Top Balance PATIENCE Question.

[lance]

You are probably looking at 140 hours, four LF280N are taking me between 70-76 hours to top balance with a 10 amp power supply.

<sigh> Good thing I've plenty other pieces of this puzzle to work on.

 

[lance]

Love the before and after shot ..... We should make that a sticky

It might help those of us with short attention spans. Reviewing Filter Guy's tutorial this morning I see that if I'd only made it all the way down to Note 3 under Power Supply I'd have likely avoided all of this. doh.

 

[lance]

Okay. 3+ days have passed. And, while they have gained (currently at 3.352, starting around 3.32.) During this time, and this is what concerns me, and causes me to come back in to this post, I've actually seen them go down a few 100ths' of a volt and today.... all day, they've gained 0.... zero.... nada.... zilch. I gotta ask: am I missing something or, is it take a chill pill dude? Did a quick scan through other top balance threads and saw nothing about voltage going down during top balance.

 

[Bob B]

As long as the cells are still taking current ..... carry on.

I haven't observed that phenomena .... the voltage will be very flat in that area of the charge curve. Maybe others have seen something like this.

 

[lance]

As long as the cells are still taking current ..... carry on.

Ahhh.... "current" is the amps number on the charger then, yes? And yes, that number stays fairly constant.

I haven't observed that phenomena .... the voltage will be very flat in that area of the charge curve. Maybe others have seen something like this.

And, it is a very small amount of down (2-3 100ths) but, it just feels so much like the wrong direction! ;-)

 

[time2roll]

The voltage fluctuation is normal, common and ordinary. If 10 amps is still flowing all is good.

 

[lance]

Going with the chill pill. Thanks guys.

 

[sunshine_eggo]

Going with the chill pill. Thanks guys.

Almost all charging occurs below 3.40-3.45V.

Watching paint drying or grass growing is outright ACTION PACKED compared to watching voltage on LFP go up during a top balance charge.

You have at least 1120Ah of capacity you need to input (8 * 50% * 280Ah). You're charging with 10A.. that's 10/(8 * 280) = 0.0045C - voltage crawls at such a low level.

The last few hours will be "exciting."

 

[lance]

Watching paint drying or grass growing is outright ACTION PACKED compared to watching voltage on LFP go up during a top balance charge.

Good to know. Today though, I'm going to head out to a parking lot with a lawn chair to sit and watch the cars rust.... not sitting around here watching the voltage go down on my top balance today!

 

[sunshine_eggo]

Good to know. Today though, I'm going to head out to a parking lot with a lawn chair to sit and watch the cars rust.... not sitting around here watching the voltage go down on my top balance today!

Be careful. The dramatic increase in stimuli may overwhelm your senses.

 

[lance]

Be careful. The dramatic increase in stimuli may overwhelm your senses.

We laugh but, it actually was a little quickened pulse inducing watching the voltage marching steadily upwards every few seconds!

 

[lance]

And, it is done! Thank you all for the hand holding.....





Now, they've still got some time before they see any real action... maybe a couple of weeks or so they'll have the BMS connected, and the inverter/charger connected. Much longer before solar and charge controller come on board. I'm guessing it is likely best to keep them in parallel up until I've got the busbars made to bring them in to their final in-series configuration in their battery box. Just for the sake of keeping their SOC synched. Does that make sense? Or any suggestions for how best to handle them now, or maybe none of it really matters now they've been top balanced?

 

[time2roll]

Now the final assembly can commence. Looking real good.

 

[papab]

I'm curious what the consensus is one when it is done. I've seen some varying opinions on some howto blogs. I see 1.11 amps on lance's meter ...

 

[Bob B]

And, it is done! Thank you all for the hand holding.....


View attachment 79655


Now, they've still got some time before they see any real action... maybe a couple of weeks or so they'll have the BMS connected, and the inverter/charger connected. Much longer before solar and charge controller come on board. I'm guessing it is likely best to keep them in parallel up until I've got the busbars made to bring them in to their final in-series configuration in their battery box. Just for the sake of keeping their SOC synched. Does that make sense? Or any suggestions for how best to handle them now, or maybe none of it really matters now they've been top balanced?

Good to see you got it done .... I would leave them in parallel and monitor occasionally

Don't be concerned if they fall back to 3.5 or a little lower.

 

[lance]

I'm curious what the consensus is one when it is done. I've seen some varying opinions on some howto blogs. I see 1.11 amps on lance's meter ...

Hopefully someone else will chime in on this but, my guiding rule was that the measured voltage from the multimeter was at 3.65. The voltage number on the charger was really erratic, and the amperage would fluctuate a lot, including showing zero from time to time. That said to me that they were done.

 

[sunshine_eggo]

Hopefully someone else will chime in on this but, my guiding rule was that the measured voltage from the multimeter was at 3.65. The voltage number on the charger was really erratic, and the amperage would fluctuate a lot, including showing zero from time to time. That said to me that they were done.

FWIW, most LFP cells are fully charged at 3.65V and 0.05C, i.e., on a 280Ah cell, it's fully charged at 3.65V and 14A.

When cells are in parallel, the convention is to run it to near zero to ensure all cells are truly full. The fluctuations were as the individual cells hit full. They stopped accepting current abruptly. This causes slight current and voltage fluctuations.

 

[lance]

Not quite sure the best place to ask this question so, I'm going to start with this existing thread.....

Everything is connected! No, that is not some zen existentialistic statement. Actually, I'm lying: I've yet to actually connect the batteries to the system but, I've connected the 24v power supply to it, and all seems to be working right. I've also got the AC side of the inverter fully connected, including a temp "shore power" with a male plug on 12AWG wire, and a temp outlet on a 20amp breaker, ready to test the AC side, and (I think) do a load test on the batteries. It will be awhile before there's solar and a SCC attached. I'm assuming it is ok for this to come into play later, and for testing purposes to just use the charger side of the inverter to keep the batteries flush.

This brings me to my question: Once the inverter/charger comes on, I'm assuming it needs to have charging profile parameters set in it right away. My memory is that there was a resource, possibly created by Will, that lived on this site that listed charging parameters profiles for various batteries. But, my search has yielded nothing so far.

Anyone up for holding my hand a little on this stage and letting me know the right sequence of moving forward? I'm really leery of putting power, whether 24v or 120v into this thing even though I'd essentially done so with the power supply. I'm just fearing any risk of damaging the batteries once they're connected to the current system.

Also: the battery balancing wires are not attached to the batteries or BMS yet. They're built but, I'm waiting for Batrium to answer my latest round of questions before going further with that.

Attaching a pic that shows part of the set up.

 

[time2roll]

Also: the battery balancing wires are not attached to the batteries or BMS yet. They're built but, I'm waiting for Batrium to answer my latest round of questions before going further with that.

Not sure how the Batrium system works.... however I would not charge or discharge in series without BMS fully connected and protecting the cells.

Most important charging parameter is the charging voltage. Nothing too much will happen as the inverter/charger is connected and you get into the settings for a few minutes.

 

[lance]

however I would not charge or discharge in series without BMS fully connected and protecting the cells.

This makes sense.