56.75V Charger voltage on BMSBattery Headway pack (16S)

[chvidgov.bc.ca]

I just got a couple of their Headway packs, and in the past the charger voltage was set to 58.4 volts (3.65 per cell). The new chargers that came with these packs are set to 56.75V, which is only 3.54 per cell. Is it ok to leave the voltage as is, from the vendor, or should I try to tinker with the chargers to elevate the voltage up to the "normal" 58.4? The chargers shut off normally, and I assume that they are balancing to 3.54

I have had good luck with the BMSes they use for these packs.

Perhaps they have lowered the voltage a bit, to promote longevity?

 

[dnmun]

it is not possible for the BMS to balance a pack if the final voltage is below the voltage at which the BMS is programmed to balance the cells. so if it is set up to balance at 3.60v/cell then you have to put almost 58v. it just takes a long time to balance when the balance voltage is reduced form 59v down to 58V. but it looks like the plating at high currents at full voltage above 3.60V may shorten cell life. it seems to be a smaller impact that other types of abuse, but the cells are designed to compensate for the loss of anode surface area and the problem does not appear until late in life when the current becomes cathode area restricted.

 

[chvidgov.bc.ca]

Would they set the BMS balancing level lower than 58.4? I kinda doubt it. I suppose I should tinker with a charger to get its voltage up to 58.4, if that is possible.

 

[Takemehome]

Check your cells to see if they are balanced.
Go for a long ride to discharge the pack and charge it back until it finishes balancing. ( green light still for 5 minutes )
If your cells are all at 3.54 then keep it that way.

 

[999zip999]

Set of balance wires work good for cell monitoring ect. If balanced at 3.54v great.

 

[dogman dan]

Find out, if possible, what voltage your bms should have. If it needs 58v then your charger needs to be 58v.

No way bms battery could send you the wrong thing by mitake.

 

[dnmun]

Would they set the BMS balancing level lower than 58.4? I kinda doubt it. I suppose I should tinker with a charger to get its voltage up to 58.4, if that is possible.

the origianl ping signalab BMS would bbalance at 3.65V but the newer v2.5 signalab BMS would balance to 3.60V.

i have no idea why that guy would deliberately misinform you that you could balance the pack at 3.54V by leaving the green light on for 5 minutes.

your voltmeter may be reading several volts low too. almost all the kingpan chargers are set to 58.4V except ping orders his set to almost 60V. he does this so that the packs are forced to balance sooner because the balancing current is higher at 58.4V that way. so the low cells can catch up faster. if the voltage is set right at the 3.6Vx16 then it takes a long long time to ever get the pack balanced. essentially has to stay on the charger on balancing current all the time. but if the output is set to 3.6Vx16 then there is no balancing current at 57.6V.

 

[999zip999]

Check the voltage of the cells to see how well the bms is balancing the pack. So first check voltage of each cell 1-16 and write it down. If the bms does balance you are o,k.

 

[999zip999]

There nothing wrong if the bms does balance the battery. Does it ?

 

[dnmun]

no, you do not have to measure each cell to determine if the BMS is balancing. if you only have 56.75V then the pack is not ever going to balance with any BMS you can buy. period.

like i said if you put the voltage right at the 57.6V then it will not balance either because there is no balancing current then. you have to put the charger voltage a little higher and let the balancing current pull the low cells up to the balance voltage.

you can't just make stuff up and say this is how it works. sorry you get so much bad advice but when you come here everybody can say anything.

 

[chvidgov.bc.ca]

I found the pot on the charger which controls voltage and cranked it up to 58.4 volts like all the other <same model> chargers I got from them that came with the <same model that I just got> batteries that have the <same model that I just got> BMS.

These are new packs, so I don't want to tear them down to check the individual cells. If they set the new BMSes to balance lower with a charger at 56.7, my voltage will be ok in either case (ie. higher than the BMS is made for), and if they are set the same as the older BMS (58.4) then they will balance with the higher voltage that I changed the new chargers to.

I specified 58.4 on my order for the chargers, but someone screwed up I assume.

These are not ping bms. They are the two physical level ones with the big aluminum heatsink that is on the LIFPO4 batteries from bmsbattery (not the red ones, the green ones).

 

[dnmun]

yep, i have one of those for 12S that is built for 80A i think. i put a switch on the thermal breaker so i could turn the battery off. i never did establish the voltage at which it turned on the shunt transistors but if you measure the cell voltages at the BMS then you may be able to find the voltage where they turn on. when they turn on you will see a voltage drop across the shunt resistors. tiny at first and then turns on full.

 

[999zip999]

I would not cut open the pack. But would have like to know the state of charge of the 16 cells when charging at 56.75v. Turning it up to 58.4v wouldn't hurt. The cells will not stay up there very long after unplugged from the charger. I believe that some larger format cells live better at voltages 3.65v and below. Good chance the charger was set to low.
Just wonder if it was balancing at that lower end voltage. That's all.

 

[dnmun]

and i explained that the cells cannot balance at a voltage lower than the voltage set by the comparators for the shunt transistor to turn on. it is 3.60V on all the BMSs that are currently sold. the v1 signalab is no longer available. that is the only one that balanced to 3.65V. no pack can balance if it has a charged voltage less than what is needed to turn on the shunt transistor. not hard to understand really.

the problem is that now it is clear to me from the discussion that w9bk guy started that plating of lithium metal onto the surface of the SEI on the anode will occur when the cell voltage is pushed above 3.60V. i had always read that 3.65V was full charged so this has changed my understanding of what happens above the balancing threshold of 3.60V.

i do think the impact is minimal if the voltage of the charger is not too high but i now do not recommend higher voltages like the 59-60V i once thought was safe.

 

[999zip999]

And that is the question what true voltage does the shunt transistor turn on in this bms ? And is it balanced.