YamBMS JK-BMS-CAN with new Cut-Off Charging Logic (open-source)

Sleeper85 said:

In the case of an inverter with a low load (when you are away from home for several days for example), the battery voltage drops slowly and it takes a few days for the Rebulk V. condition to be true. This new criteria based on SoC makes it possible to start a new Bulk phase earlier otherwise it is possible that it will only start at an SoC of 75%.

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Sleeper85 said:

@MrPablo @Der_Hannes @shvm @arzaman and all

What do you think of a rebulk based on two criteria :

1. Rebulk V.
2. Rebulk SoC

If one of these 2 conditions is true then a new Bulk phase can begin.

In the case of an inverter with a low load (when you are away from home for several days for example), the battery voltage drops slowly and it takes a few days for the Rebulk V. condition to be true. This new criteria based on SoC makes it possible to start a new Bulk phase earlier otherwise it is possible that it will only start at an SoC of 75%.

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1. Voltage - can lead to long-term float and resulting drop in SOC over time
2. SOC - will resolve the above, but relies on accurate SOC
3. Time since last full charge - will resolve the issue with voltage, but won't work well in systems that rarely charge fully
4. Time since last bulk - will resolve the issue with voltage, should work regardless of SOC accuracy

MrPablo said:

There's several ways we can look at triggering rebulk:

1. Voltage - can lead to long-term float and resulting drop in SOC over time
2. SOC - will resolve the above, but relies on accurate SOC
3. Time since last full charge - will resolve the issue with voltage, but won't work well in systems that rarely charge fully
4. Time since last bulk - will resolve the issue with voltage, should work regardless of SOC accuracy

SOC is likely the easiest to implement.

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Sleeper85 said:

The SoC can become inaccurate when there is very little time to fully recharge. That said, in Portugal, I was able to compare the SoC of a JK-BMS 8S against a Junctek Shunt and even without 100% recharging for several days the SoC of the JK-BMS was often equal to the shunt.

Here is the graph over a period of 1 month without 100% charging every day.

View attachment 230605

So I think that a well calibrated JK-BMS for correct measurement of a 5A current (this is my procedure) can be reliable.

Let's imagine a Rebulk with 85% SoC, what would be the problem if the real SoC is 80% or 90%? None from my point of view.

Let's not forget that in the future it will be possible to take Voltage, Current, Power and SoC information from a shunt. That would be the next step on my list.

So I add the Rebulk condition based on the SoC?

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Sleeper85 said:

The SoC can become inaccurate when there is very little time to fully recharge. That said, in Portugal, I was able to compare the SoC of a JK-BMS 8S against a Junctek Shunt and even without 100% recharging for several days the SoC of the JK-BMS was often equal to the shunt.

Here is the graph over a period of 1 month without 100% charging every day.

View attachment 230605

So I think that a well calibrated JK-BMS for correct measurement of a 5A current (this is my procedure) can be reliable.

Let's imagine a Rebulk with 85% SoC, what would be the problem if the real SoC is 80% or 90%? None from my point of view.

Let's not forget that in the future it will be possible to take Voltage, Current, Power and SoC information from a shunt. That would be the next step on my list.

So I add the Rebulk condition based on the SoC?

Click to expand...

Sleeper85 said:

@silverstone

View attachment 230706

Here is the graph of version 1.17.3 with an inverter with low load (max 150W) while we were in Portugal. I just tell myself that it might be interesting to recharge more often and not leave the SoC below 80% which would be a conservative default value.

In the case of a large load on the inverter the Rebulk V. would probably be reached more quickly so these two conditions would be complementary.

I added it to the version being tested at home. This will be part of version 1.4.2.

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silverstone said:

Sure, it is a good idea as I also said . Just IMHO (especially if you have the same issues that I do) the SOC threshold shouldn't be set too low.

80% would be fine. If you do NOT have that weird SOC drift that I had, then 90% would also probably work. Keep at 80% for default though .

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Sleeper85 said:

I have no problems calculating SoC with the latest JK-BMS and even better since it integrates the two new reset voltage parameters 0% and 100%.

SoC rebulk will be set to 80% by default

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Sleeper85 said:

In the case of a large load on the inverter the Rebulk V. would probably be reached more quickly so these two conditions would be complementary.

I added it to the version being tested at home. This will be part of version 1.4.2.

Click to expand...

arzaman said:

complementary ==> OR of the two conditions right ?
So idea is to start bulk charging when either Voltage is <= Rebulk Voltage threshold OR SoC <= new threshold (80% default)

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silverstone said:

I can understand that now (especially with multiple Batteries) your code will calculate a "Global SOC" so you can of course "manipulate" (in a positive Way ) and filter out these BUGs by the JK BMS Board.

Or do you mean that now, with your code, you even might go a Step further: you do NOT expose the "JK BMS" SOC anymore but you fully control how the SOC is calculated by yourself (e.g. doing Coulomb Counting / Capacity = Integral of Current, and then when at say 55.2 VDC for > 0.5h AND Tail Current < [X] ADC AND Balancer OFF, then you do a SOC = 100% Reset / Recalibration) ?

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  # +--------------------------------------+
  # | Battery State of Charge (SOC)        |
  # +--------------------------------------+
  - platform: template
    name: ${name} ${yambms_name} Battery SoC
    id: ${yambms_id}_battery_soc
    unit_of_measurement: "%"
    device_class: battery
    update_interval: ${yambms_update_interval}
    accuracy_decimals: 0
    filters:
      - or:
        - throttle: 10s
        - delta: 1
    lambda: |-
      float soc = id(${yambms_id}_state_of_charge).state;
      float min_cell_v = id(${yambms_id}_min_cell_voltage).state;
      float cell_uvpr = id(${yambms_id}_cell_uvpr).state;
      if (min_cell_v <= cell_uvpr) return 0;                          // Real 0% Sending 0%
      else if (soc < 1) return 2;                                     // False 0% sending 2%
      else if (soc < 99) return soc;                                  // SOC < 99% => Sending BMS SOC
      // Useful for some inverters, will not send 100% until charging is complete
      else if (id(${yambms_id}_eoc) == true) return soc;              // End Of Charge => Sending BMS SOC
      else return 98;

arzaman said:

complementary ==> OR of the two conditions right ?

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Sleeper85 said:

The best solution is to add a reliable measuring shunt.

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silverstone said:

But "do I really need it" is the Primary Question I guess .

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Sleeper85 said:

I don't think this is really necessary, it might be a little more precise.

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arzaman said:

The "rebulk" SoC condition could help by forcing the system back into bulk charging, thereby aiding in battery balancing.

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