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diy solar

SOC vs resistance vs solar hrs in the day

Stewfish

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Oct 20, 2020
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I would like to top balance my cells and I'm 100% off grid.

Based on charging algorithms if I set the bulk charge to 14.4 or 57.6 for my 48v batteries then it will take a long time to get that last 5% to 10% as the resistance increases and the amps decrease. Then there is the lack of power after sunset to trickle it in at the lower amperage for a few days.

If you sat an watched the voltage to be safe - has anyone ever set the bulk to say 15v or 20v (maybe 68v for my 48v system) to get it charged up to 14.4 /57.6 in a day, then when it gets to 57.6v reset the bulk back to the normal 57.6 and let the batrium actively balance in bypass mode to balance it?

I have 28kwh (32 cells) and that last 5% to 10% would take a long time to achieve at lower amperages. I was at 90% soc at sunset yesterday and down to 82% this morning, now 54.45v for the past few hours and it's peak solar time and I have 1000s of watts available and not being drawn in. I reset my voltage from the longlife Battle born 56.1v that is in Will's sticky thread. I set it to 57.6 and I think I got about half an hr of increased power from the controller and bumped the cell max to 3.46v from 3.45v. Now it looks like I'm back to trickling bc while using Batriums' heat bypass to bring up the other cells, everything is at a stand still. My minimum cell voltage is 3.33v way below 3.46v and I'm trying to get power to balance the batteries.

I have the MPP LV6548, with 32 basen cells, and the Batrium Core/K9 setup
 
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I would like to top balance my cells and I'm 100% off grid.

Based on charging algorithms if I set the bulk charge to 14.4 or 57.6 for my 48v batteries then it will take a long time to get that last 5% to 10% as the resistance increases and the amps decrease. Then there is the lack of power after sunset to trickle it in at the lower amperage for a few days.

If you sat an watched the voltage to be safe - has anyone ever set the bulk to say 15v or 20v (maybe 68v for my 48v system) to get it charged up to 14.4 /57.6 in a day, then when it gets to 57.6v reset the bulk back to the normal 57.6 and let the batrium actively balance in bypass mode to balance it?

I have 28kwh (32 cells) and that last 5% to 10% would take a long time to achieve at lower amperages. I was at 90% soc at sunset yesterday and down to 82% this morning, now 54.45v for the past few hours and it's peak solar time and I have 1000s of watts available and not being drawn in. I reset my voltage from the longlife Battle born 56.1v that is in Will's sticky thread. I set it to 57.6 and I think I got about half an hr of increased power from the controller and bumped the cell max to 3.46v from 3.45v. Now it looks like I'm back to trickling bc while using Batriums' heat bypass to bring up the other cells, everything is at a stand still. My minimum cell voltage is 3.33v way below 3.46v and I'm trying to get power to balance the batteries.

I have the MPP LV6548, with 32 basen cells, and the Batrium Core/K9 setup

Well after reading this thread. I changed my float setting to 57.6 and the voltages jumped right up. After about 2 minutes when a couple cells hit 3.6 I turned it back down. My 3.3 cells didn't rise up so I'm stuck trying to too balance the packs.

I may just have to set 3.3 x 16s as my max to avoid unbalances of 3.45 to 3.3 everyday. 11 cells just wont go.above 3.3v.
 
I would bring them up to 3.65v per cell individually with a bench power supply. This prevents holding them at a high state of charge for very long.
 
I would bring them up to 3.65v per cell individually with a bench power supply. This prevents holding them at a high state of charge for very long.

Yeah. I may have to to take apart one of the batteries (32 cells in16s) at a time and fiddle with it over a week
 
You can leave them all wired in series and just put your bench power supply on the one cell you are trying to charge. This way there is no extra work to break the battery apart
 
You can leave them all wired in series and just put your bench power supply on the one cell you are trying to charge. This way there is no extra work to break the battery apart

Ah yes, good idea!

Thinking:
Can I leave it on a wall timer to turn off before the sun comes up, so I can leave it all connected and charge the cells individually at night? It would have a max draw across the two 16s batteries at night of about 500w to 650w, but ussually 150w, laptop running batrium as Inset this system up. I wonder if the desktop supply would only loose a little to loads.and still charge fine
 
I know no loads would be better, but I think I could still see if the cell will go above 3.3v
 
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