My DIY battery stays much better balanced than my server rack battery.

[hwy17]

I've been middling the battery bank for a couple months now and I brought it up to full charge to observe and the DIY Eve 304 pack is still at a <.10 delta while the server rack is at .56 delta.

This could be cell quality.

I also wonder if it's balancing parameters.

The DIY battery only balances cells above 3.437, which is my highest charge voltage (absorb and float). The server rack might start balancing at 3.4-3.425 I'm not sure.

I wonder if the server rack battery was getting into some counterproductive balancing activity too low in the leg during less than full charge.

 

[740GLE]

What type of balancing does each unit have?

Also 100mv isn’t something to brag about

500mv is down right assault.

It’s prob because how often are you aren’t bringing each battery above 3.4v to balance a little bit each day.

 

[SomethingAppropriate]

What type of balancing does each unit have?

Also 100mv isn’t something to brag about

It’s prob because how often are you bringing each battery above 3.4v daily to balance a little bit each day.

Right! Im hoping there is some math mixed up here.

 

[sunshine_eggo]

What type of balancing does each unit have?

Also 100mv isn’t something to brag about

Unless it's 3.60 and 3.50, and then it really doesn't matter much.

Now, 3.35 and 3.45 - that's a different story.

 

[740GLE]

I haven’t seen anyone state that start balance at 3.4v is causing harm, also you gotta make sure there is some “absorb time” when cells are held at that voltage (if not up to 3.5v).

 

[Brucey]

I've been middling the battery bank for a couple months now and I brought it up to full charge to observe and the DIY Eve 304 pack is still at a <.10 delta while the server rack is at .56 delta.

This could be cell quality.

I also wonder if it's balancing parameters.

The DIY battery only balances cells above 3.437, which is my highest charge voltage (absorb and float). The server rack might start balancing at 3.4-3.425 I'm not sure.

I wonder if the server rack battery was getting into some counterproductive balancing activity too low in the leg during less than full charge.

The eg4s apparently have some kind of crazy limit on their balancing where it only balances the top 6 cells. Needs a reset to maybe pickup some other cells. at least their life power 4s not sure if that applies to the LLs or 14kWh units.

 

[740GLE]

The eg4s apparently have some kind of crazy limit on their balancing where it only balances the top 6 cells. Needs a reset to maybe pickup some other cells. at least their life power 4s not sure if that applies to the LLs or 14kWh units.

Yet again another reason to test all batteries “will it balance test”

Balancing cells is so vital to battery health, everyone should know what they need to do to keep the cells all in check.

 

[houseofancients]

I've been middling the battery bank for a couple months now and I brought it up to full charge to observe and the DIY Eve 304 pack is still at a <.10 delta while the server rack is at .56 delta.

This could be cell quality.

I also wonder if it's balancing parameters.

The DIY battery only balances cells above 3.437, which is my highest charge voltage (absorb and float). The server rack might start balancing at 3.4-3.425 I'm not sure.

I wonder if the server rack battery was getting into some counterproductive balancing activity too low in the leg during less than full charge.

I assume your server rack is running a BMS that has a passive balancer, usually they only do very small amounts of current, therefor your cells need to be well into the voltage curve before they make any dent in imbalances

 

[hwy17]

I always screw up that decimal, I should stop trying to use it and stick to speaking in millivolts. 10 and 50 of those I mean. .010/.050

Both DIY and server rack battery have a passive balancer. 150mA on the DIY 304Ah and I believe 100mA on the server rack 100Ah.

 

[Steve_S]

Not sure what BMS' you are using. I am using JK's and just transitioned to the Inverter Models. On Both versions, I start Active Balancing at 3.420 where my Float is just over that at 3.449 and allowing for 0.005 deviation. Within 15-20 minutes of entering into float all cells in all packs are within specs I set. My Packs are EVE 280AH cells from LF280 V1 through to LF-280K V3. Even the 280V1 from 2018 (manufacture date) hum along happily.

 

[740GLE]

I always screw up that decimal, I should stop trying to use it and stick to speaking in millivolts. 10 and 50 of those I mean. .010/.050

Both DIY and server rack battery have a passive balancer. 150mA on the DIY 304Ah and I believe 100mA on the server rack 100Ah.

Ahhh much better, yeah I’d have no issues with that, again just as long as you routinely keep voltages high enough to allow balancing you should be good to go.

I’m sure if you let the rack battery bake it’ll bring that 50mv down to 10mv. Even with 50mv you aren’t losing any major capacity.

 

[hwy17]

I’m sure if you let the rack battery bake it’ll bring that 50mv down to 10mv. Even with 50mv you aren’t losing any major capacity.

Agreed. It's all functional, and confirms to me that 2 months is about as long as I should let them middle without an intentional balancing charge. For the server rack battery at least.

I am just surprised and slightly wanted to brag a little bit that it's my DIY battery that's staying better balanced, lol.

 

[740GLE]

My newly commissioned Luyan cells were all right at .001 delta as I startled tickling 3.38v, this was on the first charge too, no top balance. I left the camp and have to imagine they will all be at 3.42 when I arrive possibly this weekend.

 

[Cuemaker]

Agreed. It's all functional, and confirms to me that 2 months is about as long as I should let them middle without an intentional balancing charge. For the server rack battery at least.

I am just surprised and slightly wanted to brag a little bit that it's my DIY battery that's staying better balanced, lol.

What BMS are you using?

 

[hwy17]

What BMS are you using?

Orion

 

[Brucey]

Orion

 

[Cuemaker]

Orion

Do you have a 16s-48v BMS's? Where did you buy?

 

[hwy17]

Do you have a 16s-48v BMS's? Where did you buy?

Yeah I have one JR2 so far that I got secondhand from another member here. It took me 6 months of work to learn it, design my contactor controls, and build it. Like on and off on weekends, maybe 100+ hours total.

Not that it's rocket science, but in many different ways the Orion manual just says "here's a problem for you" and leaves you to find the answer. Like the contactor signal is provided as a single contact that opens/closes to the BMS power supply's negative can only accept a 100mA load.

But now that I understand the quirks and my own solutions I'm hooked on their simplicity. I'm going to try to explore a way to use one of 180s BMS2 to protect and balance multiple parallel 16A banks. The designer of them would not support that at all but I think it can work with some compromises.