CHEAP NEW ORIGINAL 18650 21700 BATTERY CELLS, POUCHES AND PACKS
- Thread starter tumich
- Start date
Allex
100 MW
4.25 V+-0.025 on that BMS
So you can have 4.275V in worst case when fully charged
Nice to know that it will slowly destroy the cells
Or can they reprogram it for lower values like 4.15?
So you can have 4.275V in worst case when fully charged
Nice to know that it will slowly destroy the cells
Or can they reprogram it for lower values like 4.15?
cwah
100 MW
Do you sell enclosure and NCR18650BE cells?
Also, what's the shipping cost for 200 cells in the uk? Do I have to pay customs?
Thanks
Also, what's the shipping cost for 200 cells in the uk? Do I have to pay customs?
Thanks
Allex said:4.25 V+-0.025 on that BMS
So you can have 4.275V in worst case when fully charged
Nice to know that it will slowly destroy the cells
Or can they reprogram it for lower values like 4.15?
I will have the BMS programmed to 4.225V.
You can still charge the battery to a lower voltage if you want.
The Mighty Volt
1 MW
Hi Tumich, what do you have in stock right now and how much are you asking for it, thank you.
Allex
100 MW
Just ordered 80 cells NCR18650PF for a new build.
999zip999
100 TW
Allex does that mean 72v 11ah pack to be use at 22amps. ?
dnmun
1 PW
miuan said:Allex said:4.25 V+-0.025 on that BMS
So you can have 4.275V in worst case when fully charged
Nice to know that it will slowly destroy the cells
Or can they reprogram it for lower values like 4.15?
I will have the BMS programmed to 4.225V.
You can still charge the battery to a lower voltage if you want.
you should not have your BMS you order from Bestechpower set with a balance voltage of 4.225V whcih i don't think they offer in any case.
there is no problem having the HVC set to 4.25V since it is unusual for a cell to reach it when it has been balanced already and has not been damaged or have one cell short out a lot of charge.
most people have no clue how the BMS functions so they select some obscure rational for saying why that is proof of why a BMS is not useful.
if the cell reaches the HVC of 4.25v then it cuts off the charging and you have to discharge the battery back down to 4.05V in order to reset the charging.
the only time a cell will reach the HVC is when you initially balance the pack and the cells are all so far out of balance.
once the pack has been balanced and has several cycles to bring them all to the same state of charge then the only time it would hit the HVC after that is if there is a problem during the charge.
999zip999
100 TW
Dmnun please explain your charging practice after riding and why ?
Allex
100 MW
999zip999 said:
14s4p
I will try them to cope with 25A peak, about 2C per cell. If they don't hold up I will add one more P, rest will probably go to a "Neato Botvac".
dnmun, did not get your post. Should we buy from best or not?
There is always cell drift during a charge, some of them will always charge up faster. So if I understand it right, the BMS starts to discharge a cell only when it hits 4.25+- This could be a little harsch on them.
No, allex, it doesn't work that way. It has separate trip point's for balancing, and for HVC.
You see, when the cell gets to 4.2 V, it will start bleeding, but the charging won't turn of, because the bleeding would stop immediately, and this process would go on and on. But if that cell that first got to the 4.2 V and started bleeding was very far from the rest of the cells, it would get to 4.25 V , and then the charging would stop, because the cells are out of balance and you should do something. But in normal conditions, cells would bleed until they are the same, and if there is a little difference, maybe some cell would start to bleed first, but would only reach like 4.21 or something like that, but after some time, all cells will be balanced equally.
And panasonic PF is rated at 10A, so for a 4p pack you can draw 40A, but you will see a voltage drop. 2C is not a problem for those cells.
You see, when the cell gets to 4.2 V, it will start bleeding, but the charging won't turn of, because the bleeding would stop immediately, and this process would go on and on. But if that cell that first got to the 4.2 V and started bleeding was very far from the rest of the cells, it would get to 4.25 V , and then the charging would stop, because the cells are out of balance and you should do something. But in normal conditions, cells would bleed until they are the same, and if there is a little difference, maybe some cell would start to bleed first, but would only reach like 4.21 or something like that, but after some time, all cells will be balanced equally.
And panasonic PF is rated at 10A, so for a 4p pack you can draw 40A, but you will see a voltage drop. 2C is not a problem for those cells.
dnmun said:miuan said:Allex said:4.25 V+-0.025 on that BMS
So you can have 4.275V in worst case when fully charged
Nice to know that it will slowly destroy the cells
Or can they reprogram it for lower values like 4.15?
I will have the BMS programmed to 4.225V.
You can still charge the battery to a lower voltage if you want.
you should not have your BMS you order from Bestechpower set with a balance voltage of 4.225V whcih i don't think they offer in any case.
there is no problem having the HVC set to 4.25V since it is unusual for a cell to reach it when it has been balanced already and has not been damaged or have one cell short out a lot of charge.
I don't order from Bestechpower. The seller is Leo@Greentime who offers to adjust both discharge current and HVC at customer's request.
4.25V is useless for me since there are 8 cells paralleled and I charge at mere 4A. I am manually balancing the cells upon arrival.
Are you sure the cells start bleeding at 4.2V? It would be more practical if the bleeding started a bit sooner.
Allex
100 MW
My guess that at 10Amps they will be pretty hot and you will get around 2500Mah of 2900. But perhaps tumich know better, if he tried to discharge at 10A, what they can deliver.
Riba, yes this is what I ment in the first post. Some of the cells will always go beyond 4,2 and hit HVC at 4,25 during a charge. Charger usually works faster than the BMS can drain down cell row, or?
Riba, yes this is what I ment in the first post. Some of the cells will always go beyond 4,2 and hit HVC at 4,25 during a charge. Charger usually works faster than the BMS can drain down cell row, or?
It does, but if the cells are at the same level, they will all charge equally, and they will all reach 4.2 V at the same time, and that is the max voltage that the charger inputs. So once they are balanced, no cell can be over 4.2 V, because the charger is set at 4.2V x number of cells in series.
Here is the graph with Panasonic PF (and lg mh1 and panasonic BE) at 10A:
http://www.dampfakkus.de/highamps/537-at%2010A.png
These cells actually deliver more mah at high rate than at 1C, because they get warm and drop their IR, so you get more capacity on 5A than on 3A. But Wh are probably the same or less at higher rate.
Here is the graph with Panasonic PF (and lg mh1 and panasonic BE) at 10A:
http://www.dampfakkus.de/highamps/537-at%2010A.png
These cells actually deliver more mah at high rate than at 1C, because they get warm and drop their IR, so you get more capacity on 5A than on 3A. But Wh are probably the same or less at higher rate.
dnmun
1 PW
no, the charger does not push more current than the BMS can balance. i have my charger set so that the charger pushes the 175mA of balancing current at the final full charge voltage. as i said most don't understand how they work to balance a pack. few understand how the balancing chargers work either.
dnmun said:
That's not true in case that one cell is at higher SOC, and for that cell balancing will happen before the final phase of charging when current drops enough. So than one cell will be balanced at 175ma, but the charger will be pushing full current since the CV phase hasn't been reached, and the voltage on that cell will rise until hvc event occurs and bms shuts down charging.
999zip999
100 TW
Dnmun please explain your charging method after a ride.
dnmun
1 PW
riba2233 said:
no, again this is misinformation. once the battery pack has been balanced initially all of the cells remain almost identical in SOC.
when charging all of the cells climb in voltage up to the same identical point. there is not one cell that somehow goes and overcharges while the others are charging.
the reason the HVC is there is to prevent the cells from overcharging in the event of cell failures where some are shorted and lose charge and force the other cells to reach HVC early. so the BMS in this case is fulfilling it's primary task to prevent damage when the pack has lost one cell or somehow has been damaged.
in normal operation, when charged, the pack will never have a cell reach or get close to the HVC. the highest any of my cells ever reach when i charge the 21S pack up is only 4.218/4.22V and i have 350mA of balancing current from 2 BMS balance boards to prevent it climbing higher.
Communication was great.