I guess I'll see what I can work out with SOK.If the battery can't be charged to the 14.4-14.6V spec without triggering BMS cut-off, send it back. It doesn't meet spec.
I guess I'll see what I can work out with SOK.If the battery can't be charged to the 14.4-14.6V spec without triggering BMS cut-off, send it back. It doesn't meet spec.
If the battery can't be charged to the 14.4-14.6V spec without triggering BMS cut-off, send it back. It doesn't meet spec.
Most of these Chinese batteries spec it as 14.4 +-0.2
So 14.2v is probably the best they guarantee
Then they need to change their datasheet:
SK12V100 Spec Sheet.pdf
drive.google.com
View attachment 130738
One always tries for the lowest but I would suggest that at the knees not more than 150mV but on the flat part of the curve about 20 - 50mV , lower being a bonus. I have an active 5A balancer connected permanently , charge or discharge. Works for me , others may differ.So what balance voltage/delta should I say its 'good enough at'? 50mV? 20mV? Or am I expecting too much here?
IMHO a 2A or 4A charge won’t make much difference- whatever charge voltage you set, they will taper current as the battery voltage reaches that setting. Some chargers have a duration, some sense tail current - a level that is decidedly full charge and terminate.Rookie question here, but should I have stuck with the 2Amp charger? Or is 4Amps low enough to see if the BMS could actually balance that cell?
Or should I take the battery cover off and try to drain that single cell to try to force it some into balance?
On full discharge, its actually lower then the first 2 cells...so it makes me think that maybe there is something wrong with that cell. But since this is my first LiFePo4 rodeo, I have nothing to compare this to other than the 2 other SOK batteries that are all part of the same shipment.
Also, keep in mind I don’t really use BMS’s unless it’s a pack I know I’m not going to monitor so I’m free to charge up to 3.65 on a balance charger if I want to so long as my charge current is low enough for the balance current to stop any runners. I couldn’t fathom having an off the shelf battery with no access to the balance leads with how slow most of these BMS’s balance and worst of all the non Bluetooth BMS’s that have balance start set to 3.60V
Do whatever makes you happy. Maybe take notice that these BMS’s aren’t making you very happy.
Some BMSs don't balance unless the BMS is registering >= ~3 amps charge current.IMHO a 2A or 4A charge won’t make much difference- whatever charge voltage you set, they will taper current as the battery voltage reaches that setting.
I suspect you misunderstand me.My JBD balances at milliamperes. And not very darn much, half an amp or something. Balancing isn’t very impressive, or I’m just impatient. Lol
Please report back. Thinking I have a similar situation here but really not sure about the details brought up in this thread so skillfully by participating diysolar members.I guess I'll see what I can work out with SOK.
IMHO a 2A or 4A charge won’t make much difference- whatever charge voltage you set, they will taper current as the battery voltage reaches that setting. Some chargers have a duration, some sense tail current - a level that is decidedly full charge and terminate.
Bleeding one cell at high knee is a quick way to bring it down to the level of the other cells. I have done this several times on my diy battery, and is very well balanced up to about 3.55Vpc.
You may need to repeat the process again at an interval. A severely degraded cell that doesn’t match the others is a warranty claim on a bought battery.
I use a 12V auto headlight bulb to bleed individual cells - done near full charge while charging to assist bms balancing. Only takes a minute or two to drop a cell down and let others catch up before the whole pack reaches the full voltage charge setting.
I don’t bounce off the bms over volt settings.
So SOK is telling me not to worry that it will balance itself out. Direct quote:Please report back. Thinking I have a similar situation here but really not sure about the details brought up in this thread so skillfully by participating diysolar members.
I believe both could be correct. Generally more voltage, less time. For light daily cycling... charging at the lower end and less time will still get over 95% and extend the life of the battery some. For occasional use, like fishing, perfectly OK to charge on the high side and get out on the water faster with 100% charge.This thread is very valuable because of the discussion of where to set the absorption voltage. How long should absorption be? Victron default was what, an hour? CurrentConnected says 15 minutes?
Max charging voltage is 4.2V per cell.
I’m sure someone will get all bent out of shape about that one sentence. It is the true max safe charging voltage just like most lithium ion chemistries but common sense will tell you that past 3.35V you start to see the voltage climb rapidly and if your charging current is a fixed value then 2+2= there’s not much capacity up there. You decide for yourself how high you want to go. Most of the research and real world experience has shown us that past 3.50V you’re seeing maybe the last one or two percent of capacity. This also depends on how your charger cuts the current off. Most people follow the 0.05C rule.
Also, keep in mind I don’t really use BMS’s unless it’s a pack I know I’m not going to monitor so I’m free to charge up to 3.65 on a balance charger if I want to so long as my charge current is low enough for the balance current to stop any runners. I couldn’t fathom having an off the shelf battery with no access to the balance leads with how slow most of these BMS’s balance and worst of all the non Bluetooth BMS’s that have balance start set to 3.60V
Do whatever makes you happy. Maybe take notice that these BMS’s aren’t making you very happy.