EG4-LifePower4 problem

[Brianadams90]

First time poster.

I have a EG4-LifePower4 server rack with 6 batteries and the topmost battery shows a lower charge state. These batteries were at similar voltages when installed. Is my setup wrong on the bus bars? Is this normal for the first battery?

I have 2 eg4 6500ex in 2 phase configuration. I have them set to custom charge configuration to 53.2v for about a month now. Is this a problem with not charging to 100%?

Thank you.

 

[timselectric]

Is this a problem with not charging to 100%?

Partially, yes.
The only time they can equalize is at the top or bottom of the charge/discharge curve. The middle of the curve is too flat. The same voltage can be anywhere from 30% to 70%.

 

[rodrick]

You max charge is low your only charging to 3.32 volts which will not even activate the bms cell balance features

I would set to max voltage of 3.55 volts per cell = 56.8 volts you are in the gray zone where actual charge values are a guess you need to bring them to full charge sometimes just to sync everything

 

[DIYrich]

Recommended Charge Profile for DIY LiFePO4 Batteries *Sticky Post*

12V 4S LiFePO4 Battery w/ BMS: Absorption: 14.5V Float: 13.6V Inverter Cut-off: 10.7V-12V (depending on size of load and voltage drop etc) 24V 8S LiFePO4 Battery w/ BMS Absorption: 29V Float: 27.2V Inverter Cut-off: 21.4V-24V 48V 16S LiFePO4 Battery w/ BMS Absorption: 58V Float: 54.4V...

diysolarforum.com

 

[Brianadams90]

I appreciate the replies. I had the voltages set at 54.4 prior and things were fine. I did some reading that lower voltages were better for cycles.

 

[Ampster]

I had the voltages set at 54.4 prior and things were fine.

I use 55.2 (3.45 V per cell) so the active cell balancer would have some time to work. My system charges from solar and I usually get 3 or 4 hours of CV charging per day. The last couple of hours are at low amperage. I tried higher voltages and the cells show some signs of imbalance so I figured 55.2 volts was close to 95 per cent SOC and that would give me longer life. For some odd reason after the current drops to 20Amps on my 840 Ahr pack the voltage actually goes up to 54.5 for the last hour as the Amps continue to taper down. This is a SolArk bug that does not seem to affect my pack.

 

[DIYrich]

I appreciate the replies. I had the voltages set at 54.4 prior and things were fine. I did some reading that lower voltages were better for cycles.

True, but... Cycling in the 80-20 range is best, but you need to go to 100% once a week or so to keep everything calibrated.

 

[Brianadams90]

This may be a dumb question, but I may have it confused how the bulk/float charge settings work. I know under charge the voltage is higher but under no load the voltage is lower. With setting my inverter to 53.2 I figured I was setting my batteries to charge to 80%, but depending on if that is just the charge voltage I may have set my batteries to a lower than planned at rest voltage. If that makes sense?
The recommended bulk charge voltage from the manual for this battery is 56.4 and float of 54.4. Does the higher charge voltage hurt cycle counts or is it the at rest voltage?

 

[Ampster]

but you need to go to 100% once a week or so to keep everything calibrated.

I learned some time ago that 100 percent does not always mean a pack charged to the max. As far as I can tell all my EVs have a built in cushion and when the EV says the pack is 100 percent it may be 95-98 percent SOC. Even though I usually charge them to 80-90 percent, I sometimes go to 100 parcent because that insures that the balancers have some time to work. I often do that before depaerting on a long trip, because I do not like to leave the pack at a high state for a long time. The same thing applies to how I adjust my BMS settings. when I charge to 3.45 per cell my BMS sees that as 100 percent and it resets the Coulomb counter to 100. I rely on that BMS and use those values through closed communication to my SolArk. I am not necessarily disagreeing with your statement, I am just offering an alternative that may accomplish the same thing. The two important issues are to give the BMS some time near the knee of the charge curve to balance the pack, and to reset the Coulomb counter.

 

[Ampster]

This may be a dumb question, but I may have it confused how the bulk/float charge settings work.

It is not a dumb question. Those terms are derived from Lead Acid practices and terminology. I think it is dumb that these terms have persisted when the terms Constant Current and Constant Voltage explain what is actually happening. Voltage is the most important variable but current should not exceed the manufacturers recomendations. Voltage and Current are typically measured and reported and that is why those terms make more sense to me. Sometimes we have to adapt because our devices use antiquated terminology.
Bulk is simply a Constant Current charge stage which transitions at a set voltage ( the CV stage). That voltage is then held constant and the current tapers off as the charge controller reduces current to keep the voltage from increasing. In Lead Acid terminology that is often called Absorb.
Float is a term used in Lead Acid because Lead Acid tends to lose charge quickly and Float maintains that charge. Float is not needed in Lithium charging but some people use it to maintain batteries at resting voltage often when charging from solar and one wants the pack to be fully charged when the sun goes down. Because it is not healthy to leave Lithium batteries at high voltage, a Float setting of 3.3 - 3.35 can be used as long as it is not used for more than a few hours. Float is a Contant Voltage stage which is also at a reduced current.
I should also mention that when charging from solar the term Constant Current is not always correct as the output of solar may vary and therefore the current can change but it should never exceed the CC setting.

 

[Brianadams90]

Thank you for that explanation of bulk and float. While I'm sure don't grasp it fully, I do have a better understanding now what these settings do.

 

[Ampster]

While I'm sure don't grasp it fully, I do have a better understanding now what these settings do

Feel free to ask any clarifying questions, since this thread will benefit other readers.

 

[SniperX]

It is not a dumb question. Those terms are derived from Lead Acid practices and terminology. I think it is dumb that these terms have persisted when the terms Constant Current and Constant Voltage explain what is actually happening. Voltage is the most important variable but current should not exceed the manufacturers recomendations. Voltage and Current are typically measured and reported and that is why those terms make more sense to me. Sometimes we have to adapt because our devices use antiquated terminology.
Bulk is simply a Constant Current charge stage which transitions at a set voltage ( the CV stage). That voltage is then held constant and the current tapers off as the charge controller reduces current to keep the voltage from increasing. In Lead Acid terminology that is often called Absorb.
Float is a term used in Lead Acid because Lead Acid tends to lose charge quickly and Float maintains that charge. Float is not needed in Lithium charging but some people use it to maintain batteries at resting voltage often when charging from solar and one wants the pack to be fully charged when the sun goes down. Because it is not healthy to leave Lithium batteries at high voltage, a Float setting of 3.3 - 3.35 can be used as long as it is not used for more than a few hours. Float is a Contant Voltage stage which is also at a reduced current.
I should also mention that when charging from solar the term Constant Current is not always correct as the output of solar may vary and therefore the current can change but it should never exceed the CC setting.

Best explanation I have seen. Thank you!