Charging Voltage and Current Settings - Mixed Batteries

[RotEvery]

I have a Quattro 48/15000/200-100/100 Inverter; two SmartSolar MPPT RS 450|100 Charge Controllers and Cerbo GX which I was using with a Wakatek 48V 300AH LFP battery pack which does not have any communication cable. I have DVCC enabled with max charge voltage 55.8V / max charge current 75A per Wakatek supplier requirement. For each charge controller, VictronConnect was also used to set absorption voltage / float voltage /max charge current at 55.8V/55.5V/75A. VEConfigure was also used to make the same settings on the Quattro. Worked fine.

Now I have just added two parallel Felicitysolar 48V 200AH battery packs model numer LPBF48200-N in parallel to the existing Wakatek 48V 300AH battery pack. The installer has changed the DVCC settings to max charge voltage 55.8V / max charge current 136A. Based on my current solar panels capacity (6.55KW of CanadianSolar panels) I can't generate more than about 136A. (I will soon add another 3.3KW of solar panels). But the Felicitysolar battery pack datasheet calls for 57.6V absorption and 57.6V float settings.

My questions:

1. Are these settings correct / optimal?

2. Does the charge controller setting in VictronConnect for max charge current apply to each charge controller or to the batteries on the DC busbar? For example, if each of the two charge controllers is set at max charge current of 75A, does that represent a max charge current of 150A to the batteries or still a max charge current of 75A to the batteries on the busbar? Just want to be sure.

3. Is it okay to continue to operate the Wakatek battery pack along with the Felicitysolar battery packs?

 

[sunshine_eggo]

I have a Quattro 48/15000/200-100/100 Inverter; two SmartSolar MPPT RS 450|100 Charge Controllers and Cerbo GX which I was using with a Wakatek 48V 300AH LFP battery pack which does not have any communication cable. I have DVCC enabled with max charge voltage 55.8V / max charge current 75A per Wakatek supplier requirement. For each charge controller, VictronConnect was also used to set absorption voltage / float voltage /max charge current at 55.8V/55.5V/75A. VEConfigure was also used to make the same settings on the Quattro. Worked fine.

Now I have just added two parallel Felicitysolar 48V 200AH battery packs model numer LPBF48200-N in parallel to the existing Wakatek 48V 300AH battery pack. The installer has changed the DVCC settings to max charge voltage 55.8V / max charge current 136A. Based on my current solar panels capacity (6.55KW of CanadianSolar panels) I can't generate more than about 136A. (I will soon add another 3.3KW of solar panels). But the Felicitysolar battery pack datasheet calls for 57.6V absorption and 57.6V float settings.

My questions:

1. Are these settings correct / optimal?

2. Does the charge controller setting in VictronConnect for max charge current apply to each charge controller or to the batteries on the DC busbar? For example, if each of the two charge controllers is set at max charge current of 75A, does that represent a max charge current of 150A to the batteries or still a max charge current of 75A to the batteries on the busbar? Just want to be sure.

3. Is it okay to continue to operate the Wakatek battery pack along with the Felicitysolar battery packs?

1) the DVCC limit of 75A is global. It will not permit more than 75A TOTAL from all sources.

55.8V is 3.49V/cell - totally acceptable. In Expert, set time to fixed and duration to 1 hour. This is also a global value. Any GX connected chargers will be limited to this voltage.
Recommend you set float to 54V.

Do you have a suitable source for voltage, current and temperature sensing like a BMV-702/712 or smartshunt or Lynx shunt? If so, do you have SVS, SCS and STS enabled in DVCC?

2) Each. Restore MPPTs to 100A. When you change it in the MPPT, it's an absolute limit. The DVCC setting is specific to CHARGING. If you're charging at 75A, and you need another 50A in loads, the DVCC setting will allow additional PV power for loads. The MPPT set at 75A will not go above that for any reason even if you have the available PV.

3) if they are the same chemistry and cell count (nominal voltage), yes.

 

[RotEvery]

1) the DVCC limit of 75A is global. It will not permit more than 75A TOTAL from all sources.

55.8V is 3.49V/cell - totally acceptable. In Expert, set time to fixed and duration to 1 hour. This is also a global value. Any GX connected chargers will be limited to this voltage.
Recommend you set float to 54V.

Do you have a suitable source for voltage, current and temperature sensing like a BMV-702/712 or smartshunt or Lynx shunt? If so, do you have SVS, SCS and STS enabled in DVCC?

2) Each. Restore MPPTs to 100A. When you change it in the MPPT, it's an absolute limit. The DVCC setting is specific to CHARGING. If you're charging at 75A, and you need another 50A in loads, the DVCC setting will allow additional PV power for loads. The MPPT set at 75A will not go above that for any reason even if you have the available PV.

Thank you so much @sunshine_eggo for the clear answers. Very helpful.

1) In VEConfigure, for the Quattro, charge curve is set to fixed and both absorption time / repeated absorption time are set to 1 hour. Repeated absorption interval is set to 7 days. I charge with Solar like virtually all the time. So, I will check the settings for the charge controllers in VictronConnect Expert mode and make changes if necessary. Should I make the tail current to be 0.1A or zero (disabled)?

2) I plan to install BMV-712 or Lyns shunt asap as well as temperature sensor. Do I need a separate shunt trip for the Wakatek battery pack? Or do I just connect one to the -Ve DC busbar? The installer turned ON SVS, STC and SCS. See attached. Not sure why. For now, the system is working fine.
,

 

[sunshine_eggo]

Note that without a shunt, I'm not sure how DVCC will be able to limit current. I'm not confident that it will since it doesn't know how much current is going to the battery. It MIGHT try to limit both MPPT to a total of 75A, but you need to confirm that. Since it does know how much is coming in from the MPPT AND how much is going out in the quattro, so it might be smart enough to say that the difference is going to the battery and keep it at that.

If 75A is a hard limit, and the GX doesn't limit both to a total of 75A output, you will need to set each MPPT to 37A. Note that this also restricts power as well. Under no circumstances can either MPPT output more than 37A even if you need more for loads.

1) Quattro sounds fine. You generally don't want to run absorption or float when charging with grid/generator unless you really need to. It gets notaly less efficient when the Quattro isn't delivering max charge current. Leave MPPT tail current off. You don't want it cutting off early.

2) SVS, SCS and STS take an appropriate device, like a BMV-712, and feed the voltage, current and temperature it senses to all equipment that need that info. Once you install and connect the BMV with a VE.Direct cable (sold separately), it should sense it as the shared device and send that info to all devices.

 

[RotEvery]

Thanks again @sunshine_eggo.
Charge controller settings updated. See attachments. Will let you know when I install BMV-712 or Lyns shunt.

 

[RotEvery]

Note that without a shunt, I'm not sure how DVCC will be able to limit current. I'm not confident that it will since it doesn't know how much current is going to the battery. It MIGHT try to limit both MPPT to a total of 75A, but you need to confirm that. Since it does know how much is coming in from the MPPT AND how much is going out in the quattro, so it might be smart enough to say that the difference is going to the battery and keep it at that.

The DVCC has indeed shown itself smart enough by saying the difference between what's coming in from the MPPT's and what's going out in the Quattro is going to the battery (actually batteries but DVCC thinks it's only one battery / doesn't care anyway).

 

[sunshine_eggo]

Both appear to be 55.5 absorption and 75A current limit.

Recommend:
55.8V as previously discussed. if I told you to lower that, I didn't mean to.
Set to 100A so the MPPT can deliver max current if the loads need it.

The second one has rebulk at 2.8V, temp comp enabled and low temp charge protection disabled.

Recommend:
0.4 rebulk
very important that temp comp be disabled.
5°C low temp charge protection

(make it match the other)

The DVCC has indeed shown itself smart enough by saying the difference between what's coming in from the MPPT's and what's going out in the Quattro is going to the battery (actually batteries but DVCC thinks it's only one battery / doesn't care anyway).

That is very good to know. Thank you for confirming.

 

[RotEvery]

Both appear to be 55.5 absorption and 75A current limit.

Recommend:
55.8V as previously discussed. if I told you to lower that, I didn't mean to.
Set to 100A so the MPPT can deliver max current if the loads need it.

The second one has rebulk at 2.8V, temp comp enabled and low temp charge protection disabled.

Recommend:
0.4 rebulk
very important that temp comp be disabled.
5°C low temp charge protection

(make it match the other)

Lowering to 55.5V was result of separate follow up discussion with Wakatek battery supplier. He also asked that the float be 54.5V so considering changing that also. Your thoughts on this please.
Will update the temp comp and low temp charge protection settings to be per your recommendations. Will make the settings on both SCCs match one another.
Thanks!

 

[RotEvery]

That is very good to know. Thank you for confirming.

I also have 150A MCCB for the Wakatek battery and another 150A MCCB for the combination of the two Felicitysolar batteries.

 

[sunshine_eggo]

Lowering to 55.5V was result of separate follow up discussion with Wakatek battery supplier. He also asked that the bulk be 54.5V so considering changing that also. Your thoughts on this please.
Will update the temp comp and low temp charge protection settings to be per your recommendations. Will make the settings on both SCCs match one another.
Thanks!

Bulk and absorption are the same voltage - it's the transition voltage between the two phases. Bulk is the max current charging UNTIL bulk/absorption voltage is hit. When the voltage is held, and current is tapered - that's absorption.

I'm not sure why they would have two recommendations for the same voltage.

I also have 150A MCCB for the Wakatek battery and another 150A MCCB for the combination of the two Felicitysolar batteries.

MCCB?

 

[RotEvery]

Bulk and absorption are the same voltage - it's the transition voltage between the two phases. Bulk is the max current charging UNTIL bulk/absorption voltage is hit. When the voltage is held, and current is tapered - that's absorption.

I'm not sure why they would have two recommendations for the same voltage.

Sorry it was a mistake. I've now edited it. Their latest recommendation bulk/absorption 55.5V; float 54.5V. Thanks.

 

[RotEvery]

MCCB?

Yes. Picture attached.

 

[RotEvery]

Note that without a shunt, I'm not sure how DVCC will be able to limit current. I'm not confident that it will since it doesn't know how much current is going to the battery. It MIGHT try to limit both MPPT to a total of 75A, but you need to confirm that. Since it does know how much is coming in from the MPPT AND how much is going out in the quattro, so it might be smart enough to say that the difference is going to the battery and keep it at that.

If 75A is a hard limit, and the GX doesn't limit both to a total of 75A output, you will need to set each MPPT to 37A. Note that this also restricts power as well. Under no circumstances can either MPPT output more than 37A even if you need more for loads.

1) Quattro sounds fine. You generally don't want to run absorption or float when charging with grid/generator unless you really need to. It gets notaly less efficient when the Quattro isn't delivering max charge current. Leave MPPT tail current off. You don't want it cutting off early.

2) SVS, SCS and STS take an appropriate device, like a BMV-712, and feed the voltage, current and temperature it senses to all equipment that need that info. Once you install and connect the BMV with a VE.Direct cable (sold separately), it should sense it as the shared device and send that info to all devices.

The system / DVCC is accurately measuring the dc current to and from the batteries (by subtracting what the inverter is drawing for direct use from total MPPTs generation) and is controlling the actual current to the batteries at a chosen set point (now 136A; different than the settings on the individual MPPTs). This is confirmed. When the MPPTs are finishing absorption stage and during the switch to float stage, the DVCC sometimes switches off the MPPTs for some short period while it discharges the batteries to supply the load, moves the MPPTs / batteries to float voltage and turns on generation by the MPPTs again.

Each battery pack has in-built BMS. The Felicitysolar packs have communication cables (not yet in use) while the Wakatek battery pack doesn't.

The Quattro inverter/charger has protection settings for output short circuit and output overload to prevent too-high battery discharge current. It has charge current limit that can prevent too high battery charge current. It has low battery voltage alarm and cut-off settings to prevent over-discharge of batteries.

With all the above, why is a shut trip needed, considering that the shunt trip is interacting with the rest of the system via communication link? The shunt trip still relies on the rest of the system to take any executive action of preventing or stopping a fault. Why not wire the Quattro relay to battery breaker (with trip coil) that trips when limit / fault condition is detected?

With use of fuses, I don't see why shunt trip is required unless separate shunt trips are installed for each battery pack in the battery bank.

Another probably more effective way of still using shunt trip is to install breaker with integral shunt trip complete with its current sensor that trips based on current setting without depending on communication link.

Please share your thoughts.

 

[sunshine_eggo]

The system / DVCC is accurately measuring the dc current to and from the batteries (by subtracting what the inverter is drawing for direct use from total MPPTs generation) and is controlling the actual current to the batteries at a chosen set point (now 136A; different than the settings on the individual MPPTs). This is confirmed. When the MPPTs are finishing absorption stage and during the switch to float stage, the DVCC sometimes switches off the MPPTs for some short period while it discharges the batteries to supply the load, moves the MPPTs / batteries to float voltage and turns on generation by the MPPTs again.

Given that LFP voltage is slow to settle, that sounds pretty normal. On lead-acid, the voltage plummets to float under even a slight load, and transition to float is essentially instantaneous. Under light load, the described behavior sounds right.

Each battery pack has in-built BMS. The Felicitysolar packs have communication cables (not yet in use) while the Wakatek battery pack doesn't.

The Quattro inverter/charger has protection settings for output short circuit and output overload to prevent too-high battery discharge current. It has charge current limit that can prevent too high battery charge current. It has low battery voltage alarm and cut-off settings to prevent over-discharge of batteries.

With all the above, why is a shut trip needed, considering that the shunt trip is interacting with the rest of the system via communication link? The shunt trip still relies on the rest of the system to take any executive action of preventing or stopping a fault. Why not wire the Quattro relay to battery breaker (with trip coil) that trips when limit / fault condition is detected?

With use of fuses, I don't see why shunt trip is required unless separate shunt trips are installed for each battery pack in the battery bank.

Another probably more effective way of still using shunt trip is to install breaker with integral shunt trip complete with its current sensor that trips based on current setting without depending on communication link.

Please share your thoughts.

I missed the shunt trip question earlier. If you're confident in the existing protections, then you're good. I have a BMV-702, so I could have an additional shunt trip safety if I wanted. I could also enable that in my Batrium, but my safeties are purely based on individual cell voltages and temperatures.

 

[RotEvery]

I missed the shunt trip question earlier. If you're confident in the existing protections, then you're good. I have a BMV-702, so I could have an additional shunt trip safety if I wanted. I could also enable that in my Batrium, but my safeties are purely based on individual cell voltages and temperatures.

I see. Is the batrium in-built in your LFP battery pack(s)?
Is it safe to assume that battery packs with built-in BMS, have charge and discharge interrupters included in them?

Does anyone know which BMS is in-built in Wakatek battery packs? Which BMS is in-built in Felicitysolar battery packs? It seems not easy to get this information from the manufacturers or suppliers. Both suppliers told me the packs have BYD cells but don't seem to know which make of BMS's are included. If proprietary BMS's are included, then where can I find information on details of what these particular BMS's actually include and do?

 

[sunshine_eggo]

I see. Is the batrium in-built in your LFP battery pack(s)?

No. I have a DIY NMC-LMO battery built from PHEV cells.

Is it safe to assume that battery packs with built-in BMS, have charge and discharge interrupters included in them?

Pretty much. I can't think of any complete battery offered that doesn't already include a BMS that performs the functions you describe except for Valence and Victron - those require specific external BMSs.

Does anyone know which BMS is in-built in Wakatek battery packs? Which BMS is in-built in Felicitysolar battery packs? It seems not easy to get this information from the manufacturers or suppliers. Both suppliers told me the packs have BYD cells but don't seem to know which make of BMS's are included. If proprietary BMS's are included, then where can I find information on details of what these particular BMS's actually include and do?

It's pretty common for battery manufactures to not indicate the brand of BMS even when explicitly asked. Battery specifications should give some clue as to what protections are offered.