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I assume you mean this?
Not exactly, you still do not have your head wrapped around what Bulk, Absorb, and Float are.
There are only two charge modes of either Constant Current or Constant Voltage. Bulk, Absorb, Float, Equalize, Refresh are all just confusing terms to make a consumer confused.
Bulk is constant Current, all the rest are Constant Voltage. If you were to buy a Float Charger for lead acid, or CC/CV for lithium is the exact same charger. Both have a Bulk (CC) ,and Float (CV) stages. All modes be it Bulk or whatever stage you want to call it like Hocus Pokus have a voltage set point. For a 4S lithium and Pb is 14.4 volts. Absolutely no difference. When you connect a charger, let's say a 20 amp charger, to a discharged battery of let's say 12 volts. When you connect the discharged battery you are not going to see 14.4 volts. Nothing remotely close to 14.4 volts. For demonstration purpuses let's say both batteries are 100 AH, and each has an internal resistance of .02 Ohms. From here it is simple math.
Battery Under Charge Voltage = OCV + [Ri x Charge Current] We already defined OCV of 12 volts or a fully discharged battery, and with a 20 amp charger (C/2 on a 100 AH battery) you will initially only see 12 volts + [20 amps x .02 Ohms] = 12.4 volts. The battery OCV forced the charger to become a Constant Current source. The Charger has a current regulator that will not allow it to deliver more than 20 amps. As the battery charges up, the OCV will rise and continue to rise for 4 to 5 hours. When the OCV of the battery is 14.0 volts, will begin the Absorb Phase. When the battery OCV reaches 14.1 volts there will only be 14.4 - 14.1 volts / .02 Ohms = 15 amps. At 14.2 is 10 amps. At 14.3 is 5 amps. At 14.4 both charger and battery OCV are equal and current stops.
Nothing magic happened, nothing switched on or off. It is pure Ohms Law of voltage and resistance relationship. Now we can add a circuit to do something like change the Voltage Set Point or Turn the Charger Off. Example we add a current measurement with some simple logic that says if Current = 5 amps or less, we do something. One thing we can do is lower the Voltage to say 13.6 volts and call it Abracadbra. No lets call it FLOAT so we fool Karrak and the John Doe homeowner. Sounds better. Why 5 amps and 13.6 volts? Because 5 amps on a 100 AH Pb and LFP is the point both batteries are fully charged. If we were to hold 14.4 volts on either battery would be an over charge. On Pb battery we would gas the batteries and corrode the plates. On a Lithium battery becomes unstable and plating lithium metal onto the anodes.
So you roll the voltage back on both. When you do that the Surface Charge on the plates will bleed off and hold at full charge. Any power demands from that point come from the charger if it remains. However very few chargers made for lithium will fall back to a lower voltage. They shut off.
Now if you were to watch the voltage on a PB and LFP battery, you would see they are not alike. A Pb battery would be a nice straight slope slope from 12 to 14.4 volts. On a LFP would look radically different like the slope you seen in Karrak's graph. It would jump up very quickly from 12 volts to 13,2 volts and pretty much stay there struggling upwards to 13.6 volts when it reaches about 90% SOC, then shoots up real fast that last 10% to 14.4 where you do not want to go.
Solar is a piss poor choice to charge LFP batteries because the charge current is unknown at any point in time. That means you cannot use a current trigger. Your battery could be 50% SOC at noon with only 5 amps and falsely trips the circuit because a cloud or haze passes over. There are no charge controllers that can work properly with Lithium. It takes an external control, a damn BMS. So what do you do? Simple choose 1 voltage of roughly 3.4 volts and allow the battery to saturate and FLOAT. That would be 13.6 volts on a 4S battery.
So far you are not ready to do anything. You have not balanced your batteries. Until you do that, you are spinning your wheels and risking damage. Decide Top or Bottom period. To do that you must connect all cells in parallel and walk away for a few hours. Then either discharge them to 2.5 volts, or charge them to 3.65 volts. Take your pick. Once balanced, lithium batteries do not go unbalanced quickly unless you have a BMS or Voltage Monitor taps. Those wil be a parasitic loads of uneven current draw. Both my Ev's only need balanced about once a year. If your batteries are in good shape has a self discharge of about 1% a month. Some maybe .8% and some 1.2% a month. So it takes a long time for any imbalance to occur. If you TOP balance periodically check cell voltages. All should be within .01 volts at the TOP. If you Bottom Balance should be within .01 volts near the bottom.
Now here is the difference betwen Bottom and Top Balance. With Top Balance the only thing that is known is 100% SOC. It does not tell you what capacity the pack is. Chi-Com cells especially Winston cells are notorius and can be +/- 10% of rated capacity. So when at 100% SOC you can have one cell at 90 AH and another at 110 AH which means you only have a 90 AH pack. That 90 AH pack i sin real danger of being over discharged. Th eother 3 cells wil eat and destroy it if the cell voltage goes to 2.5 volts or less.
Bottom Balance you know exactly what the capacity and SOC is. At 2.5 volts per cell capacity = 0 AH and SOC is exactly 0%. When you charge the cells in series, every cell has the exact same capacity. When they discharge, all cells voltages will be the same at the low end. Eliminates over discharge. Set you LVD from 11 to 12 or more volts, and you are safe.
however, pnjunction, if my charging limit voltage is 13.85, then should no float happen, isnt it? float in my scenario based on those values should go like this:
until 13.75v - bulk
13.75 - absorb starts and lasts 10 minutes based on set counter RaisDur: 10
then float - charging voltage goes down to specified 13.65v
if even afterward SOC rises, charging will be completly shutoff at specified charging limit 13.85v set.
this is how i understand these settings vs process flow now, after your explanations. is it right?
until 13.75v - bulk
13.75 - absorb starts and lasts 10 minutes based on set counter RaisDur: 10
then float - charging voltage goes down to specified 13.65v
if even afterward SOC rises, charging will be completly shutoff at specified charging limit 13.85v set.
this is how i understand these settings vs process flow now, after your explanations. is it right?
There are only two charge modes of either Constant Current or Constant Voltage. Bulk, Absorb, Float, Equalize, Refresh are all just confusing terms to make a consumer confused.
Bulk is constant Current, all the rest are Constant Voltage. If you were to buy a Float Charger for lead acid, or CC/CV for lithium is the exact same charger. Both have a Bulk (CC) ,and Float (CV) stages. All modes be it Bulk or whatever stage you want to call it like Hocus Pokus have a voltage set point. For a 4S lithium and Pb is 14.4 volts. Absolutely no difference. When you connect a charger, let's say a 20 amp charger, to a discharged battery of let's say 12 volts. When you connect the discharged battery you are not going to see 14.4 volts. Nothing remotely close to 14.4 volts. For demonstration purpuses let's say both batteries are 100 AH, and each has an internal resistance of .02 Ohms. From here it is simple math.
Battery Under Charge Voltage = OCV + [Ri x Charge Current] We already defined OCV of 12 volts or a fully discharged battery, and with a 20 amp charger (C/2 on a 100 AH battery) you will initially only see 12 volts + [20 amps x .02 Ohms] = 12.4 volts. The battery OCV forced the charger to become a Constant Current source. The Charger has a current regulator that will not allow it to deliver more than 20 amps. As the battery charges up, the OCV will rise and continue to rise for 4 to 5 hours. When the OCV of the battery is 14.0 volts, will begin the Absorb Phase. When the battery OCV reaches 14.1 volts there will only be 14.4 - 14.1 volts / .02 Ohms = 15 amps. At 14.2 is 10 amps. At 14.3 is 5 amps. At 14.4 both charger and battery OCV are equal and current stops.
Nothing magic happened, nothing switched on or off. It is pure Ohms Law of voltage and resistance relationship. Now we can add a circuit to do something like change the Voltage Set Point or Turn the Charger Off. Example we add a current measurement with some simple logic that says if Current = 5 amps or less, we do something. One thing we can do is lower the Voltage to say 13.6 volts and call it Abracadbra. No lets call it FLOAT so we fool Karrak and the John Doe homeowner. Sounds better. Why 5 amps and 13.6 volts? Because 5 amps on a 100 AH Pb and LFP is the point both batteries are fully charged. If we were to hold 14.4 volts on either battery would be an over charge. On Pb battery we would gas the batteries and corrode the plates. On a Lithium battery becomes unstable and plating lithium metal onto the anodes.
So you roll the voltage back on both. When you do that the Surface Charge on the plates will bleed off and hold at full charge. Any power demands from that point come from the charger if it remains. However very few chargers made for lithium will fall back to a lower voltage. They shut off.
Now if you were to watch the voltage on a PB and LFP battery, you would see they are not alike. A Pb battery would be a nice straight slope slope from 12 to 14.4 volts. On a LFP would look radically different like the slope you seen in Karrak's graph. It would jump up very quickly from 12 volts to 13,2 volts and pretty much stay there struggling upwards to 13.6 volts when it reaches about 90% SOC, then shoots up real fast that last 10% to 14.4 where you do not want to go.
Solar is a piss poor choice to charge LFP batteries because the charge current is unknown at any point in time. That means you cannot use a current trigger. Your battery could be 50% SOC at noon with only 5 amps and falsely trips the circuit because a cloud or haze passes over. There are no charge controllers that can work properly with Lithium. It takes an external control, a damn BMS. So what do you do? Simple choose 1 voltage of roughly 3.4 volts and allow the battery to saturate and FLOAT. That would be 13.6 volts on a 4S battery.
So far you are not ready to do anything. You have not balanced your batteries. Until you do that, you are spinning your wheels and risking damage. Decide Top or Bottom period. To do that you must connect all cells in parallel and walk away for a few hours. Then either discharge them to 2.5 volts, or charge them to 3.65 volts. Take your pick. Once balanced, lithium batteries do not go unbalanced quickly unless you have a BMS or Voltage Monitor taps. Those wil be a parasitic loads of uneven current draw. Both my Ev's only need balanced about once a year. If your batteries are in good shape has a self discharge of about 1% a month. Some maybe .8% and some 1.2% a month. So it takes a long time for any imbalance to occur. If you TOP balance periodically check cell voltages. All should be within .01 volts at the TOP. If you Bottom Balance should be within .01 volts near the bottom.
Now here is the difference betwen Bottom and Top Balance. With Top Balance the only thing that is known is 100% SOC. It does not tell you what capacity the pack is. Chi-Com cells especially Winston cells are notorius and can be +/- 10% of rated capacity. So when at 100% SOC you can have one cell at 90 AH and another at 110 AH which means you only have a 90 AH pack. That 90 AH pack i sin real danger of being over discharged. Th eother 3 cells wil eat and destroy it if the cell voltage goes to 2.5 volts or less.
Bottom Balance you know exactly what the capacity and SOC is. At 2.5 volts per cell capacity = 0 AH and SOC is exactly 0%. When you charge the cells in series, every cell has the exact same capacity. When they discharge, all cells voltages will be the same at the low end. Eliminates over discharge. Set you LVD from 11 to 12 or more volts, and you are safe.
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