I think it uses the cell voltages to determine SOC at the extreme ends only to stop over charge and discharge.
Wouldn't this just be simple over and under voltage protection though? I.e. cut charging at x voltage, cut discharging at y voltage
I think it uses the cell voltages to determine SOC at the extreme ends only to stop over charge and discharge.
yesWouldn't this just be simple over and under voltage protection though? I.e. cut charging at x voltage, cut discharging at y voltage
I don't see a need for the 8th cell if each provides a nominal 3.6V. With 7 cells you will see a nominal voltage of 25.2V - within range for your 24V equipment.I’d love to include my 8th module but I don’t see an 8s BMS.
So maybe the Daly 7S is the answer.I don't see a need for the 8th cell if each provides a nominal 3.6V. With 7 cells you will see a nominal voltage of 25.2V - within range for your 24V equipment.
I don't see a need for the 8th cell if each provides a nominal 3.6V. With 7 cells you will see a nominal voltage of 25.2V - within range for your 24V equipment.
View attachment 665
Also, I posted this elsewhere sometime ago:
Quick update for advanced LiFePO4 raw cell systems using a Daly BMS:
On my website I recommended using a separate port BMS for over voltage protection for the mppt connection (if common port BMS is used, possibility of destroying mppt during low voltage disconnect).
Well yesterday, a viewer and I finally received our separate port BMS from Daly, and the amp rating was not as advertised on the listing. The separate port can only handle 10 amps!
Considering the likelihood of over voltage situation from most high quality mppt, and the chance of matched LiFePO4 cells going out of balance is rare (and BMS will correct for cell drift over time), and that LiFePO4 can be over charged to 4.2v per cell before electrolyte degradation... I would say its safe to connect mppt directly to the battery bank, and bypass the BMS entirely. We have been doing it this way for years, but people still want to use a BMS.
I would say use BMS for loads, and not for chargers. If you have mismatched cells, and some hit a higher voltage at high SOC quicker than others, drop the upper limit voltage of your controller. 14.0-14.2v is a safe charging voltage that can give full capacity with LiFePO4 12v.
I hope this helps! I bet most people building these systems will figure this out when they see this problem, but if you are a beginner trying to build an advanced level system, then this bit of information will be very useful. Let me know if you have any questions
The Electrodacus bms does continuous battery balancing while charging. (Cell balancing is done as soon as there is more than 300mA of charge current and delta between cells is higher than 10mV)Having read all the above discussions and looked at my setup, which includes an All-In-One SCC/Inverter, I've realized something. There is no way to isolate the charging versus inverter load current with an All-In-One, short of buying a separate inverter. There is only one connection between the All-In-One and the battery which serves both for charging and discharging through the inverter. Any BMS that is used in this situation is going to disconnect the battery from the All-In-One.
DC and separate Inverter could be isolated, but having to buy a separate inverter defeats the purpose of the All-In-One.
So, I'm left with the conclusion that I need to run my batteries within a safe SOC zone. Now that safe zone could be made broader I there was a BMS that aggressively balanced cells. Is anyone aware of which BMS is the best at balancing cells quickly?
Second, it seems from the discussion that using a relay to cut charging is not good for the SCC. Having observed my SCC's operation that makes sense. It does not just suddenly jump from absorption to float charging but rather ramps down over about a minute. This can be seen by observing the current and voltage as this change occurs.
Hi Will,View attachment 665
Also, I posted this elsewhere sometime ago:
Quick update for advanced LiFePO4 raw cell systems using a Daly BMS:
On my website I recommended using a separate port BMS for over voltage protection for the mppt connection (if common port BMS is used, possibility of destroying mppt during low voltage disconnect).
Well yesterday, a viewer and I finally received our separate port BMS from Daly, and the amp rating was not as advertised on the listing. The separate port can only handle 10 amps!
Considering the likelihood of over voltage situation from most high quality mppt, and the chance of matched LiFePO4 cells going out of balance is rare (and BMS will correct for cell drift over time), and that LiFePO4 can be over charged to 4.2v per cell before electrolyte degradation... I would say its safe to connect mppt directly to the battery bank, and bypass the BMS entirely. We have been doing it this way for years, but people still want to use a BMS.
I would say use BMS for loads, and not for chargers. If you have mismatched cells, and some hit a higher voltage at high SOC quicker than others, drop the upper limit voltage of your controller. 14.0-14.2v is a safe charging voltage that can give full capacity with LiFePO4 12v.
I hope this helps! I bet most people building these systems will figure this out when they see this problem, but if you are a beginner trying to build an advanced level system, then this bit of information will be very useful. Let me know if you have any questions
UnderVoltage*Protection i guessMessage not understood.
Please resend.
Over.
Yes indeed. I changed it to LVD Sorry Joey.UnderVoltage*Protection i guess
Having read all the above discussions and looked at my setup, which includes an All-In-One SCC/Inverter, I've realized something. There is no way to isolate the charging versus inverter load current with an All-In-One, short of buying a separate inverter. There is only one connection between the All-In-One and the battery which serves both for charging and discharging through the inverter. Any BMS that is used in this situation is going to disconnect the battery from the All-In-One.
This is an interesting discussion. I originally ordered the separate port and realized in the difference in charge/load values later. As I'm scaling up the batteries in the future, I ordered a new common port BMS 16s 48v 200ah and it just arrived. This thing is huge, 2x the size of previous BMS. I actually had a bypass for when using my 240v welder and plasma cutter. With this one I'm going try and see how much current I can draw through it.
It also looks different than pictures shown on the sellers site. It has double 6awg p- and b-.
I just recemy bms which looks exactly like yours with one label being different.
I love the size, weight and large cables.
It states Discharge 200A, Charge 100A. That works for me.
One question, why the dual cables for each?
Do they provide any benefit? How?
Cables are 6 awg, 200°CThey double up smaller cables because they are more flexible and fit the solder pads better than 1 large cable.
What gage and temperature rating are the cables?
Also if this is a commodity BMS you should derate both the charge and discharge current by .5.
2x 6awg is equivalant to 1x 3 awg.Cables are 6 awg, 200°C
Any reason I shouldn't use them both on different posts of the battery?
That all depends- the MPP solar units will cut charging if the detected voltage reaches the pre programmed cut off point. It will also pass the load off to line (or just disconnect load)if the voltage is below the set point. In general, while fuses are good, they technically should serve no purpose as the wire gauge should be able to carry more than the MPPsolar unit can draw or charge at.Only one positive and negative connection to the MPP Solar all in one inverter which means if the the BMS (or fuse, circuit breaker, etc.) disconnects the battery the built in MPPT controller is in an open circuit condition and the array goes to Voc. I am going to guess (perhaps someone with an all in one can verify) that disconnecting the battery does not damage the built in MPPT controller, as that is a likely condition at some point.
With an all in one seems unnecessary to have a BMS with seperate charge and discharge disconnects, one is all that is needed.