS: in my experience most cells I got from Dr Bass werr almost exactly the same DCIR... All VTC4 i got tested 22+/- 2 mOhm and all VT4 tested 27+/-1 mOhm. Out of 290 cells, only 4 i got were sigbificantly off of these values, so i didnt use these 4 cells. Other than that, as long as your carfull to not mistaken VTC4 cells with VT4 cells, you can almost assume all the VTC4 you got are 22 mOhms. Thus don t worry too much about DCIR mismatch, especially with the VTC4.

Matador

Tx john and matador for your help. i see you take care.
when charged to 4,2 ( i beleive opus concretly only put 4,18 in them but that is a detail) and let sit for month as i said some came down to 4,15 some ot 4,10
1Correct me if im wrong but from what i understand it is ok to have 4,10 and 4,15 cell in a same parallel group.0,05 variation is acceptable right? (cause neighter of you spoke about it)
2 what i also understand is that similar total capacity is more important dans trying to reduce the volt difference in a same parallel group.
3 i understand the resistance you talk about but i ll do as you say and just trust the quality of dr bass cell
4 for the years manufactured , i understand and find it quite logical not to mix different ages . I thank you for that also cause i didnt think about this it was in a blind spot. this specific point concerns the longevity of the pack through time and here is what i think i ll prioritise in this perspective instead of the manufactured years: i was a noob and still is amateur so some of my cells 1 have scratched i made by dremelling it a bit to much during disassembling. it is sad but some are perfect some are just scratched some are like somehow la bit deeperscratches . so ill do 2 packs ( of 4p13s); 1 with the most damaged cells and another one with the perfect ones (wich should last longer without corosion .)
Does what i say make sens? do you understand.

You keep talking about voltages matching.

Voltage is a temporary passing attribute, says little about the cell itself. The thing about voltage matching is just for at the time you connect them, so the "natural equalizing" flow from higher to lower doesn't shock you, melt your connectors etc.

Yes within a 0.05V difference is fine for that purpose.

But as far as testing / sorting what cells go to which packs, vs getting discarded, you need to match based on capacity and IR as above, great post matador.

Best is to just avoid secondhand cells, save your pennies and buy quality ones brand new.

hi yes it is true that i did bring back the volatge difference in a parrallel group back . the reason is that it is the usual 2 advice i read around the first is parallel than serie not the opposite and te second is the have similar voltage in the parallel group.

I assumed those statements were the most important but now i understant the second statement is less important that resistance and year of manufacture. So that s why i needed clarification on this.

0.05V is fine for paralleling cells. Don't let the V difference be much bigger than 0.10V, because the higher cell will dump a surge of current into the lower voltage cell... And this ca result in exceeding charge curent rating and damaging cells... But I'd be much more concerned if the V difference was bigger (ex : 3.5V and 4.0V)... Once paralled l the cells will have an avereage voltage value between the two and the difference won t matter. Just like John said.

The other thing... Voltage drift over time... This is an indirect way to measure if your cells have a current leak.... Which could be explained by very high DCIR or even internal short in a cell.
If the cell loses voltage over time... Let s say you charge to 4.20V and a week later the cell is at 4.07V, that is a indirect way to tell you this cell has a fault and will fail sooner or later...

If you let your cells sit fully charged for a month... Let's say they were at 4.18V, the good cells should really not go much below 4.15V (hysteresis ?). I would keep maybe the ones at 4.13 or 4.12V... but below 4.10V, you got a leaky cell... This is kinda subjective thrrshold, and it s just my personnal feeling. But below these value, test cells for Vdrop umder load dcir and capacity to make sure they ar healthy... Cells that lose coltage over time will drag other cells in the same P group with them and imbalance between seried group will be accelerated.

Matador

want to build said:

now i understant the second statement is less important that resistance and year of manufacture.

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Capacity matching IMO is #1

After charging is finished

if you really did charge to Full

take the "surface charge" voltage off, maybe .5% of SoC

and/or let them sit isolated for a few hours.

That voltage is then your benchmark point to investigate self-discharge rate.

The voltage just after charging is not stable, will fall over time.

Just like right after a load is cut, need to wait for bounceback to get a resting voltage.