Battery charging flow 'chart' (JK BMS)

[empowered]

So when charging 15/16 jump up to 3.50v immediately? How long has it been trying to balance those 2 out? The balancer should be able to eventually fix it. How long has it been trying to fix the issue? If you can get to the cells you might want to verify with a voltmeter directly on those cells terminals that the cell voltage is really screwed up. an issue with the welds on those 2 cells could manifest as higher resistance/voltage like this under charging. But it could also be those cells were at a higher charge when put into the pack.

i only got this pack online like 2 days ago. yes, i verified the voltage with a meter independently.

 

[rogerheflin]

i only got this pack online like 2 days ago. yes, i verified the voltage with a meter independently.

So probably just no balancing from the factory.

The balancer should fix this, but it could take a while.

 

[empowered]

just let it play out?

 

[Brucey]

just let it play out?

Its common for a new battery to take quite a few cycles before achieving complete balance.

i'm open loop, so charging is all voltage based. inverter set to charge to 58.4v, and my bms RCV is 56.8.

58.4V is too high, you'll easily get the pack into a high cell state that way. Set the inverter to charge to 56.8V or below.

You mentioned you are charging each pack individually, are you charging from solar or inverter/AC? If individually via solar available charge current is prob getting up there unless you limit it (in Victron land by enabling dvcc and setting a max limit on solar to battery).

With the two high cells being adjacent double check your bms sense leads and connections.

 

[empowered]

Its common for a new battery to take quite a few cycles before achieving complete balance.



58.4V is too high, you'll easily get the pack into a high cell state that way. Set the inverter to charge to 56.8V or below.

You mentioned you are charging each pack individually, are you charging from solar or inverter/AC? If individually via solar available charge current is prob getting up there unless you limit it (in Victron land by enabling dvcc and setting a max limit on solar to battery).

With the two high cells being adjacent double check your bms sense leads and connections.

so much conflicting info... Will keeps preaching 58v charging, other people say lower, would be nice to have some fucking consensus...

 

[Brucey]

so much conflicting info... Will keeps preaching 58v charging, other people say lower, would be nice to have some fucking consensus...

The amount of available power between 58.6 and 56.6 is effectively nothing. Couple percent. Zero reason to go to 3.65V per cell unless you have some potato eg4 battery that requires such a high level to start balancing (may have been finally been fixed in v2 with firmware updates)?

Much easier life for the cells at ~3.5V, given you have significant battery capacity and minimal loads

 

[empowered]

The amount of available power between 58.6 and 56.6 is effectively nothing. Couple percent. Zero reason to go to 3.65V per cell unless you have some potato eg4 battery that requires such a high level to start balancing (may have been finally been fixed in v2 with firmware updates)?

Much easier life for the cells at ~3.5V, given you have significant battery capacity and minimal loads

fair points, and once i get this pack to balance i'll lower it for normal use i think.

 

[RCinFLA]

What absorb voltage to set for charging depends on your charging bulk current rate, which should be based on your use case and how fast you want to charge battery.

The level of bulk charging current affects the level of required overpotential voltage. Higher bulk charging current results in higher overpotential voltage to drive the higher cell current requiring a higher absorb voltage setting to provide the necessary overpotential voltage overhead to maintain the level of bulk charging current.

This comes into play as cells approach full charge. Not setting absorb voltage high enough for given bulk current results in starving needed overpotential voltage overhead to maintain bulk current rate. It just lengthens the charge time as bulk current starts to cut back early.

 

[empowered]

What absorb voltage to set for charging depends on your charging bulk current rate, which should be based on your use case and how fast you want to charge battery.

The level of bulk charging current affects the level of required overpotential voltage. Higher bulk charging current results in higher overpotential voltage to drive the higher cell current requiring a higher absorb voltage setting to provide the necessary overpotential voltage overhead to maintain the level of bulk charging current.

This comes into play as cells approach full charge. Not setting absorb voltage high enough for given bulk current results in starving needed overpotential voltage overhead to maintain bulk current rate. It just lengthens the charge time as bulk current starts to cut back early.

so i have 12 'packs' right now, with my inverter being able to supply a max of 200 amps, so highest each pack would NORMALLY see is 16.6a. what should absorb be set to?

all of my packs are balanced really well except one thats still giving me hell. few cells still running away to over .25v difference. i currently dont have it connected to the inverter for charging/discharging. bought a 60v dc charger and also have a 30v. 60v is hooked up at pack level, max 5a on that one. then the smaller charger i'm hooking up to individual cells that are low to try to bring them up a bit faster, this one goes at about 3amps. i'm guessing this will be long and painful

 

[empowered]

Look at this shit... ugh

 

[RCinFLA]

With 12 parallel battery arrays, how close to equal is the current sharing (the 16.6 amps to each parallelled battery)

 

[empowered]

With 12 parallel battery arrays, how close to equal is the current sharing (the 16.6 amps to each parallelled battery)

Pretty close, under 2 amp difference