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Renogy 48v 3500w - Sako/Jasaki 12v 100ah packs - max 10a charge rate?

Blistovmhz

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Jul 15, 2022
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This is my first installation so bear with me.
I've got a Renogy 48v 3500w inverter/charger/controller, 4x 100ah 12v Lifepo4 packs from Jasaki (identical to Sako) wired in series. Got my generator powering the load.
One of the packs wouldn't turn on when I received it. Cracked it open, found the balance lead unplugged. 3 cells were 3.4v, 1 cell at 2.4v :(. Plugged in the balance (carefulling), and it seemed to charge the cell up no issue (plugged in a 12v panel/controller).
Everything looking good, I wired up all 4 packs in series for 48v and started charging.
Renogy is set to 16string LifePO4 (though I've also tested pretty much every possible combination of user settings at this point), but absolutely nothing I can do to get the batteries to charge at >10a or around 500w. The Renogy is supposed to be able to handle 40a from AC/Util and another 80a from solar. My generator is a 5kw unit and has no problem holding 5k all day, but for some reason, either the Renogy refuses to provide the current/voltage, or the packs are somehow limiting their charge current.
Renogy claims battery input voltage at 54.3v right now. Been charging ALL DAY. 12 hours at 500w average.
1. I don't understand why Renogy seems to be limiting voltage to 54.3. It's always perpetually about 0.2v above the packs total voltage, which seems odd to me? I thought we should be blasting LifePo packs with 57 to 58v.
Am I missing something obvious here, or is there a problem with my charger or packs? Could the packs internal BMS be limiting us because of the single bad (potentially) cell? 10a seems crazy low. I'm used to charging my LiPo's at least at 5-10c minimum. We're getting what... 0.25c right now? At this rate, my tiny 600w PV is making more power than my 400ah batteries can use.
 
IMHO, you have a defective battery, and you need to return it.

3 cells at 3.4V are full.
1 cell at 2.4V is empty.

That means there is a 100Ah difference in their current state of charge.

The 2.4V cell needs 100Ah put into it without putting anything else into the other 3 cells. The balancing capability of the BMS will likely take as much as 2,500 hours (not a typo, two thousand five hundred hours) to balance it provided you can keep the other 3 cells at or above 3.4V.

You're failing to get above 54.3 because the bad battery now has 3 cells at or over max and one cell probably a little over 3V and at a very low SoC, so the battery BMS is protecting the 3 cells from being overcharged.

Again, you have a bad battery, and the performance will suffer until you get 100Ah into the bad CELL or you replace it.
 
Currently all cells are dead nuts balanced at 3.345+/-0.002v. I let it charge with the genny all night. Continued drawing roughly 500-700w all night (or 10a). I disconnected the balance leads on all 4 packs and let'm sit for a while. Zero change. Put them back on the charger without balance leads, and they're all charging perfectly (or at least they're all retaining the exact same voltage with respect to each other.
So I guess part of what threw me off is that I keep thinking LiPo, not LiFePo. I keep coming back to expecting closer to 4v/cell, and the charger is showing me at 70% capacity (it's set for LiFePo4), which it seems to think should be 57.4v, but my pack voltage is only 53.52v.
I really wonder if this is just Renogy being dumb? Bad firmware?
I'm about to test a big, sustained current draw with balance disconnected to make sure all cells discharge equally.
 
Yea, I'm just derping out as well as the Renogy controller was just confused, which confused me further. I think nothing is wrong. Ran a 4kw load for about 15 minutes and cells all stayed dead balanced. Let it charge on both PV and gen for 20 minutes, and again, dead balanced, so I plugged the balance leads back in and reset the entire system. Now Renogy says battery capacity is 100%.
I've only got 6x100w panels (though somehow they're making about 120w each in good sun at around 40* off perpendicular), and I'm making around 650-700w currently. Running the 12v battery charger, laptop charger, starlink, and my clothes washer, and we're still putting 100-150w into the batteries!
Huzah!
So I'll just triple my PV and double my storage, and honestly, I think I'd be able to squeek through winter without any shore power.
 
Currently all cells are dead nuts balanced at 3.345+/-0.002v.

Cells in the working range almost always show negligible voltage deviation. This is not balance. This is the nature of LFP's flat voltage curve.

I let it charge with the genny all night. Continued drawing roughly 500-700w all night (or 10a). I disconnected the balance leads on all 4 packs and let'm sit for a while. Zero change. Put them back on the charger without balance leads, and they're all charging perfectly (or at least they're all retaining the exact same voltage with respect to each other.

You can't push 10A into cells that are full. Either you have not disclosed something, or your initial report is in error. Cells at 3.4V are full and a cell at 2.4V is beyond empty. You need to get 100Ah into the empty cell without adding anything to the others.

The only uncertainty here is the rate at which the BMS can balance. Robust balancers are 0.2A. Typical are 0.03-0.07A.

Even active balancers are disappointing. Active balancers report 2A, 4A or 6A or whatever. What they don't tell you is that's proportional to the voltage difference. Commonly, those rating are for a 1V difference between cells, so if you're only 0.1V difference, you're only getting 10% of the rated balancing.

So I guess part of what threw me off is that I keep thinking LiPo, not LiFePo. I keep coming back to expecting closer to 4v/cell, and the charger is showing me at 70% capacity (it's set for LiFePo4), which it seems to think should be 57.4v, but my pack voltage is only 53.52v.

A charger reporting capacity is a useless value unless it's for a chemistry that has a strong voltage to SoC correlation, or it's being fed by the BMS communicating back to the charger. LiPo and LFP have completely different behaviors. LFP has very poor voltage to SoC correlation unless the battery has been sitting for at least 30 minutes with no charge or discharge of any kind.

I really wonder if this is just Renogy being dumb? Bad firmware?

Most likely a disparity between your understanding, expectations and reality. Though Renogy kinda sucks IMHO.

Yea, I'm just derping out as well as the Renogy controller was just confused, which confused me further. I think nothing is wrong. Ran a 4kw load for about 15 minutes and cells all stayed dead balanced.

Again, cells in the working voltage range show negligible deviation and does not indicate "balance." When all cells are the same voltage in the 3.45-3.65V range, then one can say they are "balanced."

Let it charge on both PV and gen for 20 minutes, and again, dead balanced, so I plugged the balance leads back in and reset the entire system. Now Renogy says battery capacity is 100%.

Were all voltages above 3.45V? If not, they were not balanced.

I've only got 6x100w panels (though somehow they're making about 120w each in good sun at around 40* off perpendicular), and I'm making around 650-700w currently. Running the 12v battery charger, laptop charger, starlink, and my clothes washer, and we're still putting 100-150w into the batteries!
Huzah!

Solar availability reduces/eliminates demand on the battery.

So I'll just triple my PV and double my storage, and honestly, I think I'd be able to squeek through winter without any shore power.

Charge to 56.8V and report cell voltages. Then I'll buy it that they're "balanced."
 
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